Recombinant Rhesus Macaque IL-12 Protein

Interleukin 12 (IL-12) is a 70 - 75 kDa heterodimeric glycoprotein that belongs to the IL-12 family of cytokines (1 - 3). Monkey IL-12 consists of two disulfide-linked subunits which are 35 kDa and 40 kDa in size. They show no meaningful amino acid (aa) similarity (4). The mature 35 kDa subunit (p35; also IL-12A) is an alpha-helix, 197 aa in length, that contains seven cysteines and two potential N-linked glycosylation sites (4). Mature Rhesus monkey p35 is 94%, 98%, 97%, 57%, 81%, and 82% aa identical to human, mangabey, baboon, mouse, equine and porcine mature p35, respectively. The mature 40 kDa subunit (p40; alsoIL-12B) is 306 aa in length and contains one intrachain disulfide bond plus three potential N-linked glycosylation sites. Mature Rhesus p40 is 96%, 97%, 99%, 67%, 85%, and 80% aa identical to human, mangabey, baboon, mouse, equine, and porcine p40, respectively. While p35 is reminescent of a hematopoietin ligand, p40 strongly resembles the N-terminus of a hematopoietin receptor, exhibiting a WSXWS motif, an immunoglobulin-like domain, and one fibronectin type III domain (5). This has led to the suggestion that IL-12 may be a cytokine-receptor analog to the IL-6/soluble IL-6R complex (6 - 8). Notably, while p40 may circulate as a monomer or homodimer, p35 is never found by itself. Cells known to produce IL-12 include macrophages and dendritic cells, monocytes, Langerhans cells, neutrophils, and keratinocytes. Functionally, IL-12 has been shown to both enhance cytotoxic activity and induce interferon-gamma (IFN-gamma) production in NK cells and T cells. In response to infection, IL-27 is released initially, promoting a Th0 to Th0/1 transition state. IL-12 follows next, generating Th1 effector cells. With IL-18, IL-12 creates Th1 memory cells out of effector cells (1 - 3, 6, 7).