Since carriage of this variant (or others in high linkage disequilibrium with R381Q) confers decreased susceptibility to immune mediated diseases such as inflammatory bowel disease, ankylosing spondylitis and psoriasis [52], [53], [54], this indicates a potential unidentified role of IL-17+ CD8+ T cells in the pathogenesis of these diseases. This evidence concerns the gene IL17A and psoriasis.