title: The role of cytophilic IgG3 antibody in T cell-mediated resistance to infection with the extracellular bacterium, Pseudomonas aeruginosa.
abstract: Previous studies have demonstrated that T lymphocytes from mice immunized with a high m.w. polysaccharide Ag from Fisher-Devlin immunotype I Pseudomonas aeruginosa can adoptively transfer protection against challenge with the homologous bacterial strain to susceptible mice. This T cell-mediated resistance has been found to be B cell dependent, although serum from immunized mice is incapable of passively transferring protection to nonimmune mice. The current studies demonstrate that T cells from immunized mice possess receptors that permit them to be adsorbed to IgG3-secreting hybridomas, but not to IgM-secreting hybridomas. Cross-linking of antibody on the surface of immune T cells results in release of a soluble factor that inhibits bacterial growth. Treatment of T cells to remove cytophilic antibody eliminates their ability to adoptively transfer protection to nonimmune mice, and the protective ability can be restored by co-incubating the T cells with monoclonal P. aeruginosa-specific IgG3 antibody before adoptive transfer to nonimmune mice. These observations are consistent with a model in which T lymphocytes from immunized mice are activated by cross-linking of FcR for IgG3 to secrete an antibacterial lymphokine. The ability of IgG3 at low antibody concentrations to act synergistically with T lymphocytes to inhibit bacterial growth could explain the evolutionary selection of this antibody isotype as the predominant subclass of IgG secreted in response to bacterial capsular polysaccharide Ag.
authors.affiliation: Department of Immunology and Infectious Diseases, Johns Hopkins Medical Institutions, Baltimore, MD 21205.
authors.forename: R B
authors.initials: RB
authors.lastname: Markham
authors.forename: G B
authors.initials: GB
authors.lastname: Pier
authors.forename: J R
authors.initials: JR
authors.lastname: Schreiber
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D007111:Immunity, Cellular; D007116:Immunization, Passive; D007074:Immunoglobulin G / Q000276:immunology*; D008222:Lymphokines / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D011135:Polysaccharides, Bacterial / Q000276:immunology; D011552:Pseudomonas Infections / Q000276:immunology*; D011550:Pseudomonas aeruginosa / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D007074:Immunoglobulin G; D008222:Lymphokines; D011135:Polysaccharides, Bacterial