human IL-21 ELISA kit (96 Wells)

Interleukin-21(IL-21) and its receptor play an important role in the regulation of the immune system. IL-21R, also called NILR (novel interleukin receptor), is a type I cytokine receptor with 4 conserved cysteine residues and an extracellular WSXWS motif. The biological effects of IL-21 include induction of differentiation of T-cells-stimulated B-cells into plasma cells and memory B-cells, stimulation (in conjuction) with IL-4 of IgG production, and induction of apoptotic effects in naive B-cells and stimulated B-cells in the absence of T-cell signaling. Additionally, IL-21 promotes the anti-tumor activity of CD8+ T-cells and NK cells. IL-21 exerts its effect through binding to a specific type I cytokine receptor, IL-21R, which also contains the gamma chain found in other cytokine receptors including IL-2, IL-4, IL-7, IL-9 and IL-15. The IL21/IL21R interaction appears to play an important role in B and T cell proliferation after antigen stimulation and NK cell maturation.

For the quantitative determination of human interleukin 21 (IL-21) concentrations in cell culture supernates, serum, and plasma.

Principle of the assay: This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for IL-21 has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any IL-21 present is bound by the immobilized antibody. Following incubation unbound samples are removed during a wash step, and then a detection antibody specific for IL-21 is added to the wells and binds to the combination of capture antibody- IL-21 in sample. Following a wash to remove any unbound combination, and enzyme conjugate is added to the wells. Following incubation and wash steps a substrate is added. A colored product is formed in proportion to the amount of IL-21 present in the sample. The reaction is terminated by addition of acid and absorbance is measured at 450nm. A standard curve is prepared from seven IL-21 standard dilutions and IL-21 sample concentration determined.