While IL-17F and IL-17A exhibit similar activities in models of autoimmunity and pathogen clearance including experimental autoimmune encephalomyelitis (EAE) and Citrobacter rodentium infection26,27, their functions diverge in models of airway inflammation25 and colitis28 suggesting that the functions of IL-17F and IL-17A are likely to be tissue- and disease model-specific. This evidence concerns the gene IL17A and Autoimmunity.