[Fc-receptor proteins of Streptococcus pyogenes and pathogenesis of post-infection complications].

Phenomenon and mechanism of non-immune binding of immunoglobulins G and A by various emm-genotypes of group A streptococcus and in particular M-family proteins--main factors of pathogenicity of this causative agent of widespread human diseases are examined. The role of these receptor proteins in pathogenesis of post-streptococcal damage of kidneys (glomerules) and heart (myocarditis) are proved. Results of long-term studies that confirm hypothesis of initiating function of Fc-receptor M proteins in genesis of immune inflammation in organ tissues that precede development of glomerulonephritis and myocarditis are provided. According to the basic position, Fc-binding of an immunoglobulin by M proteins initiates production of anti-IgG, immune complexes of various composition and complement activation, deposition of those in tissues results in lymphocyte infiltration and production of pro-inflammatory cytokines. Literature data on the role of Fc-binding proteins in genesis of IgA-nephropathies and rheumatoid factor is also examined. An important role of other factors of the microbe is discussed such as cross-reacting antigens, erythrogenic toxin B, system of streptokinase-plasmin receptor or endostreptosin in post-streptococcal processes in kidneys. Their participation in the process must be mediated by an inflammation reaction in the tissue that is initiated by interaction of immunoglobulins with Fc-binding proteins of the microbe. A novel approach to understanding the nature of this pathology allowed to establish the ability of Fc-fragments of immunoglobulin G to suppress the development of the process.