Cross-reactions between streptococcal M proteins and human transplantation antigens.

Allogeneic antiserums against human lymphocytes were specifically inhibited by M protein from beta hemolytic group A Streptococcus pyogenes, type 1. Analogous M proteins from streptococcus types 3, 4, 5, 6, 12, and 14 had little or no inhibitory activity. The specific inhibition by M protein is not a result of anticomplementary activity or of coating of the lymphocyte surface. Streptococcal polysaccharide and 73 other polysaccharides were inactive. Because all seven HL-A specificities tested were inhibited, it is inferred that M1 protein has a structure common to human histocompatibility antigens.