RESUMO
Objective The aim of our study is to establish and characterize the animal model for au- toimmune myositis.Methods Fifty male SD rats were randomly divided into 2 groups:model group(n=40) and control group(n=10).The model group rats were immunized with muscle homogenate every week for 5 weeks and received an injection of 2?g pertussis toxin at the first and second week.As controls,10 SD rats were injected with an equal volume of normal saline.Tissue specimens from limb skeletal muscles were ob- tained at 1,2,3,4,5 weeks after injection.At the same time,the blood samples were collected,and the level of CPK was measured.Results The model group had significantly elevated serum CPK levels.There were multiple inflammatory lesions in the skeletal muscles.Local degeneration and necrosis of muscle fibers with disappeared transverse striation,mononuelear cell infiltration in the interstitial could be observed.The patho- logic grade was mainly 2a.The infiltrating mononuclear cells were predominantly CD8~+T cells that mainly lo- cated in the endnmysium.MHC classⅠantigen expression on muscle fiber membranes in the model group was upregulated.Conclusion The experimental autoimmune myositis induced by syngeneic skeletal muscle ho- mogenate in SD rat is pathologically similar to human myositis.It can be used as a good model for human myositis and provides the basis for the etiopathology and therapeutical studies.