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. This evidence concerns the gene FOXP3 and aortic aneurysm.