Background and Objec-tives Autoimmune reaction may play an importantrole in the pathogenesis and progress in virus my-oearditis. Dendritic cells are the initiators of immunereaction to foreign antigens and are considered to be keyplayers in the induction and maintenance of autoim-mune reactions. This study was undertaken to investi-gate the role of DC in mice with virus myocarditis.Methods and Results Fifty Balb/c mice were in-jected Coxsackie B3 virus to induce myocarditis and tenmice were injected culture liquid as control group. Thehearts of virus - infected mice were harvested on day 3,7, 14, 28 after the injection. All the hearts were slicedto do HE staining, MHC II antigen and S - 100 proteinimmunohistochemical staining. The inflammation re-sponse and expression of MHC II antigen and S- 100protein positive stained cells were observed. The MHCII antigen positive score were 1.42 ± 0.95, 2.24 1.00, 3.23 ± 1.16, 2.58 ± 1.05 respectively in group3 d, 7 d, 14 d, 28 d, which were significant differentfrom control group(0.50 ±0.75, P ＜0.05). The S -100 positive staining cells in control group was 3.2±1.0. And the numbers were 6.7+1.4, 16.4±2.5 ,21.2±3.3 , 13.4±2.3 respectively in group 3 d, 7d, 14 d, 28 d, and there were significant differencescompared with the control group ( P ＜ 0.01) . Con-clusions Immune reaction was involved in thepathogenesis in Coxsackie B3 virus-induced my-oearditis in mouse, and dendritic cell might play animportant role in the immune reaction.