Identification and characterization of CD4(+)AT2(+) T lymphocyte population in human thoracic aortic aneurysm.

Thoracic aortic aneurysm (TAA) is progressive fatal aortic pathological dilation. However, the underlying molecular mechanisms are still largely unknown. Evidences suggest that endothelial cells and renin-angiotensin system may participate in the pathogenesis of TAA. This study aimed to investigate whether angiotensin II type 2 receptor (AT2) positive cells are involved in TAA formation. The mRNA level of AT2 is dramatically elevated in TAA compared with in controls. CD4(+)AT2(+) cells increased in both aortic wall and circulation of TAA patients. The levels of IL-1β and IL-17B in CD4(+)AT2(+) cells were lower than those in CD4(+)AT2(-) cells. When compared with endothelial cells (ECs) cultured alone, CD4(+)AT2(+) cells showed an inhibitory effect on proliferation and MMP2 expression in ECs, but CD4(+)AT2(-) cells promoted proliferation and MMP2 expression in ECs. Both CD4(+)AT2(+) and CD4(+)AT2(-) cells suppressed apoptosis of ECs. In conclusion, we have identified a novel population of CD4(+)AT2(+) T lymphocytes that show protective effect in TAA through inhibition of growth, apoptosis, and MMP2 expression in ECs.