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-? (IFN-?) and Tumor Necrosis Factor ? (TNF-?) from T cells and Natural Killer cells. Mouse IL-12 is active on human and mouse cells.