IL1RN and aortitis: Since accumulation of Th2 cells as well as Th1 cells was observed in inflamed lesions of aortitis in Il1rn−/− mice21, we suspected that IL-25 may be involved in suppression of IL-1–, TNF– and IL-17–mediated aortitis in Il1rn−/− mice by enhancing Th2 cell activation.