Phagocytosis inhibits the production of C2 by human monocytes

Production of the second complement component by cultured human monocytes was suppressed by the addition of a variety of phagocytosable particles. The degree of suppression was related to the concentration of particles, but was unrelated to particle size, the presence of surface sialic acid, antibody or C3b. The failure to reverse suppression by prostaglandin synthetase inhibitors indicates that it is not mediated by prostaglandins.