Pathological severity index, which was calculated based on the level of aortic wall degradation and immune infiltrate34, showed that both female and male Apoe−/− and Apoe−/−Il27ra+/− mice displayed more advanced stages of AAA (IV stage) compared with IL-27R-deficient Apoe−/− mice, where AAA progression, if any, was restricted to the early stages (I–II) (Supplementary Fig. 1d). Here, IL27RA is linked to triple-A syndrome.