title: Role of IL-12 in intrathymic negative selection.
abstract: Cytokines are central regulatory elements in peripheral lymphocyte differentiation, but their role in T cell ontogeny is poorly defined. In the present study, we evaluated the role of IL-12 in thymocyte selection more directly by determining its role in two models of in vivo negative selection. In initial studies we demonstrated that abundant intrathymic IL-12 synthesis occurs during OVA peptide-induced negative selection of thymocytes in neonatal OVA-TCR transgenic mice, and such synthesis is associated with increased IL-12R beta2-chain expression as well as STAT4 intracellular signaling. In further studies, we showed that this form of negative selection was occurring at the alphabetaTCRlowCD4lowCD8low stage and was prevented by the coadministration of anti-IL-12. In addition, the IL-12-dependent thymocyte depletion was occurring through an intrathymic apoptosis mechanism, also prevented by administration of anti-IL-12. Finally, we showed that IL-12 p40-/- mice displayed aberrant negative selection of double positive CD4+CD8+ thymocytes when injected with anti-CD3 mAb. These studies suggest that intact intrathymic IL-12 production is necessary for the negative selection of thymocytes occurring in relation to a high "self" Ag load, possible through its ability to induce the thymocyte maturation and cytokine production necessary for such selection.
authors.affiliation: Mucosal Immunity Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA. Bludviksson@atlas.niaid.nih.gov
authors.forename: B R
authors.initials: BR
authors.lastname: Lúdvíksson
authors.forename: R O
authors.initials: RO
authors.lastname: Ehrhardt
authors.forename: W
authors.initials: W
authors.lastname: Strober
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000276:immunology; D000941:Antigens / Q000008:administration & dosage / Q000276:immunology; D017209:Apoptosis / Q000276:immunology; D015704:CD4 Antigens / Q000096:biosynthesis; D016827:CD8 Antigens / Q000096:biosynthesis; D002454:Cell Differentiation / Q000276:immunology; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D007106:Immune Sera / Q000008:administration & dosage / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D018664:Interleukin-12 / Q000096:biosynthesis / Q000276:immunology / Q000502:physiology*; D008212:Lymphocyte Depletion; D008231:Lymphopenia / Q000276:immunology / Q000517:prevention & control; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D010446:Peptide Fragments / Q000008:administration & dosage / Q000276:immunology; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000235:genetics; D018123:Receptors, Interleukin / Q000096:biosynthesis; D053707:Receptors, Interleukin-12; D050797:STAT4 Transcription Factor; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D000941:Antigens; D015704:CD4 Antigens; D016827:CD8 Antigens; D004268:DNA-Binding Proteins; C508443:Il12rb2 protein, mouse; D007106:Immune Sera; D010446:Peptide Fragments; D011948:Receptors, Antigen, T-Cell; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D050797:STAT4 Transcription Factor; C494091:Stat4 protein, mouse; D015534:Trans-Activators; D018664:Interleukin-12; D010047:Ovalbumin