IgG-binding proteins of bacteria.

Proteins capable of non-immune binding of immunoglobulins G (IgG) of various mammalian species, i.e. without the involvement of the antigen-binding sites of the immunoglobulins, are widespread in bacteria. These proteins are located on the surface of bacterial cells and help them to evade the host's immune response due to protection against the action of complement and to decrease in phagocytosis. This review summarizes data on the structure of immunoglobulin-binding proteins (IBP) and their complexes with IgG. Common and distinctive structural features of IBPs of gram-positive bacteria (staphylococci, streptococci, peptostreptococci) are discussed. Conditions for IBP expression by bacteria and their functional heterogeneity are considered. Data on IBPs of gram-negative bacteria are presented.