Even prior to the discovery of Th17 cells, which produce IL-17A, IL-17F and IL-22, IL-17 was noted to be overexpressed in a number of inflammatory/autoimmune conditions including MS [39], RA [40, 41], systemic lupus erythematosus (SLE) [42, 43] and airway inflammatory diseases [44] and thus has been implicated in their pathogenesis. Here, IL17F is linked to systemic lupus erythematosus.