FOXP3+ Treg cells were abundant in aortic aneurysms, especially in AAA groups (Figure 5B; Supplementary Figure S6B) and displayed high expression of exhausted genes CTLA4, TIGIT, TNFRSF14, ICOS, and CD28 (Supplementary Figures S6C, D). Here, FOXP3 is linked to aortic aneurysm.