Background— Although monocytes in peripheral blood are no longer considered to be a homogeneous population, associations between distinct monocyte subsets and cardiovascular disease have not been highlighted in large epidemiological studies. Methods and Results— The study included 700 randomly selected subjects from the cardiovascular arm of the Malmö Diet and Cancer study. Among these, 123 subjects experienced ischemic cardiovascular events during the follow-up until December 2008. Mononuclear leukocytes frozen at the baseline investigation in 1991 to 1994 were thawed and analyzed with flow cytometry to enumerate monocyte subsets, based on CD14 and CD16 expression. The percentage and number of classical CD14 ++ CD16 − monocytes were increased in the cardiovascular-event group compared with the event-free subjects (median, 69% [interquartile range, 62% to 76%] versus 67% [59% to 72%], P =0.017; 344 [251 to 419] cells/μL versus 297 [212 to 384] cells/μL, P =0.003). The hazard ratio was 1.66 for suffering a cardiovascular event in the highest tertile of the number of CD14 ++ CD16 − monocytes compared with the lowest tertile, even after adjustment for common risk factors (HR, 1.66; 95% CI: 1.02 to 2.72). CD14 ++ CD16 − monocytes did not, however, associate with the extent of atherosclerosis at baseline. In contrast, the percentage of monocytes expressing CD16 was negatively associated to the extent of carotid atherosclerosis measured as intima-media thickness at baseline. The chemokine receptors CCR2, CX3CR1, and CCR5 were not differentially expressed between cases and controls on any of the monocyte subsets, but CCR5 expression on CD14 + CD16 ++ monocytes was negatively associated to carotid intima-media thickness. Conclusions— This study shows that classical CD14 ++ CD16 − monocytes can predict future cardiovascular risk independently of other risk factors in a randomly selected population.

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Objective— Regulatory T cells (Tregs) protect against atherosclerosis in experimental models, but their association with cardiovascular disease in humans remains to be elucidated. The aim of the present study was to determine whether circulating Tregs predict the development of acute cardiovascular events in humans. Methods and Results— The study cohort consisted of a random sample of participants (n=700), aged 68 to 73 years, from the Malmö Diet and Cancer Study. Mononuclear leukocytes, stored at −140 ○ C at the baseline investigation in 1991–1994, were thawed and Tregs, defined by the expression of FoxP3 in CD4+ T cells, were analyzed by flow cytometry. There was no detectable loss of cells during storage, and the viability of thawed leukocytes was 95%. A low fraction of both CD4+FoxP3+ and CD4+CD25+FoxP3+ T cells was associated with a higher release of proinflammatory cytokines from activated mononuclear leukocytes, and this association was strongest for CD4+FoxP3+ cells. Eighty-four coronary events and 66 strokes were registered during follow-up until December 31, 2008. In a Cox proportional hazard regression model adjusting for major risk factors, low levels of baseline CD4+FoxP3+ T cells were associated with an increased risk for the development of acute coronary events but not stroke. There were no associations between CD4+CD25+FoxP3+ T cells and development of an acute coronary event or stroke. Conclusion— This study provides prospective evidence for the role of Tregs in the development of myocardial infarction. The findings are in accordance with previous experimental studies and provide clinical support for a protective role of Tregs in atherosclerosis. The lack of association between Tregs and stroke may reflect the more heterogeneous cause of this disease.