IL1RN and aortitis: Although IL-25 is known to induce production of type 2 cytokines by various types of cells27,28, the expression levels of Il4 and Il13 mRNA were comparable in the aortae of Il25−/−Il1rn−/− mice and Il1rn−/− mice (Fig. 5), suggesting that IL-25 is not crucial for induction of such type 2 cytokines in the lesions of aortitis.