IL17A and ankylosing spondylitis: The role of the IL-17 signaling pathway has been described in several diseases, including those with an immune etiology, and this pathway has been successfully targeted therapeutically in human diseases such as psoriasis and ankylosing spondylitis.13, 14 The IL-17 family of ligands comprises 6 members, IL-17A to IL-17F, along with its corresponding 5-member receptor family (IL17RA-IL17RE).15