@article{mbs:/content/journal/jmm/10.1099/00222615-9-1-73, author = "Widdowson, Jean P. and Maxted, W. R. and Pinney, Alison M.", title = "Immunological heterogeneity among the massociated protein antigens of group-A streptococci", journal= "Journal of Medical Microbiology", year = "1976", volume = "9", number = "1", pages = "73-88", doi = "https://doi.org/10.1099/00222615-9-1-73", url = "https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-9-1-73", publisher = "Microbiology Society", issn = "1473-5644", type = "Journal Article", abstract = "Summary 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.", }