RESUMO
Objective To establish a new murine model of experimental autoimmune myositis by immunizing with MYBPC2 protein. Methods The purified Myosin-binding protein C, fast type (MYBPC2) was emulsified with complete Freundˊs adjuvant, then C57BL/6 mice were immunized by multi-point subcutaneous injection (0, 7 days), and intraperitoneal injection of pertussis toxin 2 μg simultaneously. The pathological changes of mice with different immunizing dose at the preconceived time were ex-plored. Mean-while, mice were immunized with 600 μg each time, and the muscle endurance was tested on the 21th day. The expression of major histocompatibility complex (MHC) class-Ⅰ and the surface biomarkers of the inflammatory cells in muscle tissues were observed. Mann-Whitney U test was used for statistical analysis. Results ① With the increase of immunizing dosage, muscle damage and inflammation tended to be more serious. On the 21th and 28th day, muscle lesions were most significant. Muscle fiber degeneration and necrosis and inflammatory cell infiltration could be seen in the experimental group. ② Compared with the control group, muscle endurance of mice in the experimental group decreased significantly [(6.1 ±1.3) min versus (9.2±1.6) min, U=2.00, P=0.017]. The MHC class-Ⅰ on the muscle fiber surface of the experimental group was positive, scattered infiltration of CD4 +, CD8+ T ly-mphocytes and CD68 + macrophages between muscle fibers and around the vascular areas could be observed, and CD20+B lymphocytes mainly distributed in the area around the blood vessels, nevertheless rarely seen between muscle fibers. Conclusion Exper-imental autoimmune myositis models of mice have been successfully induced by immunizing with MYBPC2 in China for the first time, and similar clinical and pathological features of human polymyositis could be observed. This new model can be used for studying the pathogenesis of autoimmune myositis.