title: Imaging Tolerance Induction in the Classic Medawar Neonatal Mouse Model: Active Roles of Multiple F1-Donor Cell Types.
abstract: The immature immune system is uniquely susceptible to tolerance induction and thus an attractive target for immunomodulation strategies for organ transplantation. Newborn mice injected with adult semi-allogeneic lymphohematopoietic cells accept transplants without immunosuppressive drugs. Early in vivo/in situ events leading to neonatal tolerance remain poorly understood. Here, we show by whole body/organ imaging that injected cells home to lymphoid organs and liver where various F1-donor cell types selectively alter neonatal immunity. In host thymus, F1-donor dendritic cells (DC) interact with developing thymocytes and regulatory T cells suggesting a role in negative selection. In spleen and lymph nodes, F1-donor regulatory T/B cells associate with host alloreactive cells and by themselves prolong cardiac allograft survival. In liver, F1-donor cells give rise to albumin-containing hepatocyte-like cells. The neonatal immune system is lymphopenic, Th-2 immunodeviated and contains immature DC, suggesting susceptibility to regulation by adult F1-donor cells. CD8a T cell inactivation greatly enhances chimerism, suggesting that variable emerging neonatal alloreactivity becomes a barrier to tolerance induction. This comprehensive qualitative imaging study systematically shows contribution of multiple in vivo processes leading simultaneously to robust tolerance. These insights into robust tolerance induction have important implications for development of strategies for clinical application.
authors.affiliation: Departments of Pediatrics, Surgery and Medical Microbiology/Immunology, Alberta Transplant Institute, University of Alberta, Edmonton, Canada.
authors.forename: R A
authors.initials: RA
authors.lastname: Bascom
authors.affiliation: Departments of Pediatrics, Surgery and Medical Microbiology/Immunology, Alberta Transplant Institute, University of Alberta, Edmonton, Canada.
authors.forename: K S
authors.initials: KS
authors.lastname: Tao
authors.affiliation: Departments of Pediatrics, Surgery and Medical Microbiology/Immunology, Alberta Transplant Institute, University of Alberta, Edmonton, Canada.
authors.forename: S L
authors.initials: SL
authors.lastname: Tollenaar
authors.affiliation: Departments of Pediatrics, Surgery and Medical Microbiology/Immunology, Alberta Transplant Institute, University of Alberta, Edmonton, Canada.
authors.forename: L J
authors.initials: LJ
authors.lastname: West
mesh_terms: D064591:Allografts; D000818:Animals; D000831:Animals, Newborn; D001402:B-Lymphocytes / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D020285:Cryoelectron Microscopy; D003713:Dendritic Cells / Q000276:immunology*; D006085:Graft Survival / Q000276:immunology; D016027:Heart Transplantation; D006789:Host vs Graft Reaction / Q000276:immunology*; D007108:Immune Tolerance / Q000276:immunology*; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D013154:Spleen / Q000276:immunology / Q000637:transplantation*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D060168:Thymocytes / Q000276:immunology; D014019:Tissue Donors
keywords: animal models: murine; tolerance: experimental; tolerance: mechanisms