Abstract: Objective To investigate the association between proliferative response of T cells and plaque stability in coronary heart disease. Methods A total of 66 subjects were recruited in the study, including 13 patients with acute myocardial infarction (AMI), 22 with unstable angina pectoris (UAP), 15 with stable angina pectoris (SAP) and 16 control subjects without coronary heart disease. The proliferative response of T cells to phytohemagglutinin (PHA), oxidized low-density lipoprotein (oxLDL) and low-density lipoprotein (LDL) was examined by MTS/PMS colorimetric assay. Results Significantly stronger proliferative response of T cells to PHA was noted in AMI and UAP groups than in SAP and control groups (P<0.05), as with the response to oxLDL (at doses of 5 and 1 μg/ml, P<0.05). T cell proliferative response to oxLDL (at the doses of 10, 5 and 1 μg/ml) appeared significantly stronger than that to LDL (at the same dose as oxLDL) in AMI group and UAP group (P<0.05). Conclusion Cellular immunity mediated by T cells, especially the immune response to oxLDL, may play an important role in the instability of plaque and the occurrence of acute coronary syndrome (ACS).