title: Antigen presentation by hapten-specific B lymphocytes. V. Requirements for activation of antigen-presenting B cells.
abstract: Splenic B cells specific for the haptens, 2,4,6-trinitrophenyl (TNP) or fluorescein isothiocyanate (FITC) were cultured with a range of concentrations of unmodified or TNP- or FITC-conjugated conalbumin and the conalbumin + I-Ak-specific, interleukin (IL) 1-dependent helper T cell clone, D10 . G4, in the presence and absence of IL-1. Lymphokine secretion, T cell proliferation, and antibody secretion by B cells all exhibited identical antigen dose responses. Thus, hapten-binding B cells presented low concentrations of haptenated conalbumin for activation of both the T and the antigen-presenting B cells. Whereas proliferation of D10 . G4 required the addition of IL-1, both lymphokine production and stimulation of B cells to antibody secretion occurred without exogenous IL-1. These results demonstrate that when B lymphocytes function as presenting cells for antigens that bind to their immunoglobulin receptors, activation of the responding T cells and the B cells themselves occur at similar concentrations of antigen. Moreover, for functional T-B interactions, antigen-presenting B and responding T lymphocytes constitute a complete system that requires no other accessory stimuli, whereas clonal expansion of T cells is dependent on accessory factors such as IL-1. Finally, since D10 . G4 secretes IL-4 but neither IL-2 nor interferon-gamma, our results demonstrate that differentiation of B cells as a consequence of direct ("cognate") interactions with helper T cells as well as of bystander B cells can occur in the absence of IL-1, IL-2, and interferon-gamma.
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D003207:Conalbumin / Q000276:immunology; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins / Q000276:immunology; D006241:Haptens; D007375:Interleukin-1 / Q000502:physiology; D015847:Interleukin-4; D007378:Interleukins / Q000502:physiology; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008222:Lymphokines / Q000502:physiology; D051379:Mice; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology; D013861:Thiocyanates / Q000276:immunology; D014301:Trinitrobenzenes / Q000276:immunology
chemical_list: D005452:Fluoresceins; D006241:Haptens; D007375:Interleukin-1; D007378:Interleukins; D008222:Lymphokines; D013861:Thiocyanates; D014301:Trinitrobenzenes; D003207:Conalbumin; D015847:Interleukin-4; D016650:Fluorescein-5-isothiocyanate