IL12P40 (interleukin 12 subunit beta), also known as natural killer cell stimulatory factor 2, or cytotoxic lymphocyte maturation factor 2, p40, belongs to the type I cytokine receptor family. This protein is a cytokine that can act as a growth factor for activated T and NK cells, enhance the lytic activity of NK/lymphokine-activated killer cells, and stimulate the production of IFN-gamma by resting PBMC. Interleukin 12 is a disulfide-linked heterodimer composed of the 40 kD cytokine receptor like subunit encoded by this gene, and a 35 kD subunit encoded by IL12A.