However, we unexpectedly found that Il25−/−Il1rn−/− mice showed attenuated development of aortitis, accompanied by reduced accumulation of inflammatory cells such as dendritic cells, macrophages and neutrophils and reduced mRNA expression of Il17a and Tnfa—but not Il4 or Il13—in local lesions compared with Il1rn−/− mice. The gene discussed is IL4; the disease is aortitis.