Cutting edge: IL-17F, a novel cytokine selectively expressed in activated T cells and monocytes, regulates angiogenesis and endothelial cell cytokine production

A novel secreted cytokine, termed IL-17F, was cloned using nested RACE PCR. This cytokine bears homology to IL-17. IL-17F was expressed only in activated CD4⁺ T cells and activated monocytes. Recombinant human IL-17F did not stimulate the proliferation of hematopoietic progenitors or the migration of mature leukocytes. However, it markedly inhibited the angiogenesis of human endothelial cells and induced endothelial cells to produce IL-2, TGF-β, and monocyte chemoattractant protein-1.