[Interrelationship between the structure of IGG and its FC-fragment and their ability to react with protein A of Staphylococcus aureus].

7S monomeric form of rabbit IgG, their dimers, IgG with the reduced interheavychain disulfide bond and proteolytic cleaved fragments from rabbit IgG were tested by hemagglutination inhibition test for their ability to bind staphylococcal protein A (SPA). SPA was found to combine with monomers of IgG and their papain Fc fragment. Facb, F(ab')2, Fab and pFc' fragments failed to react with SPA. At molar level Fc fragment retained 15% of IgG binding activity of SPA. After cleavage of the interheavychain disulfide bond of the IgG molecule its ability to react with SPA decreased 3-fold. As a result of spontaneous dimerization the IgG binding activity of SPA increased twelve-fold. The evidence obtained suggests an interrelationship between the IgG Fc fragment structure and its ability to interact with protein A is discussed.