Aim The changes of human leukocyte antigen DR (HLA DR) antigens expression on the peripheral blood T lymphocyte in patients with acute myocardial infarction were studied with flow cytometric analysis. Methods Blood samples or cultured blood samples were mixed with monoclonal antibody. Whole peripheral blood mononuclear cells were obtained from blood sampies. The mononuclear cells were incubated with fluorescein (fluorescein isothiocyanate, FITC;or phycoerythrin,PE) labeled monoclonal antibodies. The samples were analyzed with flow cytometry (FACStar) on the dual labeling. Results ①There are no significant differences between the patients with acute myocardial infarction and normal controls in CD3+ cells. The CD8+ cells and the human leukocyte antigen DR+ cells had significantly increased in patients with acute myocardial infarction. The CD4+ cells and the CD4/CD8 ratio had significantly decreased in patients with acute myocardial infarction; ②In patients with acute myocardial infarction, the percentages of CD3+DR+ cells and CD4+DR+ cells increased significantly , the CD4 DR/CD8 DR ratios were increased. ③Under the induction of phytohemagglutinin, phorbol dibutyrate or phorbol dibutyrate +ionomycin, the competence of human leukocyte antigen DR expression on CD3+ cell in patients with acute myocardial infarction are decreased significantly. The competence of human leukocyte antigen DR expression on CD8+ cell in patients with acute myocardial infarction have no difference from normal control. Conclusion There are abnormal human leukocyte antigen DR expression on T lymphocyte and its subsets in patients with acute myocardial infarction. 还原