Rheumatic fever and smooth muscle antibodies.

Rheumatic fever is a nonsuppurative sequelae to Group A streptococcal pharyngitis. Valvulitis resulting from cardiac involvement in this disease, is the main cause of morbidity in rheumatic fever. The study of rheumatic fever sera on cryostat sections of a variety of tissues using indirect immunofluorescence is described. A 95% incidence of smooth muscle antibody was found in 236 rheumatic fever sera, from 55 patients. Sera from hospital patients with a variety of diseases had an overall incidence of 12% for smooth muscle antibodies. The pattern and distribution of tissue staining strongly suggests that the smooth muscle antibodies described in rheumatic fever sera have antiactin specificity. This finding raises many questions concerning the immunopathogenesis and immunogenetics of rheumatic fever, and the pathogenesis of a number of diseases in which streptococci have not previously been considered.