Ex vivo expanded umbilical cord blood T cells maintain naive phenotype and TCR diversity

BACKGROUND

Umbilical cord blood (CB) is a promising source of hematopoietic stem cells for allogeneic transplantation. However, delayed engraftment and impaired immune reconstitution remain major limitations. Enrichment of donor grafts with CB T cells expanded ex vivo might facilitate improved T-cell immune reconstitution post-transplant. We hypothesized that CB T cells could be expanded using paramagnetic microbeads covalently linked to anti-CD3 and anti-CD28 Ab.

METHODS

CB units were divided into three fractions: (1) cells cultured without beads, (2) cells cultured with beads and (3) cells cultured with beads following CD3+ magnetic enrichment. All fractions were cultured for 14 days in the presence of IL-2 (200 IU/mL).

RESULTS

A mean 100-fold expansion (range 49-154) of total nucleated cells was observed in the CD3+ magnetically enriched fraction. Following expansion, CB T cells retained a naive and/or central memory phenotype and contained a polyclonal TCR diversity demonstrated by spectratyping.

DISCUSSION

Our data provide evidence that naive and diverse CB T cells may be expanded ex vivo and warrant additional studies in the setting of human CB transplantation.

Fludarabine/melphalan conditioning for allogeneic transplantation in patients with multiple myeloma

The purpose of the study was to determine the feasibility and efficacy of a reduced intensity conditioning regimen of fludarabine and melphalan for allogeneic transplantation in patients with multiple myeloma. From August 1996 to December 2000, 22 patients received a reduced intensity conditioning regimen with fludarabine and melphalan. Median age was 51 years (range, 45-64), median time from initial therapy to transplant was 36 months (range, 3-135 months). Disease phase prior to transplant was primary refractory in two patients, refractory relapse in 11 patients, sensitive relapse in eight patients and initial remission consolidation in one patient. The median number of prior therapies was five (range, 1-7), and median beta 2 microglobulin prior to transplant was 3.0 mg/l (range, 1.0-7.3). All patients received unmanipulated grafts from either HLA matched sibling donors (n = 13) or matched unrelated donors (n = 9). Eighteen patients received fludarabine 30 mg/m(2) for 4 days with melphalan 140 mg/m(2) as a single dose and four patients received fludarabine 25 mg/m(2) for 5 days with melphalan 90 mg/m(2) daily for 2 days. All 21 patients evaluable for engraftment achieved a neutrophil count of >0.5 x 10(9)/l after a median of 12 days (range, 9-24), 18 patients achieved platelet transfusion independence after a median of 14 days (range, 8-47). All engrafting patients had 100% donor cell engraftment. Seven patients achieved a complete remission. Six patients are currently alive with a median follow-up of 15 months (range, 10-47 months). The actuarial survival and progression-free survival is 30 +/- 11% and 19 +/- 9% at 2 years. Non-relapse mortality at 100 days was 19 +/- 10% and 40 +/- 10% at 1 year. Fludarabine/melphalan combinations are feasible and allow consistent engraftment of allogeneic progenitor cells from both related and unrelated donors in patients with multiple myeloma and should be explored in patients with less advanced disease.

Diagnostic utility of flow cytometric immunophenotyping in myelodysplastic syndrome

The myelodysplastic syndromes (MDSs) are characterized by bilineage or trilineage dysplasia. Although diagnostic criteria are well established for MDS, a significant number of patients have blood and bone marrow findings that make diagnosis and classification difficult. Flow cytometric immunophenotyping is an accurate and highly sensitive method for detection of quantitative and qualitative abnormalities in hematopoietic cells. Flow cytometry was used to study hematopoietic cell populations in the bone marrow of 45 patients with straightforward MDS. The results were compared with those obtained in a series of patients with aplastic anemia, healthy donors, and patients with a history of nonmyeloid neoplasia in complete remission. The immunophenotypic abnormalities associated with MDS were defined, and the diagnostic utility of flow cytometry was compared, with morphologic and cytogenetic evaluations in 20 difficult cases. Although morphology and cytogenetics were adequate for diagnosis in most cases, flow cytometry could detect immunophenotypic abnormalities in cases when combined morphology and cytogenetics were nondiagnostic. It is concluded that flow cytometric immunophenotyping may help establish the diagnosis of MDS, especially when morphology and cytogenetics are indeterminate. (Blood. 2001;98:979-987)

Nonmyeloablative preparative regimens for allogeneic hematopoietic transplantation

Allogeneic hematopoietic transplantation is an effective therapy for a range of malignancies. High doses of myelosuppressive chemotherapy or radiation have been used in preparative regimens with the goal of preventing graft rejection and eradicating malignancy. Much of the benefit of transplantation, however, results from graft-versus-malignancy effects, mediated by donor immunocompetent cells. An alternative approach is to utilize less toxic, nonmyeloablative preparative regimens to achieve engraftment and allow graft-versus-malignancy effects to develop. This strategy reduces the risk of treatment-related mortality and allows transplantation for elderly or medically infirm patients not eligible for myeloablative therapy. Nonmyeloablative preparative regimens appear promising in diagnoses sensitive to graft-versus-malignancy effects and provide a platform for further development of cellular immunotherapy. Controlled clinical trials are warranted to define the role of nonmyeloablative allogeneic transplants in a range of hematologic malignancies and selected solid tumors.

Melphalan and purine analog-containing preparative regimens: reduced-intensity conditioning for patients with hematologic malignancies undergoing allogeneic progenitor cell transplantation

A reduced-intensity preparative regimen consisting of melphalan and a purine analog was evaluated for allogeneic transplantation in 86 patients who had a variety of hematologic malignancies and were considered poor candidates for conventional myeloablative therapies because of age or comorbidity. Seventy-eight patients received fludarabine 25 mg/m(2) daily for 5 days in combination with melphalan 180 mg/m(2) (n = 66) or 140 mg/m(2) (n = 12). Eight patients received cladribine 12 mg/m(2) continuous infusion for 5 days with melphalan 180 mg/m(2). The median age was 52 years (range, 22-70 years). Disease status at transplantation was either first remission or first chronic phase in 7 patients, untreated first relapse or subsequent remission in 16 patients, and refractory leukemia or transformed chronic myelogenous leukemia in 63 patients. Nonrelapse mortality rates on day 100 were 37.4% for the fludarabine/melphalan combination and 87.5% for the cladribine/melphalan combination. The median percentage of donor cells at 1 month in 75 patients was 100% (range, 0%-100%). The probability of grade 2-4 and 3-4 acute graft-versus-host disease was 0.49 (95% CI, 0.38-0.60) and 0.29 (95% CI, 0.18-0.41), respectively. Disease-free survival at 1 year was 57% for patients in first remission or chronic phase and 49% for patients with untreated first relapse or in a second or later remission. On multivariate analysis the strongest predictor for disease-free survival was a good or intermediate risk category. In summary, fludarabine/melphalan combinations are feasible in older patients with associated comorbidities, and long-term disease control can be achieved with reduced-intensity conditioning in this population.

Cryofibrinogenemia and skin necrosis in a patient with diffuse large cell lymphoma after high-dose chemotherapy and autologous stem cell transplantation

A 34-year-old woman with diffuse mediastinal B cell large cell lymphoma presented 60 days after high-dose chemotherapy and autologous stem cell transplantation, and post-transplant immunotherapy with interleukin-2, with skin necrosis in the ears and extremities. Extensive work-up revealed the presence of cryofibrinogenemia and associated thrombotic vasculopathy. The patient was successfully treated with corticosteroids and therapeutic plasma exchange. However, she had recurrence of large cell lymphoma a few weeks later and died of progressive disease. Cryfibrinogenemia and skin necrosis may have occurred secondary to the imminent relapse, or as a rare complication of high-dose chemotherapy or treatment with interleukin-2.

High-dose ifosfamide and etoposide with filgrastim for stem cell mobilization in patients with advanced ovarian cancer

High-dose chemotherapy combined with autologous peripheral blood stem cell transplantation has shown promise as treatment for recurrent or persistent epithelial ovarian cancer. We evaluated the stem cell mobilization regimen of high-dose ifosfamide plus etoposide in 32 patients with epithelial ovarian cancer, who had a positive second-look laparatomy or recurrent disease. Ifosfamide was given at 10 g/m2 by continuous i.v. from days 1 to 3. Etoposide was given at 150 mg/m2 every 12 h for six doses on days 1-3. Filgrastim was given at 10 microg/kg/d s.c. from day 5 until the completion of peripheral blood stem cell harvest. Fourteen of 32 patients had measurable or evaluable disease before mobilization therapy and were assessed for response. In nine (64%) of the 14 patients, treatment response was demonstrated, and these patients received a second cycle of mobilization therapy. The target CD34+ cell dose (>8 x 106 cells/kg) was achieved with a median of one apheresis (range 1-5). A median of 25.1 (range 8.0-122.5) x 106 CD34+ cells/kg body weight was collected. Non-hematologic toxicity was limited to grade 2 renal dysfunction in one patient and grade 2 hepatic dysfunction in three patients. In this patient group, high-dose ifosfamide plus etoposide with filgrastim support was well tolerated, lead to successful stem cell harvest and had antitumor activity.

Myelodysplastic syndrome and aplastic anemia: distinct entities or diseases linked by a common pathophysiology?

It is often difficult to distinguish myelodysplastic syndrome (MDS) from severe aplastic anemia (SAA) because both can present with profoundly hypocellular bone marrows. The distinction matters because although both conditions are complicated by pancytopenia, the risk of progression to acute leukemia is much greater in MDS. This chapter reexamines the relationship between SAA and MDS. The clinical and morphological features and pathophysiology of AA (including moderate and severe forms of acquired AA) are compared with MDS and hypoplastic MDS, with particular reference to new observations implicating autoimmune processes in both conditions. SAA and hypoplastic MDS (HMDS) are discussed in the light of these findings and attempts to separate nonevolving bone marrow failure syndromes from marrow failure progressing to acute leukemia are reviewed. The weight of evidence supports a common pathophysiology and, more speculatively, a common etiology for at least some forms of AA and MDS.

High-dose corticosteroid therapy for diffuse alveolar hemorrhage in allogeneic bone marrow stem cell transplant recipients

In a series of 74 patients with hematological malignancies undergoing allogeneic bone marrow or peri- pheral blood stem cell transplants from an HLA-identical sibling donor, four developed diffuse alveolar hemorrhage (DAH) between days 0 and 23 post transplant. Diagnosis was made by the radiographic finding of diffuse bilateral lung opacities, and bloody lavage fluid on bronchoscopy. Two patients required mechanical ventilatory support. They were treated with methylprednisolone 0.25-1.5 g/day for at least 4 days with slow tapering thereafter. All patients showed an immediate response and two became long-term survivors with normal respiratory function. Two had a relapse of DAH, developed acute respiratory distress syndrome (ARDS) and died with multi-organ failure. Risk factors for DAH were one or more courses of intensive chemotherapy pretransplant vs no treatment or low-dose chemotherapy (4/4 DAH vs 23/70 no DAH; P = 0.015), and second transplants (2/2 DAH vs 1/70 with no DAH; P = 0.006). These results indicate that DAH is life-threatening but is potentially reversible by prompt treatment with high doses of steroids.

Allogeneic hematopoietic transplantation as adoptive immunotherapy. Induction of graft-versus-malignancy as primary therapy

An immune-mediated graft-versus-malignancy effect is important to prevent relapse after allogeneic bone marrow transplant for a range of hematologic malignancies and potentially some solid tumors. Graft-versus-leukemia (GVL) effects as seen in response to donor lymphocyte infusions have been most prominent against indolent malignancies including chronic myelogenous leukemia, chronic lymphocytic leukemia, and low-grade lymphoma. Acute myelogenous leukemia and multiple myeloma may also respond. An alternative strategy for allogeneic transplantation is to avoid the toxicity of high-dose chemoradiotherapy and use a relatively nontoxic, nonablative preparative regimen to achieve engraftment, allowing subsequent infusion of additional donor lymphocytes to mediate GVL. Fludarabine-based nonablative chemotherapy agents, using standard dose combinations, produce moderate myelosuppression but are sufficiently immunosuppressive to allow engraftment of an allogeneic hematopoietic transplant and generation of graft-versus-malignancy effects.

Carmustine, etoposide, cytarabine and melphalan as a preparative regimen for allogeneic transplantation for high-risk malignant lymphoma

BACKGROUND

The combination of carmustine, etoposide, cytarabine and melphalan (BEAM) is an effective autologous transplantation preparative regimen for lymphoma and has little toxicity, but the feasibility and tolerance of BEAM as a preparative regimen for allogeneic transplantation has not been established.

PATIENTS AND METHODS

Thirty adults with primary refractory or recurrent intermediate- or low-grade lymphoma were treated on a prospective phase II study with carmustine 300 mg/m2 i.v. day -6, etoposide 200 mg/m2 i.v. followed by cytarabine 200 mg/m2 i.v. twice daily days -5 to -2, melphalan 140 mg/m2 i.v. day -1, and marrow or blood stem cells from an HLA-identical donor on day 0. Tacrolimus and methotrexate were used to prevent graft-vs.-host disease (GVHD).

RESULTS

Median time from transplantation was 20 mos (range 6-32 months). Median maximal regimen-related toxicity grade was 2, and four patients (13%) had a grade 3-4 regimen-related toxicity. Two patients had idiopathic interstitial pneumonitis. One patient had primary graft failure, and a second had autologous reconstitution documented at three months posttransplant. Grades 2-4 acute GVHD occurred in 31%, grades 3-4 in 16%, and chronic GVHD in 54%. Day-100 survival was 70%. Twenty-three patients achieved a complete response. The two-year relapse rate was 23%, survival was 48%, and disease-free survival (DFS) was 42%.

CONCLUSIONS

BEAM supports engraftment of allogeneic transplants and is a tolerable preparative regimen for allogeneic transplantation for lymphoma.

Reinventing bone marrow transplantation: reducing toxicity using nonmyeloablative, preparative regimens and induction of graft-versus-malignancy

Bone marrow transplantation was initially developed as a means to deliver supralethal doses of chemotherapy and radiation for treatment of malignancies. Myelosuppression is the dose-limiting toxicity for many chemotherapy drugs and whole-body radiation. Many malignancies exhibit a steep dose-response relationship to chemotherapy or radiotherapy. Bone marrow transplantation allows escalation of doses beyond those levels which produce severe bone marrow toxicity. Doses of many agents, particularly alkylating agents and whole body radiation, can be increased three- to fivefold above their conventional maximally tolerated dose. Marrow transplantation was considered a supportive care modality to restore hematopoiesis. It has become clear, however, that the high dose therapy does not eradicate the malignancy in many patients, and that the therapeutic benefit of allogeneic marrow transplantation is largely related to an associated immune-mediated graft-versus-malignancy effect.

Donor-recipient polymorphism of the proteinase 3 gene: a potential target for T-cell alloresponses to myeloid leukemia

The curative effect of allogeneic bone marrow transplantation (BMT) is in part due to an alloresponse of donor lymphocytes against recipient leukemia termed the graft versus leukemia (GvL) effect. To identify target antigens for the GvL response on leukemia cells, we looked for polymorphism of proteinase 3, a primary granule protein overexpressed in myeloid leukemias. The study was carried out in 10 patients with hematologic diseases and their HLA-identical marrow donors. By polymerase chain reaction (PCR)-single strand conformation polymorphism assay, followed by direct sequencing of the PCR products, we found seven DNA polymorphisms. One of them encodes for either an isoleucine or a valine at position 119 of the amino acid sequence. Peptides that span the polymorphic site, at amino acids 115-124, were shown to bind in vitro to the HLA-A2 molecule. We screened 23 HLA-A2 patients with myeloid leukemia and their HLA-identical donors for this polymorphism. No relapse was found in the group of 4 evaluable patients who possessed at least one allele absent in their donor, whereas 7 of the 15 remaining evaluable patients relapsed. These data support the possibility that T-cell responses to allelic differences of proteinase 3 could be used as a basis for designing leukemia-specific adoptive T-cell therapy in acute and chronic myeloid leukemias.

A technique for dual determination of cytotoxic and helper lymphocyte precursor frequency by a miniaturized dye release method

Helper (HTLPf) and cytotoxic (CTLPf) lymphocyte precursor frequency assays are increasingly used in bone marrow stem cell and organ transplant compatibility testing. Current techniques require large cell numbers and radioisotopes. To improve the technique, we developed a miniaturized fluorescent read-out combined HTLPf/CTLPf limiting dilution assay. The assay requires only 5 x 10(6) stimulators, 2 x 10(6) responders and 0.24 x 10(6) target cells in Terasaki plates (40 microl/well). For the HTLPf, culture supernatants from each well were assayed for IL-2 production. The IL-2-dependent proliferation of the mouse 9.12 cell line was detected by a semi-automated fluorescent dye technique. After addition of rhIL-2 (recombinant human IL-2) on days 3 and 7, CTLPs were detected on day 10 by measuring the lysis of dye-labeled targets. Results were comparable to standard radioisotope-based techniques. The assay had a coefficient of variation of approximately 30%. The assay detected helper CD4 cells, pure cytotoxic CD8, helper CD8 cells and helper/cytotoxic CD8 cells. Discrimination was demonstrated between HLA-matched related and non-related pairs. The ease of testing and small cell numbers required should facilitate further evaluation of HTLPf and CTLPf for compatibility testing in unrelated donor transplantation and monitoring immune responses following adoptive transfer of lymphocytes.

Polymorphism in CD33 and CD34 genes: a source of minor histocompatibility antigens on haemopoietic progenitor cells?

Following bone marrow stem cell transplantation allo-responses against haemopoietic progenitor cells (HPC), causing graft rejection and graft-versus-leukaemia effects, can be induced by donor T cells recognizing peptides derived from polymorphic endogenous proteins present in HPC. Since CD33 and CD34 are both expressed on HPC, we looked for genetic polymorphisms that might be the source of minor histocompatibility antigens (mHA) on such cells. Bone marrow from 14 donors and their HLA-identical recipients undergoing BMT for haematological malignancies were studied. Using non-radioactive single-strand conformation polymorphism analysis (cold SSCP) of complementary DNA encoding CD33 and CD34, three DNA polymorphisms, two in CD33 and one in CD34 were found and sequenced. Two were in non-coding regions, but in CD33, ATA or ATG at codon 183 resulted in an Ile or Met in the protein sequence. Nonapeptides derived from both alleles were predicted to bind to HLA A68.1. Thus two alleles of CD33 protein exist that could be mHA. With an alternate allele frequency of < 10%, allo-responses against CD33 would be uncommon after marrow transplantation. However, donors homozygous for this allele could be used to generate cytotoxic T cells against the frequent CD33 allele, for adoptive therapy of leukaemia.

Specific depletion of alloreactive T cells in HLA-identical siblings: a method for separating graft-versus-host and graft-versus-leukaemia reactions

Accumulating evidence indicates that alloreactive donor T cells confer both graft-versus-host (GVH) and graft-versus-leukaemia (GVL) reactivity following allogeneic bone marrow transplantation. We have developed a method to deplete alloreactive donor T cells with an immunotoxin targeting the alpha chain of the IL-2 receptor. In patients with chronic myeloid leukaemia and their HLA-identical sibling donors, we measured donor helper T-lymphocyte precursor frequencies (HTLPf) against recipient peripheral blood mononuclear cells (PBMNC; donor versus host), recipient leukaemia cells (donor versus leukaemia) and third-party PBMNC, before and after the depletion. In seven pairs there was a 4.3-fold reduction of donor-versus-host HTLPf (P=0.017), without a significant change in the donor frequencies against third party (P=0.96). In eight further donor-recipient pairs, immunotoxin-depleted donor versus patient PBMNC HTLPf 4.5-fold (mean 1/155,000 before and 1/839,000 after depletion, P=0.007). There was a smaller non-significant 1.8-fold reduction in donor-versus-leukaemia HTLPf from 1/192,000 to 1/334,000 (P=0.19). These results suggest that selective T-cell depletion can significantly deplete donor anti-host reactivity while conserving anti-leukaemia reactivity in HLA-matched donor-recipient pairs.

T cell-depleted bone marrow transplantation and delayed T cell add-back to control acute GVHD and conserve a graft-versus-leukemia effect

Thirty-eight patients with hematological malignancies, received T cell-depleted marrow transplants (BMT) and cyclosporine to prevent acute graft-versus-host disease (aGVHD), followed by delayed add-back of donor lymphocytes to prevent leukemia relapse. In 26 patients scheduled for donor T cell add-back of 2 x 10(6) cells/kg on day 30 and 5 x 10(7) cells/kg on day 45 (schedule 1), the overall probability of grade > or = II aGVHD developing was 31.5%, with a 15.5% probability of aGVHD occurring after T cell add-back. In 12 patients receiving 10(7) donor T cells/kg on day 30 (schedule 2), the probability of grade > or = II aGVHD was 100%. The incidence of grade III-IV aGVHD was higher in schedule 2 than in schedule 1 (P=0.02). Of 24 evaluable patients, 10 (46%) developed chronic GVHD which was limited in eight and extensive in two. Current disease-free survival for 18 patients at standard risk for relapse (chronic myeloid leukemia (CML) in chronic or accelerated phase, acute myeloid leukemia in remission) vs 20 patients with more advanced leukemia or multiple myeloma were respectively 72% vs 12% (P < 0.01) with a 29% vs 69% probability of relapse (P=0.08). In 12 CML patients surviving more than 3 months, PCR analysis of the BCR/ABL transcript showed that minimal residual disease after T cell add-back was transient except in two patients who developed hematological relapse. Results indicate that the risk of acute GVHD is low following substantial T cell doses, transfused 45 days after transplant, using cyclosporine prophylaxis. Furthermore a graft-versus-leukemia effect was conserved.

T cell-depleted granulocyte colony-stimulating factor (G-CSF) modified allogenic bone marrow transplantation for hematological malignancy improves graft CD34+ cell content but is associated with delayed pancytopenia

To increase the stem cell content of T cell-depleted bone marrow transplants (BMT), we treated 12 patients with hematological malignancies with BMT from HLA-identical sibling donors given G-CSF 10 microg/kg/day for 5 days before marrow harvest. After CD34+ cell selection, patients received a median of 1.7 (range, 0.82-3.1) x 10(6) CD34+ cells/kg and 2.3 (range, 0.25-4.0) x 10(5) CD3+ cells/kg. All patients had initial engraftment but four developed pancytopenia between days 55-130 post-BMT. In two patients, this required a second infusion of G-CSF-mobilized donor peripheral blood progenitor cells. We observed no delayed pancytopenia in a matched historical group of 24 patients receiving T cell-depleted BMT without prior G-CSF stimulation. Compared to this control group, G-CSF-stimulated marrow recipients showed a significant decline in neutrophil and monocyte counts after 8 weeks. However, outcome after BMT was otherwise comparable, with a similar incidence of acute graft-versus-host disease and transplant-related mortality. Disease-free survival was 63 vs 67% for controls matched for CD34+ cell dose (P = NS). These results indicate that G-CSF stimulation can increase the CD34+ cell content of T cell-depleted marrow but carries a risk of late graft failure.

Preferential usage of T cell receptor (TCR) V beta by allogeneic T cells recognizing myeloid leukemia cells: implications for separating graft-versus-leukemia effect from graft-versus-host disease

New understanding of the alloresponse following bone marrow transplantation supports the possibility that the graft-versus-host disease (GVHD) response can be separated from a favorable graft-versus-leukemia (GVL) effect. We used chronic myeloid leukemia (CML) cells to generate 122 recipient-reactive T cell clones from a closely HLA-matched sibling responder. Clones were tested for their proliferative response to stimulator CML cells or PHA-transformed (non-leukemic) lymphoblasts. Of 78 clones tested, 32 recognized both leukemia cells and PHA blasts, 19 only CML and four only PHA blasts. The remainder were non-specific responders. This functional specificity corresponded to distinct patterns of T cell receptor (TCR) V beta usage: clones recognizing CML cells preferentially used V beta 5, V beta 6/7 while clones recognizing both CML and PHA blasts or only PHA blasts preferentially used V beta 3 and V beta 8. It may therefore be possible to identify in vitro-generated myeloid leukemia-restricted donor T cells by their pattern of V beta usage. TCR V beta antibodies could thus be used to select and expand leukemia-restricted donor T cells for transfusion after BMT to specifically enhance the GVL response.

Immune escape from a graft-versus-leukemia effect may play a role in the relapse of myeloid leukemias following allogeneic bone marrow transplantation

We studied patients relapsing with myeloid leukemias following allogeneic bone marrow transplantation (BMT) for evidence of immune escape by clonal evolution of the leukemia. Relapsed cells from four out of five patients had a reduced ability to stimulate proliferation of lymphocytes from an HLA-mismatched responder. There was decreased susceptibility to lysis by CTL in three and reduced susceptibility to NK-mediated lysis in one. Relapsed leukemias had marked alterations in expression of critical surface molecules involved in immune responsiveness. Three had decreased expression of MHC class I and II, with no change or increase in CD54 (ICAM-1) or CD80 (B7.1). None of these responded to treatment with donor lymphocytes. Three patients showed no change, or increased expression of MHC with no change or decrease in ICAM-1 or B7.1. Two achieved remission - one in response to donor lymphocytes and one following withdrawal of cyclosporine. In one patient transplanted with myelodysplastic syndrome in transformation, interferon-gamma upregulated expression of MHC molecules in relapsed cells and increased their stimulatory capacity and target susceptibility to unmatched responder lymphocytes. These results suggest that immune escape through clonal evolution of the leukemia is a common occurrence in patients who relapse with myelogenous leukemias after BMT.

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.

Targeted T-cell therapy for human leukemia: cytotoxic T lymphocytes specific for a peptide derived from proteinase 3 preferentially lyse human myeloid leukemia cells

Proteinase 3 is present in high concentration in the primary granules of acute and chronic myeloid leukemia blasts, and may represent a potential T-cell target antigen. We screened proteinase 3 against the binding motif of HLA-A2.1. Based on its high predicted binding, a 9-mer peptide, "PR-1," was synthesized and tested for binding to HLA-A2.1 using the T2 cell line. PR-1 at 100 micrograms/mL significantly increased expression of HLA-A2.1, with median channel of fluorescence increasing from 22 to 294. Binding half-life was determined to be 1,460 minutes by I125-labeled beta 2-microglobulin incorporation. HLA-A2.1+ peripheral blood mononuclear cells from a normal donor were used to generate a T-cell line specific for PR-1. The line demonstrated 85% PR-1-specific lysis at an E:T ratio of 50:1, compared with 20% lysis without PR-1, using T2 cells as targets. It also showed 79% specific lysis to fresh chronic myelogenous leukemia blasts, 54% to fresh acute myelogenous leukemia blasts, and only background lysis (< 20%) to HLA-A2.1+ normal allogeneic marrow cells. The amount of lysis of HLA-A2.1+ myeloid cells was proportional to cytoplasmic proteinase 3 expression. Thus, HLA-A2.1-restricted cytotoxic T cells, raised against a peptide contained in proteinase 3, preferentially lysed fresh human leukemic cells.

Alloreactive CD4+ T lymphocytes can exert cytotoxicity to chronic myeloid leukaemia cells processing and presenting exogenous antigen

Existing evidence supports that CD4+ T lymphocytes play a role in the graft-versus-leukaemia (GVL) reaction after allogeneic bone marrow transplantation (BMT) for chronic myeloid leukaemia (CML), not only as initiators of the immune response but also as effectors of GVL. In BMT between HLA-identical pairs this CD4-mediated GVL would require CML cells to process and present antigens through MHC class II molecules. To investigate whether CML cells are capable of processing and presenting antigens, and suitable targets for CD4+ T-cell-mediated cytotoxicity, we generated HLA-DR1-restricted CD4+ cytotoxic T-cell clones that specifically recognized tuberculous purified protein derivative (PPD). We have shown that CML cells and B lymphoblastoid cell line (B-LCL) cells but not PHA-blasts from patients with CML processed exogenous antigen, PPD, and induced proliferative and cytotoxic CD4+ T-cell responses. Antigen presentation was blocked by antibodies to HLA-DR but not to MHC class I and by treatment with chloroquine and brefeldin. This indicates that CML cells use a classic MHC class II antigen processing pathway to present PPD antigens to CD4+ T cells. Cytotoxicity to CML was shown by antibody blocking studies to be mediated mainly through fas antigen. These findings indicate that donor CD4+ T cells alone are sufficient to mediate GVL effects following allogeneic BMT for CML.

Interaction of natural killer cells with MHC class II: reversal of HLA-DR1-mediated protection of K562 transfectant from natural killer cell-mediated cytolysis by brefeldin-A

Major histocompatibility complex (MHC) class I antigens on tumour cell surfaces have been shown to modulate target susceptibility to natural killer (NK) cell-mediated lysis in some, although not all, systems investigated. MHC class II expression may also affect NK cell function, but the mechanism by which MHC class II antigen regulates NK cell activity has not been fully examined. In this study we induced HLA-DR1 expression by gene transfection into the classic NK-sensitive K562 cell line to study the interaction of NK cells with MHC class II molecules and the effect of brefeldin-A (BFA), an endogenous antigen-processing pathway blocker, on NK-target cell interaction. We demonstrated that the expression of HLA-DR1 on the cell surface reduced K562 cell susceptibility to NK lysis by peripheral blood monuclear cells and a NK cell line. The effect was demonstrable in prolonged (8 hr) cytotoxicity assays and was blocked by pretreatment of target cells with anti-HLA-DR antibody. Treatment of K562 DR transfectant with BFA abrogated the resistance of K562 transfectant to NK-mediated cytolysis. These findings indicate that HLA class II molecules regulate NK cell function and target recognition, and suggest that endogenous peptides presented through MHC molecules are responsible for regulating NK cytolysis.