CD4 and aortic aneurysm: Hence, we transferred CD45.2+ Tconvs (CD4+CD45.2+Foxp3–) into CD45.1 mice and observed a small population of donor‐derived CD45.2+ Tregs (CD4+CD45.2+Foxp3+) in aortic aneurysms, spleens and lymph nodes, and the frequency of CD45.2+ Tregs in aortic aneurysms was higher than that in lymphoid organs (Figure S3d, Supporting Information), verifying the conversion of Tconvs to Tregs in AAA.