T cell-mediated immune mechanisms in myositis.

Advances in molecular biologic techniques and the availability of novel immunologic reagents have allowed new approaches to understanding the pathogenesis of human autoimmune diseases, including the idiopathic inflammatory myopathies. Indirect evidence that autoreactive T cells mediate muscle inflammation in the human myositis syndromes has been strengthened by recent studies describing restricted T cell receptor gene expression in certain clinical and/or serologic groups of myositis patients. These findings are supported by other investigations documenting abnormal patterns of cytokine, adhesion molecule, and major histocompatibility complex antigen expression within inflammatory lesions. The major challenge of future studies is to identify the specific antigen(s) responsible for initiating and perpetuating these harmful immune responses.