Mitogen and muscle extract induced in vitro proliferative responses in myasthenia gravis, dermatomyositis, and polymyositis.

We have compared the lymphocyte in vitro proliferative response induced by muscle extract, phytohaemagglutinin, and pokeweed mitogen in peripheral blood lymphocytes of patients with myasthenia gravis, polymyositis, dermatomyositis, and normal subjects. Similar mean responses to antigen and mitogen were seen in cells of all groups of patients. The proliferative responses induced by muscle did not differ in thymic cells from myasthenics as compared with those from cardiac surgery controls. Our findings do not support the hypothesis that cell-mediated immunity to muscle or major impairment of lymphocyte responses to mitogens occurs in these diseases.