title: In vivo activation of naive T cells by antigen-presenting B cells.
abstract: In vivo experiments were performed to determine if the cross-linking of mlg on antigen-presenting B cells could induce them to present Ag to naive T cells in a stimulatory rather than a tolerogenic fashion. Mice were injected with a foreign mAb to a B cell Ag (Fc epsilon RII or CR1), and/or a self-anti-IgD mAb. Injection of either mAb alone failed to induce an Ab response; however, simultaneous injection of the foreign anti-B cell mAb plus the self-anti-IgD mAb stimulated a large response. Inasmuch as injection of the anti-IgD mAb should not have facilitated transfer of the foreign mAb to dendritic cells, this observation suggests that cross-linking of B cell mlg can induce B cells to acquire the ability to present Ag to naive T cells in an activating manner. Furthermore, when injected with anti-IgD mAb, both foreign anti-B cell mAbs were more potent in inducing Ab responses in this system than were isotype-matched control mAbs, consistent with the hypothesis that T cells were activated by Ag-presenting B cells. Results of dose-response and cell transfer studies, however, suggested that stringent cross-linking of B cell mlg on large numbers of B cells is required for B cell Ag presentation to induce T cell activation rather than tolerance. Therefore, these observations suggest that professional APCs usually are required to activate naive T cells, and that B cell Ag presentation can only activate naive T cells under unusual circumstances.
authors.affiliation: Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
authors.forename: S C
authors.initials: SC
authors.lastname: Morris
authors.forename: A
authors.initials: A
authors.lastname: Lees
authors.forename: F D
authors.initials: FD
authors.lastname: Finkelman
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D007108:Immune Tolerance; D007072:Immunoglobulin D / Q000276:immunology; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011947:Receptors, Antigen, B-Cell / Q000276:immunology; D017463:Receptors, Complement 3b / Q000276:immunology; D017455:Receptors, IgE / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D007072:Immunoglobulin D; D011947:Receptors, Antigen, B-Cell; D017463:Receptors, Complement 3b; D017455:Receptors, IgE