Experimental studies in mice have attributed T-helper (Th) 1 and Th2 cells important roles in atherosclerosis, but the clinical importance of these cells in cardiovascular disease (CVD) remains to be clarified. Here, we investigated associations between Th1 and Th2 cells, carotid intima-media thickness, and cardiovascular risk.

Blood drawn at baseline and incident cardiovascular events during 15-year follow-up were assessed in 700 participants. Baseline Th1 (CD3⁺CD4⁺interferon-γ⁺) and Th2 (CD3⁺CD4⁺interleukin-4⁺) cells were analyzed by flow cytometry, and cytokine-release from activated mononuclear leukocytes was measured by multiplex technology. High numbers of Th2 cells were independently associated with decreased mean common carotid intima-media thickness. High numbers of Th2 cells were also independently associated with a reduced risk of acute myocardial infarction in women (hazard ratio, 0.19; 95% confidence interval, 0.06–0.56; P=0.002 for the highest versus the lowest tertile of Th2 cells). Moreover, release of the Th2 cytokine interleukin-4 from activated mononuclear leukocytes was independently associated with a reduced risk of CVD. No independent associations between Th1 cells and carotid intima-media thickness or CVD risk were found.

Our observations provide the first clinical evidence for a protective role of Th2 immunity in CVD. They also suggest this protection is more prominent in women than in men. In spite of convincing evidence from experimental studies, we found no support for a role of Th1 immunity in CVD.