Open AccessPrevalence of IgA receptors in clinical isolates of Streptococcus pyogenes and Streptococcus agalactiae ; Serologic distinction between the receptors by blocking antibodies
Author(s) -
Schalén Claes
Publication year - 1993
Publication title -
fems immunology & medical microbiology
Language(s) - English
Resource type - Journals
eISSN - 1574-695X
pISSN - 0928-8244
DOI - 10.1111/j.1574-695x.1993.tb00379.x
Subject(s) - streptococcus agalactiae , microbiology and biotechnology , biology , serotype , streptococcus pyogenes , epitope , streptococcus , group a , antibody , serology , immunoglobulin a , immune system , myeloma protein , receptor , streptococcaceae , immunoglobulin g , virology , immunology , bacteria , staphylococcus aureus , antibiotics , medicine , biochemistry , genetics
Group A and B streptococci ( Streptococcus pyogenes and Streptococcus agalactiae ) are the only known bacterial pathogens expressing IgA Fc‐receptors. However, the IgA binding proteins of the two species have been found genetically unrelated. In the present investigation the binding of human IgA among clinical isolates of group A and group B streptococci was studied and the respective IgA‐binding epitopes were compared serologically. Surface binding of radiolabelled, monoclonal human IgA1 occurred in 38% of 115 unselected group A streptococcal isolates. Comparing four predominant T‐types, IgA‐binding was found in 77% and 85%, respectively, of types T4 and T28 strains but only in 5% and 25%, respectively, of T1 and T12 strains. In group B streptococci, 70% of 58 type Ib strains but only 2% of 399 strains of other serotypes bound IgA. Using rabbit immune sera raised to the two streptococcal species it was found that strains exhibiting IgA Fc‐receptors often induced antibodies blocking the binding of IgA to bacteria. Furthermore, the blocking shown by an individual serum was restricted to the streptococcal group used for immunization showing that also the IgA‐binding epitopes in group A and B streptococci are conformationally distinct. Though infections with serotypes often binding IgA, compared to other types, are not known to differ, it is assumed that the non‐immune binding of IgA might favour mucosal colonization of the organisms.