Lymphocyte sensitivity to skeletal muscle in patients with polymyositis and other disorders.

The transformation response of peripheral blood lymphocytes in vitro to human muscle antigen has been studied in patients with polymyositis, polymyalgia rheumatica and rheumatoid arthritis. Lymphocytes from patients with polymyositis and polymyalgia rheumatica, but not rheumatoid arthritis, showed transformation responses significantly higher than those in control groups, and the highest responses were found in patients with evidence of the most active clinical disease at the time of testing. The significance of finding hypersensitivity to crude muscle antigen in both these conditions is discussed.