Expression of myositis specific autoantigens during post-natal myogenesis.

Idiopathic inflammatory myopathies such as polymyositis (PM) and dermatomyositis (DM) are a group of rare autoimmune diseases, characterized by an inflammatory infiltrate within the skeletal muscle and high titer of circulating autoantibodies in the patient's serum. The etiopathogenesis of these diseases is not known and the relationship between the specific muscle involvement and the ubiquitary presence of the targeted antigens is still unclear. The enhanced expression of myositis specific autoantigens in regenerating muscle fibers from biopsies of PM and DM patients compared to normal muscle has been recently demonstrated. In order to understand whether candidate autoantigens in myositis are expressed during post-natal myogenesis, we performed immunolocalization studies of myositis specific autoantigens in skeletal muscle from newborn and adult rats. Our observations indicate the presence of myositis specific autoantigens during post-natal myogenesis, with possible implications for the induction and/or amplification of the immune-inflammatory response, in patients affected with autoimmune myositis.