title: Normal B cells fail to secrete interleukin-12.
abstract: Interleukin-12 is a key regulatory cytokine produced by antigen-presenting cells (APC) which drives the development of interferon-gamma (IFN-gamma)-producing cells and promotes cell-mediated immunity. Following subcutaneous immunization with protein antigen in adjuvant, dendritic cells (DC) but not small nor large B cells in immune lymph nodes express antigenic complexes and secrete substantial amounts of bioactive IL-12 p75 upon antigen-specific interaction with T cells. We have analyzed secretion of IL-12 p40 and p75 by cell populations enriched in DC, macrophages or B cells in response to nonspecific stimulation or to interaction with antigen-specific CD4+ cells. These APC populations do not produce IL-12 constitutively but, upon stimulation with heat-fixed Staphylococcus aureus and IFN-gamma, IL-12 p40 and p75 are secreted by DC and macrophages, whereas B cells fail to produce IL-12. B cells also fail to secrete IL-12 in response to stimulation with LPS and IFN-gamma. Co-culture with CD4+ T hybridoma cells and antigen induces IL-12 secretion by DC. Up-regulation of IL-12 secretion by interaction with antigen-specific CD4+ T cells is abrogated by anti-class II monoclonal antibodies (mAb), by soluble CD40 molecules and by anti-CD40 ligand mAb, demonstrating a positive feedback between T cells and DC mediated by TCR-peptide/class II and by CD40-CD40 ligand interactions. Expression of class II and CD40 molecules is comparable in B cells and DC, and both APC types activate CD4+ T cells. Yet, even upon interaction with antigen-specific T cells, B cells fail to secrete IL-12. The capacity of B cells to present antigen but not to secrete IL-12 may explain their propensity to selectively drive T helper type 2 cell development.
authors.affiliation: Roche Milano Ricerche, Italy.
authors.forename: J C
authors.initials: JC
authors.lastname: Guéry
authors.forename: F
authors.initials: F
authors.lastname: Ria
authors.forename: F
authors.initials: F
authors.lastname: Galbiati
authors.forename: L
authors.initials: L
authors.lastname: Adorini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000942:Antigens, Bacterial / Q000494:pharmacology; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D019013:CD40 Antigens / Q000096:biosynthesis / Q000502:physiology; D002469:Cell Separation; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D000939:Epitopes / Q000502:physiology; D005260:Female; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000502:physiology; D018664:Interleukin-12 / Q000096:biosynthesis / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D008211:Lymphocyte Cooperation; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D019013:CD40 Antigens; D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D008070:Lipopolysaccharides; D018664:Interleukin-12