Autologous Dendritic Cells Prolong Allograft Survival Through Tmem176b-Dependent Antigen Cross-Presentation

Abstract

z Both authors contributed equally.x Senior authors.The administration of autologous (recipient-derived) tolerogenic dendritic cells (ATDCs) is under clinical evaluation. However, the molecular mechanisms by which these cells prolong graft survival in a donorspecific manner is unknown. Here, we tested mouse ATDCs for their therapeutic potential in a skin transplantation model. ATDC injection in combination with anti-CD3 treatment induced the accumulation of CD8 þ CD11c þ T cells and significantly prolonged allograft survival. TMEM176B is an intracellular protein expressed in ATDCs and initially identified in allograft tolerance. We show that Tmem176b À/À ATDCs completely failed to trigger both phenomena but recovered their effect when loaded with donor peptides before injection. These results strongly suggested that ATDCs require TMEM176B to crosspresent antigens in a tolerogenic fashion. In agreement with this, Tmem176b À/À ATDCs specifically failed to cross-present male antigens or ovalbumin to CD8 þ T cells. Finally, we observed that a Tmem176b-dependent cation current controls phagosomal pH, a critical parameter in cross-presentation. Thus, ATDCs require TMEM176B to cross-present donor antigens to induce donor-specific CD8 þ CD11c þ T cells with regulatory properties and prolong graft survival.

Combining Autologous Dendritic Cell Therapy with CD3 Antibodies Promotes Regulatory T Cells and Permanent Islet Allograft Acceptance

“…In this study, we implemented these results in a fully mismatched pancreatic islet transplantation model, demonstrating a similar synergistic effect that led to permanent graft acceptance. Importantly, as discussed below, the immune mediators responsible for this sustained islet allograft survival were distinct from those reported previously (23).…”

“…We also showed that by combining these ATDCs with suboptimal treatment with LF 15-0195, a potent and less toxic derivative of the immunosuppressive drug 15-deoxyspergualine, whose main mode of action was reported to be the inhibition of DC maturation in vivo, we were able to promote transplant tolerance (19)(20)(21)(22). Recently, we showed in a minor mismatched skin allograft model in mice that the combined administration of ATDCs and a short course of a CD3-specific mAb prolonged allograft survival (23).…”

“…Indeed, we showed in experimental models of islet or heart allografts that CD3 Abs, applied at the time of allogeneic effector T cell priming, could induce Ag-specific tolerance (27,28). Recently, we showed synergy when combining a low-dose CD3 Ab treatment with ATDCs in a minor mismatched skin allograft model at the time of transplantation (23). In this study, we implemented these results in a fully mismatched pancreatic islet transplantation model, demonstrating a similar synergistic effect that led to permanent graft acceptance.…”

“…Its role remains to be addressed. In the minor Ag skin graft mouse model, allograft survival that was induced by the combination of CD3 Abs and ATDCs was due to the capacity of ATDCs to cross-present alloantigens to CD8 + CD11c + Tregs, as revealed by the use of Tmem176b-deficient ATDCs that failed to synergize with CD3 Abs (23). Tmem176b has been involved in a phagosomal cation current required for the control of phagosomal pH, a crucial parameter in the cross-presentation pathway (37).…”

Compensatory Regulatory Networks between CD8 T, B, and Myeloid Cells in Organ Transplantation Tolerance

“…Interestingly, we observed a significant increased expression of IL-6 and IL-10, two cytokines that have been linked with Bregs and RegMCs (24,25), in CD8a-depleted recipients compared with controls. We also observed a significant increase in PirB, Tmem176b, and heme oxygenase-1 (HO-1) expression, and several tolerogenic molecules that are important for the maintenance of tolerance in the graft (23,(26)(27)(28). We also observed a significant upregulation of To explore the potential increase in antiallogeneic effector mechanisms in the CD8a-depleted CD40Ig-treated recipients, possibly through Bregs and RegMCs, as such killer activity has been described for both in the literature (30, 31),we analyzed the cytotoxic activity of splenocytes 120 d after transplantation toward 51 Cr-labeled syngeneic, allogeneic, or third-party Con A blasts.…”