T-cell immunity in acute coronary syndromes

Acute coronary syndromes (ACS) are complications of atherosclerotic vascula r disease that are triggered by the sudden rupture of an atheroma. Atherosc lerotic plaque stability is determined by multiple factors, of which immune and inflammatory pathways are critical. Unstable plaque is characterized b y an infiltrate of T cells and macrophages, thereby resembling a delayed hy persensitivity reaction. On activation, T cells secrete cytokines that regu late the activity of macrophages, or the T cells may differentiate into eff ector cells with tissue-damaging potential. Constitutive stimulation of T c ells and macrophages in ACS is not limited to the vascular lesion but also involves peripheral immune cells, suggesting fundamental abnormalities in h omeostatic mechanisms that control the assembly, turnover, and diversity of the immune system as a whole. This review gives particular attention to th e emergence of a specialized T-cell subset, natural killer T cells, in pati ents with ACS. Natural killer T cells have proinflammatory properties and t he capability of directly contributing to vascular injury.