Interleukin 12, also known as natural killer cell stimulatory factor (NKSF) or cytotoxic lymphocyte maturation factor (CLMF), is a heterodimeric pleiotropic cytokine made up of a 40 kDa (p40) subunit and a 35 kDa (p35) subunit. IL-12 is produced by macrophages and B lymphocytes and has been shown to have multiple effects on T cells and natural killer (NK) cells. Some of these IL-12 activities include the induction of IFN-gamma and TNF in resting and activated T and NK cells, the enhancement of cytotoxic activity of resting NK and T cells, the stimulation of resting T cell proliferation in the presence of a comitogen, and the enhancement of NK cell proliferation. Current evidence indicates that IL-12 is a key mediator of cellular-immunity and induces the differentiation of Th1 cells from precursor T helper cells. Based on its activities, it has been suggested that IL-12 may have therapeutic potential as a vaccine adjuvant that promotes cellular-immunity and as an anti-tumor and anti-viral agent.
Porcine IL-12 subunits p35 and p40 share about 85% homology to the human subunits, but differ by containing a 3 aa addition in the p35 subunit and a 4 aa deletion in the p40 subunit. Porcine IL-12 induces proliferation of human lymphoblasts and IFN-gamma secretion by human and porcine lymph nodes. Porcine IL-12 has been detected in lymphoid tissues including inguinal and mesenteric lymph nodes, Peyer's patches, spleen and thymus.
