IL-21 is expressed in activated CD4-positive T-cells but not in CD8-positive T-cells, B-cells, or monocytes, and in HL-60 and THP-1 cell lines. This protein-A purified antibody has been tested for use in ELISA and western blotting. Specific conditions for reactivity should be optimized by the end user. Expect a band approximately 15.1 kDa in size corresponding to bovine IL-21 protein by western blotting in the appropriate cell lysate or extract.