The main effects of IL-21 are Stimulation of B-cell proliferation after CD40 cross-linking Stimulation of NK cells Costimulation of T cells Stimulation of bone marrow precursor cell proliferation Clinical relevance of IL-21 includes In clinical trials, stimulation of cytotoxic T-cells and NK cells in cancer For IL-21 antagonists, potential in the treatment of autoimmune disorders IL-22 is produced by NK cells, Th17 cells, and gamma-delta T cells.