ALBERT

Description: Graft rejection after marrow transplantation is generally thought to be mediated by alloreactive immune effector cells of host origin. Transfused blood products also contain immune cells capable of alloreactivity against both donor graft and host. To reduce the risk of transfusion-associated graft-versus-host disease (GVHD) and graft rejection, standard procedure is to irradiate all blood products with at least 1,500 rad before transfusion. We report a patient with chronic myelogenous leukemia who developed graft rejection and GVHD after receiving a T-cell-depleted transplant from a serologically HLA-A, B, DR/DQ matched and mixed lymphocyte culture (MLC) nonreactive unrelated donor. Cytogenetic analysis of marrow cells collected at the time of graft rejection revealed a PH1-negative female karyotype that was not consistent with donor cells. Use of specific minisatellite DNA probes (YNH 24, H-RAS, and 3′ HVR) revealed the exclusive presence of third- party (neither donor nor recipient) restriction-fragment-length polymorphisms (RFLP) in both peripheral blood and marrow. Repeat RFLP analysis 3 days later showed persistence of this unique third-party banding pattern. DNA-based HLA-typing, using polymerase chain reaction (PCR) and oligonucleotide probe hybridization, also showed these cells to be derived from an individual whose HLA-DR type was distinct from donor and recipient. Together, these findings suggested the presence of a proliferating population of transfused cells possessing alloreactivity against both donor graft and host, despite prior irradiation of all blood products with 2,000 rad. Limiting dilution analysis to assess the frequency of irradiated lymphocytes able to respond to mitogen revealed an approximate 5- to 6-log reduction at 1,500 to 2,000 rad as compared with unirradiated controls. These data indicate that a small percentage of lymphocytes can survive irradiation at these doses and suggest that existing blood-product irradiation guidelines may require reassessment, especially in T-cell-depleted transplant recipients.

Description: Disease relapse after allogeneic bone marrow transplantation (BMT) is a major cause of treatment failure and is thought to evolve from clinically occult residual disease in the recipient. However, the demonstration of minimal residual disease (MRD) in individual patients is of uncertain prognostic significance because the detection of residual disease has not consistently correlated with subsequent relapse. Moreover, the optimal therapeutic approach in patients with MRD after allogeneic BMT is unknown. The study of these issues has been hindered by the lack of clinically relevant animal models. In this report, we characterize a novel murine model for the study of MRD after allogeneic BMT. This model was designed to simulate high-risk BMT in humans in which patients receive transplants in relapse and disease recurrence in the major cause of treatment failure. The H-2-compatible, mixed lymphocyte culture nonreactive murine strains, AKR (H-2k) and CBA (H-2k), were chosen to parallel marrow transplants from HLA-matched siblings, which represent the majority of allo-transplants in humans. Male AKR leukemia cells were used in female donor/host chimeras permitting the Y chromosome to serve as a leukemia-specific marker for MRD. Detection of residual male leukemia cells in the peripheral blood of the primary host was facilitated by use of the polymerase chain reaction (PCR) and sequence-specific oligonucleotide probe hybridization (SSOPH). Use of PCR/SSOPH was highly predictive of clinical outcome (relapse or cure) in animals receiving transplants (P 〈 .00002) and detected disease recurrence earlier than comparative flow cytometric analysis studies. This murine model will be useful in evaluating the efficacy of therapeutic strategies aimed at reducing disease relapse posttransplant and can be adapted to other transplant murine tumor systems for the study of MRD.

Description: The development of graft-host tolerance after bone marrow transplantation (BMT) is crucial to avoid the problems of graft-versus-host disease (GVHD) and graft rejection. GVHD can be eliminated by depleting mature donor T cells from the BM inoculum, thereby facilitating the development of graft-host tolerance. However, T-cell depletion often results in an increased incidence of graft rejection and an increased frequency of leukemia relapse. Thus, although graft-host tolerance is a desirable outcome, it can pose a significant threat to leukemia-bearing hosts. Using a major histocompatability complex (MHC)-matched allogeneic model of BMT (B10.BR into AKR), we found that irradiated recipients given donor BM alone displayed mixed T-cell chimerism and did not develop GVHD. Graft-host tolerance developed by 8 weeks after BMT in these chimeras, and they were susceptible to low-dose leukemia challenge. When sufficient numbers of donor spleen cells, as a source of T-cells, were added to the BM graft, AKR hosts developed severe and lethal GVHD. Antihost reactive donor T cells persisted in chimeras undergoing GVHD, indicating that graft-host tolerance did not develop. When administration of the spleen cells was delayed for 7 to 21 days after BMT, there was significantly less mortality because of GVHD. Day 21 was the optimal time for infusion of cells without development of GVHD. Graft-host tolerance was broken by the delayed infusion of donor cells, as indicated by the persistence of antihost-reactive donor T cells in these chimeras in T-cell receptor cross-linking and mixed lymphocyte reaction assays. Importantly, the persistence of antihost-reactive donor T cells correlated with along-term antileukemic effect that was still present at 100 days after transplant. Multiple infusions of immunocompetent donor cells could be administered without increasing the risk for GVHD if delayed until 21 days post-BMT. Delayed infusions of donor spleen cells also resulted in a long-term antileukemic effect in the absence of GVHD in an MHC-haplotype-mismatched model of BMT (SJL into [SJL x AKR]F1). Although delayed infusion of normal donor cells did not induce GVHD, spleen cells from donors previously sensitized to host alloantigens induced GVHD when infused 21 days after BMT. Thus, the ability of previously activated cells to induce GVHD was not inhibited in the same manner as naive cells. Results from limiting dilution analysis assays indicated that alloactivated interleukin-2-secreting CD4+ T cells were preferentially inhibited over cytolytic T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Description: Graft rejection after marrow transplantation is generally thought to be mediated by alloreactive immune effector cells of host origin. Transfused blood products also contain immune cells capable of alloreactivity against both donor graft and host. To reduce the risk of transfusion-associated graft-versus-host disease (GVHD) and graft rejection, standard procedure is to irradiate all blood products with at least 1,500 rad before transfusion. We report a patient with chronic myelogenous leukemia who developed graft rejection and GVHD after receiving a T-cell-depleted transplant from a serologically HLA-A, B, DR/DQ matched and mixed lymphocyte culture (MLC) nonreactive unrelated donor. Cytogenetic analysis of marrow cells collected at the time of graft rejection revealed a PH1-negative female karyotype that was not consistent with donor cells. Use of specific minisatellite DNA probes (YNH 24, H-RAS, and 3′ HVR) revealed the exclusive presence of third- party (neither donor nor recipient) restriction-fragment-length polymorphisms (RFLP) in both peripheral blood and marrow. Repeat RFLP analysis 3 days later showed persistence of this unique third-party banding pattern. DNA-based HLA-typing, using polymerase chain reaction (PCR) and oligonucleotide probe hybridization, also showed these cells to be derived from an individual whose HLA-DR type was distinct from donor and recipient. Together, these findings suggested the presence of a proliferating population of transfused cells possessing alloreactivity against both donor graft and host, despite prior irradiation of all blood products with 2,000 rad. Limiting dilution analysis to assess the frequency of irradiated lymphocytes able to respond to mitogen revealed an approximate 5- to 6-log reduction at 1,500 to 2,000 rad as compared with unirradiated controls. These data indicate that a small percentage of lymphocytes can survive irradiation at these doses and suggest that existing blood-product irradiation guidelines may require reassessment, especially in T-cell-depleted transplant recipients.

Description: Graft rejection, mixed chimerism, graft-versus-host disease (GVHD), leukemia relapse, and tolerance are interrelated manifestations of immunologic reactivity between donor and host cells that significantly affect survival after allogeneic bone marrow transplantation (BMT). In this report, a mouse model of BMT, in which the donor and host were compatible at the major histocompatibility complex (MHC), was used (1) to examine the interrelationship of pretransplant conditioning and T- cell content of donor BM with regard to lymphoid chimerism and GVHD and (2) to determine how these factors affected graft-versus-leukemia (GVL) reactivity and donor-host-tolerance. AKR (H-2k) host mice were administered optimal or suboptimal total body irradiation (TBI) as pretransplant conditioning followed by administration of BM cells from B10.BR (H-2k) donor mice with or without added spleen cells as a source of T lymphocytes. Transplanted mice were injected with a supralethal dose of AKR leukemia cells 20 and 45 days post-BMT to assess GVL reactivity in vivo. The pretransplant conditioning of the host and T- cell content of the donor marrow affected the extent of donor T-cell chimerism and the severity of GVH disease. GVL reactivity was dependent on transplantation of mature donor T cells and occurred only in complete chimeras. Transplantation of T-cell-deficient BM resulted in the persistence of host T cells, ie, incomplete donor T-cell chimerism, even when lethal TBI was used. Mixed chimerism was associated with a lack of GVL reactivity, despite the fact that similar numbers of donor T cells were present in the spleens of mixed and complete chimeras. In this model, moderate numbers of donor T cells facilitated complete donor T-cell engraftment, caused only mild GVHD, and provided a significant GVL effect without preventing the subsequent development of tolerance after conditioning with suboptimal TBI. In contrast, severe, often lethal, GVHD developed when the dose of TBI was increased, whereas tolerance and no GVH/GVL reactivity developed when the T-cell content of the marrow was decreased.

Description: Graft rejection, mixed chimerism, graft-versus-host disease (GVHD), leukemia relapse, and tolerance are interrelated manifestations of immunologic reactivity between donor and host cells that significantly affect survival after allogeneic bone marrow transplantation (BMT). In this report, a mouse model of BMT, in which the donor and host were compatible at the major histocompatibility complex (MHC), was used (1) to examine the interrelationship of pretransplant conditioning and T- cell content of donor BM with regard to lymphoid chimerism and GVHD and (2) to determine how these factors affected graft-versus-leukemia (GVL) reactivity and donor-host-tolerance. AKR (H-2k) host mice were administered optimal or suboptimal total body irradiation (TBI) as pretransplant conditioning followed by administration of BM cells from B10.BR (H-2k) donor mice with or without added spleen cells as a source of T lymphocytes. Transplanted mice were injected with a supralethal dose of AKR leukemia cells 20 and 45 days post-BMT to assess GVL reactivity in vivo. The pretransplant conditioning of the host and T- cell content of the donor marrow affected the extent of donor T-cell chimerism and the severity of GVH disease. GVL reactivity was dependent on transplantation of mature donor T cells and occurred only in complete chimeras. Transplantation of T-cell-deficient BM resulted in the persistence of host T cells, ie, incomplete donor T-cell chimerism, even when lethal TBI was used. Mixed chimerism was associated with a lack of GVL reactivity, despite the fact that similar numbers of donor T cells were present in the spleens of mixed and complete chimeras. In this model, moderate numbers of donor T cells facilitated complete donor T-cell engraftment, caused only mild GVHD, and provided a significant GVL effect without preventing the subsequent development of tolerance after conditioning with suboptimal TBI. In contrast, severe, often lethal, GVHD developed when the dose of TBI was increased, whereas tolerance and no GVH/GVL reactivity developed when the T-cell content of the marrow was decreased.

Description: Disease relapse after allogeneic bone marrow transplantation (BMT) is a major cause of treatment failure and is thought to evolve from clinically occult residual disease in the recipient. However, the demonstration of minimal residual disease (MRD) in individual patients is of uncertain prognostic significance because the detection of residual disease has not consistently correlated with subsequent relapse. Moreover, the optimal therapeutic approach in patients with MRD after allogeneic BMT is unknown. The study of these issues has been hindered by the lack of clinically relevant animal models. In this report, we characterize a novel murine model for the study of MRD after allogeneic BMT. This model was designed to simulate high-risk BMT in humans in which patients receive transplants in relapse and disease recurrence in the major cause of treatment failure. The H-2-compatible, mixed lymphocyte culture nonreactive murine strains, AKR (H-2k) and CBA (H-2k), were chosen to parallel marrow transplants from HLA-matched siblings, which represent the majority of allo-transplants in humans. Male AKR leukemia cells were used in female donor/host chimeras permitting the Y chromosome to serve as a leukemia-specific marker for MRD. Detection of residual male leukemia cells in the peripheral blood of the primary host was facilitated by use of the polymerase chain reaction (PCR) and sequence-specific oligonucleotide probe hybridization (SSOPH). Use of PCR/SSOPH was highly predictive of clinical outcome (relapse or cure) in animals receiving transplants (P 〈 .00002) and detected disease recurrence earlier than comparative flow cytometric analysis studies. This murine model will be useful in evaluating the efficacy of therapeutic strategies aimed at reducing disease relapse posttransplant and can be adapted to other transplant murine tumor systems for the study of MRD.