title: Effect of protein A on staphylococcal opsonization.
abstract: To study the effect of wall protein A on bacterial opsonization, phagocytosis of 10 strains of Staphylococcus aureus with high and low protein A contents was measured. Those strains that contained the highest concentrations of protein A were phagocytized by human neutrophils at a slower rate than strains with little or no protein A when normal human serum and purified immunoglobulin G (IgG) were used as opsonic sources. When IgG-deficient serum was used as an source, however, protein A-rich strains were phagocytized more rapidly than protein A-deficient strains. Extracellular (purified) protein A decrease the opsonic activity of all sera tested including IgG-deficient serum. It is proposed that when IgG is not present in the opsonic medium, cell wall protein A is capable of activating complement at the bacterial surface and thereby opsonization is promoted.
mesh_terms: D001426:Bacterial Proteins; D002473:Cell Wall; D003165:Complement System Proteins; D006801:Humans; D007962:Leukocytes / Q000276:immunology; D010587:Phagocytosis; D013211:Staphylococcus aureus / Q000276:immunology*
chemical_list: D001426:Bacterial Proteins; D003165:Complement System Proteins