title: Cross-protective antigens of group A streptococci types 3 and 31 and types 46 and 51.
abstract: Reciprocal cross-protective antigens have been demonstrated between types 3 and 31 cocci, and one-way cross-protective antigens have been demonstrated between types 46 and 51 cocci. The reciprocal cross-protective antigen of types 3 and 31 is distinct from the specific M protein of either type. In the one-way cross relationship, type 46 cocci contain both type 46 and type 51 M proteins and therefore stimulate protective antibodies against both types. Type 51 cultures contain only the homologous M antigen. These relationships were demonstrated by capillary precipitin tests, indirect bactericidal tests, and in agar-gel diffusion patterns. The practical significance of these relationships in the serological typing of group A streptococci is discussed along with their possible role in immunity to streptococcal infections in man.
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D003429:Cross Reactions; D007106:Immune Sera; D005779:Immunodiffusion; D011233:Precipitin Tests; D011817:Rabbits / Q000276:immunology; D013291:Streptococcus / Q000276:immunology*
chemical_list: D000942:Antigens, Bacterial; D007106:Immune Sera