Interleukin-2 levels are associated with carotid artery intima-media thickness

Objective: To show that serum interleukin levels are associated with carotid intima-media thickness (IMT). Background: Inflammation is hypothesized to play a central role in atherogenesis, and serum markers of inflammation are predictive of cardiovascular disease. Interleukin-2, a pro-inflammatory cytokine produced largely by naive CD4 T cells and Th1 (pro-inflammatory) T cells, has been found in a high proportion of carotid plaques. Methods: High-resolution ultrasound of the carotid arteries and serum cytokine levels were measured in stroke-free participants. The mean of the maximum IMT in bilateral bifurcation, common and internal carotid artery segments was measured. Serum levels of interleukin (IL)-1beta, IL-2, IL-6, C-reactive protein, tumor necrosis factor (TNF) alpha and TNF receptors were measured using enzyme-linked immunosorbent assay. Results: IL-2 levels were significantly correlated with IMT (r = 0.33, P < 0.0001), but other cytokines were not. Each unit increase in IL-2 was significantly associated with a mean increase in IMT of 0.18 mm (P = 0.0001). After adjusting for other atherosclerotic risk factors, the association was unchanged (mean increase in IMT per unit increase IL-2 = 0.18 mm, P < 0.0001). Each standard deviation increase in the level of IL-2 was associated with an increased risk (adjusted odds ratio 1.80, 95% CI 1.12-2.89) for an IMT ≥ 1.0 mm (75th percentile for IMT). Conclusion: Serum levels of IL-2, a pro-inflammatory cytokine, are associated with carotid artery IMT, a predictor of stroke and vascular disease. Serum inflammatory markers may provide a novel marker of atherosclerotic risk, and inflammation may provide a new therapeutic target for stroke prevention.