Autoantibodies in infections of the respiratory tract with Mycoplasma pneumoniae or influenza virus A.

The sera from 26 patients with serological evidence of infection with Mycoplasma pneumoniae and 23 patients with influenza virus A infection were examined for autoantibodies to smooth muscle, cell nuclei and 'reticulin'. There is an increased incidence of autoantibodies to smooth muscle (46%) in the serum of patients infected with M. pneumoniae. There is no increase in autoantibodies to cell nuclei or 'reticulin' in these patients. There is no increased incidence of autoantibodies in patients infected with influenza virus A. The possible aetiology of the raised incidence of smooth muscle autoantibodies in the patients with M. pneumoniae is discussed.