Donor Lymphocyte Transfusions Research Articles

Retrospective Comparison of Using or Not Using Donor Lymphocyte Transfusion in the Treatment of Hematological Relapse after Allogeneic Stem Cell Transplantation in 489 Adults with Acute Myeloid Leukemia.

Relapsed AML after allogeneic SCT has a poor prognosis. So far, no standard therapy could be defined. Donor lymphocyte transfusion (DLT) has been effective in a minority, however, no data is available to identify patients who will benefit from the procedure. Neither, the outcome of patients treated with or without DLT have been compared. We retrospectively evaluated overall survival (OS) of 489 adults with de novo AML in hematological relapse after SCT, receiving DLT (n=190) or not (n=299). DLT and noDLTgroups were well balanced in terms of patient age (median:37y in both groups), donor age, cytogenetics (good:5vs7%, intermediate:83vs79%, poor:12%vs14%), WBC at diagnosis, donor type (geno-id:71vs72%, MUD:18% both, mismatched:11vs10%), status at transplantation (CR1:38vs41%, CR2:13vs15%, advanced:49vs44%), conditioning, source of stem cells, and time from transplant to relapse (5vs4.5 months). However, DLT patients had a median of 39% BM blasts, as compared to 54% for the noDLT group (p=0.03). Follow-up was 32 and 30 months. Within the DLT group, chemotherapy was additionally given in 130 cases. Nevertheless, only 33% of patients received DLT in CR or aplasia, 67% had measurable disease. AGvHD developed in 41% of patients following DLT. CR and PR were achieved in 31.1% and 4.8% of DLT patients. In a multivariate analysis, younger patient age (<36 years) (HR=1.53,p=0.02) and a longer interval (> 5 months) from transplant to relapse (HR=7.74,p=0.002) were associated with better OS after DLT. When comparing the outcome of patients receiving or not DLT, OS at 2 years was 10±1% for the entire cohort, 18±3% for DLT and 6±1% for noDLT (p<.0001). In a multivariate analysis, use of DLT (HR=2.11,p<0.0001); recipient's age<36 y (HR=1.69, p<0.001); longer interval (>5 months) from transplant to relapse (HR=2.40, p<0.0001) and number of BM blasts (<48%) at relapse (HR=1.56,p=0.002) were favorable for OS. In this retrospective analysis the results suggest that DLT may be of advantage in the treatment of AML relapse post transplant, at least in younger patients with a longer post transplant remission and relapsing with smaller amounts of blasts in BM. However, patients receiving DLT might represent a positive selection among all relapsed cases, since a considerable number from the noDLT cohort had died too early to proceed to DLT. An intetion-to-treat analysis and further prospective studies should investigate the role of DLT and other approaches, such as second reduced intensity SCT.

Durable Remission after Prophylactic Donor Lymphocyte Transfusion Following Allogeneic Stem Cell Transplantation with Reduced Conditioning for High-Risk AML and MDS.

Prophylactic transfusion of donor lymphocytes (pDLT) is an attractive form of maintenance therapy after allogeneic stem cell transplantation in patients with high risk of relapse. However, clinical experience is limited, and disease response is often achieved at the expense of severe graft-versus-host disease (GvHD). We here report our data on pDLT in high-risk AML and MDS. Cells were given within a prospective protocol that contained a sequence of chemotherapy, reduced intensity conditioning for allogeneic transplantation, and pDLT (FLAMSA-regimen). For pDLT, patients had to be in CR at least 120 days from transplantation, off immunosuppression for 30 days, and free of GvHD. 22/86 patients alive at day +120 fulfilled the criteria for pDLT. They had been transplanted for refractory or relapsed leukemia (n=9 each) or in CR1 because of unfavorable cytogenetics (n=4). 14 patients had an unfavorable karyotype, 8 with complex aberrations. Reasons for withholding pDLT in 64 patients included cGvHD or prolonged immunosuppression (n=38), refractory or relapsed leukemia (n=15), refusal of patient or donor (n=4 each), a history of grade IV acute GvHD (n=2), and chronic infections (n=3). The median time from transplant to first pDLT was 167 days (range 120–297). Median follow up of transfused patients is 696 days (range 209–1341). Ten patients received 1, 6 patients received 2, and 6 patients received 3 transfusions in escalating doses, containing a median of 1x106, 5x106 and 1x107 CD3+ cells/kg at pDLT 1, 2 and 3, respectively. Reasons for giving less than 3 transfusions were GvHD, relapse or refusal of the patient. Induction of GvHD was the main complication; grade III acute GvHD developed in 1, and chronic GvHD in 7 patients. So far, 5 patients have relapsed despite pDLT. One died of refractory leukemia, whereas 2 achieved secondary CR following adoptive immunotherapy. Two patients are currently under treatment. At present, 18/22 patients are alive and in CR at a median of 423 days post DLT. The current leukemia free survival at two years from first pDLT is 79%. Nineteen patients were complete chimeras at time of pDLT. pDLT converted mixed into complete bone marrow chimerism in 1, but failed in 2 cases. In our experience, pDLT is safe after allogeneic transplantation for high risk AML, when given at low doses and to a selected group of patients. Results are encouraging, and long term survival can be achieved. However, further studies need to define more precisely the contribution of pDLT to the therapeutic effect of the entire procedure.

In-vivo generation of leukaemia-derived dendritic cells

Adoptive immunotherapy with transfusion of donor lymphocytes in allogeneic stem cell chimeras has been successful in the treatment of recurrent chronic myelogenous leukaemia (CML) and some patients with acute myeloid leukaemia (AML). The hypothesis that the graft-vs-leukaemia effect (GVL) is promoted by leukaemia-derived dendritic cells has been supported by the concurrent treatment of patients with cytokines that are known to induce differentiation of leukaemia cells towards dendritic cells. In combination with donor lymphocyte transfusions, treatment with interferon-α and granulocyte-macrophage colony-stimulating factor has been studied in patients with recurrent CML and AML, and pre-emptively in patients with high-risk AML. Long-term remissions have been observed in cytokine-treated patients, indicating the beneficial effect of cytokine stimulation of GVL reactions. This is likely to be due to differentiation of leukaemia progenitor cells towards dendritic cells in vivo.

In-vivo generation of leukaemia-derived dendritic cells

Adoptive immunotherapy with transfusion of donor lymphocytes in allogeneic stem cell chimeras has been successful in the treatment of recurrent chronic myelogenous leukaemia (CML) and some patients with acute myeloid leukaemia (AML). The hypothesis that the graft-vs-leukaemia effect (GVL) is promoted by leukaemia-derived dendritic cells has been supported by the concurrent treatment of patients with cytokines that are known to induce differentiation of leukaemia cells towards dendritic cells. In combination with donor lymphocyte transfusions, treatment with interferon-alpha and granulocyte-macrophage colony-stimulating factor has been studied in patients with recurrent CML and AML, and pre-emptively in patients with high-risk AML. Long-term remissions have been observed in cytokine-treated patients, indicating the beneficial effect of cytokine stimulation of GVL reactions. This is likely to be due to differentiation of leukaemia progenitor cells towards dendritic cells in vivo.

A single-centre assessment of long-term quality-of-life status after sibling allogeneic stem cell transplantation for chronic myeloid leukaemia in first chronic phase.

A total of 75 patients underwent sibling allogeneic stem cell transplantation (SCT) for chronic myeloid leukaemia in first chronic phase from 1984 to 2000. Of these patients, 51 (68%) were alive at a median follow-up of 98 months (range 34-217 months). Nine (18%) patients relapsed and seven (14%) received donor lymphocyte transfusions. Quality of life (QoL) was assessed cross-sectionally using the EORTC QLQ-C30, a Leukaemia-BMT-specific module and questionnaires on sexual functioning, fertility and late effects. A total of 46 (90%) replied. Scores for Role (P=0.018) and Cognitive (P<0.001) function were significantly lower when compared to an age-adjusted general population. Dyspnoea (P=0.022) and Financial Difficulties (P<0.001) were significantly more common in the SCT group. No difference was found for scores in the Physical, Emotional and Social domains or the overall Global Health Status/QoL. Decreased sexual functioning was found in one-third of respondents. Although most BMT recipients reported a good QoL, a minority have difficulty with reintegration into professional roles and consequent monetary problems. Identified cognitive and sexual impairments highlight the need for long-term access to psychosocial support.

Cellular immunotherapy after allogeneic stem cell transplantation in hematologic malignancies.

The chimeric state after allogeneic stem cell transplantation provides an ideal platform for adoptive immunotherapy of hematologic malignancies using donor-derived cells. The present review aims to summarize recent results of the transfusion of donor-derived cells with regard to the diseases treated, the cells used for treatment, and the origin of these cells. The transfusion of donor lymphocytes has been studied widely, not only in patients with recurrent disease, persistent disease, and mixed chimerism but also in a variety of hematologic malignancies. Donors of lymphocytes and hematopoietic stem cells have been HLA-identical siblings, HLA-matched unrelated donors, and HLA-different haploidentical family members. A variety of cells have been used for adoptive immunotherapy, including plain lymphocytes, selected T cells, T cell lines, and T cell clones. The possible therapies have been expanded by natural killer cells and natural killer T cells as well as antibodies directing the effector cells toward the malignancy. Adoptive immunotherapy in chimeras has become not only a routine form of treatment of recurrent hematologic malignancy but also a prophylactic measure in high-risk leukemia and lymphoma.

Adoptive Immunotherapy in Chimeras with Donor Lymphocytes

Allogeneic stem cell transplantation has a well-defined indication in the treatment of hematological malignancies. The beneficial immune effect of allogeneic marrow transplantation has long been known, but only recently have methods been developed to separate the graft-versus-leukemia (GVL) effect from graft-versus-host disease (GVHD). Animal experiments have shown that lymphocytes from the marrow donor can be transfused without causing severe GVHD if stable chimerism and tolerance is established. First clinical studies have been preformed in patients with recurrent chronic myelogenous leukemia. In these patients complete molecular remissions were induced that persist without further maintenance treatment. These results have been confirmed in larger multicenter studies in Europe and the USA. The best results were obtained in chronic myelogenous leukemia (CML); repeated successes have been reported in relapsing acute myeloid leukemia (AML), myelodysplastic syndromes and multiple myeloma (MMY), and rare responses were reported for acute lymphoid leukemia. Contrary to animal experiments GVHD has been observed in human patients although to a lesser extent than expected in transplants not given immunosuppression. Secondly myelosuppression has been observed in patients treated with relapsing CML. In CML the incidence of GVHD could be reduced by depleting CD8+ T cells from the donor lymphocyte concentrate. Alternatively only small numbers of T lymphocytes can be transfused and in the case of failing responses, the numbers of donor lymphocytes may be increased. Results in recurrent AML have been improved by the use of low-dose cytosine arabinoside, granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor mobilized blood cells as compared to lymphocytes only. In MMY the response rate is higher than in AML, but the remissions are of limited duration in most patients. Several protocols have been designed to include preemptive donor lymphocyte transfusion in patients with a high relapse risk after transplantation. Problems remain to avoid chronic GVHD and to circumvent the immune escape mechanisms of leukemia.

Donor Lymphocyte Transfusion for Epstein-Barr Virus-Associated Lymphoproliferative Disorder Following Unrelated Allogeneic Bone Marrow Transplantation in a Patient with Hypoplastic MDS

Donor Lymphocyte Transfusion for Epstein-Barr Virus-Associated Lymphoproliferative Disorder Following Unrelated Allogeneic Bone Marrow Transplantation in a Patient with Hypoplastic MDS

Levels of soluble FasL and FasL gene expression during the development of graft‐versus‐host disease in DLT‐treated patients

Three patients with different clinical symptoms of graft-versus-host disease (GVHD) who had received donor lymphocyte transfusion (DLT) for the treatment of relapsed leukaemia after an allogeneic bone marrow transplantation (BMT) from HLA-matched sibling donors were analysed for the presence of soluble FasL (sFasL) in the sera and for the expression of the Fas ligand (FasL) gene in the peripheral blood mononuclear cells (PBMNC). Two patients who demonstrated liver damage with increased levels of serum bilirubin showed significantly increased levels of serum sFasL. The increase in the sFasL level was observed prior to the increase in the bilirubin during the clinical courses of both patients. The high dose of methyl predonisolone administered to one of these patients greatly reduced the levels of sFasL in the serum. The bilirubin levels were also reduced thereafter. The third patient (without liver damage) did not show any increase in the serum sFasL level. The expression of the FasL gene in the PBMNC of these three patients was examined. All three patients showed increased levels of the FasL gene expression during their clinical courses. However, only one patient showed a parallel alteration of FasL gene expression with sFasL in the serum. These cases provide evidence that the Fas/FasL system is closely associated with human GVHD, especially in the development of liver GVHD.

Adoptive immunotherapy for leukemia: donor lymphocytes transduced with the herpes simplex thymidine kinase gene for remission induction. HGTRI 0103.

This study will evaluate the safety and efficacy of allogenic donor lymphocyte infusions in patients who have relapsed hematologic malignancies after allogeneic bone marrow transplantation (BMT). Donor lymphocyte transfusions have resulted in the cure of some patients with relapsed leukemia or lymphoproliferative disorder after allogeneic BMT, but has been complicated by the development of graft versus host disease (GvHD). We hypothesize that a retroviral vector containing the Herpes simplex thymidine kinase (HStk) gene will allow for retention of the anti-leukemia response of transfused donor lymphocytes while allowing for the adverse effects of GVHD to be mitigated. Patients with relapsed hematologic malignancies after allogeneic BMT will be infused with ex vivo gene modified donor lymphocytes. The Herpes Simplex thymidine kinase (HStk) gene will be transduced into the cells ex vivo using LTKOSN. 1 vector supernate. Insertion of the HStk gene into lymphocytes confers a sensitivity to the anti-herpes drug ganciclovir (GCV). This selective destruction of donor lymphocytes in situ will be used to abrogate the effect of graft versus host disease, if it develops.

10 Graft-versus-leukaemia

The high relapse rate after T-cell depleted bone marrow transplantation (BMT) for chronic myeloid leukaemia (CML) and the ability of donor lymphocyte transfusions to induce stable remission in patients relapsing after BMT has emphasized the importance of alloreacting donor T-lymphocytes in the graft-versus-leukaemia (GVL) effect in this disease. The mechanisms underlying the GVL response and its relationship with graft-versus-host disease are becoming better defined. There is accumulating evidence that the CD4+ T-cell plays a central role in the GVL response. The prominent role of GVL in the cure of CML after BMT may be associated with the fact that CML cells are strongly immunogenic. New transplant strategies are being devised to separate GVL from graft-versus-host reactions. Future developments focus on the identification of leukaemia-specific antigens and the amplification of T-cell responses against them.

Sequential molecular monitoring of chimerism in chronic myeloid leukemia patients receiving donor lymphocyte transfusion for relapse after bone marrow transplantation

Recent observations of chimerism in patients relapsed following an allotransplant suggest the persistence of immunotolerance, thus offering a biologic rationale for the use of donor lymphocyte transfusion (DLT). In this study, we have analyzed by PCR amplification of several VNTR regions, sequential bone marrow and peripheral blood DNA samples in four patients who received DLT for CML relapse after bone marrow transplantation. Prior to DLT, all patients showed mixed chimerism in peripheral blood cells while two had mixed chimerism and two no chimerism in the BM. None of these four patients showed evidence of chimerism at the cytogenetic level (all had 100% +ve metaphases). After DLT, a complete hematologic and molecular remission (ie disappearance of the BCR/ABL fusion transcript) was obtained in the two patients who had bone marrow mixed chimerism prior to DLT. The two patients without evidence of marrow chimerism prior to DLT converted to a pattern of mixed chimerism after DLT, but both developed a severe bone marrow aplasia occurring at day 56 and 36, respectively. With regard to the sequential analysis of bone marrow chimerism after DLT we observed that: (1) the disappearance of BCR/ABL +ve cells paralleled the conversion to a pattern of full donor chimerism; and (2) the time interval to achieve CR was inversely correlated with the percentage of donor DNA in bone marrow. In conclusion, we have shown here that the assessment of bone marrow pre-DLT chimerism by PCR analysis might predict the response in patients with favorable characteristics, and also might identify patients at high risk of developing severe myelosuppression.

Adoptive immunotherapy with donor lymphocyte transfusions.

Adoptive immunotherapy denotes the transfer of immunocompetent cells for the treatment of leukemia, cancer, or viral disease. It has regained much interest through the success of treating recurrent leukemia after allogeneic bone marrow transplantation with the transfusion of donor lymphocytes. Chimerism and transplantation tolerance toward the donor offer the possibility of adoptive immunotherapy using donor lymphocytes. In animal studies, donor lymphocytes could be transfused into the chimeric animal, if the transfusion was delayed after marrow transplantation. Transfused lymphocytes exhibit a graft-versus-leukemia effect and increase chimerism. Immunity could be transferred and immune reactivity toward new antigens improved. In human patients transfusion of donor lymphocytes was studied in leukemia recurring after marrow transplantation. It was very effective in the treatment of chronic myelogenous leukemia recurring after marrow transplantation. It was also effective in some patients with acute myeloid leukemia, myelodysplastic syndrome and myeloma; in acute lymphoblastic leukemia and lymphoma responses were rare. Responses in solid tumors as breast cancer have been described. Major complications are graft-versus-host disease and myelosuppression. Myelosuppression could be compensated by the transfusion of marrow. Graft-versus-host disease can be modified by the depletion of CD8-positive T cells from the lymphocyte concentrate or by transfusing very low numbers of cells and increasing doses in a stepwise fashion. The role of concomitant treatment with cytokines and activation of T cells by dendritic cells and vaccination remains to be defined.

Adoptive immunotherapy in canine chimeras.

Chimerism and tolerance after bone marrow transplantation provide excellent conditions for adoptive immunotherapy with T cells of the marrow donor. We studied adoptive immunotherapy in dog leukocyte antigen-identical canine littermate chimeras. Mixed chimeras were produced by conditioning treatment with total body irradiation of a dose of 10 Gy, a uniformly lethal dose in dogs, and infusion of between 1 x 10(8) and 2 x 10(8)/kg mononuclear marrow cells treated with absorbed antithymocyte globulin for inactivation of T cells. Donors were of opposite sex. Persistent mixed chimerism was induced in six of nine dogs, chimerism was complete in one dog, and only transient in two dogs. Tolerance to donor skin grafts was demonstrated in eight dogs, including a dog without cytogenetic evidence of chimerism. Lymphocytes of the marrow donor (between 3.2 x 10(8)/kg and 4.1 x 10(8)/kg) were transfused at various times after transplantation. Nontransfused dogs survived without graft-versus-host disease (GVHD), whereas dogs transfused on days 1 and 2 and dogs transfused on days 21 and 22 developed GVHD and died. In contrast, dogs transfused on days 61 and 62 or later survived without GVHD. Chimerism converted from mixed to complete in six of six transfused dogs and in one of eight nontransfused dogs (P<0.005). Donor lymphocyte transfusions 2 years and 4.5 years after transplantation induced split chimerism with lymphoid cells of donor origin and myeloid cells of host origin in one dog and complete chimerism in the other dog. Before lymphocyte collection, donors were immunized against tetanus toxin. Seven days after lymphocyte transfusion, recipients were given booster injections of tetanus toxoid and primary immunization against diphtheria toxin. In transfused animals, antibody titers against tetanus were demonstrated already before the booster injection. Transfused animals developed higher titers of antibody against tetanus and diphtheria toxin than nontransfused animals. Donor lymphocytes converted mixed chimerism into complete chimerism without producing GVHD, when the transfusion was delayed for 2 months or later after transplantation. Transfusion of donor lymphocytes transferred immune reactivity against tetanus toxin and improved reactivity against diphtheria toxin as a new antigen.

Biology and treatment of chronic myeloid leukemia.

The BCR-ABL gene rearrangement, the initial event in the development of chronic myeloid leukemia, primarily produces clonal expansion in CML by blocking apoptosis, a genetically programmed process of autonomous cell death. The mechanism by which BCR-ABL blocks apoptosis remains unclear, although recent data are beginning to shed light on the signaling pathway. As with other antiapoptotic signals, BCR-ABL induces cellular resistance to a wide spectrum of cytotoxic antitumor agents. However, apoptosis induced by both cytotoxic T lymphocytes and natural killer or lymphokine-activated killer cells is not blocked by BCR-ABL. A substantial number of patients with chronic myeloid leukemia can now be cured, and the prognosis has improved even for those patients who are not cured. Interferon-alpha has emerged as the treatment of choice for patients who do not undergo an allogeneic bone marrow transplantation. The availability of allogeneic bone marrow transplantation has been increased by the ability to find unrelated donors, although graft-versus-host disease remains a major problem. Adoptive immunotherapy with donor lymphocyte transfusions will induce durable remissions and possibly cures in many patients who relapse after allogeneic BMT. Moreover, a number of investigational approaches, especially autologous BMT, appear promising.

CD34+ Cell Dose Predicts Survival, Posttransplant Morbidity, and Rate of Hematologic Recovery After Allogeneic Marrow Transplants for Hematologic Malignancies

After autologous or allogeneic transplants of peripheral blood stem cells (PBSC), an adequate dose of CD34+ cells is necessary to ensure early and sustained hematopoietic engraftment and favorable clinical outcome. There are no comparable data on the relationship between CD34+ cell dose and recovery after allogeneic bone marrow transplants (BMT). Twenty-eight patients with hematologic malignancies received a BMT from an HLA-identical sibling, using T-cell depletion and cyclosporin for graft-versus-host disease prophylaxis and delayed donor lymphocyte transfusions in an attempt to prevent leukemia relapse. The treatment-related mortality (TRM), primarily due to infections and cytopenias, was significantly higher for 13 patients receiving less than 1 x 10(6) CD34+ cells/kg (64.9% +/- 12.8% v 6.9% +/- 6.4%, P = .003). Survival at a median follow-up of 1 year was also lower in the group receiving less than 1 x 10(6) CD34+ cells/kg (30.8% +/- 12.8 v 74.3% +/- 13.7%, P = .005). The CD34+ cell dose was the only variable significantly associated with TRM. The dose of CD34+ cells also correlated with speed of hematopoistic recovery. Patients receiving more than 2 x 10(6) CD34+ cells/kg showed significantly earlier recovery of monocytes and a trend for earlier recovery of lymphocytes. They achieved platelet and red blood cell transfusion independence earlier, required less granulocyte colony-stimulating factor support during ganciclovir treatment, and spent fewer days in the hospital after transplantation. These results suggest that, for allogeneic T-cell-depleted BMT, the higher CD34+ cell doses may improve outcome in engrafting patients.

The graft-versus-leukemia effect.

Although the graft-versus-leukemia effect was predicted from animal experiments almost 40 years ago, only recently has its role in clinical bone marrow transplantation become better defined. The graft-versus-leukemia effect was initially considered to be a minor component of the graft-versus-host reaction. However, more recent analyses of clinical bone marrow transplants and the successful treatment of relapsed leukemia with donor lymphocyte transfusions indicate that the graft-versus-leukemia effect can be very powerful and to some degree independent of graft-versus-host disease. Results of donor lymphocyte transfusions draw attention to wide variability in response according to the nature of the relapsed leukemia and also to additional therapies that may enhance the efficacy of donor lymphocyte transfusions. Although natural killer lymphocytes may play a role in the graft-versus-leukemia effect, attention is focusing increasingly on T lymphocytes as potent mediators of the effect. Both CD4+ and CD8+ cells, together with the cytokines they produce, can interact with leukemia cells to deliver a cytotoxic hit on the malignant clone. Although leukemia cells undoubtedly share common antigens with other tissues of the recipient resulting in nonspecific graft-versus-host and graft-versus-leukemia reactions, there is also the possibility that distinct antigens are presented to T cells by the leukemia cells, providing a basis for separating the graft-versus-leukemia from graft-versus-host reactions. The current clinical challenge is to devise strategies for separating the graft-versus-leukemia response from graft-versus-host disease.

Graft-Versus-Leukemia Effect of Donor Lymphocyte Transfusions in Marrow Grafted Patients

The immune reactivity of allogeneic lymphocytes plays a major role in the control of leukemia after bone marrow transplantation. In patients with recurrent leukemia after marrow transplantation, chimerism and tolerance provide ideal conditions for adoptive immunotherapy with donor lymphocytes. We studied the effect of donor lymphocyte transfusions on acute and chronic leukemia in relapse after bone marrow transplantation. One hundred thirty-five patients with chronic myeloid leukemia (CML) (N = 84), acute myeloid leukemia (AML) (N = 23), acute lymphoblastic leukemia (ALL) (N = 22), myelodysplastic syndrome (MDS) (N = 5), and polycythemia vera with osteomyelofibrosis (PCV) (N = 1) were treated with transfusions of donor lymphocytes. Patients were monitored for response of leukemia, including in CML, the use of the polymerase chain reaction for bcr/abl mRNA transcripts and for the occurrence of graft-versus-host disease (GVHD) and myelosuppression. Complete remissions were induced by donor lymphocyte transfusions in 54 patients with CML (73%) and in the patient with PCV; complete remissions were also induced in five patients (29%) with AML and a patient with MDS. In contrast, ALL did not respond to adoptive immunotherapy with donor lymphocyte transfusions. Remissions were durable in patients treated for CML in chronic phase (probability of remission: 87% at 3 years). Lymphocyte transfusions were also given to 18 patients with ALL, AML, MDS, and transformed phase CML who were in remission after chemotherapy. These remissions were not durable. Fifty-two patients (41%) developed GVHD of grade 2 or more, and 41 patients (34%) showed signs of myelosuppression. Seventeen patients died without leukemia, 14 patients with GVHD and/or myelosuppression. Donor lymphocyte transfusions exert strong effects against myeloid forms of leukemia and induce durable remissions in CML.