CD4 and acute coronary syndrome: CD4+ CD28null T-cells from patients with acute coronary syndromes and those with at least one of atherosclerosis risk factors (hypertension, diabetes, dyslipidemia, or smoking) express higher levels of cytotoxic mediators than those with stable angina or those in a control group (although the frequencies of this population are comparable among the four groups), indicating CD4+ CD28null cells may participate in the initial phases of atherosclerosis [51].