Rapid achievement of complete donor chimerism and low regimen-related toxicity after reduced conditioning with fludarabine, carmustine, melphalan and allogeneic transplantation.
(1/523)
Between August 1998 and July 1999, 21 patients received a novel protocol of reduced conditioning with fludarabine, carmustine and melphalan (FBM) followed by matched-related allogeneic peripheral blood stem cell transplantation (PBSCT) in a prospective multi-center phase I/II study. Cyclosporin A and 'mini-methotrexate' were used for GVHD prophylaxis. Patients were included because of age, advanced disease, previous transplantation or co-morbidity. Hematopoietic engraftment after allogeneic transplantation was rapid with a median white blood count (WBC) >1 x 10(9)/l on day +11 (range 10-17) and a median platelet count >20 x 10(9)/l on day +13 (range 9-36). Donor chimerism was complete in 16/21 (76%) patients at all time points during follow-up and mixed at least on one occasion in 5/21 (24%) patients. The conditioning regimen was well tolerated with low toxicity even in previously transplanted patients. Thirteen patients (62%) developed acute GVHD grades II-IV. Nineteen out of 21 patients achieved complete (CR, n = 15) or partial remission (PR, n = 4) with a median patient follow-up of 354+ days (range 258-577) for patients alive. The reduced intensity protocol FBM is feasible with rapid engraftment, early achievement of complete donor chimerism, low toxicity, especially in heavily pretreated patients, and good response rates in advanced disease patients. (+info)
Treatment of leukemic relapse following unrelated umbilical cord blood transplantation with interleukin-2: potential for augmenting graft-versus-leukemia and graft-versus-host effects with cytokines.
(2/523)
In comparison to bone marrow, umbilical cord blood has decreased intrinsic immune responsiveness allowing transplantation across HLA barriers with lower rates of graft-versus-host disease. However, laboratory models have also suggested that cord blood may be extremely sensitive to stimulation by cytokines. We report an adult recipient of an ex vivo expanded, HLA-mismatched, unrelated cord blood transplant who experienced a late extramedullary relapse while still in hematologic remission. Despite demonstrating immune tolerance on minimal immunosuppressive agents, a brief course of intravenous interleukin-2 resulted in rapid, aggressive graft-versus-host and graft-versus-leukemia reactions. This case highlights the potential of cytokine immunomodulation following cord blood transplantation, but also suggests caution in stimulating these cells. (+info)
Nondepleting anti-CD154 (CD40 ligand) mAbs have proven effective in inducing transplantation tolerance in rodents and primates. In the induction phase, anti-CD154 Ab therapy is known to enhance apoptosis of Ag reactive T cells. However, this may not be the sole explanation for tolerance, as we show in this study that tolerance is maintained through a dominant regulatory mechanism which, like tolerance induced with CD4 Abs, manifests as infectious tolerance. Therefore, tolerance induced with anti-CD154 Abs involves not only the deletion of potentially aggressive T cells, but also a contagious spread of tolerance to new cohorts of graft-reactive T cells as they arise. (+info)
Acceptance reaction: intragraft events associated with tolerance to renal allografts in miniature swine.
(4/523)
Inbred miniature swine that are treated for 12 d with a high dose of cyclosporin A develop tolerance to MHC class II matched, class I-mismatched renal allografts. The aim of this study was to clarify the intrarenal allograft events associated with the development of tolerance in this protocol. Morphologic and immunologic studies were performed in serial biopsies from accepting grafts after 12 d of cyclosporin A treatment (n = 4) and were compared with those from untreated control rejecting grafts (n = 4). In accepting grafts with stable function, a transient interstitial infiltrate developed. The cellular infiltrate had many similarities to that in rejecting grafts; both had T cells and macrophages, similar proportions of T-cell subsets, and a similar frequency of in situ nick end labeling (TUNEL)+ apoptotic infiltrating cells. However, the cellular infiltrate in the acceptance reaction was distinguished by less T-cell activation (interleukin-2 receptor+), less proliferation (proliferating cell nuclear antigen+) of infiltrating cells, and less graft cell apoptosis in arteries, tubules, glomeruli, and peritubular capillaries. Thereafter, the infiltrate in the accepting grafts progressively resolved with decreased cell proliferation, activation, and apoptotic graft parenchymal cell injury, but the high frequency of apoptosis persisted in graft-infiltrating cells. In parallel to the intragraft events, donor-specific unresponsiveness developed as assessed by cell-mediated cytotoxicity by blood mononuclear cells in vitro. In conclusion, the acceptance reaction in transplanted grafts is characterized by progressive resolution of T-cell proliferation and activation and of cell-mediated graft injury, as well as prolonged T-cell apoptosis. These intragraft events suggest that both T-cell anergy and T-cell deletion occur in the graft during the development of tolerance. Some of the described immunopathologic findings (activation, proliferation, apoptosis) may be useful in distinguishing acceptance from rejection, as well as in predicting later graft acceptance in tolerance induction protocols. (+info)
Production of a recombinant form of early pregnancy factor that can prolong allogeneic skin graft survival time in rats.
(5/523)
Early pregnancy factor (EPF), an extracellular chaperonin 10 homologue, has immunosuppressive and growth factor properties. In order to carry out more extensive studies on the in vivo characteristics of EPF, a recombinant form of the molecule has been prepared. Recombinant human EPF (rEPF) was expressed in Escherichia coli using the plasmid pGEX-2T expression system. Potency of rEPF in vitro in the rosette inhibition test, the bioassay for EPF, was equivalent to that of native EPF (nEPF), purified from human platelets, and synthetic EPF (sEPF). However, the half-life of activity (50% decrease in the log value) in serum, following i.p. injection, was significantly decreased (3.2 h, compared with nEPF 6.2 days, sEPF 5.8 days). This was thought to be due to modification of the N-terminus of the recombinant molecule inhibiting binding to serum carrier proteins. Because EPF can modify Th1 responses, the ability of the recombinant molecule to suppress allogeneic graft rejection was investigated. Following skin grafts from Lewis rats to DA rats and vice versa, rEPF was delivered locally at the graft site and the effect on survival time of the allografts noted. Results demonstrated that rEPF treatment significantly prolonged skin graft survival time by as much as 55% in stringent models of transplantation across major histocompatibility barriers. (+info)
Targeting signal 1 through CD45RB synergizes with CD40 ligand blockade and promotes long term engraftment and tolerance in stringent transplant models.
(6/523)
The induction and maintenance of allograft tolerance is a daunting challenge. Although combined blockade of CD28 and CD40 ligand (CD40L)-costimulatory pathways prevents allograft rejection in some murine models, this strategy is unable to sustain engraftment in the most immunogenic allograft and strain combinations. By targeting T cell activation signals 1 and 2 with the novel combination of anti-CD45RB and anti-CD40L, we now demonstrate potent enhancement of engraftment in C57BL/6 recipients that are relatively resistant to costimulatory blockade. This combination significantly augments the induction of tolerance to islet allografts and dramatically prolongs primary skin allograft survival. Compared with either agent alone, anti-CD45RB plus anti-CD40L inhibits periislet infiltration by CD8 cells, B cells, and monocytes; inhibits Th1 cytokines; and increases Th2 cytokine expression within the graft. These data indicate that interference with activation signals one and two may provide synergy essential for prolonged engraftment in situations where costimulatory blockade is only partially effective. (+info)
Tolerance to solid organ transplants through transfer of MHC class II genes.
(7/523)
Donor/recipient MHC class II matching permits survival of experimental allografts without permanent immunosuppression, but is not clinically applicable due to the extensive polymorphism of this locus. As an alternative, we have tested a gene therapy approach in a preclinical animal model to determine whether expression of allogeneic class II transgenes (Tg's) in recipient bone marrow cells would allow survival of subsequent Tg-matched renal allografts. Somatic matching between donor kidney class II and the recipient Tg's, in combination with a short treatment of cyclosporine A, prolonged graft survival with DR and promoted tolerance with DQ. Class II Tg expression in the lymphoid lineage and the graft itself were sequentially implicated in this tolerance induction. These results demonstrate the potential of MHC class II gene transfer to permit tolerance to solid organ allografts. (+info)
Transplantation tolerance and autoimmunity after xenogeneic thymus transplantation.
(8/523)
Successful grafting of vascularized xenografts (Xgs) depends on the ability to reliably induce both T cell-independent and -dependent immune tolerance. After temporary NK cell depletion, B cell suppression, and pretransplant infusion of donor Ags, athymic rats simultaneously transplanted with hamster heart and thymus Xgs developed immunocompetent rat-derived T cells that tolerated the hamster Xgs but provoked multiple-organ autoimmunity. The autoimmune syndrome was probably due to an insufficient development of tolerance for some rat organs; for example, it led to thyroiditis in the recipient rat thyroid, but not in simultaneously transplanted donor hamster thyroid. Moreover, grafting a mixed hamster/rat thymic epithelial cell graft could prevent the autoimmune syndrome. These experiments indicate that host-type thymic epithelial cells may be essential for the establishment of complete self-tolerance and that mixed host/donor thymus grafts may induce T cell xenotolerance while maintaining self-tolerance in the recipient. (+info)