Interleukin-17F (IL-17F) is a cytokine that shares sequence similarity with IL17. The most notable role of IL-17 is it involvement in inducing and mediating proinflammatory responses. IL-17 is commonly associated with allergic responses. IL-17F is expressed by activated T cells, and was expressed only in activated CD4+ T cells and activated monocytes. IL-17F has been shown to stimulate the production of several other cytokines, including IL6 and IL8. This cytokine is also found to inhibit the angiogenesis of endothelial cells and induce endothelial cells to produce IL2, TGFB1/TGFB, and monocyte chemoattractant protein-1. 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-{beta}, and monocyte chemoattractant protein-1. IL-17F stimulates the production of other cytokines and granulocyte colony-stimulating factor, and can regulate cartilage matrix turnover. IL-17F stimulates PBMC and T-cell proliferation. It also function in inhibiting angiogenesis By similarity. IL-17F plays a role in the induction of neutrophilia in the lungs and in the exacerbation of antigen-induced pulmonary allergic inflammation.