Effective graft-versus-leukemia effects independent of graft-versus-host disease after T cell-depleted allogeneic bone marrow transplantation in a murine model of B cell leukemia/lymphoma. Role of cell therapy and recombinant IL-2

After allogeneic bone marrow transplantation (BMT) for leukemia, beneficial graft-vs-leukemia (GVL) effects are usually accompanied by potentially serious graft-vs-host disease (GVHD). Because T cell depletion is the only effective way to prevent GVHD it seems important to understand whether effective GVL can develop after BMT with T cell depletion in GVHD-free recipients. Well-established C57BL/6-->BALB/c chimeras that were free of GVHD, reconstituted with T cell-depleted allogeneic bone marrow cells, and inoculated 3 mo after BMT with a high inoculation of murine B cell leukemia (BCL1) showed no evidence of disease, whereas all control mice developed leukemia and died within 58 days. Results from adoptive transfer experiments in secondary naive BALB/c recipients indicated that all BCL1 cells were eliminated in the chimeras within 14 days. Hence, complete resistance to BCL1 developed in the chimeras despite complete tolerance to host alloantigens. The GVL effects observed in tolerant chimeras were further amplified by administration of immunocompetent allogeneic C57BL/6 spleen cells, low dose rIL-2, or both for 5 days. Our data suggest that GVL effects can develop even after T cell depletion in the absence of clinically overt GVHD and that GVL can be further amplified by rIL-2, either with or without use of additional immunocompetent donor T cells. Our data may provide the basis for new approaches to induce effective GVL after allogeneic BMT with cell therapy and rIL-2 at the stage of minimal residual disease, while avoiding early GVHD induced by the BMT procedure.

Effective graft-versus-leukemia effects independent of graft-versus-host disease after T cell-depleted allogeneic bone marrow transplantation in a murine model of B cell leukemia/lymphoma. Role of cell therapy and recombinant IL-2

After allogeneic bone marrow transplantation (BMT) for leukemia, beneficial graft-vs-leukemia (GVL) effects are usually accompanied by potentially serious graft-vs-host disease (GVHD). Because T cell depletion is the only effective way to prevent GVHD it seems important to understand whether effective GVL can develop after BMT with T cell depletion in GVHD-free recipients. Well-established C57BL/6-->BALB/c chimeras that were free of GVHD, reconstituted with T cell-depleted allogeneic bone marrow cells, and inoculated 3 mo after BMT with a high inoculation of murine B cell leukemia (BCL1) showed no evidence of disease, whereas all control mice developed leukemia and died within 58 days. Results from adoptive transfer experiments in secondary naive BALB/c recipients indicated that all BCL1 cells were eliminated in the chimeras within 14 days. Hence, complete resistance to BCL1 developed in the chimeras despite complete tolerance to host alloantigens. The GVL effects observed in tolerant chimeras were further amplified by administration of immunocompetent allogeneic C57BL/6 spleen cells, low dose rIL-2, or both for 5 days. Our data suggest that GVL effects can develop even after T cell depletion in the absence of clinically overt GVHD and that GVL can be further amplified by rIL-2, either with or without use of additional immunocompetent donor T cells. Our data may provide the basis for new approaches to induce effective GVL after allogeneic BMT with cell therapy and rIL-2 at the stage of minimal residual disease, while avoiding early GVHD induced by the BMT procedure.

Detection of minimal residual disease state in chronic myelogenous leukemia patients using fluorescence in situ hybridization

Detection of minimal residual disease and relapse remain major problems in chronic myelogenous leukemia (CML) patients following bone marrow transplantation (BMT). In order to disclose the 9;22 Philadelphia translocation, we used a fluorescence in situ hybridization (FISH) technique. BCR and ABL gene fragments were used as probes for the detection of the BCR/ABL fusion product in peripheral blood and bone marrow cells from 11 CML patients in which 5 were post-BMT. The sensitivity and specificity of this approach were compared to conventional cytogenetic and polymerase chain reaction (PCR) methods. FISH demonstrated a high degree of sensitivity (1%) for the detection of the BCR/ABL translocation in these patients. A linear correlation was found between FISH detection of the BCR/ABL fusion product and routine chromosomal analysis (r = 0.995; p < 0.001). Detection of the BCR/ABL signal by FISH was observed in all patients showing a positive PCR signal. A significant reduction in BCR/ABL signal was observed post-transplant (p < 0.001). However, the BCR/ABL translocation was detected in four of five transplanted patients immediately (0.75-2.5 months) following transplant and was found in patients with a low expression of the translocation.

Eosinophils activation in post-autologous bone marrow transplanted patients treated with subcutaneous interleukin-2 and interferon-alpha 2A immunotherapy

We evaluated eosinophils morphology, physical properties and antileukemic activity in autologous bone marrow transplanted (ABMT) patients treated with subcutaneous recombinant interleukin 2 (rIL-2) and recombinant human interferon alpha 2a (IFN alpha) given as outpatient immunotherapy. All patients receiving rIL-2/IFN alpha therapy developed peripheral blood eosinophilia of 20-40% peaking at 2-4 weeks of therapy. While on rIL-2/IFN alpha therapy the eosinophils became hypodense and hypersegmented. The antibody dependent cell-mediated cytotoxic activity (ADCC) of the eosinophils against the human B-cell lymphoma cell line (Raji) was depressed post-ABMT. Prolonged (28 days) in vivo rIL-2/IFN alpha immunotherapy enhanced ADCC activity of the eosinophils and brought them to normal levels. Similarly, rIL-2/IFN alpha immunotherapy enhanced the depressed cytotoxic activity of neutrophils post-ABMT to normal levels. Thus, eosinophils and neutrophils from rIL-2/IFN alpha-treated ABMT recipients may be targeted toward tumor cells by antibody, and express tumoricidal activity. No effect of rIL-2/IFN alpha was observed on monocyte-dependent ADCC activity which remained normal post-ABMT. We conclude that in addition to their effect on lymphocytes, cytokine-mediated immunotherapy consisting of subcutaneous low doses of riL-2 and IFN alpha may mediate their therapeutic effects in cancer therapy by increasing the number of eosinophils and enhancing the antitumor activity of eosinophils and neutrophils, provided that tumor-specific or tumor-associated antibodies are present.

Development of antibodies to hepatitis B virus surface antigen in bone marrow transplant recipient following treatment with peripheral blood lymphocytes from immunized donors

Bone marrow transplantation (BMT) recipients are immunosuppressed and are at risk for contracting severe infections. Recently, adoptive transfer of immunity against hepatitis B virus (HBV) was documented in BMT recipients receiving bone marrow from 'naturally' HBV-infected individuals who recovered spontaneously, or those transplanted with bone marrow cells obtained from actively immunized donors. Furthermore, reconstitution of the immune system in a BMT recipient who was a hepatitis surface antigen (HBsAg)+/HBV DNA+ carrier with HBV immune bone marrow cells led to clearance of the replicating virus, presumably through adoptive cell-mediated immunotherapy. We report three cases of induction of immunity to HBV by selective adoptive transfer by i.v. injection of peripheral blood lymphocytes (PBL) obtained from BMT donors who were actively immunized against HBV after harvesting of bone marrow. All three BMT recipients developed anti-HBs antibodies. In one BMT case in whom antibodies to HBsAg developed following adoptive transfer of immune PBL, a mild booster effect was documented in the BMT recipient upon immunization with a recombinant hepatitis B vaccine. The two remaining patients lost their antibodies to HBsAg in association with relapse of leukaemia. This immune manipulation may open the door to evaluation of adoptive transfer of immunity to HBV through selective transplantation of HBV immune lymphocytes in selected patients such as those with persistent HBV infection, as well as liver transplant recipients who require protection of the graft against HBV re-infection.

Health care reform as perceived by first year medical students

Our study objective was to evaluate the attitudes of first year medical students toward the health care system using a self administered questionnaire to all first year medical students at the medical schools in the University of California system. Of 631 students surveyed, 94% completed the instrument. Students were asked about their attitudes toward and familiarity with concepts in health services, access to care, and managed care. Our findings indicated that most students were unfamiliar with concepts related to health services. Students were concerned about access to care; sixty-six percent of students favor a national health insurance plan. A majority of students supported allowing patients access to the current health care system regardless of the cost or utility of a medical test or procedure. Thirty-nine percent felt that rationing health care in any form (transplants, access to the intensive care unit, etc.) is contrary to the way medicine should be practiced. 72% felt that practicing physicians had a major responsibility to help reduce health care costs. When asked about specific changes intended to control health costs, students identified reform of medical malpractice system (63%) and increased spending on preventive health (60%) as the two proposals most likely to be effective. Students generally held negative attitudes toward managed care organizations; only 10% would chose to receive their care in HMOs. We conclude that first year medical students generally have little understanding of the health care system. Despite this, they hold strong opinions about access to care, managed care organizations and strategies intended to reduce health care spending. It is up to medical educators to find creative methods of introducing these content areas into an already bulging curriculum.

Prediction by a modified mixed leukocyte reaction assay of graft-versus-host disease and graft rejection after allogeneic bone marrow transplantation

In this report we describe a modified, sensitive MLR test that appears to detect fine antigenic disparities between HLA-identical siblings confirmed as such by serology and the standard MLR test. In a group of 40 consecutive allogeneic bone marrow transplants, reactivity detected by the modified MLR test correlated with the development of rejection of matched marrow grafts and onset of acute graft vs. host disease (aGVHD). Thus, 13/15 positively reacting patient/donor pairs developed one of these complications (P < 0.001), while only 2/25 developed aGVHD in the negatively reacting group. This test may be useful for selecting the most compatible donor when several potential donors are available.

Ciprofloxacin enhances hematopoiesis and the peritoneal neutrophil function in lethally irradiated, bone marrow-transplanted mice

We analyzed the effect of in vivo ciprofloxacin and ceftazidime treatment on the development of myeloid progenitors and on the survival of lethally irradiated mice rescued with syngeneic bone marrow transplantation (BMT). Ciprofloxacin treatment (15 mg/kg per dose three times daily for 5 days) enhanced myeloid progenitor (colony-forming cell [CFU-C]) number in the bone marrow and the survival of mice transplanted with suboptimal doses (1 x 10(5) of s[Ngeneic bone marrow cells (BMC). Twenty days postirradiation, 50% (38 of 76) of saline-treated mice transplanted with 1 x 10(5) cells died compared with 25% (19 of 76) of ciprofloxacin-treated mice (p < 0.05). Similarly, ciprofloxacin treatment enhanced survival of mice transplanted with 1 x 10(6) syngeneic bone marrow cells: 50% (38 of 76) of saline-treated mice died within 20 days vs. 15% (12 of 80) of ciprofloxacin-treated mice. In contrast, treatment with ceftazidime did not affect progenitor cell number or survival. On day 8 postirradiation, although lethally irradiated mice transplanted with 1 x 10(5) BMC treated with ciprofloxacin demonstrated similar white blood cell (WBC) and red blood cell (RBC) counts as saline-treated mice, a (1.9 +/- 0.2)-fold increase in the percentage of polymorphonuclear cells (PMN) was observed in the peripheral blood of ciprofloxacin-treated mice. On day 5 postirradiation, ciprofloxacin-treated mice showed a (1.6 +/- 0.2)-fold increase in the number of peritoneal PMN and a 6.5-fold increase in their antibacterial activity towards Salmonella typhimurium in comparison with saline-treated mice.

Entering first-year medical students' attitudes toward managed care

PURPOSE

To study the attitudes of entering first-year medical students toward reform of the U.S. health care system.

METHOD

All 631 first-year medical students at the five medical schools in the University of California System were asked during orientation (late summer of 1992) to complete a self-administered questionnaire regarding their attitudes toward and knowledge about health care reform. Statistical methods used were chi-square tests and factor analyses.

RESULTS

Of the 631 students, 594 (94%) responded. Of the respondents, 392 (66%) felt that there should be a national health insurance plan, and 428 (72%) felt that practicing physicians had a major responsibility to help reduce health care costs. When asked about specific changes intended to control health care costs, the students identified reform of the medical malpractice system (374, 63%) and increased spending on preventive health (356, 60%) as the most likely to be effective. The students generally held negative attitudes toward managed care organizations; only 59 (10%) indicated they would choose to receive care in health maintenance organizations.

CONCLUSION

The students held strong opinions about access to care, managed care organizations, and strategies intended to reduce health care spending. Medical educators not only need to find creative methods of introducing these content areas into medical school curricula but should also anticipate the need for strategies to deal with negative attitudes held by students.

Effect of total lymphoid irradiation on natural killer cells and cytotoxic and primed T lymphocytes

Total lymphoid irradiation (TLI), which results in prolonged depression of the number and function of T and B cells, augments the natural killer (NK) cell activity. Small doses of irradiation (200-400 cGy) in vitro did not reduce the lytic activity of TLI-induced NK cells, whereas irradiation with 1,500 and 3,000 cGy decreased NK function by 50-70%. Addition of TLI spleen cells, containing a high proportion of large mononuclear cells, to cytotoxic T lymphocytes (CTL), generated in vitro by one-way mixed lymphocyte reaction and tested against 51Cr labeled target cells, suppressed the lytic activity 27-57% of that observed following the addition of normal spleen cells. The suppressive effect induced by spleen cells of TLI-treated mice was H2 nonrestrictive. Primed T lymphocytes (PTL) stimulated with irradiated allogeneic cells were inhibited by cocultured TLI spleen cells, causing inhibition of 57% as measured by secondary proliferative response and 86% inhibition by primary response to a third strain of cells. Our results, together with previously published data, indicate that TLI-induced suppressor cells inhibit the generation of PTL and CTL. Secondary proliferative responses of T cells primed to alloantigens are suppressed, as is the lysis of target cells by CTL. All suppressive phenomena presented here are antigen nonspecific.

Detection of minimal residual disease after sex-mismatch bone marrow transplantation in chronic myelogenous leukemia by fluorescence in situ hybridization

Detection of minimal residual disease is one of the major goals in bone marrow transplantation. We used a fluorescence in-situ hybridization technique to detect residual Philadelphia-chromosome positive cells in chronic myelogenous leukemia (CML) patients after sex-mismatch BMT. We analyzed the level of detection using probes for the BCR/ABL fusion product by comparison with results obtained with probes for the Y and X sex chromosomes. Detection of sex-mismatch chromosomes was significantly higher than that of the BCR/ABL translocation. In contrast, a higher specificity of residual tumor cell detection by the BCR/ABL probe was demonstrated because most of the sex-mismatch cells detected by FISH had a normal karyotype. Tumor-specific markers probes are thus superior and more accurate than sex-mismatch probes for detection of MRD in CML patients after BMT.

Potential use of interleukin-6 in bone marrow transplantation: effects of recombinant human interleukin-6 after syngeneic and semiallogeneic bone marrow transplantation in mice

The potential of recombinant glycosylated human interleukin-6 (rhIL-6) for enhancing immunohematopoietic reconstitution and survival after syngeneic and semiallogeneic bone marrow transplantation (BMT) in BALB/c mice subjected to total body irradiation (TBI) was investigated. rhIL-6 produced enhanced reconstitution of white blood cells as assessed on days 8 and 14 after syngeneic BMT and of platelets as assessed on day 10. Moreover, rhIL-6 treatment produced significant improvement of survival in lethally irradiated mice receiving either syngeneic or semiallogeneic BMT with limiting number of BM cells. This effect of IL-6 was not seen with large BM cell inocula producing high survival by themselves. rhIL-6 showed no toxic effects and did not affect the survival of mice that were lethally irradiated but not reconstituted by BM cells. However, the sensitivity of mice to sublethal irradiation was increased by rhIL-6 in the absence of BM cell transplantation. In experimental conditions inducing graft-versus-host disease (GVHD), in which lethally irradiated (BALB/c x C57BL/6)F1 mice received mixtures of BM and spleen cells from C57BL/6 donors, rhIL-6 was found to enhance GVHD manifestations. No consistent enhancement of T-cell in vitro proliferative responses to allogeneic spleen cells or T- and B-cell-dependent mitogens were seen in the splenocytes obtained from recipients of syngeneic or semiallogeneic BMT. Our data suggest that rhIL-6 may be useful in BMT procedures to enhance thrombopoiesis and hematologic recovery, as well as to increase overall survival rates. In addition, the potentiation of GVHD, which is considered to correlate with graft-versus-leukemia effects, may be of interest in enhancing GVHD-dependent antitumor effects in protocols combining radiochemotherapy with BMT.

Intracranial haematomas following bone marrow transplantation

Intracranial haemorrhage (ICH) is a known grave complication of leukaemia and has been described post mortem following bone marrow transplantation (BMT). Ante mortem following BMT, the incidence and significance of ICH is not well defined. The records of 471 bone marrow transplantation recipients over 11 years at the Hadassah University Hospital Bone Marrow Transplantation Department were reviewed. The relevant data of all patients with ICH were analysed. A resolute diagnostic and treatment protocol for subdural haematomas had been employed. The indication for transplantation in 273 of the patients was leukaemia. Thirteen of these patients developed subdural haematomas within 42 days of the transplant, and nine of these haematomas were bilateral. None of the 198 patients with other malignancies or nonmalignant indications for BMT (predominantly aplastic anaemia and beta thalassaemia major) had subdural haematomas. One thalassaemia patient and three leukaemia patients had intracerebral haematomas. There was no mortality or major morbidity from the subdural haematomas, which were all successfully resolved. In contrast, all of the patients with intracerebral haematomas consequently died. Subdural haematomas occur in approximately 5% of patients with leukaemia following BMT, but the clinical outcome is relatively benign. Intracerebral haematomas are a sporadic, lethal complication following BMT.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of chronic myelogenous leukemia with recombinant human interleukin-2 and interferon-alpha 2a

The safety, tolerance, and clinical effects of combined therapy with recombinant interferon-alpha (IFN-alpha) and interleukin-2 (rIL-2) administered subcutaneously for 2 courses of 4 weeks each, with 4 weeks interval between courses, given as outpatient therapy have been assessed in 10 patients with Philadelphia chromosome (Ph1)-positive chronic myelogenous leukemia (CML). All patients were previously treated with conventional chemotherapy and 3 failed to respond to IFN-alpha administered prior to our study. Median duration of disease from diagnosis was 36 months. Seven patients were in first chronic phase and the other 3 were in blast crisis, second chronic phase, and relapse post-bone marrow transplantation (BMT), respectively. Hematological response (median follow-up 16 months) was observed in 9 patients, with a decline in number of white blood cells and platelets. Elimination of Ph1 was observed in the patient who relapsed post-BMT with complete elimination bcr/abl RNA by polymerase chain reaction. Rebound lymphocytosis and eosinophilia were observed in most of the patients. Toxicity was acceptable. The main adverse effects were fever, chills, fatigue, anorexia, nausea, and vomiting. The side effects were reversible and no interruption of treatment was required. There was no treatment-related hospitalization or deaths. These data suggest that simultaneous subcutaneous IFN-alpha and rIL-2 home therapy is feasible, reasonably well tolerated, and potentially beneficial in CML patients. These observations may have important implications for the treatment of minimal residual disease following allogeneic and autologous marrow transplantation.

Successful purging of murine plasmacytoma by mafosfamide (ASTA-Z)

Mafosfamide (ASTA-Z) is a chemotherapeutic agent currently in use for in vitro purging of tumor-bearing human BM cells prior to autologous bone marrow transplantation (ABMT). We tested the efficacy of ASTA-Z against mouse plasmacytoma cells MOPC-315 (MOPC), a model of human multiple myeloma. BALB/c mice were injected intraperitoneally with different doses of MOPC preincubated with ASTA-Z. All control mice receiving > or = 10(4) MOPC intraperitoneally (ip) died within 23 days. All recipients of ASTA-Z pretreated MOPC remained healthy for > 180 days. To simulate the clinical situation, BALB/c mice received lethal doses of 10(3) MOPC ip prior to ABMT. Subsequently, mice were treated with cyclophosphamide 200 mg/kg one day prior to syngeneic BMT with 10(7) BMC containing 10(6) MOPC; 90% of the mice receiving unpurged syngeneic BMC died within 45 days whereas all mice transplanted with ASTA-Z-treated BMC/MOPC mixtures remained disease-free for > 100 days. Our results suggest that a similar approach may be successful in patients with multiple myeloma and residual disease prior to cryopreservation of their BM for ABMT. Bone marrow purging with ASTA-Z is effective and under certain conditions could be critical for prevention of relapse following ABMT, provided that effective elimination of residual disease in the host can be achieved by the conditioning regimen prior to ABMT.

Total lymphoid irradiation, anti-lymphocyte globulin and Campath 1-G for immunosuppression prior to bone marrow transplantation for aplastic anemia after repeated graft rejection

Allogeneic BMT for severe aplastic anemia is associated with a significant rate of graft rejection, especially in patients who have been previously transfused. We report a child with aplastic anemia who rejected donor marrow twice despite adequate immunosuppression as part of the conditioning therapy but engrafted successfully following combined administration of three modalities of immunosuppression: antithymocyte globulin, total lymphoid irradiation and the monoclonal antibody Campath-1G. Restriction fragment length polymorphism studies > 1 year after BMT show full donor hematopoiesis with no evidence of autologous recovery.

Inhibition of metastatic cell colonization in murine lungs and tumor-induced morbidity by non-peptidic Arg-Gly-Asp mimetics

The spreading and colonization of tumor cells require their migration to metastatic sites via blood vessels. To penetrate blood-vessel walls, cells, including malignant ones, must recognize and associate with the sub-endothelium extracellular matrix (ECM) and its glycoproteins. Recognition of ECM-glycoproteins, such as fibronectin (FN) and vitronectin (VN), is mediated by integrin receptors expressed on various cell types, including platelets, leukocytes and tumor cells. The Arg-Gly-Asp (RGD)-containing peptide, a major adhesive ligand of ECM, is present in various plasma and matrix glycoproteins, such as FN and VN. Non-peptidic mimetics of RGD, consisting of carboxylate and guanidinium groups of Asp and Arg divided by a linear atom spacer, express a high affinity for the alpha IIb-beta 3 integrin and inhibit platelet aggregation. Herein, the ability of RGD mimetics to inhibit adhesive interactions between tumor cells and RGD, and tumor progression in vivo, was examined. RGD-containing peptides and the RGD mimetic, compound SF-6,5, but not the Arg-Gly-Glu (RGE) peptide or the corresponding mimetic, specifically inhibited B16-F10 melanoma cell adhesion to immobilized VN and FN. Daily administration in vivo of SF-6,5 to mice inhibited the formation of B16-F10 colonies in experimental and spontaneous models of metastases. Moreover, SF-6,5 could prevent mouse death caused by massive colonization of tumor cells in the lungs. The therapeutic effect of RGD-containing peptides on tumor metastasis formation was marginal, probably due to the small amounts used, and its susceptibility to proteolysis in situ. Thus, non-peptidic mimetics of small adhesive epitopes may provide a novel therapeutic tool to prevent an adverse pathological event involving integrin-dependent cell-cell and cell-ECM interactions.

Inhibition of acute, experimental autoimmune encephalomyelitis by the synthetic immunomodulator linomide

Linomide (LS-2616, quinoline-3-carboxamide) is a synthetic immunomodulator that stimulates natural killer cell activity and activates several lymphocytic subpopulations in experimental animals and humans. In this study we determined the effect of oral treatment with linomide on the development of experimental autoimmune encephalomyelitis, an animal model for immune-mediated human demyelinating disorders. Experimental autoimmune encephalomyelitis was induced in SJL/J mice and in an outbred strain of rats (Sabra) by subcutaneous injection of spinal cord homogenate in adjuvant followed by inoculation with Bordetella pertussis. Linomide was administered in drinking water, at an estimated dose of 50 to 100 mg/kg/day. None of the linomide-treated mice (0/41) and Sabra rats (0/15) developed any clinical or pathological signs of experimental autoimmune encephalomyelitis, whereas almost all control animals (48/53 and 18/19, respectively) were severely paralyzed and 64.5% died from the disease. Lymphocytes obtained from linomide-treated animals had reduced in vitro proliferative responses to guinea pig myelin basic protein, proteolipid protein of the myelin, and tuberculin-purified protein derivative, unlike antigen-independent proliferation which was rather unaffected. Natural killer cell activity (tested by a cytotoxic assay on radiolabeled YAC-1 target cells) was significantly enhanced in mice treated with linomide. Our results indicate that modulation of the immune system with linomide leads to complete inhibition of experimental autoimmune encephalomyelitis in the absence of systemic immunosuppression. Linomide could therefore be of use in future clinical trials for the treatment of human autoimmune demyelinating disorders.

Spontaneous and IL-2-induced anti-leukemic and anti-host effects against tumor- and host-specific alloantigens

The graft-vs-leukemia (GVL) effect and its connection to graft-vs-host disease (GVHD) were studied in F1 hybrid mice after parental bone marrow transplantation. (BALB/c x C57BL/6) F1 mice (F1) were sublethally and lethally irradiated and inoculated with 10(4) BCL1 cells, a murine leukemia of BALB/c (BALB) origin. Subsequently mice were transplanted with F1 (syngeneic), BALB (allogeneic to the host but syngeneic to the tumor), C57BL/6 (B6) (allogeneic to both host and tumor) spleen cells, or spleen cells mixed with syngeneic (F1) bone marrow cells, respectively. Fresh BALB (H-2d) and B6 (H-2b) spleen cells, which induce equally strong GVHD in the F1 recipient against H-2b and H-2d alloantigens, respectively, were assayed for their ability to induce GVL effects on BCL1 (H-2d) cells with and without in vivo administration of human rIL-2. In order to increase the GVL effects, spleen cells were incubated for 4 days with rIL-2 to generate IL-2-activated killer cells. The results of adoptive transfer experiments showed that only immunocompetent B6 cells led to consistent eradication of leukemia. Neither BALB nor syngeneic F1 cells induced curative GVL effects regardless of whether spleen cells were further stimulated with rIL-2 in vitro, in vivo, or both. Our data support the theory that GVL effects are caused by T cell-dependent immune responses of allogeneic T cells and not by MHC-nonrestricted NK or rIL-2-activated NK cells, independently of the GVHD process itself. Hence, recognition and killing of tumor cells is most probably a MHC-restricted T cell-dependent process.

Effects of CAMPATH-1 antibodies on the functional activity of monocytes and polymorphonuclear neutrophils

The rat antihuman lymphocyte monoclonal antibodies CAMPATH-1M and CAMPATH-1G (IgM kappa and IgG2b kappa, respectively) recognize cell surface antigens (CDW52) present on normal T and B lymphocytes as well as on monocytes, with weak expression on neutrophils. In previous studies, when peripheral blood mononuclear cells were treated with CAMPATH-1M and human complement, more than 99% of lymphocytes were killed. The present study indicates that both CAMPATH-1M and -1G bind to peripheral blood neutrophils and monocytes and do not affect the activity of the former cells but decrease the functional activity of monocytes. Decreased functional activity includes suppressed superoxide production by monocytes in response to phorbol myristate acetate (PMA), reduced activation of the cells as indicated by decreased ability to reduce 3-(4.5-dimethylthiazol-2-yl)-2.5 diphenyl-tetrazolium bromide (MTT), reduced tumoricidal activity, and reduced capability to kill Candida albicans. The ability of CAMPATH-1 to suppress the functional activity of monocytes in vitro suggests that in vivo administration of CAMPATH-1G may also affect the function of monocytes.

Spontaneous and IL-2-induced anti-leukemic and anti-host effects against tumor- and host-specific alloantigens

The graft-vs-leukemia (GVL) effect and its connection to graft-vs-host disease (GVHD) were studied in F1 hybrid mice after parental bone marrow transplantation. (BALB/c x C57BL/6) F1 mice (F1) were sublethally and lethally irradiated and inoculated with 10(4) BCL1 cells, a murine leukemia of BALB/c (BALB) origin. Subsequently mice were transplanted with F1 (syngeneic), BALB (allogeneic to the host but syngeneic to the tumor), C57BL/6 (B6) (allogeneic to both host and tumor) spleen cells, or spleen cells mixed with syngeneic (F1) bone marrow cells, respectively. Fresh BALB (H-2d) and B6 (H-2b) spleen cells, which induce equally strong GVHD in the F1 recipient against H-2b and H-2d alloantigens, respectively, were assayed for their ability to induce GVL effects on BCL1 (H-2d) cells with and without in vivo administration of human rIL-2. In order to increase the GVL effects, spleen cells were incubated for 4 days with rIL-2 to generate IL-2-activated killer cells. The results of adoptive transfer experiments showed that only immunocompetent B6 cells led to consistent eradication of leukemia. Neither BALB nor syngeneic F1 cells induced curative GVL effects regardless of whether spleen cells were further stimulated with rIL-2 in vitro, in vivo, or both. Our data support the theory that GVL effects are caused by T cell-dependent immune responses of allogeneic T cells and not by MHC-nonrestricted NK or rIL-2-activated NK cells, independently of the GVHD process itself. Hence, recognition and killing of tumor cells is most probably a MHC-restricted T cell-dependent process.

Minimal residual disease in murine B-cell leukemia (BCL1) detected by PCR

Small proportions of leukemic cells escaping chemo-radiotherapy and/or dormant leukemic cells present in undetectable amounts in patients post therapy, i.e. minimal residual disease (MRD), are a source for relapse. The study of MRD and its treatment in a murine model for human B-cell leukemia/lymphoma, (BCL1), should lead to an improved understanding of the human disease. The standard assay for MRD in experimental mice is the adoptive transfer of spleen cells from experimental animals into naive secondary syngeneic recipients. We describe here the detection of MRD in BCL1-carrying BALB/c mice using the polymerase chain reaction (PCR). A BCL1 specific sequence from the rearranged VH-region was amplified yielding a 456 bp long fragment. PCR products hybridized to the cloned BCL1 sequence allowed the detection of a single BCL1 cell. This assay, therefore, reveals the presence of very small numbers of leukemic cells without sacrificing experimental animals.

Effect of bone marrow T lymphocytes treated with CAMPATH 1G on megakaryocyte colony formation

Specific populations of lymphocytes play a significant role in the regulation of megakaryocyte (MK) development. CAMPATH 1G (C1G) and CAMPATH 1M (C1M) are T lymphocyte (TL)-specific monoclonal antibodies (MABs) that are routinely employed to reduce graft-vs.-host disease (GVHD) in allogeneic bone marrow transplantation (BMT). Following BMT, engraftment of the erythroid and myeloid lineages is prompt, but prolonged thrombocytopenia often prevails. We therefore studied the effect on MK colony formation of treating donor bone marrow (BM) with the CAMPATH MABs. MK colonies were grown in plasma clots using postirradiation aplastic canine serum (PICS-J) as MK colony-stimulating factor (MK-CSF). C1M, which causes TL destruction by complement-dependent lysis, had no effect on MK cloning efficiency. C1G is not lytic but causes the elimination of TL in the BMT recipients via antibody-dependent cell cytotoxicity (ADCC). Treatment of donor BM with C1G significantly enhanced the number of early burst-forming units (BFU-MK) and late colony-forming units (CFU-MK) and had no effect on granulocyte-macrophage (CFU-GM) or erythroid (BFU-E) colonies. Enhancement of MK cloning efficiency was concentration-dependent between 0.03 and 3 micrograms MAB/10(6) BM mononuclear cells (MNC). Similar results were observed when C1G-treated TL or purified CD4+ TL were co-cultured with untreated autologous BMMNC or peripheral blood (PB) MNC. Conditioned medium (CM) from C1G-treated TL and CD4+ TL contained soluble factors that, when combined with suboptimal doses of PICS-J, potentiated MK growth. C1G in combination with PICS-J also stimulated TL proliferation in a dose-dependent manner. The T cell CM did not contain elevated levels of interleukin-3 (IL-3), IL-6, IL-1 beta, or GM-CSF. Our data provide additional evidence for the involvement of activated TL, and perhaps novel soluble T cell products, in the immunomodulation of megakaryocytopoiesis.