M proteins of group g streptococci: mechanisms of resistance to phagocytosis

Rafael E. Campo, Duane R. Schultz, Alan L. Bisno

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28 Scopus citations


Group G streptococci that express M protein and resist phagocytosis in human blood (virulent strains) were compared with strains of groups G and A that are readily phagocytosed (avirulent). Virulent group G streptococci were less effective (P < .05) as activators of the alternative complement pathway (ACP) than were avirulent streptococci. In immunofluorescence studies, C3 bound more avidly to avirulent than to virulent group G streptococci. Resistance of virulent group G strains to ACP opsonization and to phagocytosis was markedly diminished by removal with pepsin of the type- specific portion of the M molecule. Preincubation with fibrinogen did not diminish ACP activation or C3 binding by virulent group G and A streptococci but did exert an antiphagocytic effect. Given the similarity of M proteins of groups G and A in structure and function, other microbial constituents are likely responsible for differences in the spectra of illnesses attributable to the two serogroups.

Original languageEnglish (US)
Pages (from-to)601-606
Number of pages6
JournalJournal of Infectious Diseases
Issue number3
StatePublished - Mar 1995

ASJC Scopus subject areas

  • Immunology and Allergy
  • Infectious Diseases


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