Recombinant Canine IL-2 (Cys147Ser) Protein

Interleukin 2 was initially identified as a T cell growth factor that is produced by T cells following activation by mitogens or antigens (1). Since then, it has been shown that IL-2 can also stimulate the growth and differentiation of B cells, natural killer (NK) cells, lymphocyte activated killer (LAK) cells, monocytes/macrophages, and oligodendrocytes (2). The biological activity of IL-2 is mediated by the binding to cell surface receptor complexes composed of three subunits designated as alpha, beta, and gamma subunits (3). IL-2 binds the  alpha subunit with low affinity. The functional high affinity IL-2 receptor is a heterotrimeric complex of the alpha, beta, and gamma subunits. IL-2 binds with intermediate affinity to the complex containing the  beta and  gamma subunits, which is also capable of transducing IL-2 signals (4). In T cells, the beta and gamma subunits are shared with the IL-15 receptor complex (5). The gamma subunit of the IL-2 receptor complex has also been shown to be a subunit of the receptor complexes of IL-4, IL-7, and IL-9 (6). At the amino acid sequence level, canine IL-2 shares 90%, 86%, 85%, 76%, and 75% sequence similarities to feline, human, equine, mouse, and bovine IL-2, respectively (7).