title: Immunological heterogeneity among the M-associated protein antigens of group-A streptococci.
abstract: Different serotypes of group-A streptococci share common antigens that are closely associated with the type-specific determinant of M protein. By the use of selected human sera containing antibody to these M-associated antigens, we have shown that group-A streptococci can be divided into three categories. The majority of the opacity-factor-negative respiratory serotypes possess a shared M-associated antigen or antigens, to which high titres of antibody are common in patients with rheumatic fever, or patients recovering from upper respiratory infections with certain opacity-factor-negative serotypes. The antibody in these sera has a demonstrable but limited affinity for the M-associated antigens of strains belonging to a second category of M types, the majority of which are opacity-factor-positive serotypes of "throat" or "skin" origin. A third group, consisting mainly of opacity-factor-negative pyoderma serotypes, gave variable results and seemed to be intermediate between the other two categories. Complement-fixation-inhibition tests and absorption studies showed a marked degree of cross-reactivity between the M-associated antigens of the three categories.
mesh_terms: D000208:Acute Disease; D000907:Antibodies, Bacterial / Q000032:analysis; D000942:Antigens, Bacterial / Q000032:analysis*; D001426:Bacterial Proteins / Q000276:immunology*; D003429:Cross Reactions; D000939:Epitopes; D005921:Glomerulonephritis / Q000276:immunology; D006801:Humans; D007169:Impetigo / Q000276:immunology; D010612:Pharyngitis / Q000276:immunology; D012213:Rheumatic Fever / Q000276:immunology; D012703:Serotyping; D013290:Streptococcal Infections / Q000276:immunology; D013291:Streptococcus / Q000145:classification / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D000939:Epitopes