Antigenic diversity of IgA receptors in Streptococcus pyogenes

• Published in: FEMS immunology and medical microbiology 1993-06, Vol.7 (1), p.47-54
• Main Authors: Burova, Larissa A., Schalén, Claes
• Format: Article
• Language: English
• Subjects: Animals; Fc‐receptor; IgA; Immune Sera - immunology; Immunoglobulin A - metabolism; Molecular Weight; Rabbits; Receptors, Fc; Receptors, Immunologic - analysis; Receptors, Immunologic - immunology; Streptococcus pyogenes; Streptococcus pyogenes - immunology
• ISSN: 0928-8244; 1574-695X
• DOI: 10.1111/j.1574-695X.1993.tb00380.x

In a previous study, group A and group B streptococcal IgA receptors were shown to differ serologically, in agreement with their known structural unrelatedness. The present study was undertaken to serologically compare the IgA binding epitopes of group A streptococcal strains representing various serotypes by the use of antisera to this species. It was found that blocking antibodies occurred in antisera to IgA binding but not to non‐binding strains and that binding of IgA to a streptococcal strain was generally blocked by antiserum to the homologous type. However, cross‐testing of a panel of 11 IgA binding strains, representing various M and T serotypes, with 10 different antisera to group A streptococci, demonstrated that IgA receptors were inhibited to a highly variable degree and that inhibition patterns were unique for each type. Comparing solubilized IgA receptors of various strains in immunoblot experiments, a variation in the molecular mass, between approximately 35 and 45 kDa, emerged. The IgA binding epitopes, analogous to protective sites of streptococcal M‐protein, thus exhibited hypervariability which may suggest that IgA binding also plays a key role for evading host immune defence mechanisms.