Purity >95% as determined by SDS-PAGE. Interleukin 12 (IL-12) is an inducer of cell-mediated immunity and is produced by dendritic cells, macrophages, and B cells after antigen stimulation. IL-12 functions to promote naive T cell differentiation into the type 1 T helper cell (Th1) lineage. IL-12 also stimulates the production of interferon gamma (IFN?) and tumor necrosis factor alpha (TNF?) from T cells and natural killer cells. Mouse IL-12 is active on human and mouse cells.