Allograft tolerance induced by intact active bone co-transplantation and anti-CD40L monoclonal antibody therapy1

We report on a novel approach aimed at preventing acute vascular rejection (AVR), one of the major unresolved hurdles of clinical transplantation. In a C3H-to-BALB/c heterotopic heart transplant model, we demonstrate that free bone transplantation combined with cyclosporin A suppresses antidonor Ab responses, induces indefinite cardiac allograft survival (>100 days), and preserves graft architecture. In contrast, untreated- or cyclosporin A alone-treated recipients rejected their cardiac grafts on days 7.7 ± 0.6 and 15.5 ± 1.1, respectively, with graft histology indicative of AVR. Splenic dendritic cells from nonrejecting recipients expressed low levels of MHC II, CD40, and CD86, reduced ability to stimulate donor cell proliferation, and augmented IL-10 production of responding T cells in vitro. Adoptive transfer of dendritic cells from long-term surviving recipients 1 day before cardiac grafting was able to confer hyporesponsiveness to naive BALB/c recipients of cardiac allografts. To determine whether graft survival was associated with hematopoietic or stromal elements of the transplanted free bone, we administered isolated bone marrow mononuclear cells or free bone that was irradiated to deplete hematopoietic elements. Although bone marrow mononuclear cells had no effect on cardiac graft survival, irradiated free bone transplantation was capable of prolonging graft survival. Most interestingly, the prolongation effect was Ag nonspecific, because third party irradiated bone graft was also effective. Due to the fact that current immunosuppressive approaches are clinically ineffective at preventing AVR, this study provides promise for further investigations of BM components as a means of addressing a currently unmet medical need.

Section: Discussionmentioning

confidence: 56%

mentioning

confidence: 99%

Free Bone Graft Attenuates Acute Rejection and in Combination with Cyclosporin A Leads to Indefinite Cardiac Allograft Survival

Wang

Ge²,

Arp³

et al. 2009

“…Another important costimulatory interaction results from the binding of CD154 on activated T cells with CD40, which is constitutively expressed on APC (5). Experimental blocking of the CD40-CD154 or the CD80/ CD86-CD28 costimulatory interactions has been shown to prolong allograft survival in rodent models (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). However, in nonhuman primate studies, blockade of a single pathway is not enough to induce tolerance and only prevents the acute rejection of solid allografts as long as the blockade is maintained (18).…”

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confidence: 99%

Contribution of Regulatory T Cells and Effector T Cell Deletion in Tolerance Induction by Costimulation Blockadel

Verbinnen

Billiau²,

Vermeiren

et al. 2008

Blocking of costimulatory signals for T cell activation leads to tolerance in several transplantation models, but the underlying mechanisms are incompletely understood. We analyzed the involvement of regulatory T cells (Treg) and deletion of alloreactive cells in the induction and maintenance of tolerance after costimulation blockade in a mouse model of graft-vs-host reaction. Injection of splenocytes from the C57BL/6 parent strain into a sublethally irradiated F1 offspring (C57BL/6 × C3H) induced a GVHR characterized by severe pancytopenia. Treatment with anti-CD40L mAb and CTLA4-Ig every 3 days during 3 wk after splenocyte injection prevented disease development and induced a long-lasting state of stable mixed chimerism (>120 days). In parallel, host-specific tolerance was achieved as demonstrated by lack of host-directed alloreactivity of donor-type T cells in vitro and in vivo. Chimerism and tolerance were also obtained after CD25+ cell-depleted splenocyte transfer, showing that CD25+ natural Treg are not essential for tolerance induction. We further show that costimulation blockade results in enhanced Treg cell activity at early time points (days 6–30) after splenocyte transfer. This was demonstrated by the presence of a high percentage of Foxp3+ cells among donor CD4+ cells in the spleen of treated animals, and our finding that isolated donor-type T cells at an early time point (day 30) after splenocyte transfer displayed suppressive capacity in vitro. At later time points (>30 days after splenocyte transfer), clonal deletion of host-reactive T cells was found to be a major mechanism responsible for tolerance.

“…Donor-reactive Abs were determined by flow cytometry as previously reported (22). Briefly, C57BL/6 or C3H lymph node cells were incubated with a 1/10 dilution of mouse serum for 1 h at 4°C, then the cells were washed and incubated with PE-conjugated anti-mouse IgM (Jackson ImmunoResearch Laboratories) or FITC-conjugated anti-mouse IgG (Southern Biotechnology Associates).…”

Section: Analysis Of Donor-reactive Alloantibody and 3-83 Abs Titersmentioning

confidence: 99%

Long-Term Control of Alloreactive B Cell Responses by the Suppression of T Cell Help

Yin

et al. 2008

Self Cite

Alloantibodies can play a key role in acute and chronic allograft rejection. However, relatively little is known of factors that control B cell responses following allograft tolerance induction. Using 3-83 Igi mice expressing an alloreactive BCR, we recently reported that allograft tolerance was associated with the sustained deletion of the alloreactive B cells at the mature, but not the immature, stage. We have now investigated the basis for the long-term control of alloreactive B cell responses in a non-BCR-transgenic model of C57BL/6 cardiac transplantation into BALB/c recipients treated with anti-CD154 and transfusion of donor-specific spleen cells. We demonstrate that the long-term production of alloreactive Abs by alloreactive B cells is actively regulated in tolerant BALB/c mice through the dominant suppression of T cell help. Deletion of CD25+ cells resulted in a loss of tolerance and an acquisition of the ability to acutely reject allografts. In contrast, the restoration of alloantibody responses required both the deletion of CD25+ cells and the reconstitution of alloreactive B cells. Collectively, these data suggest that alloreactive B cell responses in this model of tolerance are controlled by dominant suppression of T cell help as well as the deletion of alloreactive B cells in the periphery.