title: Antigen-pulsed, interleukin-4-treated B cells activate primed T cells in vitro but not naive T cells in vivo.
abstract: The ability of B cells to act as effective antigen-presenting cells is a source of debate which centres on the degree of activation of either B cells or T cells. We have investigated whether B cells treated with interleukin 4 (IL-4) can express the two signals required to activate T cells: MHC Class 2/antigenic peptide complexes(signal 1) and the costimulatory molecules B7-1 and B7-2 (signal 2). We have also determined whether these cells could activate antigen-experienced T cells in vitro and whether they could prime naive T cells in vivo. We found that B cells expressed abundant MHC Class 2 molecules and moderate levels of B7-2 after 24 h culture in IL-4 with or without purified protein derivative (PPD) but B7-1 was not detectable. PPD-pulsed, IL-4 treated B cells induced antigen-experienced T cells to proliferate in vitro but these cells failed to prime naive T cells in vivo when injected into mice. We conclude that signals, in addition to those induced with IL-4, are required for B cells to initiate an immune response to antigen.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D018122:B7-1 Antigen / Q000378:metabolism; D002478:Cells, Cultured; D000949:Histocompatibility Antigens Class II / Q000378:metabolism; D015847:Interleukin-4 / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D009163:Mycobacterium bovis / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*; D014373:Tuberculin / Q000276:immunology
chemical_list: D018122:B7-1 Antigen; D000949:Histocompatibility Antigens Class II; D014373:Tuberculin; D015847:Interleukin-4