Detection of streptococcal class I M protein in psoriasis by confocal immnunofluorescent microscopy

Abstract

Epidemiological evidence implicates Streptococcus pyogenes group A) infection as a common triggering stimulus for psoriasis. Unequivocal demonstration of streptococcal antigens in psoriatic skin has been difficult due to cross-reactive antigens in both normal human tissue and group A streptococci, which complicate immunohistological analysis. In this study cryostat sections of involved psoriatic skin were stained with monoclonal antibody 111-15504 to group A streptococci. The epitope recognized by this antibody was found to be specific for group A streptococci and is associated with class I M protein. Streptococcal antigens were found in the dermal papillae and epidermis of psoriatic skin lesions of 20 out of 38 patients. These findings indicate that specific S. pyogenes antigen, associated with class I M protein, is often present in psoriatic lesions. Such an antigen, originating from focal infection elsewhere could be responsible for T- lymphocyte inflammatory responses triggering the development of psoriatic lesions.