Interleukin-12 (IL-12) was first identified in 1989 in the supernatant of B lymphocytes transformed with Epstein-Barr virus, and named “natural killer-stimulator factor” due to its ability to induce interferon (IFN)-γ and natural killer (NK) cell cytotoxicity when added to human peripheral blood lymphocytes. This pro-inflammatory, heterodimeric cytokine consists of covalently linked p40 and p35 subunits and is a member of the IL-12 cytokine family, which includes IL-12, IL-23, IL-27, IL-35 and IL-39. Both IL-12 and IL-23 are composite cytokines, sharing a common IL-12 p40 subunit and IL-12Rβ1 receptor. Cytokine specificity is derived from the unique IL-12 p35 subunit binding to IL-12Rβ2 and the IL-23p19 subunit binding to IL-23R. Both p35 and p40 genes need to be expressed within the same cell to produce the active heterodimer and subsequent IL-12 signaling.IL-12 is secreted following stimulation of phagocytes and dendritic cells by bacteria and other microorganisms. Together with antigen presentation, IL-12 directs CD4+ T cells to differentiate into IFN-γ producing T helper 1 (Th1) cells and also induces lymphokine-activated killer cells and NK cells. These Th1 cells respond to intracellular pathogens (e.g., Legionella pneumophila, Mycobacterium tuberculosis, Listeria monocytogenes and Salmonella spp.) and promote delayed-type hypersensitivity and activation of macrophages.The IL-12 Bioassay (Cat.# JA2601, JA2605) is a bioluminescent cell-based assay designed to measure IL-12 stimulation or inhibition. The IL-12 Bioassay Cells are provided in a thaw-and-use format as cryopreserved cells that can be thawed, plated and used in an assay without the need for cell propagation. The IL-12 Bioassay Cells are also available in a Cell Propagation Model (CPM; Cat.# J3042) format, as cryopreserved cells that can be thawed, propagated and banked for long-term use. The IL-12 Bioassay consists of human cells engineered to express the IL-12 receptor and a luciferase reporter driven by a response element (RE). When IL-12 binds to IL-12R, it transduces intracellular signals resulting in luminescence. The bioluminescent signal is detected and quantified using the Bio-Glo™ Luciferase Assay System (Cat.# G7940, G7941) and a standard luminometer, such as the GloMax(R) Discover System.