Anti-IL21 antibodies are used in the immunodetection of the protein interleukin 21. In humans, the canonical protein has a reported length of 162 amino acid residues and a mass of 18.7 kDa. It has been described to be a secreted protein. Up to 2 different isoforms have been reported for this protein. It is reported to be expressed in activated CD4-positive T-cells but not in CD8-positive T-cells, B-cells, or monocytes. A member of the IL-15/IL-21 protein family, IL21 is known to be involved with viral immune response and germinal center B cell differentiation. Post-translational modifications have been described, including glycosylation. IL21 is also used as a cellular marker for characterizing NK T cells. IL21 gene orthologs have been reported in the mouse, rat, bovine, frog, chimpanzee and chicken species. Over 270 citations in the literature describe the use of IL21 antibodies in research. ELISA is a widely used application for these antibodies. In addition, Western Blot is also a common application.