Reduced immunoregulatory CD31⁺ T cells in the blood of atherosclerotic mice with plaque thrombosis

Objective - Lymphocyte activation is thought to play a major role in the pathogenesis of atherosclerotic complications such as plaque thrombosis. Circulating CD31⁺ T cells have been shown to regulate human T cell activation. Aim of this study was to evaluate whether the proportion of circulating immunoregulatory CD31⁺ T cells is correlated to the occurrence of plaque thrombosis in aged apolipoprotein (apo) E knockout (KO) mice. Methods and Results - CD31⁺ T cell depletion of spleen T cells enhanced proliferation (P<0.05) and interferon-γ production (P<0.01) while reducing interleukin (IL)-4 (P<0.001) and IL-10 (P=0.001) secretion in response to minimally modified low-density lipoprotein. CD31⁺ T cells were counted in 65 apoE KO mice (46-week-old) by flow cytometry. Organizing thrombi could be documented in 28 of 195 (14%) lesions and in at least one of the aorta root lesions in 23 of 65 mice (35%). CD31⁺ T cell count was significantly reduced in mice showing plaque thrombosis (72.3 ± 1.5% versus 84.1 ± 1.2%; P < 0.0001), but such reduction did not follow induced plaque rupture or experimentally controlled thrombosis. Conclusions - Reduced CD31⁺ T cells in circulating blood is a hallmark of atherosclerotic plaque thrombosis. Our data suggest that CD31 ⁺ T cells may play an important regulatory role in the development of plaque thrombosis.