Cytokine with immunoregulatory activity. May promote the transition between innate and adaptive immunity. Induces the production of IgG(1) and IgG(3) in B-cells (By similarity). May play a role in proliferation and maturation of natural killer (NK) cells in synergy with IL15. May regulate proliferation of mature B- and T-cells in response to activating stimuli. In synergy with IL15 and IL18 stimulates interferon gamma production in T-cells and NK cells. During T-cell mediated immune response may inhibit dendritic cells (DC) activation and maturation. {ECO:0000250, ECO:0000269|PubMed:11081504, ECO:0000269|PubMed:15178704}. Biological Activity: Fully biologically active when compared to standard. The ED50 as determined by by a cell proliferation assay using human N1186 T cells is less than 20ng/ml, corresponding to a specific activity of > 5.0x10e4 IU/mg. Sequence: QGQDRHMIRM RQLIDIVDQL KNYVNDLVPE FLPAPEDVET NCEWSAFSCF QKAQLKSANT GNNERIINVS IKKLKRKPPS TNAGRRQKHR LTCPSCDSYE KKPPKEFLER FKSLLQKMIH QHLSSRTHGS EDS Molecular Weight: 15.4kD PubMed ID: 11081504, 17673207, 15815621, 15489334, 15178704, 15147560, 17565991, 22235133, 24746753 Gene Name: IL21 Swiss Prot: Q9HBE4 Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.