Cationic proteins of human granulocytes: Enhancement of phagocytosis ofStaphylococcus protein A-IgG complexes

The antibacterial chymotrypsin-like cationic protein of human granulocytes is shown to enhance the phagocytosis ofStaphylococcus protein A-IgG complexes by human granulocytes. The enhancement is time- and dose-dependent, and it is inhibited by heat inactivation of the chymotrypsin-like cationic protein. Granulocyte elastase and trypsin give a similar enhancement. The chymotrypsin-like cationic protein-mediated enhancement is poorly inhibited byα 1-antitrypsin. There is a need for approximately 20 molα 1-antitrypsin to inhibit 1 mol chymotrypsin-like cationic protein. Elastase is effectively inhibited at a 1∶1 molar relationship. Kinetic studies suggest that phagocytosis enhancement by chymotrypsin-like cationic protein may be due to modification of the Fc-receptor with concomitantly increased affinhy of the protein A-IgG complex.