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Regulatory T cells (Tregs) play a pivotal role in maintaining immunological tolerance, but they can also play a detrimental role by preventing antitumor responses. Here, we characterized T helper (Th)-like Treg subsets to further delineate their biological function and tissue distribution, focusing on their possible contribution to disease states. RNA sequencing and functional assays revealed that Th2-like Tregs displayed higher viability and autocrine interleukin-2 (IL-2)-mediated activation than other subsets. Th2-like Tregs were preferentially found in tissues rather than circulation and exhibited the highest migratory capacity toward chemokines enriched at tumor sites. These cellular responses led us to hypothesize that this subset could play a role in maintaining a tumorigenic environment. Concurrently, Th2-like Tregs were enriched specifically in malignant tissues from patients with melanoma and colorectal cancer compared to healthy tissue. Overall, our results suggest that Th2-like Tregs may contribute to a tumorigenic environment due to their increased cell survival, higher migratory capacity, and selective T-effector suppressive ability. View Publication

Peripheral blood mononuclear cells (PBMCs) were collected from a clinically diagnosed 64-year old male Parkinson's disease (PD) patient with S1647T variant in the LRRK2 gene. The PMBCs were reprogrammed with the human OSKM transcription factors using the Sendai-virus reprogramming system. The transgene-free iPSC showed pluripotency confirmed by immunofluorescent staining for pluripotency markers and differentiated into the 3 germ layers in vivo. The iPSC line also showed normal karyotype. This cellular model will be useful for further function studies and therapeutic screening. View Publication

BACKGROUND: Therapies directed at augmenting regulatory T cell (Treg) activities in vivo as a systemic treatment for autoimmune disorders and transplantation may be associated with significant off-target effects, including a generalized immunosuppression that may compromise beneficial immune responses to infections and cancer cells. Adoptive cellular therapies using purified expanded Tregs represents an attractive alternative to systemic treatments, with results from animal studies noting increased therapeutic potency of antigen-specific Tregs over polyclonal populations. However, current methodologies are limited in terms of the capacity to isolate and expand a sufficient quantity of endogenous antigen-specific Tregs for therapeutic intervention. Moreover, FOXP3+ Tregs fall largely within the CD4+ T cell subset and are thus routinely MHC class II-specific, whereas class I-specific Tregs may function optimally in vivo by facilitating direct tissue recognition. METHODOLOGY/PRINCIPAL FINDINGS: To overcome these limitations, we have developed a novel means for generating large numbers of antigen-specific Tregs involving lentiviral T cell receptor (TCR) gene transfer into in vitro expanded polyclonal natural Treg populations. Tregs redirected with a high-avidity class I-specific TCR were capable of recognizing the melanoma antigen tyrosinase in the context of HLA-A*0201 and could be further enriched during the expansion process by antigen-specific reactivation with peptide loaded artificial antigen presenting cells. These in vitro expanded Tregs continued to express FOXP3 and functional TCRs, and maintained the capacity to suppress conventional T cell responses directed against tyrosinase, as well as bystander T cell responses. Using this methodology in a model tumor system, murine Tregs designed to express the tyrosinase TCR effectively blocked antigen-specific effector T cell (Teff) activity as determined by tumor cell growth and luciferase reporter-based imaging. CONCLUSIONS/SIGNIFICANCE: These results support the feasibility of class I-restricted TCR transfer as a promising strategy to redirect the functional properties of Tregs and provide for a more efficacious adoptive cell therapy. View Publication

The presence of interleukin-2 (IL-2)-producing human immunodeficiency virus type 1 (HIV-1)-specific CD4(+) T-cell responses has been associated with the immunological control of HIV-1 replication; however, the causal relationship between these factors remains unclear. Here we show that IL-2-producing HIV-1-specific CD4(+) T cells can be cloned from acutely HIV-1-infected individuals. Despite the early presence of these cells, each of the individuals in the present study exhibited progressive disease, with one individual showing rapid progression. In this rapid progressor, three IL-2-producing HIV-1 Gag-specific CD4(+) T-cell responses were identified and mapped to the following optimal epitopes: HIVWASRELER, REPRGSDIAGT, and FRDYVDRFYKT. Responses to these epitopes in peripheral blood mononuclear cells were monitored longitudinally to textgreater1 year postinfection, and contemporaneous circulating plasma viruses were sequenced. A variant of the FRDYVDRFYKT epitope sequence, FRDYVDQFYKT, was observed in 1/21 plasma viruses sequenced at 5 months postinfection and 1/10 viruses at 7 months postinfection. This variant failed to stimulate the corresponding CD4(+) T-cell clone and thus constitutes an escape mutant. Responses to each of the three Gag epitopes were rapidly lost, and this loss was accompanied by a loss of antigen-specific cells in the periphery as measured by using an FRDYVDRFYKT-presenting major histocompatibility complex class II tetramer. Highly active antiretroviral therapy was associated with the reemergence of FRDYVDRFYKT-specific cells by tetramer. Thus, our data support that IL-2-producing HIV-1-specific CD4(+) T-cell responses can exert immune pressure during early HIV-1 infection but that the inability of these responses to enforce enduring control of viral replication is related to the deletion and/or dysfunction of HIV-1-specific CD4(+) T cells rather than to the fixation of escape mutations at high frequencies. View Publication

Human natural killer (NK) cells express an abundant level of 2B4 and CD2 on their surface. Their counter-receptors, CD48 and CD58, are also expressed on the NK cell surface, raising a question about the functional consequences of potential 2B4/CD48 and CD2/CD58 interactions. Using blocking antibodies specific to each receptor, we demonstrated that both 2B4/CD48 and CD2/CD58 interactions were essential for the development of NK effector functions: cytotoxicity and cytokine secretion. However, only 2B4/CD48, but not CD2/CD58, interactions were shown to be critical for the optimal NK cell proliferation in response to interleukin (IL)-2. IL-2-activated NK cells cultured in the absence of 2B4/CD48 or CD2/CD58 interactions were severely impaired for their ability to induce intracellular calcium mobilization and subsequent ERK activation upon tumor target exposure, suggesting that the early signaling pathway of NK receptors leading to impaired cytolysis and interferon (IFN)-γ secretion was inhibited. Nevertheless, these defects did not fully account for the reduced proliferation of NK cells in the absence of 2B4/CD48 interactions, because anti-CD2 or anti-CD58 monoclonal antibody (mAb)-treated NK cells, showing defective signaling and effector functions, displayed normal proliferation upon IL-2 stimulation. These results propose the signaling divergence between pathways leading to cell proliferation and cytotoxicity/cytokine release, which can be differentially regulated by 2B4 and CD2 during IL-2-driven NK cell activation. Collectively, these results reveal the importance of homotypic NK-to-NK cell cross-talk through 2B4/CD48 and CD2/CD58 pairs and further present their differential and overlapping roles in human NK cells. View Publication

High-dose, posttransplantation cyclophosphamide (PTCy) is an effective strategy for preventing graft-versus-host disease (GVHD) after allogeneic blood or marrow transplantation (alloBMT). However, the mechanisms by which PTCy modulates alloimmune responses are not well understood. We studied early T cell reconstitution in patients undergoing alloBMT with PTCy and the effects of mafosfamide, a cyclophosphamide (Cy) analog, on CD4(+) T cells in allogeneic mixed lymphocyte reactions (MLRs) in vitro. Patients exhibited reductions in naïve, potentially alloreactive conventional CD4(+) T cells with relative preservation of memory CD4(+)Foxp3(+) T cells. In particular, CD4(+)CD45RA(-)Foxp3(+hi) effector regulatory T cells (Tregs) recovered rapidly after alloBMT and, unexpectedly, were present at higher levels in patients with GVHD. CD4(+)Foxp3(+) T cells from patients and from allogeneic MLRs expressed relatively high levels of aldehyde dehydrogenase (ALDH), the major in vivo mechanism of Cy resistance. Treatment of MLR cultures with the ALDH inhibitor diethylaminobenzaldehyde reduced the activation and proliferation of CD4(+) T cells and sensitized Tregs to mafosfamide. Finally, removing Tregs from peripheral blood lymphocyte grafts obviated PTCy's GVHD-protective effect in a xenogeneic transplant model. Together, these findings suggest that Treg resistance to Cy through expression of ALDH may contribute to the clinical activity of PTCy in preventing GVHD. View Publication

CD4+CD25+ regulatory T cells play an important role in peripheral tolerance. Upon T cell receptor (TCR)-mediated activation, the cells fail to proliferate but are induced to have a suppressor function. The intracellular signaling events that lead to their responses have not been elucidated. In this study, we have examined the proximal TCR signaling events in freshly isolated human CD4+CD25+ regulatory T cells after TCR ligation. In contrast to CD4+CD25- T cells, TCR ligation of CD4+CD25+ regulatory T cells by anti-CD3 cross-linking resulted in a lower calcium influx and extracellular signal-regulated kinase 1/2 phosphorylation. Examination of the CD3zeta chain phosphorylation status indicated that CD4+CD25+ regulatory T cells have poor phosphorylation of the protein and consequently, reduced recruitment of zeta-associated protein-70 to the TCR immunoreceptor tyrosine motif. The adaptor protein, Src homology 2 domain-containing leukocyte phosphoprotein of 76 kDa, which relays signals to downstream signaling components, also showed reduced phosphorylation, which correlated with reduced VAV guanine nucleotide exchange factors association. Consistent with other findings, the defect is accompanied with impaired actin cap formation, implicating a failure of actin remodeling of the cells. Together, our results demonstrate that CD4+CD25+ regulatory T cells have altered TCR proximal signaling pathways, which could be critical for inducing the distinct behavior of these cells. View Publication

Natural T regulatory cells (nTregs) play a key role in inducing and maintaining immunological tolerance. Cell-based therapy using purified nTregs is under consideration for several conditions, but procedures employed to date have resulted in cell populations that are contaminated with cytokine secreting effector cells. We have established a method for isolation and ex vivo expansion of human nTregs from healthy blood donors for cellular therapy aimed at preventing allograft rejection in organ transplants. The Robosep instrument was used for initial nTreg isolation and rapamycin was included in the expansion phase of cell cultures. The resulting cell population exhibited a stable CD4(+)CD25(++bright)Foxp3(+) phenotype, had potent functional ability to suppress CD4(+)CD25(negative) T cells without evidence of conversion to effector T cells including TH17 cells, and manifested little to no production of pro-inflammatory cytokines upon in vitro stimulation. Boolean gating analysis of cytokine-expressing cells by flow cytometry for 32 possible profile end points revealed that 96% of expanded nTregs did not express any cytokine. From a single buffy coat, approximately 80 million pure nTregs were harvested after expansion under cGMP conditions; these cell numbers are adequate for infusion of approximately one million cells kg�?�¹ for cell therapy in clinical trials. View Publication

Naturally occurring regulatory T cells (Tregs) maintain self tolerance by dominant suppression of potentially self-reactive T cells in peripheral tissues. However, the activation requirements, the temporal aspects of the suppressive activity, and mode of action of human Tregs are subjects of controversy. In this study, we show that Tregs display significant variability in the suppressive activity ex vivo as 54% of healthy blood donors examined had fully suppressive Tregs spontaneously, whereas in the remaining donors, anti-CD3/CD2/CD28 stimulation was required for Treg suppressive activity. Furthermore, anti-CD3/CD2/CD28 stimulation for 6 h and subsequent fixation in paraformaldehyde rendered the Tregs fully suppressive in all donors. The fixation-resistant suppressive activity of Tregs operated in a contact-dependent manner that was not dependent on APCs, but could be fully obliterated by trypsin treatment, indicating that a cell surface protein is directly involved. By add-back of active, fixed Tregs at different time points after activation of responding T cells, the responder cells were susceptible to Treg-mediated immune suppression up to 24 h after stimulation. This defines a time window in which effector T cells are susceptible to Treg-mediated immune suppression. Lastly, we examined the effect of a set of signaling inhibitors that perturb effector T cell activation and found that none of the examined inhibitors affected Treg activation, indicating pathway redundancy or that Treg activation proceeds by signaling mechanisms distinct from those of effector T cells. View Publication

Regulatory T cell (Treg) therapy has the potential to induce transplantation tolerance so that immunosuppression and associated morbidity can be minimized. Alloantigen-reactive Tregs (arTregs) are more effective at preventing graft rejection than polyclonally expanded Tregs (PolyTregs) in murine models. We have developed a manufacturing process to expand human arTregs in short-term cultures using good manufacturing practice-compliant reagents. This process uses CD40L-activated allogeneic B cells to selectively expand arTregs followed by polyclonal restimulation to increase yield. Tregs expanded 100- to 1600-fold were highly alloantigen reactive and expressed the phenotype of stable Tregs. The alloantigen-expanded Tregs had a diverse TCR repertoire. They were more potent than PolyTregs in vitro and more effective at controlling allograft injuries in vivo in a humanized mouse model. View Publication

The T-cell surface molecule TIGIT is an immune checkpoint molecule that inhibits T-cell responses, but its roles in cancer are little understood. In this study, we evaluated the role TIGIT checkpoint plays in the development and progression of gastric cancer. We show that the percentage of CD8 T cells that are TIGIT+ was increased in gastric cancer patients compared with healthy individuals. These cells showed functional exhaustion with impaired activation, proliferation, cytokine production, and metabolism, all of which were rescued by glucose. In addition, gastric cancer tissue and cell lines expressed CD155, which bound TIGIT receptors and inactivated CD8 T cells. In a T cell-gastric cancer cell coculture system, gastric cancer cells deprived CD8 T cells of glucose and impaired CD8 T-cell effector functions; these effects were neutralized by the additional glucose or by TIGIT blockade. In gastric cancer tumor cells, CD155 silencing increased T-cell metabolism and IFNγ production, whereas CD155 overexpression inhibited T-cell metabolism and IFNγ production; this inhibition was neutralized by TIGIT blockade. Targeting CD155/TIGIT enhanced CD8 T-cell reaction and improved survival in tumor-bearing mice. Combined targeting of TIGIT and PD-1 further enhanced CD8 T-cell activation and improved survival in tumor-bearing mice. Our results suggest that gastric cancer cells inhibit CD8 T-cell metabolism through CD155/TIGIT signaling, which inhibits CD8 T-cell effector functions, resulting in hyporesponsive antitumor immunity. These findings support the candidacy of CD155/TIGIT as a potential therapeutic target in gastric cancer. Cancer Res; 77(22); 6375-88. textcopyright2017 AACR. View Publication

We used primary peripheral blood T cells, a population that exists in G(0) and can be stimulated to enter the cell cycle synchronously, to define more precisely the effects of nicotine on pathways that control cell cycle entry and progression. Our data show that nicotine decreased the ability of T cells to transit through the G(0)/G(1) boundary (acquire competence) and respond to progression signals. These effects were due to nuclear factor of activated T cells c2 (NFATc2)-dependent repression of cyclin-dependent kinase 4 (CDK4) expression. Growth arrest at the G(0)/G(1) boundary was further enforced by inhibition of cyclin D2 expression and by increased expression and stabilization of p27Kip1. Intriguingly, T cells from habitual users of tobacco products and from NFATc2-deficient mice constitutively expressed CDK4 and were resistant to the antiproliferative effects of nicotine. These results indicate that nicotine impairs T cell cycle entry through NFATc2-dependent mechanisms and suggest that, in the face of chronic nicotine exposure, selection may favor cells that can evade these effects. We postulate that cross talk between nicotinic acetylcholine receptors and growth factor receptor-activated pathways offers a novel mechanism by which nicotine may directly impinge on cell cycle progression. This offers insight into possible reasons that underlie the unique effects of nicotine on distinct cell types and identifies new targets that may be useful control tobacco-related diseases. View Publication

B cell-activating factor of the tumor necrosis factor (TNF) family, or BAFF, is mainly produced in monocytes and dendritic cells, and indispensable for proliferation, differentiation and survival of B cells. BAFF is a type II membrane-bound protein and the extracellular C-terminal fragment is released from the cells as soluble BAFF (sBAFF), which binds to specific receptors on B cells. Accumulating evidence suggests that BAFF plays an important role in the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE). In this study, we developed a sensitive sandwich ELISA system to quantify the amount of sBAFF using our own mAb. Treatment of peripheral T cells of SLE patients with an anti-CD3 antibody triggered robust expression of BAFF and subsequent release of sBAFF from the cells. On the other hand, the stimulus induced only marginal elevation of sBAFF from normal T cells. These data indicate that BAFF is expressed in T cells upon stimulation at least under pathological conditions. Expression of BAFF was also largely induced in a human T cell line, Loucy (American Type Tissue Collection CRL-2629), in response to several stimuli, while other T cell lines so far examined produced the cytokine almost constitutively. These data suggest that Loucy recapitulates some of the characteristics of SLE T cells. Investigation of molecular and cellular mechanisms of production of BAFF in Loucy demonstrated that expression of BAFF was regulated through a signal transduction pathway which involves c-jun NH2-terminal kinase and p38, and that shedding of BAFF was catalyzed by a membrane-bound protease, furin. View Publication

Endothelial cells (ECs) line the luminal surface of blood vessels and have an active role in the recruitment of leukocytes, including immune cell activation. Regulatory T cells (Tregs) are immune suppressor cells that maintain peripheral tolerance and must interact with the endothelium as they traffic into tissue. We hypothesized that human ECs could modulate Tregs and their suppressor function. Cocultures of CD4+ T cells with human umbilical vein ECs (HUVECs) or dermal microvascular ECs (HDMECs) were conducted and analyzed for activation and proliferation after 72 and 120 h using flow cytometry. In monocyte-depleted cultures, human ECs were found to support CD4+ T cell proliferation in the presence of external mitogens phytohemagglutinin or anti-CD3/28 antibodies (aCD3/28). Activation was shown by CD25 expression in these cells that also transiently expressed the Treg transcription factor FOXP3. HUVECs supported the specific concurrent proliferation of both effector T cells and Tregs when cocultured with aCD3/28. Purified Tregs were also functionally activated by prior coculture with EC to suppress effector T (Teff) cell proliferation. Both direct coculture and indirect coculture of EC and Treg showed activation of the Treg suppressive phenotype. However, whereas HUVEC showed enhancement of suppression by both mechanisms, HDMEC only supported Treg suppressive activity via the contact-independent mechanism. In the contact-independent cultures, the soluble mediators IL-6, GM-CSF, or G-CSF released from ECs following interferon-gamma$ activation were not responsible for the enhanced Treg suppressor function. Following direct coculture, Treg expression of inhibitory receptors PD-1 and OX40 was elevated while activated EC expressed the counter ligands programmed death ligand (PD-L)1 and PD-L2. Therefore, human ECs have a role in supporting T cell proliferation and increasing Treg suppressor function. This ability of EC to enhance Treg function could offer novel targets to boost Treg activity during inflammatory disorders. View Publication

Accumulating evidence suggests elements within tumors induce exhaustion of effector T cells and infiltration of immunosuppressive regulatory T cells (Tregs), thus preventing the development of durable antitumor immunity. Therefore, the discovery of agents that simultaneously block Treg suppressive function and reinvigorate effector function of lymphocytes is key to the development of effective cancer immunotherapy. Previous studies have shown that TLR ligands (TLRLs) could modulate the function of these T cell targets; however, those studies relied on cell-free or accessory cell-based assay systems that do not accurately reflect in vivo responses. In contrast, we used a human PBMC-based proliferation assay system to simultaneously monitor the effect of TLRLs on T cells (CD4(+), CD8(+), Tregs), B cells, and NK cells, which gave different and even conflicting results. We found that the TLR7/8L:CL097 could simultaneously activate CD8(+) T cells, B cells, and NK cells plus block Treg suppression of T cells and B cells. The TLRLs TLR1/2L:Pam3CSK4, TLR5L:flagellin, TLR4L:LPS, and TLR8/7L:CL075 also blocked Treg suppression of CD4(+) or CD8(+) T cell proliferation, but not B cell proliferation. Besides CL097, TLR2L:PGN, CL075, and TLR9L:CpG-A, CpG-B, and CpG-C) were strong activators of NK cells. Importantly, we found that Pam3CSK4 could: 1) activate CD4(+) T cell proliferation, 2) inhibit the expansion of IL-10(+) naturally occurring FOXP3(+) Tregs and induction of IL-10(+) CD4(+) Tregs (IL-10-producing type 1 Treg), and 3) block naturally occurring FOXP3(+) Tregs suppressive function. Our results suggest these agents could serve as adjuvants to enhance the efficacy of current immunotherapeutic strategies in cancer patients. View Publication

Mesenchymal stem cells (MSC) are part of the bone marrow that provides signals supporting survival and growth of bystander hematopoietic stem cells (HSC). MSC modulate also the immune response, as they inhibit proliferation of lymphocytes. In order to investigate whether MSC can support survival of T cells, we investigated MSC capacity of rescuing T lymphocytes from cell death induced by different mechanisms. We observed that MSC prolong survival of unstimulated T cells and apoptosis-prone thymocytes cultured under starving conditions. MSC rescued T cells from activation induced cell death (AICD) by downregulation of Fas receptor and Fas ligand on T cell surface and inhibition of endogenous proteases involved in cell death. MSC dampened also Fas receptor mediated apoptosis of CD95 expressing Jurkat leukemic T cells. In contrast, rescue from AICD was not associated with a significant change of Bcl-2, an inhibitor of apoptosis induced by cell stress. Accordingly, MSC exhibited a minimal capacity of rescuing Jurkat cells from chemically induced apoptosis, a process disrupting the mitochondrial membrane potential regulated by Bcl-2. These results suggest that MSC interfere with the Fas receptor regulated process of programmed cell death. Overall, MSC can inhibit proliferation of activated T cells while supporting their survival in a quiescent state, providing a model of their activity inside the HSC niche. Disclosure of potential conflicts of interest is found at the end of this article. View Publication

Thymus-derived CD4+ CD25+ T regulatory cells (Tregs) are essential for the maintenance of self-tolerance. What critical factors and conditions are required for the extra-thymic development of Tregs remains an important question. In this study, we show that the anti-inflammatory extracellular matrix protein, thrombospondin-1, promoted the generation of human peripheral regulatory T cells through the ligation of one of its receptor, CD47. CD47 stimulation by mAb or a thrombospondin-1 peptide induced naive or memory CD4+ CD25- T cells to become suppressive. The latter expressed increased amounts of CTLA-4, OX40, GITR, and Foxp3 and inhibited autologous Th0, Th1, and Th2 cells. Their regulatory activity was contact dependent, TGF-beta independent, and partially circumvented by IL-2. This previously unknown mechanism to induce human peripheral Tregs in response to inflammation may participate to the limitation of collateral damage induced by exacerbated responses to self or foreign Ags and thus be relevant for therapeutic intervention in autoimmune diseases and transplantation. View Publication

By retroviral overexpression of the Notch-1 intracellular domain (ICN) in human CD34+ hematopoietic stem cells (HSCs), we have shown previously that Notch-1 signaling promotes the T-cell fate and inhibits the monocyte and B-cell fate in several in vitro and in vivo differentiation assays. Here, we investigated whether the effects of constitutively active Notch-1 can be mimicked by overexpression of its downstream target gene HES1. Upon HES-1 retroviral transduction, human CD34+ stem cells had a different outcome in the differentiation assays as compared to ICN-transduced cells. Although HES-1 induced a partial block in B-cell development, it did not inhibit monocyte development and did not promote T/NK-cell-lineage differentiation. On the contrary, a higher percentage of HES-1-transduced stem cells remained CD34+. These experiments indicate that HES-1 alone is not able to substitute for Notch-1 signaling to induce T-cell differentiation of human CD34+ hematopoietic stem cells. View Publication

Our previous studies have demonstrated that a previously unrecognized role of CFTR in hematopoiesis and acute leukemia. Here, we show that CFTR inhibitor CFTR-inh172 possesses ability to inhibit human T-cell acute lymphoblastic leukemia cells. In detail, CFTR-inh172 inhibited cell proliferation, promoted apoptosis and arrested the cell cycle in human T-cell acute lymphoblastic leukemia cell CCRF-CEM, JURKAT and MOLT-4. Furthermore, transcriptome analysis reveals that CFTR-inh172 induces significant alteration of gene expression related to apoptosis and proliferation. These findings demonstrate the potential of CFTR inhibitor CFTR-inh172 in human T-cell acute lymphoblastic leukemia treatment. View Publication

The association between type 2 diabetes (T2D) pathogenesis and immune-mediated tissue damage and insulin resistance suggests that T2D patients might benefit from the suppression of pathogenic inflammation. Foxp3+ Treg cells are crucial suppressors of inflammation, but the differentiation of Foxp3+ Treg cells is not static and is subject to conversion into IL-17-producing Th17-like cells upon receiving external signals. In this study, we examined the production of IL-17 by Treg cells. Compared to non-T2D controls, T2D patients presented significantly higher levels of IL-17-expressing cells in both Foxp3- CD4 T cells and Foxp3+ Treg cells. The frequencies of IL-17-nonexpressing Foxp3+ Treg cells, on the other hand, were not changed. Interestingly, IL-17-expressing Foxp3+ Treg cells were mutually exclusive from IL-10-expressing and TGF-$\beta$-expressing Foxp3+ Treg cells, suggesting that multiple subpopulations exist within the Foxp3+ Treg cells from T2D patients. In T2D patients, the frequencies of IL-17-expressing Foxp3+ Treg cells were positively correlated with the body mass index (BMI) and the HbA1c levels of T2D patients. The frequencies of IL-10-expressing Treg cells, on the other hand, were inversely associated with the BMI of both non-T2D controls and T2D patients. In addition, the suppressive activity of Treg cells was significantly lower in T2D patients than in non-T2D controls. Together, our study uncovered a dysregulation in Foxp3+ Treg cells from T2D patients, characterized by high IL-17 expression and low suppression activity. View Publication

Induced pluripotent stem cells (iPSCs) hold enormous potential for the development of personalized in vitro disease models, genomic health analyses, and autologous cell therapy. Here we describe the generation of T lymphocyte-derived iPSCs from small, clinically advantageous volumes of non-mobilized peripheral blood. These T-cell derived iPSCs (TiPS") retain a normal karyotype and genetic identity to the donor. They share common characteristics with human embryonic stem cells (hESCs) with respect to morphology� View Publication

Vogt-Koyanagi-Harada (VKH) disease (and sympathetic ophthalmia) is an ocular inflammatory disease that is considered to be a cell-mediated autoimmune disease against melanocytes. The purpose of this study was to determine the Ags specific to VKH disease and to develop an animal model of VKH disease. We found that exposure of lymphocytes from patients with VKH disease to peptides (30-mer) derived from the tyrosinase family proteins led to significant proliferation of the lymphocytes. Immunization of these peptides into pigmented rats induced ocular and extraocular changes that highly resembled human VKH disease, and we suggest that an experimental VKH disease was induced in these rats. We conclude that VKH disease is an autoimmune disease against the tyrosinase family proteins. View Publication

The limited ability of the heart to regenerate has prompted development of new systems to produce cardiomyocytes for therapeutics. While differentiation of human embryonic stem cells (hESCs) into cardiomyocytes has been well documented, the process remains inefficient and/or expensive, and progress would be facilitated by better understanding the early genetic events that cause cardiac specification. By maintaining a transgenic cardiac-specific MYH6-monomeric red fluorescent protein (mRFP) reporter hESC line in conditions that promote pluripotency, we tested the ability of combinations of 15 genes to induce cardiac specification. Screening identified GATA4 plus TBX5 as the minimum requirement to activate the cardiac gene regulatory network and produce mRFP(+) cells, while a combination of GATA4, TBX5, NKX2.5, and BAF60c (GTNB) was necessary to generate beating cardiomyocytes positive for cTnI and α-actinin. Including the chemotherapeutic agent, Ara-C, from day 10 of induced differentiation enriched for cTnI/α-actinin double positive cells to 45%. Transient expression of GTNB for 5-7 days was necessary to activate the cardiogenesis through progenitor intermediates in a manner consistent with normal heart development. This system provides a route to test the effect of different factors on human cardiac differentiation and will be useful in understanding the network failures that underlie disease phenotypes. View Publication

Pluripotency, the ability of a cell to differentiate and give rise to all embryonic lineages, defines a small number of mammalian cell types such as embryonic stem (ES) cells. While it has been generally held that pluripotency is the product of a transcriptional regulatory network that activates and maintains the expression of key stem cell genes, accumulating evidence is pointing to a critical role for epigenetic processes in establishing and safeguarding the pluripotency of ES cells, as well as maintaining the identity of differentiated cell types. In order to better understand the role of epigenetic mechanisms in pluripotency, we have examined the dynamics of chromatin modifications genome-wide in human ES cells (hESCs) undergoing differentiation into a mesendodermal lineage. We found that chromatin modifications at promoters remain largely invariant during differentiation, except at a small number of promoters where a dynamic switch between acetylation and methylation at H3K27 marks the transition between activation and silencing of gene expression, suggesting a hierarchy in cell fate commitment over most differentially expressed genes. We also mapped over 50 000 potential enhancers, and observed much greater dynamics in chromatin modifications, especially H3K4me1 and H3K27ac, which correlate with expression of their potential target genes. Further analysis of these enhancers revealed potentially key transcriptional regulators of pluripotency and a chromatin signature indicative of a poised state that may confer developmental competence in hESCs. Our results provide new evidence supporting the role of chromatin modifications in defining enhancers and pluripotency. View Publication

The human pre-T-cell receptor alpha (TCRalpha; pTalpha) gene encodes a polypeptide which associates with the TCRbeta chain and CD3 molecules to form the pre-TCR complex. The surface expression of the pre-TCR is pTalpha dependent, and signaling through this complex triggers an early alphabeta T-cell developmental checkpoint inside the thymus, known as beta-selection. E2A transcription factors, which are involved at multiple stages of T-cell development, regulate the transcription of the pTalpha gene. Here we show that the regulatory protein Tax of the human T-cell leukemia virus type 1 (HTLV-1) efficiently suppresses the E47-mediated activation of the pTalpha promoter. Furthermore, we report that in Tax lentivirally transduced human MOLT-4 T cells, which constitutively express the pTalpha gene, the amount of pTalpha transcripts decreases. Such a decrease is not observed in MOLT-4 cells transduced by a vector encoding the Tax mutant K88A, which is unable to interact with p300. These data underline that Tax inhibits pTalpha transcription by recruiting this coactivator. Finally, we show that the expression of Tax in human immature thymocytes results in a decrease of pTalpha gene transcription but does not modify the level of E47 transcripts. These observations indicate that Tax, by silencing E proteins, down-regulates pTalpha gene transcription during early thymocyte development. They further provide evidence that Tax can interfere with an important checkpoint during T-cell differentiation in the thymus. View Publication

T lymphocytes require signals from self-peptides and cytokines, most notably interleukins 7 and 15 (IL-7, IL-15), for survival. While mouse T cells die rapidly if IL-7 or IL-15 is withdrawn, human T cells can survive prolonged withdrawal of IL-7 and IL-15. Here we show that IL-7 and IL-15 are required to maintain human T cell proliferative capacity through the STAT5 signaling pathway. T cells from humanized mice proliferate better if stimulated in the presence of human IL-7 or IL-15 or if T cells are exposed to human IL-7 or IL-15 in mice. Freshly isolated T cells from human peripheral blood lose proliferative capacity if cultured for 24 hours in the absence of IL-7 or IL-15. We further show that phosphorylation of STAT5 correlates with proliferation and inhibition of STAT5 reduces proliferation. These results reveal a novel role of IL-7 and IL-15 in maintaining human T cell function, provide an explanation for T cell dysfunction in humanized mice, and have significant implications for in vitro studies with human T cells. View Publication

Although CD31 expression on human thymocytes has been reported, a detailed analysis of CD31 expression at various stages of T cell development in the human thymus is missing. In this study, we provide a global picture of the evolution of CD31 expression from the CD34(+) hematopoietic precursor to the CD45RA(+) mature CD4(+) and CD8(+) single-positive (SP) T cells. Using nine-color flow cytometry, we show that CD31 is highly expressed on CD34(+) progenitors and stays high until the early double-positive stage (CD3(-)CD4(+)CD8α(+)β(-)). After β-selection, CD31 expression levels become low to undetectable. CD31 expression then increases and peaks on CD3(high)CD4(+)CD8(+) double-positive thymocytes. However, following positive selection, CD31 expression differs dramatically between CD4(+) and CD8(+) lineages: homogeneously high on CD8 SP but lower or negative on CD4 SP cells, including a subset of CD45RA(+)CD31(-) mature CD4(+) thymocytes. CD31 expression on TCRγδ thymocytes is very similar to that of CD4 SP cells. Remarkably, there is a substantial subset of semimature (CD45RA(-)) CD4 SP thymocytes that lack CD31 expression. Moreover, FOXP3(+) and ICOS(+) cells are overrepresented in this CD31(-) subpopulation. Despite this CD31(-)CD45RA(-) subpopulation, most egress-capable mature CD45RA(+) CD4 SP thymocytes express CD31. The variations in CD31 expression appear to coincide with three major selection processes occurring during thymopoiesis: β-selection, positive selection, and negative selection. Considering the ability of CD31 to modulate the TCR's activation threshold via the recruitment of tyrosine phosphatases, our results suggest a significant role for CD31 during T cell development. View Publication

Foxp3+ Regulatory T cells (Tregs) are pivotal for the maintenance of tolerance. Alterations in their number and/or function have been proposed to occur in the autoimmune-prone non-obese diabetic (NOD) mouse. Comparing the frequencies and absolute numbers of CD4+Foxp3+CD25+ Tregs among 4 to 6-week old NOD, B6, and BALB/c mice, we observed differences in counts and Foxp3 expression in Tregs from secondary lymphoid organs, but not in the thymus. Upon TCR and IL-2 stimulation, NOD Tregs showed lower responses than Tregs from B6 and BALB/c mice. Indeed, NOD Tregs responded with less proliferation and with smaller increments in the expression of CD25, LAP-1, CD39, PD-1, PD-L1, and LAG-3, when in vitro cultured for 3 days with anti-CD3/CD28 in the absence or presence of IL-2, Tregs from NOD mice showed to be highly dependent on IL-2 to maintain Foxp3 expression. Moreover, NOD Tregs become producers of IL-17 and INF-gamma more easily than Tregs from the other strains. In addition, NOD Tregs showed lower responsiveness to IL-2, with significantly reduced levels of pSTAT5, even at high IL-2 doses, with respect to B6 and BALB/c Tregs. Interestingly, NOD Tregs exhibit differences in the expression of SOCS3, GRAIL, and OTUB1 when compared with Tregs from B6 and BALB/c mice. Both, at steady state conditions and also after activation, Tregs from NOD mice showed increased levels of OTUB1 and low levels of GRAIL. In addition, NOD Tregs had differences in the expression of ubiquitin related molecules that play a role in the maintenance of Foxp3 cellular pools. Indeed, significantly higher STUB1/USP7 ratios were detected in NOD Tregs, both at basal conditions and after stimulation, compared to in B6 and BALB/c Tregs. Moreover, the addition of a proteasome inhibitor to cell cultures, conferred NOD Tregs the ability to retain Foxp3 expression. Herein, we provide evidence indicating a differential expression of SOCS3, GRAIL, and STUB1/USP7 in Tregs from NOD mice, factors known to be involved in IL-2R signaling and to affect Foxp3 stability. These findings add to the current knowledge of the immunobiology of Tregs and may be related to the known insufficiency of Tregs from NOD mice to maintain self-tolerance. View Publication

Recent work investigating exercise induced changes in immunocompetence suggests that some of the ambiguity in the literature is resultant from different cell isolation protocols and mitogen selection. To understand this effect, we compared post-exercise measures of T cell activation and proliferation using two different stimulation methods (costimulation through CD28 or stimulation with phytohaemagglutinin [PHA]). Further, we investigated whether exercise induced changes are maintained when T cell isolation from whole blood is delayed overnight in either a room temperature or chilled (4°C) environment. As expected, an increased proliferation response was observed post-exercise in T cells isolated from whole blood of previously trained individuals immediately after blood collection. Also, cells stimulated with PHA after resting overnight in whole blood were not adversely impacted by the storage conditions. In contrast, allowing cells to rest overnight in whole blood prior to stimulation through CD28, lessened the proliferation observed by cells following exercise rendering both the room temperature and chilled samples closer to the results seen in the control condition. Changes in early markers of activation (CD25), followed a similar pattern, with activation in PHA stimulated cells remaining fairly robust after overnight storage; whereas cell activation following stimulation through CD3+CD28 was disproportionately decreased by the influence of overnight storage. These findings indicate that decisions regarding cell stimulation methods need to be paired with the timeline for T cell isolation from whole blood. These considerations will be especially important for field based studies of immunocompetence where there is a delay in getting whole blood samples to a lab for processing as well as clinical applications where a failure to isolate T cells in a timely manner may result in loss of the response of interest. View Publication

CD4+CD25+ Tregs regulate immunity, but little is known about their own regulation. We now report that the human 60-kDa heat shock protein (HSP60) acts as a costimulator of human Tregs, both CD4+CD25int and CD4+CD25hi. Treatment of Tregs with HSP60, or its peptide p277, before anti-CD3 activation significantly enhanced the ability of relatively low concentrations of the Tregs to downregulate CD4+CD25- or CD8+ target T cells, detected as inhibition of target T cell proliferation and IFN-gamma and TNF-alpha secretion. The enhancing effects of HSP60 costimulation on Tregs involved innate signaling via TLR2, led to activation of PKC, PI3K, and p38, and were further enhanced by inhibition of ERK. HSP60-treated Tregs suppressed target T cells both by cell-to-cell contact and by secretion of TGF-beta and IL-10. In addition, the expression of ERK, NF-kappaB, and T-bet by downregulated target T cells was inhibited. Thus, HSP60, a self-molecule, can downregulate adaptive immune responses by upregulating Tregs innately through TLR2 signaling. View Publication

HIV-1 infection is characterized by a progressive decline in CD4(+) T cells leading to a state of profound immunodeficiency. IL-2 therapy has been shown to improve CD4(+) counts beyond that observed with antiretroviral therapy. Recent phase III trials revealed that despite a sustained increase in CD4(+) counts, IL-2-treated patients did not experience a better clinical outcome [Abrams D, et al. (2009) N Engl J Med 361(16):1548-1559]. To explain these disappointing results, we have studied phenotypic, functional, and molecular characteristics of CD4(+) T cell populations in IL-2-treated patients. We found that the principal effect of long-term IL-2 therapy was the expansion of two distinct CD4(+)CD25(+) T cell populations (CD4(+)CD25(lo)CD127(lo)FOXP3(+) and CD4(+)CD25(hi)CD127(lo)FOXP3(hi)) that shared phenotypic markers of Treg but could be distinguished by the levels of CD25 and FOXP3 expression. IL-2-expanded CD4(+)CD25(+) T cells suppressed proliferation of effector cells in vitro and had gene expression profiles similar to those of natural regulatory CD4(+)CD25(hi)FOXP3(+) T cells (Treg) from healthy donors, an immunosuppressive T cell subset critically important for the maintenance of self-tolerance. We propose that the sustained increase of the peripheral Treg pool in IL-2-treated HIV patients may account for the unexpected clinical observation that patients with the greatest expansion of CD4(+) T cells had a higher relative risk of clinical progression to AIDS. View Publication

Autoantigen-specific regulatory immunity emerges in the spleen of mice recovering from experimental autoimmune uveitis (EAU), a murine model for human autoimmune uveoretinitis. This regulatory immunity provides induced tolerance to ocular autoantigen, and requires melanocortin 5 receptor (MC5r) expression on antigen presenting cells with adenosine 2 A receptor (A2Ar) expression on T cells. During EAU it is not well understood what roles MC5r and A2Ar have on promoting regulatory immunity. Cytokine profile analysis during EAU revealed MC5r and A2Ar each mediate distinct T cell responses, and are responsible for a functional regulatory immune response in the spleen. A2Ar stimulation at EAU onset did not augment this regulatory response, nor bypass the MC5r requirement to induce regulatory immunity. The importance of this pathway in human autoimmune uveitis was assayed. PBMC from uveitis patients were assayed for MC5r expression on monocytes and A2Ar on T cells, and comparison between uveitis patients and healthy controls had no significant difference. The importance for MC5r and A2Ar expression in EAU to promote the induction of protective regulatory immunity, and the expression of MC5r and A2Ar on human immune cells, suggests that it may be possible to utilize the melanocortin-adenosinergic pathways to induce protective immunity in uveitic patients. View Publication

Many tumors, including Hodgkin's lymphoma, are associated with decreased cellular immunity and elevated levels of prostaglandin E(2) (PGE(2)), a known inhibitor of CD4+ T cell activation, suggested to be involved in immune deviation in cancer. To address the molecular mechanisms tumor-derived PGE(2) might have on primary human CD4+ T cells, we used a whole genome-based transcriptional approach and show that PGE(2) severely limited changes of gene expression induced by signaling through the T cell receptor and CD28. This data suggests an interference of PGE(2) at an early step of T cell receptor signaling: indeed, PGE(2) stimulation of T cells leads to inactivation of lck and reduced phosphorylation of ZAP70. Antiapoptotic genes escaped PGE(2)-induced inhibition resulting in partial protection from apoptosis in response to irradiation or Fas-mediated signaling. As a functional consequence, PGE(2)-treated CD4+ T cells are arrested in the cell cycle associated with up-regulation of the cyclin/cyclin-dependent kinase inhibitor p27(kip1). Most importantly, CD4+ T cells in Hodgkin's lymphoma show similar regulation of genes that were altered in vitro by PGE(2) in T cells from healthy individuals. These data strongly suggest that PGE(2) is an important factor leading to CD4+ T cell impairment observed in Hodgkin's lymphoma. View Publication

The AP-1 factor basic leucine zipper transcription factor, ATF-like (BATF) is important for CD4(+) Th17, Th9, and follicular Th cell development. However, its precise role in Th2 differentiation and function remains unclear, and the requirement for BATF in nonallergic settings of type-2 immunity has not been explored. In this article, we show that, in response to parasitic helminths, Batf(-/-) mice are unable to generate follicular Th and Th2 cells. As a consequence, they fail to establish productive type-2 immunity during primary and secondary infection. Batf(-/-) CD4(+) T cells do not achieve type-2 cytokine competency, which implies that BATF plays a key role in the regulation of IL-4 and IL-13. In contrast to Th17 and Th9 cell subsets in which BATF binds directly to promoter and enhancer regions to regulate cytokine expression, our results show that BATF is significantly enriched at Rad50 hypersensitivity site (RHS)6 and RHS7 of the locus control region relative to AP-1 sites surrounding type-2 cytokine loci in Th2 cells. Indeed, Batf(-/-) CD4(+) T cells do not obtain permissive epigenetic modifications within the Th2 locus, which were linked to RHS6 and RHS7 function. In sum, these findings reveal BATF as a central modulator of peripheral and humoral hallmarks of type-2 immunity and begin to elucidate a novel mechanism by which it regulates type-2 cytokine production through its modification of the Th2 locus control region. View Publication

Among different cancer immunotherapy approaches, bispecific antibodies (BsAbs) are of great interest due to their ability to recruit immune cells to kill tumor cells directly. Various BsAbs against Her2 tumor cells have been proposed with potent cytotoxic activities. However, most of these formats require extensive processing to obtain heterodimeric bispecific antibodies. In this study, we describe a bispecific antibody, BiHC (bispecific Her2-CD3 antibody), constructed with a single-domain anti-Her2 and a single-chain Fv (variable fragment) of anti-CD3 in an IgG-like format. In contrast to most IgG-like BsAbs, the two arms in BiHC have different molecular weights, making it easier to separate hetero- or homodimers. BiHC can be expressed in Escherichia coli and purified via Protein A affinity chromatography. The purified BiHC can recruit T cells and induce specific cytotoxicity of Her2-expressing tumor cells in vitro. The BiHC can also efficiently inhibit the tumor growth in vivo. Thus, BiHC is a promising candidate for the treatment of Her2-positive cancers. View Publication

Recently, induced pluripotent stem cells (iPSCs) were established as promising cell sources for revolutionary regenerative therapies. The initial culture system used for iPSC generation needed fetal calf serum in the culture medium and mouse embryonic fibroblast as a feeder layer, both of which could possibly transfer unknown exogenous antigens and pathogens into the iPSC population. Therefore, the development of culture systems designed to minimize such potential risks has become increasingly vital for future applications of iPSCs for clinical use. On another front, although donor cell types for generating iPSCs are wide-ranging, T cells have attracted attention as unique cell sources for iPSCs generation because T cell-derived iPSCs (TiPSCs) have a unique monoclonal T cell receptor genomic rearrangement that enables their differentiation into antigen-specific T cells, which can be applied to novel immunotherapies. In the present study, we generated transgene-free human TiPSCs using a combination of activated human T cells and Sendai virus under defined culture conditions. These TiPSCs expressed pluripotent markers by quantitative PCR and immunostaining, had a normal karyotype, and were capable of differentiating into cells from all three germ layers. This method of TiPSCs generation is more suitable for the therapeutic application of iPSC technology because it lowers the risks associated with the presence of undefined, animal-derived feeder cells and serum. Therefore this work will lead to establishment of safer iPSCs and extended clinical application. View Publication

Multi-parameter flow cytometry analysis of T regulatory (Treg) cells is a widely used approach in basic and translational research studies. This approach has been complicated by a lack of specific markers for Treg cells and lack of uniformity in the quantification of Treg cells. Given the central role of Treg cells in the inception and perpetuation of diverse immune responses as well as its target as a therapeutic, it is imperative to have established methodologies for Treg cell analysis that are robust and usable for studies with multiple subjects as well as multicenter studies. In this study, we describe an optimized multi-parameter flow cytometry protocol for the quantification of human Treg cells from freshly obtained and viably frozen samples and correlations with epigenetic Treg cell analysis (TSDR demethylation). We apply these two methodologies to characterize Treg cell differences between cord blood and adult peripheral blood. In summary, the optimized protocol appears to be robust for Treg cell quantification from freshly isolated or viably frozen cells and the multi-parameter flow cytometry findings are strongly positively correlated with TSDR demethylation thus providing several options for the characterization of Treg cell frequency and function in large translational or clinical studies. View Publication

The present study demonstrates that CD4(+)CD25(+) T cells, expanded in peripheral blood of HIV-infected patients receiving highly active antiretroviral therapy (HAART), exhibit phenotypic, molecular, and functional characteristics of regulatory T cells. The majority of peripheral CD4(+)CD25(+) T cells from HIV-infected patients expressed a memory phenotype. They were found to constitutively express transcription factor forkhead box P3 (Foxp3) messengers. CD4(+)CD25(+) T cells weakly proliferated to immobilized anti-CD3 monoclonal antibody (mAb) and addition of soluble anti-CD28 mAb significantly increased proliferation. In contrast to CD4(+)CD25(-) T cells, CD4(+)CD25(+) T cells from HIV-infected patients did not proliferate in response to recall antigens and to p24 protein. The proliferative capacity of CD4 T cells to tuberculin, cytomegalovirus (CMV), and p24 significantly increased following depletion of CD4(+)CD25(+) T cells. Furthermore, addition of increasing numbers of CD4(+)CD25(+) T cells resulted in a dose-dependent inhibition of CD4(+)CD25(-) T-cell proliferation to tuberculin and p24. CD4(+)CD25(+) T cells responded specifically to p24 antigen stimulation by expressing transforming growth factor beta (TGF-beta) and interleukin 10 (IL-10), thus indicating the presence of p24-specific CD4(+) T cells among the CD4(+)CD25(+) T-cell subset. Suppressive activity was not dependent on the secretion of TGF-beta or IL-10. Taken together, our results suggest that persistence of HIV antigens might trigger the expansion of CD4(+)CD25(+) regulatory T cells, which might induce a tolerance to HIV in vivo. View Publication

Monitoring genome-wide, cell-specific responses to human disease, although challenging, holds great promise for the future of medicine. Patients with injuries severe enough to develop multiple organ dysfunction syndrome have multiple immune derangements, including T cell apoptosis and anergy combined with depressed monocyte antigen presentation. Genome-wide expression analysis of highly enriched circulating leukocyte subpopulations, combined with cell-specific pathway analyses, offers an opportunity to discover leukocyte regulatory networks in critically injured patients. Severe injury induced significant changes in T cell (5,693 genes), monocyte (2,801 genes), and total leukocyte (3,437 genes) transcriptomes, with only 911 of these genes common to all three cell populations (12%). T cell-specific pathway analyses identified increased gene expression of several inhibitory receptors (PD-1, CD152, NRP-1, and Lag3) and concomitant decreases in stimulatory receptors (CD28, CD4, and IL-2Ralpha). Functional analysis of T cells and monocytes confirmed reduced T cell proliferation and increased cell surface expression of negative signaling receptors paired with decreased monocyte costimulation ligands. Thus, genome-wide expression from highly enriched cell populations combined with knowledge-based pathway analyses leads to the identification of regulatory networks differentially expressed in injured patients. Importantly, application of cell separation, genome-wide expression, and cell-specific pathway analyses can be used to discover pathway alterations in human disease. View Publication

Anthrax lethal toxin (LT) is a critical virulence factor that cleaves and inactivates MAPK kinases (MAPKKs) in host cells and has been proposed as a therapeutic target in the treatment of human anthrax infections. Despite the potential use of anti-toxin agents in humans, the standard activity assays for anthrax LT are currently based on cytotoxic actions of anthrax LT that are cell-, strain-, and species-specific, which have not been demonstrated to occur in human cells. We now report that T cell proliferation and IL-2 production inversely correlate with anthrax LT levels in human cell assays. The model CD4+ T cell tumor line, Jurkat, is a susceptible target for the specific protease action of anthrax LT. Anthrax LT cleaves and inactivates MAPKKs in Jurkat cells, whereas not affecting proximal or parallel TCR signal transduction pathways. Moreover, anthrax LT specifically inhibits PMA/ionomycin- and anti-CD3-induced IL-2 production in Jurkat cells. An inhibitor of the protease activity of anthrax LT completely restores IL-2 production by anthrax LT-treated Jurkat cells. Anthrax LT acts on primary CD4+ T cells as well, cleaving MAPKKs and leading to a 95% reduction in anti-CD3-induced proliferation and IL-2 production. These findings not only will be useful in the development of new human cell-based bioassays for the activity of anthrax LT, but they also suggest new mechanisms that facilitate immune evasion by Bacillus anthracis. Specifically, anthrax LT inhibits IL-2 production and proliferative responses in CD4+ T cells, thereby blocking functions that are pivotal in the regulation of immune responses. View Publication

We analyzed the proliferative response of the growth factor-dependent murine cell lines FDCp1, DA1-a, 32DC1, Ea3.15, 7TD1, BCL1 and of femural bone marrow cells for their sensitivity to various cytokines, viz. rhIL-1 beta, rhTNF, rhIL-2, mIL-3, rmIL-4, rmIL-5, rhIL-6, rhG-CSF and rmGM-CSF. We also tested for IL-1 and TNF-mediated cytokine secretion by several T cell lines and thymocytes. In all T cell systems, IL-1 alpha and IL-1 beta were equally active in the induction of cytokine production, except for the rat/mouse T cell hybridoma PC60. This cell line exhibited a 10-fold difference in specific activity for the induction of cytokine secretion between rhIL-1 alpha and the other human or murine IL-1 species. Furthermore, IL-1 and IL-2 synergistically induced PC60 cells to produce a factor, which was preferentially active on FDCp1-cells, provisionally called FDCp1-growth factor. SDS-PAGE analysis of partially purified FDCp1-GF showed 19 kDa and 24 kDa-associated biological activities. Amino-terminal and internal amino acid sequences of both bands were determined and on this basis, we identified FDCp1-GF as rat GM-CSF. View Publication

CD46 is a glycoprotein with important functions in innate and adaptive immune responses. Functionally different isoforms are generated by alternative splicing at exons 7-9 (BC and C isoforms) and exon 13 (CYT-1 and CYT-2 isoforms) giving rise to BC1, BC2, C1 and C2. We developed a novel real-time PCR assay that allows quantitative comparisons between these isoforms. Their relative frequency in CD4(+) T cells from 100 donors revealed a distribution with high interpersonally variability. Importantly, the distribution between the isoforms was not random and although splicing favoured inclusion of exon 8 (BC isoforms), exclusion of exon 8 (C isoforms) was significantly linked to exclusion of exon 13 (CYT-2 isoforms). Despite inter-individual differences, CD4(+) and CD8(+) T cells, B cells, NK cells and monocytes expressed similar isoform profiles intra-individually. However, memory/effector CD4(+) T cells had a significantly higher frequency of CYT-2 when compared with naïve CD4(+) T cells. Likewise, in vitro activation of naïve and total CD4(+) T cells increased the expression of CYT-2. This indicates that although splicing factors determine a certain expression profile in an individual, the profile can be modulated by external stimuli. This suggests a mechanism by which alterations in CD46 isoforms may temporarily regulate the immune response. View Publication

Wild-type (WT) NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) when given 0.05% NaI in their drinking water, whereas B cell-deficient NOD.H-2h4 mice are SAT resistant. To test the hypothesis that resistance of B cell-deficient mice to SAT was due to the activity of regulatory CD4+CD25+ T (T reg) cells activated if autoantigen was initially presented on non-B cells, CD25+ T reg cells were transiently depleted in vivo using anti-CD25. B cell-deficient NOD.H-2h4 mice given three weekly injections of anti-CD25 developed SAT 8 wk after NaI water. Thyroid lesions were similar to those in WT mice except there were no B cells in thyroid infiltrates. WT and B cell-deficient mice had similar numbers of CD4+CD25+Foxp3+ cells. Mice with transgenic nitrophenyl-specific B cells unable to secrete immunoglobulin were also resistant to SAT, and transient depletion of T reg cells resulted in severe SAT with both T and B cells in thyroid infiltrates. T reg cells that inhibit SAT were eliminated by day 3 thymectomy, indicating they belong to the subset of naturally occurring T reg cells. However, T reg cell depletion did not increase SAT severity in WT mice, suggesting that T reg cells may be nonfunctional when effector T cells are activated; i.e., by autoantigen-presenting B cells. View Publication

Although activated inflammatory monocytes (IMCs) and inflammatory dendritic cells (IDCs) are potent T cell suppressors, nonactivated IMCs and IDCs promote T cell activation and Th1/Th17 cell differentiation. In this study, we investigated how to reduce the proinflammatory properties of IMCs and IDCs and further convert them into immune regulatory dendritic cells (DCs). We found that IL-4 and retinoic acid (RA) cotreatment of GM-CSF-differentiated IDCs synergistically induced the expression of aldehyde dehydrogenase family 1, subfamily A2, a rate-limiting enzyme for RA synthesis in DCs. IL-4 plus RA-treated IDCs upregulated CD103 expression and markedly reduced the production of proinflammatory cytokines upon activation. IL-4 plus RA-treated IDCs strongly induced CD4�?�Foxp3�?� regulatory T cell differentiation and suppressed Th1 and Th17 differentiation. Mechanistically, the transcription factors Stat6 and RA receptor $$ play important roles in aldehyde dehydrogenase family 1, subfamily A2, induction. In addition, IL-4 and RA signaling pathways interact closely to enhance the regulatory function of treated DCs. Adoptive transfer of IL-4 plus RA-treated DCs significantly increased regulatory T cell frequency in vivo. Direct treatment with IL-4 and RA also markedly suppressed actively induced experimental autoimmune encephalomyelitis. Our data demonstrate the synergistic effect of IL-4 and RA in inducing a regulatory phenotype in IDCs, providing a potential treatment strategy for autoimmune diseases. View Publication

Human T-cell leukemia virus type 1 (HTLV-1) and HTLV-2 are highly related viruses that differ in disease manifestation. HTLV-1 is the etiologic agent of adult T-cell leukemia and lymphoma, an aggressive clonal malignancy of human CD4-bearing T lymphocytes. Infection with HTLV-2 has not been conclusively linked to lymphoproliferative disorders. We previously showed that human hematopoietic progenitor (CD34(+)) cells can be infected by HTLV-1 and that proviral sequences were maintained after differentiation of infected CD34(+) cells in vitro and in vivo. To investigate the role of the Tax oncoprotein of HTLV on hematopoiesis, bicistronic lentiviral vectors were constructed encoding the HTLV-1 or HTLV-2 tax genes (Tax1 and Tax2, respectively) and the green fluorescent protein marker gene. Human hematopoietic progenitor (CD34(+)) cells were infected with lentivirus vectors, and transduced cells were cultured in a semisolid medium permissive for the development of erythroid, myeloid, and primitive progenitor colonies. Tax1-transduced CD34(+) cells displayed a two- to fivefold reduction in the total number of hematopoietic clonogenic colonies that arose in vitro, in contrast to Tax2-transduced cells, which showed no perturbation of hematopoiesis. The ratio of colony types that developed from Tax1-transduced CD34(+) cells remained unaffected, suggesting that Tax1 inhibited the maturation of relatively early, uncommitted hematopoietic stem cells. Since previous reports have linked Tax1 expression with initiation of apoptosis, lentiviral vector-mediated transduction of Tax1 or Tax2 was investigated in CEM and Jurkat T-cell lines. Ectopic expression of either Tax1 or Tax2 failed to induce apoptosis in T-cell lines. These data demonstrate that Tax1 expression perturbs development and maturation of pluripotent hematopoietic progenitor cells, an activity that is not displayed by Tax2, and that the suppression of hematopoiesis is not attributable to induction of apoptosis. Since hematopoietic progenitor cells may serve as a latently infected reservoir for HTLV infection in vivo, the different abilities of HTLV-1 and -2 Tax to suppress hematopoiesis may play a role in the respective clinical outcomes after infection with HTLV-1 or -2. View Publication

BACKGROUND: The histone variant H2A.Z has been implicated in nucleosome exchange, transcriptional activation and Polycomb repression. However, the relationships among these seemingly disparate functions remain obscure.backslashnbackslashnRESULTS: We mapped H2A.Z genome-wide in mammalian ES cells and neural progenitors. H2A.Z is deposited promiscuously at promoters and enhancers, and correlates strongly with H3K4 methylation. Accordingly, H2A.Z is present at poised promoters with bivalent chromatin and at active promoters with H3K4 methylation, but is absent from stably repressed promoters that are specifically enriched for H3K27 trimethylation. We also characterized post-translational modification states of H2A.Z, including a novel species dually-modified by ubiquitination and acetylation that is enriched at bivalent chromatin.backslashnbackslashnCONCLUSIONS: Our findings associate H2A.Z with functionally distinct genomic elements, and suggest that post-translational modifications may reconcile its contrasting locations and roles. View Publication

There is no licensed vaccine against the intracellular pathogen Francisella tularensis. The use of conventional mouse strains to screen protective vaccine antigens may be problematic, given the differences in the major histocompatibility complex (MHC) binding properties between murine and human antigen-presenting cells. We used engineered humanized mice that lack endogenous MHC class II alleles but that express a human HLA allele (HLA-DR4 transgenic [tg] mice) to identify potential subunit vaccine candidates. Specifically, we applied a biochemical and immunological screening approach with bioinformatics to select putative F. tularensis subsp. novicida T-cell-reactive antigens using humanized HLA-DR4 tg mice. Cell wall- and membrane-associated proteins were extracted with Triton X-114 detergent and were separated by fractionation with a Rotofor apparatus and whole-gel elution. A series of proteins were identified from fractions that stimulated antigen-specific gamma interferon (IFN-gamma) production, and these were further downselected by the use of bioinformatics and HLA-DR4 binding algorithms. We further examined the validity of this combinatorial approach with one of the identified proteins, a 19-kDa Francisella tularensis outer membrane protein (designated Francisella outer membrane protein B [FopB]; FTN0119). FopB was shown to be a T-cell antigen by a specific IFN-gamma recall assay with purified CD4(+) T cells from F. tularensis subsp. novicida DeltaiglC-primed HLA-DR4 tg mice and cells of a human B-cell line expressing HLA-DR4 (DRB1*0401) functioning as antigen-presenting cells. Intranasal immunization of HLA-DR4 tg mice with the single antigen FopB conferred significant protection against lethal pulmonary challenge with an F. tularensis subsp. holarctica live vaccine strain. These results demonstrate the value of combining functional biochemical and immunological screening with humanized HLA-DR4 tg mice to map HLA-DR4-restricted Francisella CD4(+) T-cell epitopes. View Publication