INTERLEUKIN-15 PROMOTES ANGIOGENESIS IN-VIVO

IL-15, a cytokine with biological functions on cells of lymphoid linea ge similar to those of IL-2, mediates its activities through the beta and gamma chains of the IL-2/15R and its own alpha chain. Unlike IL-2, IL-15 also binds to endothelial cells with high affinity. We report h ere that IL-15 is a stimulator of angiogenesis in vivo. When injected subcutaneously into nude mice, IL-15 consistently induced neovasculari zation of Matrigel plugs. Endothelial cells were found to express the lL-15R alpha chain and the IL-2/15R beta and common gamma chains. IL-1 5 induced the rapid tyrosine phosphorylation of proteins in endothelia l cells, but did not stimulate endothelial cell proliferation in vitro . These findings document a previously unrecognized biological propert y of IL-15 and emphasize the role of IL-15 as an important mediator ou tside the immune system. (C) 1997 Academic Press.