Intragraft CD11b(+) IDO(+) cells mediate cardiac allograft tolerance by ECDI-fixed donor splenocyte infusions

Transient B-cell depletion combined with apoptotic donor splenocytes induces xeno-specific T- and B-cell tolerance to islet xenografts

Peritransplant infusion of apoptotic donor splenocytes cross-linked with ethylene carbodiimide (ECDI-SPs) has been demonstrated to effectively induce allogeneic donor-specific tolerance. The objective of the current study is to determine the effectiveness and additional requirements for tolerance induction for xenogeneic islet transplantation using donor ECDI-SPs. In a rat-to-mouse xenogeneic islet transplant model, we show that rat ECDI-SPs alone significantly prolonged islet xenograft survival but failed to induce tolerance. In contrast to allogeneic donor ECDI-SPs, xenogeneic donor ECDI-SPs induced production of xenodonor-specific antibodies partially responsible for the eventual islet xenograft rejection. Consequently, depletion of B cells prior to infusions of rat ECDI-SPs effectively prevented such antibody production and led to the indefinite survival of rat islet xenografts. In addition to controlling antibody responses, transient B-cell depletion combined with ECDI-SPs synergistically suppressed xenodonor-specific T-cell priming as well as memory T-cell generation. Reciprocally, after initial depletion, the recovered B cells in long-term tolerized mice exhibited xenodonor-specific hyporesponsiveness. We conclude that transient B-cell depletion combined with donor ECDI-SPs is a robust strategy for induction of xenodonor-specific T- and B-cell tolerance. This combinatorial therapy may be a promising strategy for tolerance induction for clinical xenogeneic islet transplantation.

Donor bone marrow-derived dendritic cells prolong corneal allograft survival and promote an intragraft immunoregulatory milieu

Investigations into cell therapies for application in organ transplantation have grown. Here, we describe the ex vivo generation of donor bone marrow-derived dendritic cells (BMDCs) and glucocorticoid-treated BMDCs with potent immunomodulatory properties for application in allogeneic transplantation. BMDCs were treated with dexamethasone (Dexa) to induce an immature, maturation-resistant phenotype. BMDC and Dexa BMDC phenotype, antigen presenting cell function, and immunomodulatory properties were fully characterized. Both populations display significant immunomodulatory properties, including, but not limited to, a significant increase in mRNA expression of programmed death-ligand 1 and indoleamine 2,3-dioxygenase. BMDCs and Dexa BMDCs display a profound impaired capacity to stimulate allogeneic lymphocytes. Moreover, in a fully MHC I/II mismatched rat corneal transplantation model, injection of donor-derived, untreated BMDC or Dexa BMDCs (1 × 10(6) cells, day -7) significantly prolonged corneal allograft survival without the need for additional immunosuppression. Although neovascularization was not reduced and evidence of donor-specific alloantibody response was detected, a significant reduction in allograft cellular infiltration combined with a significant increase in the ratio of intragraft FoxP3-expressing regulatory cells was observed. Our comprehensive analysis demonstrates the novel cellular therapeutic approach and significant effect of donor-derived, untreated BMDCs and Dexa BMDCs in preventing corneal allograft rejection.

Role of plasmacytoid dendritic cell subsets in allergic asthma

Plasmacytoid dendritic cells (pDCs) are major type-I interferon-producing cells that play important roles in antiviral immunity and tolerance induction. These cells share a common DC progenitor with conventional DCs, and Fms-like tyrosine kinase-3 ligand is essential for their development. Several subsets of pDCs have been identified to date including CCR9(+) , CD9(+) , and CD2(+) pDCs. Recently, three subsets of pDCs were described, namely CD8α(-) β(-) , CD8α(+) β(-) , and CD8α(+) β(+) subsets. Interestingly, CD8α(+) β(-) and CD8α(+) β(+) but not CD8α(-) β(-) pDCs were shown to have tolerogenic effects in experimentally induced allergic asthma. These tolerogenic effects were shown to be mediated by the generation of FOXP3(+) regulatory T cells through retinoic acid and the induction of retinaldehyde dehydrogenase enzymes. These newly described subsets of pDCs show high potentials for novel therapeutic approaches for the treatment of allergic diseases. In this review, we will address the new progress in our understanding of pDC biology with respect to allergic disease, in particular allergic asthma.