Frequently Asked Questions on Primary Cells

Technical tip from our dedicated team of Product and Scientific Support specialists

Find answers to frequently asked questions (FAQ) about ready-to-use fresh or cryopreserved cells from STEMCELL Technologies.

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General Information

Why use human primary cells from STEMCELL in your research?

STEMCELL offers a selection of ready-to-use fresh or cryopreserved cells, including mononuclear cells (MNCs), purified immune cells, or stem cells isolated from blood or bone marrow* to support your research. We ensure you receive ethically sourced, high-quality biological material and ship all our human primary cell products with a Certificate of Analysis (CoA) showing guaranteed quality control testing for cell count, viability, and purity. We help you get the cells you need, by meeting your requirements for custom cell collection or isolation, specific donors, cell characterization, and shipping, and by providing the option to reserve entire lots to pre-screen cells for your applications.

Learn more: Partner with the Right Human Primary Cell Supplier

*Due to government regulations, cord blood and bone marrow products may not be available in your region. Please contact us or your sales representative for the most up-to-date information on primary cell availability in your region.

Should I use cell lines or primary cells for my experiment?

STEMCELL recommends that you use primary cells for your experiments where possible. Human primary cells are increasingly recognized as an ideal model for your experiment—data obtained from in vitro assays or in vivo models using these cells have increased physiological relevance compared to those performed on cell lines. Primary cells are isolated directly from tissues, including blood and bone marrow, and are therefore more representative of the tissue being investigated than cell lines.

Learn more: Advantages of Primary Cells over Cell Lines

What are the advantages and disadvantages of using either fresh or frozen leukopaks?

Both fresh and frozen leukopaks are ideal starting materials for downstream cell isolation when large numbers of cells are required, reducing the time and reagents needed to process cells of interest. A couple of key considerations for deciding between using fresh or frozen leukopaks for your experiments are highlighted below:

  1. Experiment start date: Frozen leukopaks offer more flexibility on when you start your experiments. If needed, they may be stored at -135ºC or colder until you are ready to process the cells. In contrast, fresh leukopaks should be processed upon receipt for best results. If absolutely necessary, they may be stored at refrigeration temperature (2 - 8ºC) until you are ready to process the product; however, there is expected cell loss with extended storage after receipt. For data on this, please see Data and Publications on the product landing page.
  2. Downstream use of cells: Cells isolated from a frozen leukopak may be used for a variety of assays after thawing. However, it is not advised to re-cryopreserve and bank cells isolated from a frozen leukopak for later use. Cells tend to be sensitive post-thaw and a second freeze-thaw cycle typically results in high cell death. Fresh leukopaks, in contrast, are ideal for either immediate use or cryopreservation (banking) of isolated cell types for later experiments.

How are STEMCELL's primary cells validated?

STEMCELL’s primary cells are validated using our Quality Management System, which assesses cell count, viability, and purity. STEMCELL's Quality Management System is certified to ISO 13485:2016 Medical Devices and ISO 9001:2015.

Learn more: Partner with the Right Human Primary Cell Supplier

How can STEMCELL help me with my experiments?

STEMCELL offers a suite of products and services that help you get the results you need. Overcome challenges in your experimental procedures by engaging with our Contract Assay Services (CAS) or training programs and combining the power of STEMCELL media and reagents with the knowledge of our scientists and educators.

CAS is a contract research organization (CRO) established within STEMCELL that specializes in primary cell-based assays. CAS offers services such as the Colony-Forming Unit (CFU) assay for hematotoxicity testing, immunological assessment, and biopharmaceutical testing, as well as the development of custom assays for a variety of cell types.

Learn more: Contract Assay Services

If you would prefer to learn techniques to use yourself, STEMCELL's training programs offer comprehensive, theoretical, and hands-on training—customizable for your specific needs.

Explore: STEMCELL's Training Programs

What types of human primary cells can STEMCELL provide?

STEMCELL offers a selection of human primary cell products*, including:

Cryopreserved Human Peripheral Blood Products:

  • Peripheral blood mononuclear cells (PBMCs) isolated from normal donors (high-resolution HLA typing and CMV status available)
  • Isolated Cells: CD34+ cells, B cells, T cells, NK cells, DCs, monocytes, and other cell subsets available
  • PBMCs isolated from diseased-state donors diagnosed with: Crohn’s Disease, lupus, psoriasis, various cancer subtypes (e.g. prostate, pancreatic, ovarian cancer, etc.), and more
  • Leukopaks (collected in acid-citrate-dextrose solution A; ACDA)
  • Plasma
  • Serum
  • Human Platelet Lysate (hPL): fibrinogen-containing, fibrinogen-depleted, xeno-free, and GMP-compliant options are available

Cryopreserved Cord Blood Products*:

  • CD34+ cells from single or mixed donors
  • MNCs, T cells, B cells, NK cells, monocytes, and other cell subsets available
  • Plasma

Fresh Human Peripheral Blood Products:

  • Whole blood from normal donors (collected in ACDA, CP2D, EDTA, or Na Heparin)
  • Whole blood from cancer donors
  • Isolated cells (B cells, T cells, NK cells, monocytes, and other cell subsets available)
  • PBMCs
  • Leukopaks from normal donors (collected in ACDA)
  • Leukopaks from cancer donors
  • LRS Cones or LRS Chambers
  • Plasma
  • Serum

Learn more about STEMCELL’s human primary cell offerings: Primary Cells Overview

*Certain products are only available in select territories. Please contact your sales representative or our primary cells team directly for availability in your region.

What types of diseased cells does STEMCELL offer?

STEMCELL offers a broad range of both fresh and frozen diseased cells, including but not limited to:

  • Cryopreserved diseased peripheral blood products: PBMCs, serum, and plasma
  • Fresh diseased peripheral blood products: leukopaks and whole blood samples
  • Cells from patients diagnosed with: rheumatoid arthritis, ulcerative colitis, Crohn's Disease, COPD, lupus, osteoarthritis, celiac disease, psoriasis, diabetes type I, and diabetes type II, liquid/heme tumors, solid tumors, and various cancer subtypes (e.g. melanoma, liver, endometrial, and more)

View all diseased cell product offerings >

Diseased cell types are dependent on donor availability and regional restrictions. Please contact your sales representative or our primary cells team directly for availability in your region.

What custom primary cell products does STEMCELL offer?

Custom primary cell products include:

  • Rare or difficult-to-isolate hematopoietic cell types (normal and diseased, including cells from patients with autoimmune diseases, diabetes, asthma, cancer, etc.)
  • Cells that meet specific donor recruitment criteria
  • Collection obtained using alternative anticoagulants
  • Products in alternative size formats, e.g. bags, vial sizes, requested cell counts, etc.
  • Donor-matched collections for fresh and/or cryopreserved cells, e.g. whole blood, leukopaks, isolated cells, plasma, serum, etc. from the same donor

Learn more about our custom solutions for primary cell products or contact us directly for more information.

Does STEMCELL offer primary cells that are GMP-certified?

We do not currently offer GMP-certified cells. Our primary cell products are suitable for research purposes only and are not to be used as a starting material for cellular therapies.

Is STEMCELL compliant with the Human Tissue Act (HTA)?

The HTA 2004 regulates the use (including the removal, storage, and use of human tissue and cells) of human biological materials in the U.K. and is overseen by the HTA.

Our human primary cell products are collected in the U.S. or the U.K.. Cells sourced in the U.S. are collected using protocols and Informed Consent Forms (ICF) approved by an FDA (and HHS) registered Institutional Review Board (IRB) or equivalent agency. Cells sourced in the U.K. are collected using protocols and ICFs approved by an National Health Service (and Health Research Authority) Research Ethics Committee (REC) or equivalent agency.

We can provide IRB-approval and ICF documents, as well as a Quality and Compliance Statement to assist with your compliance needs. Please contact your regional sales representative or techsupport@stemcell.com for further information.

How does STEMCELL obtain primary cell products?

Donations for STEMCELL’s human primary cell products are performed in the United States and in the United Kingdom in compliance with applicable federal, state, and local laws, regulations, and guidance (for the United States) and consent forms and protocols approved by the HTA (Human Tissue Authority) (for the United Kingdom). Cells are obtained from donors who are voluntarily participating in a donor program approved by an Institutional Review Board (IRB), the Food and Drug Administration (FDA), Research Ethics Committee (REC) or an equivalent regulatory authority. Donors are reasonably compensated for their time and effort during their donation, in accordance with FDA regulations or as approved by an IRB. Donors are aware that the cells may be used for research applications and have waived any rights generated from the research applications. Donors are protected by strict controls on personal identifiers and researchers cannot access any identifying information about donors.

Donors are pre-screened for general health and viral status, including HIV-1, HIV-2, hepatitis B, and hepatitis C, according to our Donor Viral Screening Policy. Donors in the U.K. are additionally screened for HTLV I/II and syphilis.

All products should be handled at Biosafety Level 2 (BSL-2) or higher, and universal handling precautions for biological samples should be used. Additional screening or analysis are available upon request. Customers purchasing primary cell products from STEMCELL acknowledge that they are required to treat all products as potential biohazard materials and waive STEMCELL of any liabilities from contaminations of infectious pathogens in these products.

Contact us for further information on the collection of human primary cells by STEMCELL.

Where can I get additional product documentation, such as the Certificate of Analysis (CoA), Institutional Review Board (IRB)-approval, Informed Consent Forms (ICF), etc.?

The Certificate of Analysis (CoA) for your product can be requested by completing this form.

Any other documentation, such as IRB-approval forms, ICF, or other information about downstream usage can be provided upon request to your regional sales representative or the Product and Scientific Support team (techsupport@stemcell.com).

Donor Information

What kind of donor information is available?

You can specify your preference for donor requirements, including, but not limited to, the following:

  • Age
  • Sex
  • Ethnicity
  • Weight
  • Height
  • Smoking status
  • HLA type
  • CVM status
  • Health information (medication, alcohol)

Please note that some donor requests incur additional fees. To discuss further, please reach out to your sales representative or contact us directly.

How does STEMCELL collect donor demographic information?

STEMCELL collects donor demographic information ethically, using consent forms and protocols approved by either an Institutional Review Board (IRB), the Food and Drug Administration (FDA), the U.S. Department of Health and Human Services, and/or an equivalent regulatory authority. Donations are performed in the United States in compliance with applicable federal, state, and local laws, regulations, and guidance.

For ease of procurement, our Quality Assurance, Quality Control, and Regulatory Affairs departments are ready to assist you with any necessary documentation to meet specific institutional supplier approval requirements.

Contact us for further information on the collection of donor demographics.

What is STEMCELL's donor viral screening policy?

Bone Marrow and Peripheral Blood Products: Normal Leukopaks, Whole Blood, Purified Cells, and LRS Cones - Fresh Products*:

Donors are screened for HIV-1, HIV-2, hepatitis B, and hepatitis C.

If the donor has been screened within 90 days prior to donation and the results are negative, the product will be shipped with the negative test result and date of most recent viral testing on the Certificate of Analysis (CoA). If the donor has not been screened within 90 days prior to collection, a test sample will be taken at the time of collection and the product will be shipped before the screening results are available. In the event that a test result is positive, the customer will be contacted as soon as possible (usually within 2 - 4 business days from the time of shipment, and within 4 - 7 business days in the case of fresh LRS cones).

Mobilized Peripheral Blood Leukopaks - Fresh Products*:

For fresh mobilized leukopaks donors are screened for HIV-1, HIV-2, hepatitis B, hepatitis C, HTLV-I/-II, Syphilis, and WNV.

If the donor has been screened within 90 days prior to donation and the results are negative, the product will be shipped with the negative test result and date of most recent viral testing on the Certificate of Analysis (CoA). If the donor has not been screened within 90 days prior to collection, a test sample will be taken at the time of collection and the product will be shipped before the screening results are available. In the event that a test result is positive, the customer will be contacted as soon as possible (usually within 2 - 4 business days from the time of shipment).

Normal Leukopaks, Whole Blood, Purified Cells, and Bone Marrow - Cryopreserved Products*:

Donors are screened for HIV-1, HIV-2, hepatitis B, and hepatitis C. If the donor has tested negative within 90 days prior to donation, the product will be shipped with the negative test result and date of the most recent viral testing on the CoA.

Cord Blood Products - Cryopreserved Products*:

Testing for HIV-1, HIV-2, hepatitis B, and hepatitis C is performed on a sample of maternal blood and/or donated cord blood. Products with negative test results from the donor screening are shipped with the CoA.

Cancer Blood Products - Fresh and Cryopreserved*:

Cancer patient donors are screened once initially for HIV-1, HIV-2, hepatitis B, and hepatitis C, with the test date and results recorded on the CoA. Only products with negative test results are shipped.


*Certain products are only available in select territories. Please reach out to your sales representative or contact us for the most up-to-date information on primary cell availability in your region.

Can donors be recalled for my experiments?

Some donors can be recalled for your experiments; however, there are donors who are either not eligible for recall or are simply not interested in providing future donations. If recallable donors are desired, please specify this to your regional sales representative prior to placing an order to increase the likelihood that the recall will be successful.

Timelines for donor recalls are as follows:

  • Bone Marrow: eligible 35 days after last donation
  • Normal Leukopak: eligible 35 - 56 days after last donation
  • Whole Blood: eligible 56 days after last donation
  • Mobilized Leukopak: eligible 6 months after last donation for a non-mobilized leukopak or whole blood. Not recallable for another mobilized collection (lifetime limit of 1 donation)

Please contact us for more information.

Can I request which medications donors are or are not using?

You may request donors who are taking specific medications. However, it should be noted that this may affect lead time and, in some situations, can require the generation of a custom quote.

Please contact us for more information.

Are donors HLA-typed and if so, how are you testing donors (phenotyping or genotyping)?

HLA type can be requested for most primary cell products. The HLA results are obtained using sequence-based typing, sequence-specific oligonucleotide probes (SSOP), and/or sequence-specific primers (SSP), as needed, to obtain the required resolution. For fresh leukopaks in the U.K., HLA analysis is performed for STEMCELL Technologies by an ASHI (American Society of Histocompatibility and Immunogenetics) accredited lab. Please be advised that the request for HLA data incurs an additional fee.

Please reach out to your sales representative or contact us directly for more information.

Are STEMCELL's primary cell products from single or mixed (pooled) donors?

All of STEMCELL's primary cell products are from single donors, unless otherwise requested*, with the exception of Human Cord Blood CD34+ Cells, Frozen (Catalog #70008).

*If you would like to request other cell types from pooled donors, please reach out to your sales representative or contact us directly for more information. Please note that there may be additional fees associated.

Can I purchase multiple primary cell products (e.g. isolated cells, bone marrow, leukopaks) from the same donor?

Any combination of donor-matched fresh or frozen cell products, including isolated cells or non-isolated products (e.g. leukopaks, whole blood, bone marrow, etc.), may be available upon request.

To discuss feasibility, please reach out to your sales representative or contact us directly for more information.

Are there decreased collection efficiencies from donors undergoing leukapheresis multiple times?

Decreased collection efficiencies are seen from donors who have been recalled frequently over long periods of time. However, we guarantee that the product will meet the cell count specified on the product page. The total nucleated cell count and viability are also reported on the Certificate of Analysis (CoA) and represent the product at the time of release, prior to shipping. It is expected that some cell loss and decrease in viability will occur through the shipping process.

Product Specifications

How many of each cell type (e.g. mononuclear cells, granulocytes, hematopoietic progenitors, RBCs) can I expect to obtain from my cell source?

Our wallchart, Frequencies of Human Cell Types in Blood-Related Sources, provides information regarding the typical frequencies of each cell type in many cell sources (e.g. whole blood, PBMCs, leukopaks, LRS cones, bone marrow, cord blood, etc.). Use these values alongside the total nucleated cell count or volume of your blood-related sample to estimate how many of your desired cell type(s) are present. In your isolation procedure, it is expected that there will be some cell loss. When determining the amount of product needed to obtain desired cell counts for your experiments, be sure to account for cell loss during processing.

Example:
Source: Whole Peripheral Blood, Fresh, 1 x 10 mL in EDTA (Catalog #70508.1)
Desired Cell Type: CD3+ T cells
Typical Frequency of Desired Cell Type (obtained from the wallchart): 0.54 - 1.79 x 10^6 cells/mL
Typical Number of Desired Cell Type in 10 mL of Whole Peripheral Blood, Fresh (Catalog #70508.1): 0.54 - 1.79 x 10^7 CD3+ T cells

To discuss cell frequencies in blood-related sources or isolation procedures for your desired cell type further, please contact your regional sales representative or Product and Scientific Support (techsupport@stemcell.com).

What vial sizes do your primary cells come in?

For primary cell products that are in vials, they are typically supplied in 2 mL or 1.8 mL cryovials. Larger products, such as 10 mL samples, may be supplied in conical tubes or media bottles. The image of the product on the respective product page should provide a general idea of the type of vial that cells are generally supplied in. If you require further information regarding the plasticware that your primary cell product will be supplied in, please reach out to your sales representative or contact us directly.

What is the expected volume of cryopreservation medium in my frozen cell product (e.g. isolated cells and frozen leukopaks)?

All frozen isolated cell products are supplied in 1.5 mL of cryopreservation medium.

For frozen leukopaks, the volume of cryopreservation media used is considered proprietary and cannot be disclosed.

If you have questions regarding our specifications and/or concerns about the product you received, please contact your sales representative or Product and Scientific Support (techsupport@stemcell.com).

What is the expected viability of STEMCELL's frozen cell products?

Most frozen primary cell products have the pre-cryopreservation viability and the accepted viability upon thawing reported on the Certificate of Analysis (CoA). Provided that proper thawing technique is used and viability is assessed immediately upon thaw, the product should meet this specification. For example, frozen leukopaks have an acceptance criterion of ≥ 90% viable cells.

If you have questions regarding our specifications and/or concerns about the viability of the product you received, please contact your sales representative or Product and Scientific Support (techsupport@stemcell.com).

For a step-by-step protocol for thawing frozen primary cells, watch our protocol video.

What is the expected viability of my fresh cell sample?

The viability specification varies based on the cell type. Most fresh cell products have a viability guarantee of ≥ 80% or ≥ 90%.

For the exact viability and cell count for your fresh cell product, please refer to the Certificate of Analysis (CoA).

If you have questions regarding our specifications and/or concerns about the viability of the product you received, please contact your sales representative or Product and Scientific Support (techsupport@stemcell.com).

Are our PBMCs serum-free?

STEMCELL's fresh and frozen peripheral blood mononuclear cells (PBMCs) are not considered serum-free by STEMCELL's definition. Cryopreserved PBMC cells are shipped in CryoStor® CS10 cryopreservation medium (Catalog #100-1061), which is serum-free, but the preparation of this sample may leave trace amounts of serum. Fresh PBMCs are supplied in Iscove’s Modified Dulbecco’s Medium (Catalog #36150) with 10% fetal bovine serum (FBS).

If you require further information, please contact your sales representatives or contact us directly.

Can STEMCELL provide the original flow cytometry characterization and purity data for primary cell products?

Normal Leukopaks - Cryopreserved

The Certificate of Analysis (CoA) for frozen leukopaks manufactured after May 2022 now includes flow cytometry plots showing the percentage of monocytes (CD14+), B cells (CD19+), T cells (CD3+, CD4+, CD8+), and NK cells (CD56+CD3-).

Mobilized Leukopaks - Fresh

Flow cytometry analysis is performed for fresh mobilized leukopaks prior to shipment. The CoA includes the reported total nucleated cells, viability, frequency of CD34+ cells, standard donor information, HLA results, and full flow panel showing viable cells, CD34+ cells, monocytes (CD14+), B cells (CD19+), NK cells (CD56+CD3-), and CD4+ and CD8+ T cell populations.

Purified Cell Products - Fresh or Cryopreserved

Flow cytometry plots for purified/isolated cell types that have a purity specification noted on the CoA can typically be obtained by completing this form. Only markers included in the purity specification will be shown on the flow plots.

You can also reach out to your sales representatives or the Product and Scientific Support team (techsupport@stemcell.com) for more information.

Some products, such as fresh PBMCs and leukopaks, do not have purity specifications listed on the CoA. For these products, we do not perform any flow cytometry analysis during standard manufacturing and cannot provide flow cytometry plots retroactively. However, if flow cytometry plots and purity analysis are desired for PBMC lots, or if additional markers that are not routinely included for purity analysis of isolated cell types are of interest, they may be proactively requested for an additional fee. Please reach out to your sales representative to discuss this further.

What cryopreservation media do we use for frozen cells?

Frozen primary cells are cryopreserved in CryoStor® CS10 cryopreservation medium (Catalog #100-1061), with the exception of CD34+ and CD36+ cells (sourced from cord blood, bone marrow, or peripheral blood), which are shipped in StemSpan™ SFEM (Catalog #09600) + 10% DMSO.

Some leukopaks appear more red in color. What is the reason for this?

Leukopaks that appear more red in color have a higher RBC:WBC ratio. For a typical leukopak, a 3:1 ratio of RBCs to WBCs is observed. However, donor-to-donor variability may result in more or fewer RBCs. At this time, we do not routinely offer specifications for the number of RBCs in the sample; however, the residual RBCs do not affect the cell quality. Compared to the RBC:WBC ratio of whole blood (700:1), leukopaks are a highly enriched source of WBCs and there are minimal RBCs in the sample.

See our Frequencies of Human Cell Types in Blood-Related Sources wallchart for further information regarding the typical frequencies of each cell type in these sample sources.

How are frozen leukopaks prepared (e.g. cryopreservation medium, anticoagulant, etc.)?

Each full-sized leukopak is produced from ~2 - 3X blood volumes using the Spectra Optia® Apheresis System, with acid-citrate-dextrose solution A (ACDA) as the anticoagulant. The collected product is then cryopreserved in CryoStor® CS10 cryopreservation medium (Catalog #100-1061) in a controlled-rate freezer. The exact method for processing and the amount of CryoStor® CS10 used is proprietary.

What is the liquid volume in a fresh leukopak?

The volume of a leukopak varies based on the apheresis machine used, the collection protocol, and the donor's cell concentration and blood volume. Using two different collection protocols and healthy donors, we have seen that, when using the Spectra Optia® Apheresis System, the average volume of a full-sized leukopak ranges between 80 - 220 mL. As this is an average, some leukopak samples fall outside this range. Due to the variability, liquid volume is not a product specification for our leukopaks. We guarantee a total nucleated cell count.

If you have questions regarding our specifications or concerns about the product you received, please contact your sales representative or Product and Scientific Support (techsupport@stemcell.com).

Do immune cells (e.g. monocytes, dendritic cells) from frozen leukopaks function after thawing?

STEMCELL has observed that the majority of immune cell subsets maintain viability and retain their phenotype during cryopreservation. However, it should be noted that not all cell types survive the cryopreservation process and, depending on downstream application, some may not function as expected after thawing. More sensitive cells, such as monocytes, dendritic cells, and NK cells, tend to have greater variability in their performance (expansion, differentiation, etc.) than the cells isolated from fresh leukopaks. Hence, it is highly recommended to run an initial pilot experiment evaluating the feasibility of using frozen or fresh cells for your assays.

Explore our step-by-step protocol for proper thawing and handling of frozen cells to ensure optimal viability and recovery.

What dosage of mobilizing agents are administered to donors each day before collection of leukapheresis products?

Depending upon the regimen, donors are mobilized with either:

  1. G-CSF (NEUPOGEN®): 4 - 5 doses of G-CSF at a concentration of up to 10 μg/kg/dose prior to collection.
  2. Plerixafor (Mozobil®): a maximum of 0.24 mg/kg plerixafor for 1 day prior to collection.
  3. G-CSF (NEUPOGEN®) and plerixafor (Mozobil®): a maximum of 10 µg/kg/day of G-CSF for 4 - 5 days prior to collection and a maximum of 0.24 mg/kg/day of plerixafor for 1 - 2 days prior to collection.

NEUPOGEN and Mozobil are registered trademarks of Amgen Inc. and Genzyme Corporation, respectively.

Cell Processing & Product Storage

Is there a risk of clotting after washing the cryopreservation reagents and anticoagulant from the cells?

If washed with DNAse I and serum-containing media, there is minimal risk of cell clumping after the anticoagulant and cryopreservation media are washed off. See our thawing protocol for steps on thawing frozen isolated cells, including suggestions for DNAse I concentration and serum-containing media options.

Is it possible to wash the cells in serum-free, chemically defined media (i.e. in the absence of FBS, BSA, HSA, etc.)?

While it is possible to wash cells in serum-free, chemically defined media, the inclusion of a serum supplement (such as FBS, BSA, HSA, or human platelet lysate) is typically recommended to help maintain cell viability, mitigate cell clumping, and minimize non-specific binding of antibodies in downstream assays.

Are there any options for automated cell isolation for primary cell products, including leukopaks and whole blood samples?

STEMCELL offers multiple automation options using the RoboSep™ platform.

For more information on the optimal isolation platform for your research application, contact your sales representative or Product and Scientific Support (techsupport@stemcell.com).

Can I use RosetteSep™ with leukopaks, buffy coats, or LRS cones?

We do not recommend using RosetteSep™ with leukopaks, buffy coats, or LRS cones. RosetteSep™ isolates highly purified cells directly from whole blood by cross-linking RBCs to undesired cells via an antibody complex and pelleting down the cross-linked RBCs with a density gradient medium. Leukopaks, buffy coats, and LRS cones typically do not have sufficient RBCs (the recommended RBC:WBC ratio is 100:1) to cross-link undesired cells.

For alternative cell separation solutions, please see: Cell Isolation Technologies and Products Overview

How do I determine the concentration of cells in a suspension?

To determine the concentration of cells in a suspension, you must take both the number of cells and the dilution of the suspension into account. For tips and tricks on this process, explore our templates and resources, which have been designed to help you accurately count cells and measure cell viability.

Cell Counting Templates and Resources >

What media should I culture my primary cells in?

The optimal culture medium for your application will depend on the type of primary cell you are working with. For most of our isolated primary cells, some standard media options (e.g. RPMI, DMEM with serum) are mentioned on the Product Information Sheet (PIS). However, if you are formulating your own media, we recommend consulting the literature for the optimal basal media and supplementation (e.g. cytokines, serum, small molecules) for your cell type. Alternatively, STEMCELL offers a range of cell culture media and reagents, optimized and standardized for specific cell types. If you would like assistance determining the best option for your cell type, please contact your sales representative or Product and Scientific Support (techsupport@stemcell.com).

Please note that STEMCELL cannot guarantee the biological function or any other properties associated with the performance of cells in individual culture systems.

When isolating cells of interest, is positive or negative selection preferable?

The choice of positive vs. negative selection depends on your downstream application. Negative selection offers true untouched cell samples, which is our recommended mode of isolation where applicable. To learn more, view our resource comparing positive and negative selection.

After isolating cells from the starting sample (e.g. leukopaks, whole blood, LRS cones, umbilical cord), what cryopreservation medium should I use?

The cryopreservation medium of choice will depend on the cell type isolated. CryoStor® CS10 (Catalog #100-1061) is a serum- and animal component-free cryopreservation medium suitable for many cell types. (e.g. PBMCs, T cells, monocytes. NK cells, B cells, mesenchymal stem cells (MSCs), hematopoietic stem and progenitor cells (HSPCs), etc.).

Contact your sales representative or Product and Scientific Support (techsupport@stemcell.com) for more information on the best cryopreservation medium for your cell type.

After my cryopreserved isolated cells or frozen leukopaks have been thawed, can I refreeze them?

It is not recommended to thaw and refreeze frozen leukopaks. Mononuclear cells (MNCs) from fresh leukopaks can be subsequently cryopreserved, but it is not recommended to refreeze MNCs from cryopreserved leukopaks. Human primary cells typically do not survive multiple cryopreservation cycles very well; one can expect to see decreased viability and low cell recovery after a second freeze-thaw cycle.

Does STEMCELL recommend resting cells post-thaw, prior to downstream applications?

Generally, if cells are properly thawed following the recommended protocol well and show good viability, resting in medium prior to downstream applications is not required. However, whether you choose to rest your cells is largely dependent on your downstream assays, cell type, and experimental design. For further assistance or information about specific cell types, please contact Product & Scientific Support (techsupport@stemcell.com).

What dilution does STEMCELL recommend to process a leukopak by density centrifugation?

Diluting the leukopak 1:1 with PBS + 2% FBS works for Lymphoprep™ or Ficoll™ processing. In some cases where the leukocyte concentration is high, a 1:2 dilution (e.g. 50 mL sample + 100 mL medium) can help improve separation. Due to the concentrated nature of leukopaks, the cell layer at the interface can be quite thick. Lower dilution will result in a thicker cell layer at the interface and may reduce the efficiency of cell collection.

How long can a fresh leukopak be stored at 4°C or room temperature?

It is recommended to use the fresh leukopak immediately upon arrival and not to store it at room temperature. If storage upon arrival is required, storing the leukopak at 2 - 8°C for up to 5 days post-apheresis, may be acceptable depending on your cell type of interest.

To learn more about the stability of fresh leukopaks when stored at fridge temperature (2 - 8°C) vs. room temperature (15 - 25°C) 0 - 5 days post-collection, explore our stability study data on our Product Landing Page under the “Data and Publications” section. The stability study also includes data on the impact of total viability on the total nucleated cells, as well as mature blood cells, including T cells, B cells, NK cells, monocytes, and granulocytes.

Lysis of residual RBCs in leukopaks is often performed using an ammonium chloride solution. Should this solution be kept at room temperature or cold?

It is recommended to use cold ammonium chloride for processing leukopaks. As ammonium chloride is typically stored at -20°C for long-term storage, it is best to thaw out a working amount (aliquot) at 2 - 8°C the day before use. For further information on the storage and use of ammonium chloride solution, please refer to the Product Information Sheet (PIS) for our product or the respective product documentation from your ammonium chloride supplier.

If you are performing downstream cell isolation using an EasySep™ kit, consult the provided Product Information Sheet (PIS) to determine if red blood cell (RBC) lysis is required.

For further information, please see our protocol on processing leukopaks for downstream applications.

Can CD34+CD45lo hematopoietic stem and progenitor cells (HSPCs) be isolated from a leukopak? If so, what is the yield?

It is possible to isolate CD34+CD45lo HSPCs from a leukopak, but there are fewer present in a normal (non-mobilized) leukopak compared to other sources such as bone marrow, cord blood, or mobilized leukopaks. For example, a typical non-mobilized leukopak has between 0.07 ± 0.01% CD34+CD45lo HSPCs, whereas bone marrow tends to offer 3.3 ± 1.7% CD34+CD45lo cells.

Refer to our cell frequency wallchart for a complete list of frequencies of CD34+CD45lo HSPCs that are typically observed in various cell sources.

Downstream Applications

Can primary cells be used for any downstream application (e.g. commercial, genomic, CRISPR, etc.)?

Primary cells may be used for research in downstream applications such as disease modeling, genome editing, drug discovery, and more.

STEMCELL's primary cell products are provided for laboratory research use only: they are not suitable for diagnostic or therapeutic use and are not to be administered to humans. Primary cell products shall be used in accordance with all applicable laws, rules, and regulations, including but not limited to applicable privacy laws, and in accordance with any Product Information Sheet (PIS) or any other label or document shipped with or otherwise associated with any of the products. STEMCELL cannot guarantee the biological function or any other properties associated with the performance of cells in a researcher’s individual assay or culture systems.

Can your primary cell products be used in mouse models (humanized mice, chimera, engraftment studies etc.)?

STEMCELL's primary cell products are not approved for human or veterinary use in vivo. However, use in animal models (e.g. injections into mice for humanized mouse, chimera, engraftment studies, etc.) does not typically qualify as a veterinary use. Prior to any downstream experiments, ensure you have obtained the appropriate animal ethics approvals for research at your institution. We can provide supporting documentation, such as Institutional Review Board (IRB) or Informed Consent Form (ICF) documents, on request. If you need further information, please contact your sales representative or the primary cells team.

Can isolated, cryopreserved monocytes be differentiated to macrophages?

Using our ImmunoCult™-SF Macrophage Medium (Catalog #10961), frozen monocytes can be differentiated to macrophages; however, STEMCELL recommends using fresh samples whenever possible. Starting with frozen monocytes tends to generate lower yields of macrophages and higher variability in comparison to fresh sample sources.

What type of leukopak would STEMCELL recommend as a starting source for isolation of CD34+ stem cells?

While CD34+ can be isolated from normal peripheral blood leukopaks, the quantities are often too low to make it worth the isolation. To get an acceptable number of CD34+ stem cells from a leukopak, it is recommended to purchase either fresh mobilized leukopaks (Catalog #200-0600) or pre-isolated cryopreserved CD34+ cells from mobilized leukopaks (Catalog #70073).

CD34+ samples are collected from donors mobilized with either granulocyte colony-stimulating factor (G-CSF), plerixafor (PLX), or a combination of the two compounds. These cells are collected under industry best practices and are carefully monitored throughout the process to ensure the maximal quality of these samples.

Learn more about the features of different CD34+ cell sources, such as cord blood, bone marrow, mobilized peripheral blood, etc.,including respective CD34+ cell frequencies (%), by visiting: Sources of CD34+ Cells.

Shipping & Delivery

Where can STEMCELL deliver fresh cells?

STEMCELL can deliver fresh cells within North America, the United Kingdom, and parts of Europe.

Contact your sales representative or cellorders@stemcell.com for further information.

Where can STEMCELL deliver frozen cells?

STEMCELL can deliver frozen cells in a number of countries; availability will depend on the cell type and local government regulations.

Contact your sales representative or cellorders@stemcell.com for further information.

Is same-day delivery available?

Same-day delivery is available in select regions.

Contact your sales representative or cellorders@stemcell.com for further information.

How long does it take to schedule a fresh blood collection?

Fresh blood collection scheduling depends on your donor requirements, as outlined below:

  • No donor specifications: collection will be scheduled within 1 - 2 weeks of the request date.
  • Donor specifications: collections will be scheduled within 1 - 2 weeks of the request date; however, it may take longer to locate donors meeting your requirements.

How are frozen primary cells shipped?

Frozen primary cells are shipped in CryoStor® CS10 cryopreservation medium (Catalog #100-1061), with the exception of CD34+ and CD36+ cells (sourced from cord blood, bone marrow, or peripheral blood), which are shipped in StemSpan™ SFEM (Catalog #09600) + 10% DMSO. Frozen cells are shipped on dry ice or, if requested, liquid nitrogen.

Which cells are available in my region?

Please contact your sales representative or the primary cells team to get the most up-to-date information on primary cell availability in your region.

How are fresh leukopaks shipped?

Normal Leukopaks

Fresh normal leukopaks are shipped by default in certified refrigerated packaging capable of holding a constant internal temperature range of 2 - 8°C for a period of up to 48 hours. If preferred, you also have the option of shipping at ambient temperatures.

All fresh leukopak orders in the EU will be collected the day before delivery, then shipped for arrival on the next day. Delivery time may differ based on location.

For same-day deliveries, normal leukopaks will be shipped at ambient temperatures due to the short transit time between product collection and utilization.

Mobilized Leukopaks

For same-day or overnight deliveries, fresh mobilized leukopaks are shipped by default in certified long haul refrigerated packaging capable of holding a constant internal temperature range of 2 - 8°C for a period of up to 96 hours.

How are frozen leukopaks shipped?

Frozen leukopak products are shipped on dry ice with liquid nitrogen shipping available upon request. For best results, it is recommended to use the leukopak product immediately upon receipt. Otherwise, store at -135ºC or colder.

What is STEMCELL’s shipping and cancellation policy for human primary cell products?

The terms and conditions of service related to human primary cell products are based on geographical location, type of product, and the source of origin. For more information, visit: TERMS AND CONDITIONS OF SERVICE RELATED TO ALL PRIMARY CELL PRODUCTS.



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