Modulation of IgG effector functions by a monovalent fragment of staphylococcal protein A.
The monovalent V-1 fragment of protein A (fSpA) with a mol. wt of 13,000 obtained from an u.v. mutant of Staphylococcus aureus Cowan I strain was proved to be able to modulate significantly some of the effector functions of IgG, such as complement fixation, catabolism, attachment to Fc receptors and antibody-dependent cell-mediated cytotoxicity. Moreover fSpA-like protein A obtained from the A676 strain is mitogenic and enhances NK activity of human peripheral lymphocytes. The efficiency of fSpA was found to be lower than that of protein A with regard to its ability to inhibit complement fixation, EA rosette formation and antibody-dependent cell-mediated cytotoxicity. Both protein A and fSpA had the same efficiency in activation of the complement system after reaction with human or guinea pig IgG, and in increasing the IgG catabolism. Unlike fSpA the monovalent B fragment of protein A (with mol. wt of 7000) was not able to inhibit EA rosette formation and antibody-dependent cell-mediated cytotoxicity. The results recommend fSpA, substituting for protein A, as a molecular probe for the investigation of IgG antibody and lymphocyte effector functions.
D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D000936:Antigen-Antibody Complex; D003167:Complement Activation; D003168:Complement Fixation Tests; D006168:Guinea Pigs; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology* / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology; D008213:Lymphocyte Activation; D008938:Mitosis; D011817:Rabbits; D012397:Rosette Formation; D013205:Staphylococcal Protein A / Q000276:immunology*
D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D013205:Staphylococcal Protein A