Recombinant Human Interleukin-15 (rHuIL-15)

Interleukin 15 is a recently identified novel cytokine that shares many biological properties with IL-2, including T, B and NK cell-stimulatory activities. cDNA clones encoding this cytokine have been isolated from simian, murine and human cell sources. Human IL-15 shares approximately 97% and 73% sequence identity with simian and murine IL-15, respectively. Both human and simian IL-15 are active on murine cells. Human IL-15 cDNA encodes a 162 amino acid residue precursor protein containing a 48 amino acid residue signal peptide that is cleaved to yield the 114 amino acid residue mature protein. The IL-15 mRNA is expressed by a wide variety of cells and tissues and is most abundantly expressed by adherent peripheral blood mononuclear cells, fibroblasts and epithelial cells. However, in activated peripheral blood T lymphocytes where IL-2 is highly expressed, the expression of IL-15 is not detectable. Although IL-15 lacks sequence homology with IL-2, it has recently been shown that both the beta and gamma chains of the IL-2 receptor are utilized for IL-15 binding and signaling. In addition, an IL-15 specific binding protein has also been cloned from a mouse T cell clone. (Grabstein, K. et al., 1994, Science 264:965; Giri, J. et al., 1994, EMBO J. 13:2822) .