AimTo investigate the relationship between dendritic cells and severe atherosclerosis (As) of coronary heart disease patients and explore the possible immune mechanisms of Simvastatin.Methods According to the results of selective coronary angiography, 20 negative control (no obvious atherosclerosis, group A)，20 severe coronary heart disease patients with severe coronary stenosis without any statins (As group, group B) and 20 severe coronary heart disease patients with severe coronary stenosis with simvastatins 40 mg daily for at least 30 days (Simvastatin group, group C).20 mL blood samples were extracted through the angiographic catheter.Density gradient centrifugation was used to separate mononuclear cells (MNC).MNC were cultured in vitro and differentiated to DC in vitro.In B2 group, 100 μmol/L Simvastatin were added on day 5. Flow cytometry was used to detect the immune characteristics of DC.Percent of CD1a+ , CD1a+CD80+, CD1a+CD83+, CD1a+CD86+ cells and the mean fluorescent intensity (MFI) were measured and recorded.ResultsAfter in vitro proliferation, mononuclear cells from coronary artery could differentiate into dendritic cells and the morphology of DC did not differ between groups; Compared with negative controls, the percent of CD1a+, CD1a+CD80+, CD1a+CD83+, CD1a+CD86+ cells, MFI, MNC number, DC number and stimulation index (SI) in group B1 were significantly increased (P<0.05); Compared with group B1, the MNC number in group B2 was