Next, we analyzed the single‐cell sequencing data which was published in GEO database (GSE152583),[29] and the results (Figure S5g, Supporting Information) suggested that almost all cells expressing Tff1 expressed Foxp3, while other immune cells like CD4+ T cells and macrophages hardly expressed Tff1, further confirming our results that Tregs were the main source of Tff1 in AAA. Here, CD4 is linked to triple-A syndrome.