Extensive researchhas confirmed that Tregs can reduce infiltration of macrophages and CD4+ T cellsinto the vascular wall, as well as reduce the expression of pro-inflammatorycytokines, enhance the production of anti-inflammatory factors, reduce thesecretion of monocyte chemotactic protein-1 (MCP-1), and reduce the expressionand activity of MMP-2 and MMP-9, thereby inhibiting AAA formation in response toAng II stimulation [52, 53]. This evidence concerns the gene MMP9 and triple-A syndrome.