M proteins are the major pathogenicity factors of Streptococcus pyogenes

M proteins are the major pathogenicity factors of the widespread and potentially deadly bacterial pathogen Streptococcus pyogenes. These proteins confer to bacteria resistance against innate and adaptive immune responses. The study of the M proteins of hemolytic streptococci group A and their involvement in pathology clearly indicates that strains of streptococci, for one reason or another devoid of M proteins are unable to multiply in the macroorganism and form a focus of infection. This circumstance in itself once again underlines the leading role of M proteins in the realization of its many properties and in the development of the infectious process. The ability of M proteins to recruit plasma proteins of the macroorganism is their significant pathogenetic properties. The most important is the nonimmune binding by M proteins of human immunoglobulins, because it participates in the suppression of phagocytosis, violations of bacterial opsonization and complement activation along the classical pathway, not to mention the possible involvement of this phenomenon in the genesis of post-infectious complications of autoimmune nature. This review summarizes the current data on the structure M proteins, their functional activity, manifestations of pathogenicity, genetic regulation and methods of emm-typing.