Interleukin 17A (IL-17A) is the original member of the IL17 family of structurally related cytokines (IL-17 A to IL17F) that share a highly conserved C-terminal region but differ from one another in their N-terminal regions and in their distinct biological roles. IL-17A is a pro-inflammatory cytokine produced primarily by T cells and is commonly associated with the allergic response facilitating the release of other cytokines, chemokines and prostaglandins from a variety of cell types. IL-17A exists in vitro as a homodimer of two 132 amino acid chains.