The Human Interleukin 4 (IL-4) ELISA Kit is designed for the quantitative detection and measurement of human IL-4 in biological fluids such as serum, plasma, and cell culture supernatants. IL-4 is produced by Th2 cells, NK cells, γ/δ T cells, eosinophils, mast cells, and activated basophils. IL-4 induces Ig isotype switching in B cells, regulates the differentiation of naïve T cells into Th2 cells, and in conjunction with TNF, recruits T cells and eosinophils to sites of inflammation.

The assay is based on the sandwich ELISA method, in which samples are added to ELISA strip plates pre-coated with capture antibodies specific for the cytokine. The captured cytokine is detected by addition of a biotinylated detection antibody, followed by streptavidin-horseradish peroxidase, which binds the biotinylated antibody. Addition of the chromogenic enzyme substrate 3,3’,5,5’ tetramethylbenzidine (TMB) results in a colored product with an intensity directly proportional to the concentration of cytokine in the sample. The concentration of the cytokine is determined by comparison to a serial dilution of the cytokine standard analyzed in parallel.