Interleukin-12 subunit alpha (IL12A/IL-12p35) is also known as Cytotoxic lymphocyte maturation factor 35 kDa subunit, cytotoxic lymphocyte maturation factor 1, p35, NK cell stimulatory factor chain 1, and interleukin-12 alpha chain. IL12A/IL-12p35 is a subunit of a cytokine that acts on T and natural killer cells and has a broad array of biological activities. The cytokine is a disulfide-linked heterodimer composed of the 35-kD subunit encoded by this gene, and a 40-kD subunit that is a member of the cytokine receptor family. IL12A/IL-12p35 is required for the T-cell-independent induction of interferon (IFN)-gamma and is important for the differentiation of both Th1 and Th2 cells. The responses of lymphocytes to this cytokine are mediated by the activator of transcription protein STAT4. Nitric oxide synthase 2A (NOS2A/NOS2) is found to be required for the signaling process of this cytokine in innate immunity. In clinical, IL-12 remains a very promising immunotherapeutic agent because recent cancer vaccination studies in animal models and humans have demonstrated its powerful adjuvant properties. The immune-modulating characteristics of IL-12 considered responsible for the adjuvant effects, as well as the results of animal and human cancer vaccination studies with IL-12, applied as an adjuvant. IL12A/IL-12p35 indicates a cytokine that is important in the development of prostate cancer.