DAP12 Deficiency in Liver Allografts Enhances Donor DC Migration, Host Alloimmunity and Breaks Liver Transplant Tolerance
Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA
Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA
Meeting: 2013 American Transplant Congress
Abstract number: 424
Background: Fully MHC-mismatched mouse liver allografts are accepted without immunosuppressive therapy and induce donor-specific tolerance. Liver dendritic cells (DC) exhibit an immature phenotype that may contribute to immune regulation and the induction of tolerance after liver transplantation. DAP12 is a transmembrane protein that integrates activating or inhibiting signals through associated co-receptors. We have shown previously that DAP12 regulates liver DC maturation and that DAP12-deficient liver DC have enhanced T cell allostimulatory properties. We hypothesized that DAP12-deficient donor liver DC might induce stronger allogeneic immune responses and break liver allograft tolerance.
METHODS: 10-12 week-old male B6 WT or DAP12 KO (B6 background) livers were transplanted orthotopically into normal 10-12 week-old male C3H mice. Graft rejection was assessed by host survival and confirmed histologically. Donor-derived DC (H2-Kb+CD11c+) in the spleen and CD8+IFN-Γ+ T cells in the graft were quantified by flow cytometry. Cytokine expression in the graft were determined by RT-PCR. Anti-donor T cell proliferative responses were evaluated by CFSE-MLR, while IFN-Γ secretion in MLR supernatants was measured by cytometric bead array.
RESULTS: Unlike WT grafts, DAP12 KO livers failed to induce tolerance and were rejected (MST: WT: 75d vs DAP12 KO 12.5d; p<0.01). A greater incidence of donor-derived DC was detected in the spleens of DAP12 KO liver recipients compared with those given WT livers on day 1 post transplant (WT: 1.76±0.25% vs DAP12 KO: 5.67±1.18% of bulk CD11c+ cells; p<0.01). Moreover, IFN-Γ gene expression in the liver was significantly higher in DAP12 KO liver allografts (WT: 365±20-fold increase vs DAP12 KO: 425±23-fold increase; p<0.05) and the intensity of IFN-Γ expression by CD8 T+ cells was significantly higher in DAP12 KO liver allografts (WT: 288±38 MFI vs DAP12 KO: 932±22 MFI; p<0.05). Splenocytes from DAP12 KO liver recipients also showed greater proliferation against T cell-depleted donor splenocytes. Moreover, IFN-Γ secretion by responder T cells was higher for the DAP12 KO liver-grafted mice (WT: 145±29 pg/ml vs DAP12: 259±15 pg/ml; p<0.05).
CONCLUSIONS: DAP12 expression in donor livers appears to regulate the migration of donor DCs to host lymphoid tissue, the consequent alloimmune and transplant tolerance.
To cite this abstract in AMA style:
Yoshida O, Kimura S, Murase N, Thomson A. DAP12 Deficiency in Liver Allografts Enhances Donor DC Migration, Host Alloimmunity and Breaks Liver Transplant Tolerance [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/dap12-deficiency-in-liver-allografts-enhances-donor-dc-migration-host-alloimmunity-and-breaks-liver-transplant-tolerance/. Accessed December 11, 2024.« Back to 2013 American Transplant Congress