These findings suggest that graft-infiltrating PD-L1 CD-DCs may play a key role in the regulation of alloimmunity and in the induction of liver transplant tolerance. (Hepatology 2018;67:1499-1515).
Systemic administration of autologous regulatory dendritic cells (DCreg; unpulsed or pulsed with donor antigen [Ag]), prolongs allograft survival and promotes transplant tolerance in rodents. Here, we demonstrate that nonhuman primate (NHP) monocyte-derived DCreg pre-loaded with cell membrane vesicles from allogeneic PBMC, induce T cell hyporesponsiveness to donor alloAg in vitro. These donor alloAg-pulsed autologous DCreg (1.4–3.6 x 106/kg) were administered intravenously, one day before MHC-mismatched renal transplantation to rhesus monkeys treated with costimulation blockade (cytotoxic T lymphocyte Ag 4 [CTLA4] Ig) and tapered rapamycin. Prolongation of graft median survival time from 39.5 days (no DCreg infusion; n=6 historical controls) and 29 days with control unpulsed DCreg (n=2), to 56 days with donor Ag-pulsed DCreg (n=5), was associated with evidence of modulated host CD4+ and CD8+ T cell responses to donor Ag and attenuation of systemic IL-17 production. Circulating anti-donor antibody (Ab) was not detected until CTLA4Ig withdrawal. One monkey treated with donor Ag-pulsed DCreg rejected its graft in association with progressively elevated anti-donor Ab, 525 days post-transplant (160 days after withdrawal of immunosuppression). These findings indicate a modest but not statistically significant beneficial effect of donor Ag-pulsed autologous DCreg infusion on NHP graft survival when administered with a minimal immunosuppressive drug regimen.
Orthotopic liver transplantation in the mouse is a powerful research tool that has led to important mechanistic insights into the regulation of hepatic injury, liver immunopathology, and transplant tolerance. However, it is a technically demanding surgical procedure. Setup of the orthotopic liver transplantation model comprises three main stages: surgery on the donor mouse; back-table preparation of the liver graft; and transplant of the liver into the recipient mouse. In this protocol, we describe our procedure in stepwise detail to allow efficient completion of both the donor and recipient operations. The protocol can result in consistently high technical success rates when performed by personnel experienced in the protocol. The technique can be completed in ∼2-3 h when performed by an individual who is well practiced in performing mouse transplantation in accordance with this protocol. We have achieved a perioperative survival rate close to 100%.
Liver interstitial dendritic cells (DCs) have been implicated in the control of ischemia–reperfusion injury (IRI) and host immune responses following liver transplantation. Mechanisms underlying these regulatory functions of hepatic DCs remain unclear. We have shown recently that the transmembrane immunoadaptor DNAX‐activating protein of 12 kDa (DAP12) negatively regulates mouse liver DC maturation and proinflammatory and immune stimulatory functions. Here, we used PCR analysis and flow cytometry to characterize expression of DAP12 and its associated triggering receptor, triggering receptor expressed on myeloid cells 2 (TREM2), by mouse and human liver DCs and other immune cells compared with DCs in other tissues. We also examined the roles of DAP12 and TREM2 and their expression by liver DCs in the regulation of liver IRI. Injury was induced in DAP12–/–, TREM2–/–, or wild‐type (WT) mice by 1 hour of 70% clamping and quantified following 6 hours of reperfusion. Both DAP12 and TREM2 were coexpressed at comparatively high levels by liver DCs. Mouse liver DCs lacking DAP12 or TREM2 displayed enhanced levels of nuclear factor κB and costimulatory molecule expression. Unlike normal WT liver DCs, DAP12–/– liver DC failed to inhibit proliferative responses of activated T cells. In vivo, DAP12–/– and TREM2–/– mice exhibited enhanced IRI accompanied by augmented liver DC activation. Elevated alanine aminotransferase levels and tissue injury were markedly reduced by infusion of WT but not DAP12–/– DC. Conclusion: Our data reveal a close association between DAP12 and TREM2 expression by liver DC and suggest that, by negatively regulating liver DC stimulatory function, DAP12 promotes their control of hepatic inflammatory responses; the DAP12/TREM2 signaling complex may represent a therapeutic target for control of acute liver injury/liver inflammatory disorders.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.