Interaction between streptococcal IgG Fc receptors and human and rabbit IgG domains.
Groups A, C and G streptococci were tested for their ability to bind 125I-labelled fragments of human and rabbit IgG in order to localize their sites of interaction with IgG domains. Among the Group A streptococci, strains with IgG Fc receptors bound 85% of the added IgG Fc fragments in the test systems, whereas these strains showed practically no reactivity with F(ab')2, Facb (F(ab')2 + C gamma 2 domains) or pFc' (C gamma 3 domains). The Group C and Group G strains bound 48-100% of IgG Fc, but could also bind up to 36% of the added F(ab')2 in accordance with a previously described 'alternative' Fab reactivity. However, unlabelled IgG F(ab')2 or Facb showed no, or only slight, inhibitory capacity for the binding of 125I-labelled IgG Fc to the C and G strains. Collectively, these results indicate that Groups A, C and G streptococci require both the C gamma 2 and C gamma 3 domains for interaction with IgG, and most probably also bind in the interface region between the C gamma 2 and C gamma 3 domains as has been shown for staphylococcal protein A.
D000818:Animals; D001666:Binding Sites, Antibody; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D007141:Immunoglobulin Fc Fragments / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology*; D011817:Rabbits; D011961:Receptors, Fc / Q000276:immunology*; D013211:Staphylococcus aureus / Q000276:immunology; D013291:Streptococcus / Q000276:immunology*; D013297:Streptococcus pyogenes / Q000276:immunology
D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D011961:Receptors, Fc; C041323:immunoglobulin Facb fragment