title: Characterization of the physical interaction between antigen-specific B and T cells.
abstract: It has been assumed that physical interaction between B cells and helper T cells in the presence of specific antigen is an early and essential step in the physiologic antibody response to thymus-dependent antigens. The present studies were designed to examine this physical interaction by employing carrier-specific T hybridoma cells that can provide help to highly enriched hapten-binding B cells. Direct conjugation of the B and T cells can be visualized at both the light and electron microscopic level and the number of conjugates can be directly quantified. Before their effective conjugation with T cells, the B cells must be incubated with specific antigen for 4 to 6 hr. After this time, the T cells form conjugates with the B cells within 5 min. Conjugate formation requires hapten specificity, carrier specificity, covalent linkage between hapten and carrier, and is MHC restricted. Two types of T-B conjugates were observed by electron microscopy: an antigen-independent attachment of B cell microvilli to small portions of the T cell surface and an antigen-dependent, intimate apposition of large areas of the plasma membranes of the T and B cells. The kinetics of development of the two modes of interaction suggest that the second type may be important for signal transduction, since the number of T and B cells showing intimate interactions increases with time. Monoclonal antibodies directed against Thy-1.2, LFA-1 alpha, L3T4, and I-A partially block conjugation of the two cell types, suggesting that these surface molecules are involved in T-B interaction.
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology*; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000648:ultrastructure; D002450:Cell Communication; D002460:Cell Line; D002738:Chloroquine / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic; D005260:Female; D006825:Hybridomas / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D013601:T-Lymphocytes / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology* / Q000648:ultrastructure
chemical_list: D000941:Antigens; D002738:Chloroquine