Macrophage-Bound Antigens

Abstract

Abstract The effectiveness of macrophage-bound antigens (macrophage-antigen) and soluble antigens in inducing delayed hypersensitivity (DH) and serum antibodies in syngeneic guinea pigs were compared. Peritoneal macrophages from unimmunized guinea pigs were incubated in vitro with 125-I tetanus toxoid (tet), dinitrophenylated guinea pig albumin (GPA.DNP) or dinitrophenylated ovalbumin (OA.DNP) for 60 to 90 min at 37°C. After this incubation period the cells were washed, and the quantity of 125I antigen which had been taken up determined. Then either macrophage-antigen or soluble antigen was injected into the footpads of syngeneic nonimmune guinea pigs. A single injection of macrophage-antigen induced DH demonstrable 7 or 21 days after immunization, whereas equal or higher doses of soluble antigen did not. Immunization with macrophage-antigen followed by secondary and tertiary immunizations with macrophage-antigen induced maximal DH and only minimal antibody titers. Less DH and higher titers of antibodies developed when primary immunization with macrophage-antigen was followed by secondary and tertiary immunizations with soluble antigen. Macrophage-antigen was more effective than an equal dose of soluble antigen in priming for the production of antibodies. High doses of soluble antigen with or without secondary immunization induced antibodies as effectively as macrophage-antigen boosted with a secondary immunization of soluble antigen. Our studies suggest that macrophage-antigen interaction with thymus dependent lymphocytes (T cells) leads to their activation. Such activated T cells mediate DH and also may facilitate the production of antibodies by thymus independent cells (B cells).