Targeted immunotherapy with intentionally mismatched rIL-2 activated donor lymphocytes in an attempt to eliminate minimal residual disease in patients with high-risk metastatic cancer

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Background: Graft-versus-leukemia and graft-versus-tumor (GVT) effects following stem cell transplantation are well established, however, procedure related toxicity and mortality are unavoidable. In addition to limited efficacy following stem cell transplantation (SCT), graft-versus-host disease (GVHD) is unavoidable. Our protocol was designed to induce more potent anti-cancer immunotherapy by rIL-2 activated intentionally mismatched donor lymphocytes (MDL) at the stage of minimal residual disease (MRD) outpatient procedure with no SCT avoiding GVHD. Methods: Optimizing MDL was accomplished by cyclophosphamide 1,500 mg/m2 and 2 injections of alpha interferon (3x106IU) for more effective immunotherapy, aiming for depletion of regulatory T cells, followed by infusion of haploidentically mismatched lymphocytes activated with rIL-2 (6,000 IU/ml) for 4 days. On the day of cell infusion, patients received rIL-2 6x106 IU subcutaneously outpatient for 5 days. Results: A total of 41 (age 5–73, median 52) high risk patients were included: metastatic breast 13; colorectal 3; gastric 3; pancreatic 3; melanoma 3; head & neck 3; glioblastoma 2; and 6 with other solid tumors. Five patients had resistant hematological malignancies: multiple myeloma 2; non-Hodgkin's lymphoma 2 and Hodgkin's disease 1. 6 patients received lymphocytes with bispecific antibodies for targeted cell-therapy (3 with catumaxomab against CD3 & epithelial cell adhesion molecule (EpCAM); 3 with ertumaxomab directed against CD3 & Her-2/neu WHO toxicity >grade 2 was noted. 14 of evaluable patients are alive. 10/32 with solid tumors are alive, 7 with no evidence of disease > 9–91 (median 17) months (4 breast; 1 squamous cell; 1 head & neck; 1 prostate). Of 5 patients with hematological malignancies 4 are alive and disease free >18–96 (median 46) months. Conclusions: Safe induction of GVT effects may be accomplished by MDL, preferably targeted with bispecific antibodies after cyclophosphamide conditioning lymphocytes are more potent and act faster than matched lymphocytes and GVHD is avoided by rejection of donor lymphocytes. When applied at a stage of MRD, such treatment may result in operational cure.

No significant financial relationships to disclose.

Immunotherapy of relapsed resistant chronic myelogenous leukemia post allogeneic bone marrow transplantation with alloantigen pulsed donor lymphocytes

Allogeneic cell-mediated immunotherapy with donor lymphocyte infusion (DLI) can successfully reverse chemoradiotherapy-resistant relapse in patients with chronic myeloid leukemia treated by allogeneic bone marrow transplantation (BMT). We describe the first successful attempt in 1992 to treat DLI-resistant relapse in a patient with CML in full hematologic relapse, using immunized donor lymphocytes. Donor lymphocytes were pulsed in vitro with a mixture of irradiated peripheral blood lymphocytes (PBL) obtained from both parents, in order to trigger alloactivation of donor lymphocytes against host alloantigens presented by parental cells, using as stimulating cells maternal PBL expressing the shared maternal haplotype and paternal PBL expressing the shared paternal haplotype of the patient. Full hematologic, cytogenetic and molecular remission was induced for the first time, independently of GVH, and has persisted for more than 9 years. To the best of our knowledge, this report represents the first successful immunotherapy with donor lymphocytes activated against host-type antigens. We suggest that immune donor PBL may be superior to DLI, possibly effective even when all other modalities fail, perhaps even independently of GVHD.

Immune reconstitution following allogeneic stem cell transplantation in recipients conditioned by low intensity vs myeloablative regimen

We have investigated the immune status of patients with hematologic malignancies treated with a low intensity conditioning in preparation for allogeneic stem cell transplantation. Conditioning consisted of fludarabine, anti-T lymphocyte globulin and low-dose busulfan, followed by infusion of allogeneic blood stem cells. This protocol resulted in rapid engraftment and complete replacement of host with donor hematopoietic cells. Immunological parameters of these patients were compared to those patients who were conditioned by an aggressive myeloablative regimen. Distribution of cell surface markers of lymphocyte subsets from both groups of patients was similar, but different from that of normal control cells. Reduced intensity or non-myeloablative conditioning prior to allogeneic stem cell transplantation (NST), hardly lowered the normal T cell-dependent mitogenic response even during the early period following transplant, while the myeloablative treatments resulted in a suppressed mitogenic reaction and in slow immune recovery. Reactivity of non-MHC restricted cytotoxic T cells was also at a normal level in patients who were treated with NST. We conclude that stem cell engraftment following reduced conditioning may result in early reconstitution of immune responses assessed in vitro. We hypothesize that clinical application of NST may lead to faster development of effective immune responses against residual host-type malignant and abnormal non-malignant hematopoietic cells, although the role of fludarabine on post-transplant infections remains to be investigated in a larger cohort of patients.

Cell therapy with preimmunized effector cells mismatched for minor histocompatible antigens in the treatment of a murine mammary carcinoma

Cell therapy with allogeneic donor cells mismatched for minor histocompatible (MiHC) antigens was applied to a murine mammary carcinoma (4T1) model to test the feasibility of graft versus tumor (GVT) effect against metastatic epithelial tumor cells. BALB/c mice bearing a 4T1 tumor of BALB/c origin were given syngeneic or MiHC-mismatched splenocytes. GVT effects were determined in secondary recipients of adoptively transferred lung cells derived from primary hosts who had previously been inoculated intravenously with 4T1 cells, and injected with one of the following: 1) naive BALB/c splenocytes, 2) naive DBA/2 splenocytes, 3) 4T1-immune DBA/2 splenocytes, or 4) DBA/2 splenocytes immunized with host-derived BABL/c spleen cells. Naive DBA/2 splenocytes inhibited tumor growth only slightly and only slightly prolonged the survival of secondary recipients, in comparison with fully matched tumor/host BALB/c spleen cells. An efficient GVT reaction was demonstrated in vitro and in vivo with MiHC-mismatched DBA/2 splenocytes from mice presensitized by multiple injections of irradiated tumor or BALB/c-derived spleen cells. All 30 mice adoptively inoculated with lung cells from primary hosts that had previously been treated with these presensitized effector cells were tumor free for >250 days. Secondary recipients inoculated with lung cells from mice given naive BALB/c or DBA/2 spleen cells died of metastatic tumors within 33 to 46 days. These results suggest that preimmunized donor cells represent an effective tool against metastatic disease; hence, the next goal should be to control graft-versus-host disease while exploiting the GVT potential.

Induction of antitumor immunity by indomethacin

Irradiated tumor cells given, together with indomethacin, to syngeneic mice induced an antitumor response and conferred protection against a challenge of a lethal dose of murine mammary (4T1) and lung (3LL) carcinoma cells. Continuous administration of indomethacin was crucial throughout the entire period of immunization and challenge, as no protection was achieved when the drug was given during only one of these procedures. Antitumor immunity was long-lasting and, when tested in the 4T1 model, 48% of mice were resistant to a second challenge of lethal tumor cells. Tumor-free immune mice that were given indomethacin for more than 300 days remained healthy with normal white blood cell counts and normal spleen size. Cells isolated from immune mice were able to kill tumor cells in culture after in vitro activation by interleukin-2, in a manner similar to cells from naive normal control mice. In addition, the mitogenic response of their T cells was as high as that of the control naive mice. While indomethacin was able to induce antitumor immunity to 4T1 and 3LL murine carcinoma cells, both of which contain a high concentration of endogenic prostaglandin E(2) (PGE2), no such immunity was achieved to murine tumor cells with a low concentration of endogenic PGE2. These results suggest a correlation between PGE2 concentration and the ability of indomethacin to induce antitumor immunity. We therefore suggest that an immunotherapy protocol with long-term dispensation of a tolerable dose of an immunomodulator, given together with irradiated autologous tumor cells, may stimulate antitumor responses to tumors containing high concentrations of endogenic PGE2.

The use of soybean agglutinin (SBA) for bone marrow (BM) purging and hematopoietic progenitor cell enrichment in clinical bone-marrow transplantation

Soybean agglutin (SBA) is a plant lectin that has been used to fractionate bone marrow cells. It binds bone marrow mononuclear cells, including mature myeloid, erythroid, and lymphoid cells, but has very low binding affinity and no toxic effect to the human hematopoietic cells. In this article we describe the possibilities of enriching bone-marrow-derived CD34+ hematopoietic progenitor cells using SBA. As the method is simple and elegant. SBA is of vast importance to the field of clinical bone marrow transplantation.

Allogeneic cell therapy for a murine mammary carcinoma

The effect of allogeneic cell therapy on tumor growth was studied in a murine model of mammary carcinoma (4T1) as an experimental model of solid tumors in humans. i.v. inoculation of 4T1 (H-2d) cells into syngeneic mice [BALB/c or (BALB/cXC57BL/6)F1] (F1) carrying the H-2d histocompatible antigens results in tumor colonies in the lungs that finally cause the death of all of the mice. Sublethally irradiated F1 mice were inoculated with 4T1 cells to simulate minimal residual disease and with immunocompetent splenocytes derived from naive donors of F1 (syngeneic), BALB/c (syngeneic to the tumor but semiallogeneic to the host), or C57BL/6 (allogeneic to the tumor and semiallogeneic to the host) mice. The survival of F1 tumor-bearing mice that were treated with allogeneic C57BL/6 splenocytes was significantly prolonged (P < 0.02) compared with hosts given F1 or BALB/c-derived splenocytes that are syngeneic to 4T1 tumor cells. Adoptive transfer of lung cells that were isolated from F1 primary mice inoculated with 4T1 cells and syngeneic BALB/c or F1 splenocytes led to local tumor growth and death in secondary recipients. In contrast, only 1 of 22 secondary recipients developed tumors when inoculated with lung cells derived from F1 mice given allogeneic C57BL/6 splenocytes. All of the 21 secondary hosts survived disease-free for a follow-up time of >200 days. These results indicate that immunocompetent cells allogeneic to the mammary carcinoma cells were able to inhibit tumor development in the primary hosts and to prevent tumor growth in the adoptive recipients, which suggests that allogeneic cell therapy may be an efficient antitumor tool to eradicate minimal residual disease in human solid tumors.

Tumorigenicity and immunogenicity in a murine model of B-cell leukemia/lymphoma (BCL1)

Multiple injections of intact irradiated BCL1 cells, a murine B-cell leukemia/lymphoma can trigger a dose-dependent anti-tumor immune response in naive syngeneic mice. The ability to induce anti-BCL1 immunity and the effect of various cell-modifications on BCL1 tumorigenicity and immunogenicity was evaluated. Newcastle disease virus (NDV) infection or transfer of cytokine genes by both retroviral and Adeno 5 vectors affect neither tumorigenicity nor immunogenicity of BCL1 cells given as a non-immunogenic cell-dose. New ways will have to be developed to elicit a reliable and reproducible anti-tumor effect in spontaneously arising and non-immunogenic hematological malignancies.

Cytokine gene transduction into non-immunogeneic murine tumor cells

The effect of cytokine transduction on the tumorigenicity and immunogenicity of murine non-immunogeneic mammary carcinoma (4T1), acute myeloid leukemia (mAML) and partially immunogenic B-cell leukemia (BCL1) has been evaluated in syngeneic strains of mice. Transduction by retroviral vectors containing the genes for GM-CSF, IL-2 or IFN-gamma did not lead to a marked antitumor effect in 4T1 mammary tumor or BCL1. A reduced local tumor size was observed in mice inoculated with 4T1 cells transduced with both GM-CSF and IL-2 genes followed by an in vitro exposure to recombinant IFN-gamma, but survival was not prolonged. Tumorigenicity of mAML cells transduced with the gene coding for IFN-gamma was significantly reduced as manifested by prolonged survival of mice in comparison with animals inoculated with non-transduced mAML cells. Transduction by each of the aforementioned cytokines did not affect the immunogenicity of these tumor model cells. The results suggest that genetic modification of spontaneous and non-immunogenic experimental tumor models does not necessarily support direct utilization of cytokine gene therapy for clinical application. More effective methods have yet to be established in order to achieve an antitumor effect in spontaneous non-immunogenic malignancies.

Effect of indomethacin on tumorigenicity and immunity induction in a murine model of mammary carcinoma

Indomethacin, an inhibitor of cyclo-oxygenase given orally, reduced the tumorigenicity of cancer cells in a non-immunogenic murine model of mammary adenocarcinoma (4T1). In the presence of indomethacin, a dose-dependent immune protection could be induced most effectively by immunizing mice with 1 to 3 doses of irradiated tumor cells inoculated at intervals of 7 days prior to challenge with a tumorigenic cell dose. Three immunizations given without indomethacin resulted in tumor growth in 88% of the recipients, and indomethacin treatment started 28 days prior to the challenge dose and given without immunizations led to tumor onset in 83% of mice. In contrast, tumor was documented only in 12% of mice vaccinated with 3 immunization doses and given concomitantly indomethacin. Moreover, 53% of disease-free survivors resisted a second challenge with a high tumorigenic dose. Induction of an anti-tumor immunity in indomethacin-treated mice was further studied as a therapy for tumor-bearing mice. Complete cure was induced in 50% of mice, and a significant reduction in tumor size as well as prolonged survival time were observed in the remaining animals. Immunostimulation by tumor cell vaccination given in the presence of a tolerable dose of indomethacin, therefore, may be incorporated into immunotherapy protocols to activate an anti-tumor response against residual tumor cells that escaped surgery and/or high-dose chemo/radiotherapy.

The effect of linomide, an immunoregulator in experimental autoimmune diseases, on humoral antibody responses in mice

Linomide (quinoline-3-carboxamide), a well tolerated, orally administered compound was recently shown to be effective in the prevention and treatment of several autoimmune diseases in experimental animal models. We have investigated its effect on specific humoral immune responses directed to T-cell-dependent soluble or particulate antigens and to a T cell-independent antigen in several mouse strains. Linomide administered after antigen priming did not affect primary and secondary antibody responses directed to T-cell particulate antigens (SRBC) or soluble antigens given with or without complete Freund's Adjuvant (CFA). Linomide treatment given prior to antigen priming did not affect the antibody response to a soluble antigen (TNP-KLH) given with an adjuvant. In contrast, dose-dependent down regulation of primary antibody responses was observed when T cell-dependent (BSA-dextran) or T-cell-independent (TNP-Ficoll) antigens were administered in an immunogenic form without adjuvant after starting Linomide treatment. The primary anti-SRBC antibody response was also suppressed by high dose Linomide given prior to immunization although normal secondary responses were retained. It is worth noting that no immunosuppressive effects on antibody responses were found at low dose ranges which effectively reversed T cell dependent autoimmune manifestation.

Activated long-term peripheral blood cultures as preparation for adoptive alloreactive cell therapy in cancer patients

Different modes of in vitro activation of peripheral blood mononuclear cells (PBMC) were compared for their effect on long-term propagation. PBMC cultures were activated by short exposures to the mitogen phytohemagglutinin (PHA) and the CD3 complex, with or without secondary signals provided by ligands of CD28 costimulatory molecules. Activation and long-term cultures were carried out in the presence of recombinant interleukin-2 (rIL-2). Addition of supernatant derived from IL-2-activated PBMC improved culture cell yield. Cumulative fold expansions ranged between 10(3) and 10(5) within 21 days. The highest cell yield was found after PHA activation. Fewer cells were obtained after activation with a combination of CD3 and CD28, and even fewer were obtained after CD3 activation alone. An increase in CD8+ and CD56+ cells, without change in CD4+ cells, was found in activated cultures when compared with fresh PBMC. Non-MHC-restricted cytotoxic activity was documented in all activated cultures. Cytotoxic activity per culture was highest in PHA-activated PBMC because of the high cell yield on the day of harvest. Successful in vitro expansion of PBMC might be helpful for gene transfer into T lymphocytes, as well as for the induction of an antitumor response, particularly for prevention and treatment of relapse of hematologic malignancies following allogeneic or autologous bone marrow transplantation.

Induction of graft vs. tumor effect in a murine model of mammary adenocarcinoma

We have attempted to induce immune-mediated graft-vs.-tumor (GVT) effects against solid tumors, using a murine model of mammary adenocarcinoma derived from BALB/c(H-2d) mice. A cell line (4Tl) isolated from this tumor model was highly tumorigenic in syngeneic (BALB/c) or haplo-identical (BALB/c x C57B1/6)F1 mice (F1), was only partially tumorigenic in an H-2d congenic strain of mice (DBA/2) and was non-tumorigenic in a major histocompatible (MHC)-unrelated (H-2b) strain of mice (C57B1/6). 4Tl cells express class I MHC antigens and adhesion molecules but do not express MHC class II antigens or B7-1 co-stimulatory molecules. Female BALB/c (H-2d) or F1 (H-2d/b) mice were reconstituted with male bone marrow (BM) cells derived from minor histocompatible (MiHC)-mismatched DBA (H-2d) donors or with MHC-mismatched C57B1/6 (H-2b) BM cells, respectively, 24 hr following lethal total body irradiation. Recipient mice carrying MiHC- or MHC-mismatched donor cells were inoculated with 4Tl cells 2-3 months following BM reconstitution. Chimeras reconstituted with allogeneic donor cells that were MiHC- or MHC-incompatible with tumor cells were able to down-regulate the development of the primary tumor expressing host-ype MHC alloantigens. Tumor size in BM chimeras across MiHC or MHC antigens was significantly smaller than tumor size observed in normal BALB/c or F1 controls. The GVT effect might be of help in improving immunotherapy for solid tumors in humans.

Activated allogeneic cell therapy (allo-ACT) for relapsed chronic myelogenous leukemia (CML) refractory to buffy coat transfusions post-allogeneic bone marrow transplantation

We describe a 17-year-old male patient with chronic myelogenous leukemia (CML) in hematologic and cytogenetic relapse 4 months post-non-T cell-depleted allogeneic bone marrow transplantation for accelerated CML. Two sequential buffy coat transfusion with donor peripheral blood cells (8.9 and 4.8 x 10(7) cells/kg), the second transfusion in combination with in vivo activation of donor cells by human recombinant interleukin-2 (rIL-2) 6 x 10(6) IU/m2 subcutaneously for 3 days, failed to induce remission . The patient responded to an infusion of donor peripheral blood lymphocytes (3.4 x 10(7) cells/kg) pre-activated in vivo with rIL-2 and additionally activated in vivo with rIL-2, 6 x 10(6) IU/m2/day subcutaneously for 3 days. Elimination of the Philadelphia (Ph) clone was confirmed by cytogenetic analysis showing a normal male karyotype and by disappearance of the bcr/abl transcript, using the polymerase chain reaction (PCR). At present, the patient is 26 months post-treatment with no evidence of disease, but with chronic graft-versus-host disease. Our data indicate that allogeneic activated cell therapy (allo-ACT) may provide antitumor effector cells that successfully induce graft-versus-leukemia (GVL) effects even when cell therapy with donor buffy coats was insufficient.

Tumor-cell vaccination induces tumor dormancy in a murine model of B-cell leukemia/lymphoma (BCL1)

Immunity to murine B-cell leukemia/lymphoma (BCL1) induced by multiple injections with irradiated tumor cells, prevented leukemia development in primary and adoptive transfer recipients despite long-lasting persistence of residual tumor cells. Detection of dormant BCL1 cells was carried out by PCR analysis using the VH-rearranged DNA sequence as a BCL1 clonal marker. Dormant tumor cells were detected > 250 days following immunity induction in 40% of spleens from healthy immune mice having no detectable symptoms of disease. Tumor dormancy was not abrogated by adoptive transfer of BCL1-containing splenocytes into syngeneic recipients, indicating that cell-mediated anti-tumor immunity contributes to maintenance of the tumor dormant state and prevents renewed tumor-cell growth. Splenocytes but not sera from immune mice conferred specific radiosensitive protection from a lethal dose of BCL1 cells included in cell mixtures transferred to secondary recipients. A therapeutic effect of transferred immune splenocytes was shown in BCL1-bearing mice, which remained disease-free for > 200 days after inoculation; nevertheless, dormant BCL1 cells were detected by PCR analysis in some of the surviving mice. Our results suggest that an efficient tumor-cell vaccine can lead to induction of tumor dormancy that can be maintained by a cell-derived mechanism for a long period of time.

Induction of tumor immunity by intact irradiated leukemic B cells (BCL1) bearing a tumor-associated cell-surface idiotype and the costimulatory B7 molecule

The idioptypic (Id) determinant of immunoglobulin expressed on the cell surface of malignant B cells represents a prototypical tumor-associated antigen (TAA), which has been used in a purified soluble form for active immunization in experimental tumor models and human hematological malignancies. Using a spontaneous transplantable murine model of B cell leukemia/lymphoma (BCL1), we have demonstrated the expression of the B7 costimulatory molecules in addition to the previously described Id determinant and class II major histocompatibility antigens. Intact irradiated BCL1 cells bearing these distinct determinants induced long lasting antitumor immunity in naive syngeneic mice. Induction was dose-dependent and most effective when three doses of 30 x 10(6) intact irradiated BCL1 cells were given at intervals of 7-10 days. The induced immunity protected 96% of 28 mice inoculated with a lethal dose of 10(5)-10(6) nonirradiated BCL1 cells and 85% of 27 mice given a second challenge, whereas control mice died on day 20 after inoculation with 10(6) BCL1 cells. Adoptive transfer of splenocytes derived from immune mice did not induce leukemia in syngeneic recipients. Such splenocytes, harvested more than 365 days following immunization and administered together with fresh BCL1 cells to adoptive recipients, were able to confer protection for 90 days, even following a second challenge given 104 days after the first one. BCL1 immune splenocytes transferred into BCL1-bearing mice exerted a therapeutic effect, preventing leukemia onset for at least 180 days. Our results demonstrate the ability of tumor cells to trigger effective anti-tumor immunity. These findings could ultimately be applied to the prevention of tumor relapse in treatment of hematological and other malignancies expressing TAA, class II MHC antigen and costimulatory molecules.

Effect of various cytokine combinations on induction of non-MHC-restricted cytotoxicity

Efforts were directed to achieve an increased lymphokine-activated non-MHC-restricted killing (LAK) activity greater than that induced by rIL-2 alone. Human peripheral blood (PB) and bone marrow (BM)-derived mononuclear cells (MC) were exposed in vitro to multiple cytokine combinations, including rIL-6, rIL-7, rIFN-alpha and rIFN-gamma in the presence of either suboptimal or optimal doses of rIL-2. Our results have shown that BMMC are a potential source for induction of increased LAK activity upon exposure to multiple cytokine combinations, whereas PBMC could not be successfully stimulated under the same conditions. Fifty-five to 62% of BM-derived samples stimulated with high dose rIL-2 + rIL-7 or rIL-2 + rIL-7 + rIL-6 + rIFN-gamma exhibited a higher degree of cytotoxicity than BM samples stimulated with rIL-2 alone. Exposure of PB-derived large granular lymphocytes (LGL) to various cytokine combinations led to increased proliferation after stimulation with suboptimal dose of rIL-2 in the presence of rIL-6 and rIL-7. This increase was not observed in induction of cytotoxicity. We suggest that BMMC activated by multiple cytokine combinations could play an active role in improving antitumor response in vivo by contributing to the control of minimal residual tumor cell growth, particularly post-BM transplantation.

Immunological evaluation of patients with hematological malignancies receiving ambulatory cytokine-mediated immunotherapy with recombinant human interferon-alpha 2a and interleukin-2

Immunological parameters were evaluated in patients treated with cytokine-mediated immunotherapy (CMI) consisting of low doses of recombinant human interferon alpha 2a (rIFN alpha) and recombinant human interleukin-2 (rIL-2) administered either concomitantly or sequentially by subcutaneous self-injections in an outpatient setting. Twenty-six patients with hematological malignancies and 2 metastatic melanoma patients in a progressive stage were enrolled in this clinical trial. Of the 26 patients, 24 were at a stage of minimal residual disease, including 14 patients who had received autologous bone marrow transplantation (ABMT) 2-5 months previously, 7 chronic myelogenous leukemia (CML) and 3 acute myeloid leukemia (AML) patients. Two patients (1 CML and 1 mult. myeloma) were treated at a stage of progressive disease. Non-MHC-restricted cytotoxicity directed against natural-killer(NK)-resistant (Daudi) and NK-sensitive (K562) target cells was assessed before, during and after CMI, either in fresh peripheral blood samples (spontaneous activity) or after in vitro rIL-2 activation (induced activity). Spontaneous killing activity was low prior to treatment, but increased upon termination of treatment in 10/15 evaluated cycels. rIL-2-activated cytotoxicity in vitro was markedly elevated in 8/12 and 6/8 patients after one and two cycles, respectively, of sequential treatment, as well as in 3/8 CML and 5/6 patients after one and two cycles, respectively, of concomitant treatment. Activation of the T cell mitogenic response was demonstrated in 6/9 patients after concomitant CMI, while no such effect was observed throughout a sequential treatment in lymphoma and leukemia patients after ABMT. Although a direct correlation between immune stimulation and the in vivo antitumor response cannot yet be determined, our clinical observations support a beneficial therapeutic effect in a substantial number of patients. These results indicated that the ambulatory CMI protocol of rIL-2 and rIFN alpha could stimulate the host defense immune system and may be helpful in mediating the in vivo antitumor response in patients with minimal residual disease.

Lymphocytes as cellular vehicles for gene therapy in mouse and man

The application of bone marrow gene therapy has been stalled by the inability to achieve stable high-level gene transfer and expression in the totipotent stem cells. We show that retroviral vectors can stably introduce genes into antigen-specific murine and human T lymphocytes in culture. Murine helper T cells were transduced with the retroviral vector SAX to express both neomycin-resistance and human adenosine deaminase genes. These cells were expanded in culture and selected for expression of neomycin resistance with G418. The gene insertion, selection, and culture expansion did not alter antigen specificity or growth characteristics of the T cells in vitro. To determine if cultured T cells might be used for gene therapy, their persistence and continued expression of the introduced genes was evaluated in nude mice transplanted with the SAX-transduced T cells. G418-resistant cells could be readily recovered from the spleens of recipients of transduced T cells for several months. In addition, recovered cells continued to produce human adenosine deaminase. Based on these observations, we studied cultured human tumor-infiltrating lymphocytes as a candidate cell for a trial of gene transfer in man. Exponential cultures of interleukin-2-stimulated tumor-infiltrating lymphocytes were efficiently transduced with the neomycin-resistance gene using the retroviral vector N2. Gene insertion and subsequent G418 selection did not substantially alter the growth characteristics, interleukin 2 dependence, membrane phenotype, or cytotoxicity profile of the transduced T cells. These studies provided a portion of the experimental evidence supporting the feasibility of the presently ongoing clinical trials of lymphocyte gene therapy in cancer as well as in patients with adenosine deaminase deficiency.

The effect of in vitro T lymphocyte depletion on generation of IL2-activated cytotoxic cells

The effect of immunocompetent lymphocyte depletion on precursors and effector cells of IL2 activated non-MHC restricted cytotoxic cells (LAK) generated from bone marrow (BM) or peripheral blood was investigated. Lymphocyte depletion was carried out by using Campath-1, a monoclonal rat anti-human lymphocyte antibody recognizing CDW52, that binds human complement and is used routinely in clinical bone marrow transplantation (BMT). The results indicate that LAK precursors derived from BM cells are sensitive to Campath-1 treatment, while a variable degree of sensitivity was demonstrated in LAK precursor cells derived from peripheral blood. In contrast, effector LAK cells generated in vitro were shown to be resistant to treatment with Campath-1 and complement. We hypothesize that if indeed IL2-dependent non-MHC restricted cytotoxic cells play a role in vivo in the immediate post-BMT period, a T lymphocyte depletion procedure such as the Campath-1 may have the capacity to reduce, at least temporarily, the graft-versus leukemia effects mediated by such anti-tumor effector mechanisms.

Retrovirus-mediated gene transfer into CD4+ and CD8+ human T cell subsets derived from tumor-infiltrating lymphocytes and peripheral blood mononuclear cells

Studies were undertaken to test the susceptibility of individual T cell subpopulations to retroviral-mediated gene transduction. Gene transfer into human tumor-infiltrating lymphocytes (TIL) or peripheral blood mononuclear cells (PBMC) was carried out by transduction with an amphotropic murine retroviral vector (LNL6 or N2) containing the bacterial neoR gene. The presence of the neoR gene in the TIL population was demonstrated by Southern blot analysis, detection of the enzymatic activity of the gene product and by the ability of transduced TIL to proliferate in high concentrations of G418, a neomycin analog that is toxic to eukaryotic cells. The presence of the neoR gene in TIL did not alter their proliferation or interleukin-2 dependence compared to nontransduced TIL. The differential susceptibility of CD4+ and CD8+ lymphoid cells to the retro-virus-mediated gene transfer was then tested. Transduction of heterogeneous TIL cultures containing both CD4+ and CD8+ cells resulted in gene insertion into both T cell subsets with no preferential transduction frequency into either CD4+ or CD8+ cells. In other experiments highly purified CD4+ and CD8+ T cell subpopulations from either TIL or PBMC could be successfully transduced with the neoR gene as demonstrated by Southern blot analysis and detection of the gene product neophosphotransferase activity. No such activity of vector DNA could be detected in controls of nontransduced cells. In these highly purified cell subsets the distinctive T cell phenotypic markers were continually expressed after transduction, G418 selection and long-term growth. Clinical trials have begun in patients with advanced cancer using heterogeneous populations of CD4+ and CD8+ gene-modified TIL.

The use of parabiosis for investigating the mechanism of transplantation tolerance in bone marrow chimeras induced by total lymphoid irradiation

The mechanism of transplantation tolerance in total lymphoid irradiation (TLI)-induced semiallogeneic bone marrow chimeras without clinical evidence of graft-versus-host disease (GVHD) was investigated using the technique of surgical parabiosis. When held in parabiosis with normal BALB/c mice, BALB/c---- (BALB/c x C57BL/6)F1 (BALB----F1) chimeras survived 7-9 days, significantly (P less than 0.001) shorter than the 12-19 day survival of normal F1 hybrids kept in parabiosis with normal BALB, and in contrast to indefinite (greater than 200 days) survival of syngeneic BALB parabiotic partners. When C57 skin grafts were placed on BALB mice held in parabiosis with BALB----F1 chimeras, C57 skin grafts survived 50-60 days, in contrast to 10-14 days in normal BALB recipients (P less than 0.001). Lethal GVHD, induced in sublethally irradiated F1 recipients by 10(7) BALB spleen cells, could not be delayed or prevented by cotransfer of 10(7) to 30 x 10(7) tolerant BALB spleen cells obtained from stable BALB----F1 chimeras. GVHD reactivity of BALB spleen cells isolated from BALB----F1 chimeras tolerant of C57 could not be recovered by depletion of Lyt2 cytotoxic suppressor cells. Taken together, in the absence of suppressive capacity by suppressor cells, these data support functional clonal deletion as the primary mechanism responsible for the maintenance of unresponsiveness to host alloantigens in TLI-induced semiallogeneic chimeras, since no protection against induction of GVHD could be documented in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of effector cells of graft vs leukemia following allogeneic bone marrow transplantation in mice inoculated with murine B-cell leukemia

It is now widely accepted that immunocompetent lymphocytes in allogeneic bone marrow grafts exert an antileukemic effect that contributes to the cure of leukemia. Graft vs leukemia (GVL) effects independent of graft vs host disease were investigated in allogeneic bone marrow chimeras tolerant of host and donor alloantigens. The role of Thy1.2, L3T4 and Lyt2 T lymphocytes as effector cells of GVL were investigated in (BALB/c x C57BL/6)F1 mice inoculated with murine B-cell leukemia and subsequently conditioned with total lymphoid irradiation and cyclophosphamide (200 mg/kg). Mice were reconstituted with C57BL/6 bone marrow cells depleted of well-defined T-cell subsets or enriched for stem cells by the soybean agglutination method. Detection of residual tumor cells, an indicator for efficacy of GVL, was carried out by adoptive transfer of peripheral blood or spleen cells obtained from treated chimeras into secondary naive BALB/c recipients at different time intervals following bone marrow transplantation. Treatment of the primary marrow inoculum with monoclonal anti-Thy1.2 or anti-Lyt2 abolished the GVL effects and all secondary BALB/c recipients developed leukemia within 60 days. On the other hand, the treatment with monoclonal anti-L3T4 did not influence the effect of GVL and all treated recipients remained without leukemia. The data suggest that T cells may mediate GVL effects in the absence of graft vs host disease and in circumstances where tolerance to conventional alloantigens is elicited. Effector cells of GVL across the major histocompatibility complex (MHC) in the murine B-cell leukemia tumor model system appear to be Thy1.2+ Lyt2+ L3T4-. Induction of GVL effects by allogeneic cells tolerant of host MHC suggests that these effects may be independent of graft vs host disease.

Selective abrogation of alloreactivity via priming in the presence of aphidicolin, a specific inhibitor of DNA polymerase

Aphidicolin, a specific and direct inhibitor of eukaryotic DNA polymerase alpha, was used to investigate its impact on immunologic reactions in vitro. Dose response curve of the inhibitory effect was studied in murine and human primary allogeneic responses, as well as the proliferative responses to both PHA and Con A mitogens. The presence of aphidicolin during the allosensitization phase in secondary MLR of mice splenocytes resulted in complete abolishment of the subsequent response directed against the priming alloantigens, whereas alloreactivity to unrelated alloantigen-bearing cells was inhibited to a much lesser degree. The allosensitized aphidicolin-treated cells lost the ability to respond to subsequent PHA stimulation, but were capable of exerting a high responsiveness to Con A. The presence of aphidicolin during the allosensitization phase in secondary MLR of human mononuclear cells resulted in markedly decreased alloreactivity directed against the priming cells, but spared the subsequent response to unrelated alloantigens and to both PHA and Con A mitogenic stimuli. It is suggested that aphidicolin may be used for selective inactivation of proliferating cells without interfering with immunologic functions of other quiescent subsets. Aphidicolin may thus be a useful agent for induction of specific unresponsiveness in experimental models of allogeneic transplantation.

Selective abrogation of alloreactivity via priming in the presence of aphidicolin, a specific inhibitor of DNA polymerase

Aphidicolin, a specific and direct inhibitor of eukaryotic DNA polymerase alpha, was used to investigate its impact on immunologic reactions in vitro. Dose response curve of the inhibitory effect was studied in murine and human primary allogeneic responses, as well as the proliferative responses to both PHA and Con A mitogens. The presence of aphidicolin during the allosensitization phase in secondary MLR of mice splenocytes resulted in complete abolishment of the subsequent response directed against the priming alloantigens, whereas alloreactivity to unrelated alloantigen-bearing cells was inhibited to a much lesser degree. The allosensitized aphidicolin-treated cells lost the ability to respond to subsequent PHA stimulation, but were capable of exerting a high responsiveness to Con A. The presence of aphidicolin during the allosensitization phase in secondary MLR of human mononuclear cells resulted in markedly decreased alloreactivity directed against the priming cells, but spared the subsequent response to unrelated alloantigens and to both PHA and Con A mitogenic stimuli. It is suggested that aphidicolin may be used for selective inactivation of proliferating cells without interfering with immunologic functions of other quiescent subsets. Aphidicolin may thus be a useful agent for induction of specific unresponsiveness in experimental models of allogeneic transplantation.

Combination of magnetic and chemocytotoxic cancer cell depletion for autologous bone marrow transplantation

An artificial mixture of breast cancer cell line cells (T-47D) and normal human marrow cells was used to investigate optimal approaches for autologous BMT. The experiments were designed to test the applicability of chemocytotoxic agents, a dye-mediated photolytic agent and SBA for in vitro purging in autologous BMT of patients with advanced malignancies. Treatment with high concentration of etoposide (VP-16) (10 to 80 micrograms/ml) resulted in a maximal depletion of 1.5 log, whereas more efficient tumor cell eradication (2.5 log) was achieved by 30-min incubation with 100 micrograms/ml4HC. Photosensitization by exposure for 90 min to daylight in the presence of MC-540 could remove only 1 log of T-47D cells. The chemocytotoxic treatment with 4HC was chosen to follow initial tumor cell separation by SBA bound to polystyrene magnetic beads that had previously been shown to bind to several cancer cell types while sparing marrow progenitor cells. Artificial mixtures containing 10 to 14% T-47D cells in fresh normal BM cells were subjected to SBA-magnetic beads, and the SBA-negative fraction was further treated with 4HC. The combined two-step procedure resulted in a consistent tumor cell depletion of greater than 4 logs. The purging procedure appears acceptable for clinical marrow purging prior to cyropreservation and autotransplantation in patients with documented BM involvement of neoplastic cells sensitive to 4HC with positive binding to SBA such as breast cancer.

Removal of breast cancer cells by soybean agglutinin in an experimental model for purging human marrow

Soybean agglutinin (SBA) was used as a differential reagent to achieve selective elimination of human breast cancer cells (T-47D cell line) from human marrow contaminated with tumor cells. Two successive cycles of direct agglutination by soluble SBA resulted in depletion of 3.5 logs of tumor cells as determined by radiolabeling, whereas removal of more than 4 logs of tumor cells was demonstrated by a clonogenic bioassay. A more convenient procedure for tumor purge involved the use of SBA bound to either polyglutaraldehyde magnetic beads or to commercial polystyrene magnetic beads. After one cycle of magnetic separation, 2 to 3.5 logs of tumor cells were removed. A second separation cycle using fresh magnetic beads improved depletion to more than 4 logs. Neither of these purging procedures affected the hematopoietic potential of granuloid-macrophage colony-forming unit cells. We suggest the use of SBA bound to magnetic beads as a convenient tool for effective ex vivo purging of marrow aspirates contaminated with metastatic breast cancer cells in patients with advanced disease. A similar procedure is applicable for all SBA-positive neoplasms.

Induction of transplantation tolerance by intraportal injection of allogeneic bone marrow cells. Possible implications for intrauterine bone marrow transplantation across major histocompatibility barriers

Intraportal inoculation of C57BL/6 marrow cells into sublethally (400 rad) irradiated BALB/c recipients resulted in durable chimerism and the permanent acceptance of C57BL/6 skin allografts. Sublethally irradiated recipients of a similar number of marrow cells inoculated systemically did not develop chimerism or any significant prolongation of the survival of C57BL/6 skin allografts. Consequently, lethal graft-versus-host disease developed only in recipients of intraportal marrow allografts (80%). The intraportal injection of allogeneic C57BL/6 marrow cells into nonirradiated recipients resulted in significant, although not permanent, prolongation of skin allograft survival without durable chimerism, suggesting that the introduction of alloantigens intraportally may favor the induction of nonresponsiveness to alloantigens even across strong major histocompatibility barriers. The relevance of these findings is discussed regarding the intraportal inoculation of allogeneic bone marrow cells for the treatment of genetic disorders in utero through the induction of neonatal tolerance.

Alloantigen persistence in induction and maintenance of transplantation tolerance

Infusion of parental bone marrow cells into F1 hybrids conditioned by total lymphoid irradiation (TLI) results in chimeras with a high percentage of donor-type cells, and without clinical signs of graft-vs.-host reaction. In these chimeras, a state of tolerance has been shown to be associated with paucity of cytotoxic T lymphocyte percursors (pCTL) reactive with host-type alloantigens. To determine whether the presence of tolerizing alloantigens is essential for maintenance of unresponsiveness, lymphohematopoietic cells obtained from such tolerant chimeras were transferred into supralethally irradiated recipients of two different genotypes: in one case the adoptive recipients were syngeneic with host-type cells, and in the other they were syngeneic with donor-type cells of the original chimeras, thus providing the chimeric cells with a tolerogen-free environment. After "parking" for 4 d in syngeneic donor-type mice, the transferred cells displayed a marked increase in the frequency of pCTL directed against tolerizing alloantigens, whereas a low pCTL frequency directed against the same H-2 target cells was maintained in allogeneic tolerizing-type adoptive recipients. Multiple injections of adoptive donor-type mice with tolerizing-type cells of the original chimera reestablished a low level of cytotoxic precursors. Cytotoxic activity against unrelated alloantigens was independent of the presence of tolerogen-presenting cells in the adoptively transferred mice. Our experimental model suggests that persistence of cells bearing tolerizing alloantigens is an essential requirement for maintenance of previously established tolerance.

Purging breast cancer cells in preparation for autologous bone marrow transplantation

Mixtures of the T-47D human breast cancer cell line and normal human bone marrow cells were used for studying a new approach for purging epithelial tumor cells for autologous bone marrow transplantation (BMT) in breast cancer. Breast cancer cell line T-47D cells were shown to bind soybean agglutinin (SBA) in a specific fashion that could be blocked by D-galactose. Tumor cells were effectively purged by both SBA agglutination and depletion of cells bound to magnetic beads (0.7-5.0 micron) covalently linked to SBA. A depletion of 3-4 orders of magnitude of tumor cells was consistently accomplished by combining one step of agglutination followed by one cycle of SBA-magnetic bead depletion. Neither procedure affects stem cell recovery. We suggest that effective purging of breast cancer cells can be accomplished using SBA for autologous BMT in patients with advanced breast cancer.

Functional clonal deletion versus suppressor cell-induced transplantation tolerance in chimeras prepared with a short course of total-lymphoid irradiation

Allogeneic bone marrow (BM) chimeras induced by infusion of BM cells into recipients conditioned with total lymphoid irradiation (TLI) were shown to develop humoral and cell-mediated tolerance to host and donor-type alloantigens by a number of in vitro and in vivo assays. Spleen cells of tolerant chimeras exhibited suppressive activity of mixed lymphocyte reaction (MLR). MLR suppression was not abrogated by depletion of Lyt-2 cells, and neither could Lyt-2-positive cells sorted from the spleens of tolerant chimeras suppress MLR or attenuate graft-versus-host reactivity in vivo. Likewise, specifically unresponsive spleen cells obtained from chimeras could not be induced to respond in MLR against tolerizing host-type cells following depletion of Lyt-2 or passage through a nylon-wool column. Tolerance of chimera spleen cells to host alloantigens, best documented by permanent survival of donor-type skin allografts, could be adoptively transferred into syngeneic recipients treated by heavy irradiation but not into untreated or mildly irradiated recipients. Adoptive transfer of tolerance seemed to be associated with experimental conditions favoring engraftment of tolerant cells rather than suppression of host reactivity. We speculate that although host and/or donor-derived suppressor cells may be operating in reducing the pool of specific alloreactive clones by blocking cell proliferation in response to allogeneic challenge, the final outcome in tolerant chimeras is actual or functional deletion of alloreactive clones.

Functional clonal deletion versus active suppression in transplantation tolerance induced by total-lymphoid irradiation

Transplantation tolerance and stable chimerism were established in adult mice conditioned with a short course of total-lymphoid irradiation (TLI) followed by infusion of 30 X 10(6) allogeneic bone marrow cells. Spleen cells of tolerant mice could not exert a proliferative or cytotoxic response against host-type cells in vitro and were unable to induce graft-versus-host reaction in secondary host-type recipients. The degree of suppression assessed by coculturing tolerant splenocytes in vitro in the one-way mixed lymphocyte reaction was quite variable--and, in some cases, was not at all demonstrable, although tolerance was clearly maintained. Suppression, when apparent, could not be ascribed to T lymphocytes. Suppressor cells were found to bind soybean agglutinin and could be separated from the nonsuppressive cells by means of this lectin. Dissociation of the suppressive population (SBA+ cells) from that which is normally alloreactive (SBA- cells) resulted in a suppressor cell-depleted fraction that was still unable to respond to host-type cells but regained reactivity to unrelated cells. Limiting dilution analysis of chimeric splenocytes revealed markedly reduced frequencies of cytotoxic T lymphocyte precursors (CTL-P) directed against host-type cells, as compared with normal splenocytes reacting against the same target cells. This difference was accentuated when these cells were sensitized to host-type target cells prior to plating in limiting dilution cultures. In 1:1 mixing experiments of normal and chimeric splenocytes, there was no evidence of any in vitro suppressive activity to account for hyporeactivity of chimeric cells against host-type cells. Thus, maintenance of TLI-induced tolerance seemed not to be mediated primarily through an active suppressor cell mechanism.

Proliferative response of murine B-cell leukemia (BCL1) to poly(L-lysine)

Peripheral blood lymphocytes (PBL) isolated from BALB/c mice bearing a B-cell leukemia (BCL1) showed a marked proliferative response upon two days culturing with poly(L-lysine) (PLL) of various molecular weights. An inverse relationship was noted between the molecular weight of the PLL and the dose required for optimal proliferative response. PLL showed no proliferative activity when cultured with normal PBL or with lymphocytes isolated from the spleen or other lymphoid organs of BCL1-bearing mice. Double exposure to PLL and lipopolysaccharide (LPS) had a marked synergistic effect on BCL1 PBL stimulation but not on PBL isolated from normal mice. The data suggest that PLL, in contrast to LPS, may cause a selective proliferation of a subpopulation(s) of B-tumor cells at a particular stage(s) of differentiation.

Lectin separation of nonlymphoid suppressor cells induced by total lymphoid irradiation

Suppression of the mixed lymphocyte reaction (MLR) exerted by splenocytes derived from mice treated with fractionated total lymphoid irradiation (TLI, 200 rds x 8) was analyzed by various criteria in order to characterize the phenotype of the cell type(s) responsible for suppression. TLI-induced suppressor cells could not be eliminated by removal of cells bearing surface immunoglobulin, Thy-1, Lyt-2 and TL, and thus could not be ascribed to lymphocytes of the B or T cell lineage. Suppressor cells were large, and nonadherent to nylon wool, Sephadex G-10 and plastic surfaces. Suppressor activity of TLI splenocytes was predominantly located in fractions of cells bearing receptors for soybean agglutinin (SBA), peanut agglutinin (PNA) or both lectins. SBA+, PNA+, sequentially agglutinated (SBA followed by PNA) SBA+PNA+ and (PNA followed by SBA) PNA+SBA+ suppressor cells were radioresistant upon exposure to 1000 rds in vitro. Cells bearing the receptor for PNA but lacking that for SBA (PNA+SBA-) had sharply reduced suppressor activity. However, a radiosensitive PNA- suppressor cell subset was also documented in the spleen of TLI-treated mice. Thus, suppressor cells could best be physically separated from nonsuppressors by the SBA lectin. SBA+ suppressor cells were found, by scatter analysis, to include the population of large cells characteristic of TLI splenocytes, whereas SBA- cells were much smaller and almost exclusively devoid of suppressive capacity. The PNA receptor was found to further dissect the SBA+ suppressor cells into two distinct subpopulations: radioresistant SBA+PNA+ cells and radiosensitive SBA+PNA- cells. In summary, we suggest here the presence of at least two suppressive populations induced by TLI: radioresistant SBA+, PNA+, SBA+PNA+ or PNA+SBA+ cells, and radiosensitive PNA- and SBA+PNA- cells. Similar subsets of MLR suppressor cells can be isolated from normal bone marrow cells and splenocytes of nude mice, suggesting that suppression is mediated by large, immature, nonlymphoid cells which might migrate from shielded bone marrow compartments into the spleen of TLI-treated mice.

Resistance to mycobacteria in mice treated with fractionated total lymphoid irradiation (TLI) and in mice reconstituted with allogenic bone marrow cells following radiotherapy

The increased clinical use of total lymphoid irradiation (TLI) as an immunosuppressive adjunct in transplantation suggested the need for determining the effects of TLI on the in vivo susceptibility of animals to infections controlled by cell-mediated immunity. TLI-treated, TLI-treated and splenectomized, and chimeric mice prepared with TLI were inoculated in the hind foot pad with Mycobacterium marinum or Mycobacterium leprae. Although M. marinum organisms multiplied in greater numbers in the TLI mice, ultimately they were destroyed as effectively in TLI mice as in the non-irradiated control mice. M. leprae multiplied at the same rate and to the same maximum in TLI mice as in controls. Mice previously challenged with M. marinum in one hind foot pad, and challenged subsequently with the same organism in the opposite hind foot pad, showed a solid immunity against this reinfection. It appears that upon recovery from the immediate effects of radiotherapy TLI-treated mice are able to mount an effective immune response to experimental infection with M. marinum and M. leprae.

Suppression of cell-mediated immune responses after total lymphoid irradiation (TLI). I. Characterization of suppressor cells of the mixed lymphocyte reaction

Total lymphoid irradiation (TLI) was administered to (BALB/c X C57BL/6)F1 mice in eight daily doses of 200 rad (total 1600 rad). Spleen cells isolated from mice after treatment with TLI do not respond to alloantigens in vitro in a one-way mixed lymphocyte reaction (MLR), but normal reactivity recovers after approximately 2 mo. Radioresistant, antigen-nonspecific suppressor cells are documented in the spleens of TLI-treated mice immediately after radiotherapy, but suppressive capacity gradually disappears within 30 days. After TLI, the spleen is repopulated with large cells, the proportion of which is greatest at a time when theta-bearing cells are still depleted. Radioresistant suppression is mediated predominantly by the large cell subset and is thymus independent. Suppressor function can be abolished by lethal physicochemical procedures including formaldehyde fixation, multiple freeze-thawing, and heating to 56 degrees C, and it cannot be conferred by supernatants of TLI-suppressed MLR suspensions. Suppression cannot be overcome by adding various cell factors including T cell growth factor (TCGF) and lymphocyte-activating factor (LAF), nor is it affected by a prostaglandin inhibitor. Equally potent radioresistant suppressive activity is documented by co-culturing cells derived from other sources enriched in large, immature hematopoietic cells, including fetal liver cells and bone marrow cells obtained from normal and congenitally athymic mice. The presence of a large cell population and MLR suppressor function is also documented in the spleens of mice treated with single dose or fractionated doses of lethal whole body irradiation, followed by reconstitution with bone marrow cells obtained from normal mice. The data suggest that MLR suppressor cells, which are large, immature and predominantly radioresistant, can be induced after a short and well-tolerated TLI regimen.

Suppression of cell-mediated immune responses after total lymphoid irradiation (TLI). I. Characterization of suppressor cells of the mixed lymphocyte reaction

Total lymphoid irradiation (TLI) was administered to (BALB/c X C57BL/6)F1 mice in eight daily doses of 200 rad (total 1600 rad). Spleen cells isolated from mice after treatment with TLI do not respond to alloantigens in vitro in a one-way mixed lymphocyte reaction (MLR), but normal reactivity recovers after approximately 2 mo. Radioresistant, antigen-nonspecific suppressor cells are documented in the spleens of TLI-treated mice immediately after radiotherapy, but suppressive capacity gradually disappears within 30 days. After TLI, the spleen is repopulated with large cells, the proportion of which is greatest at a time when theta-bearing cells are still depleted. Radioresistant suppression is mediated predominantly by the large cell subset and is thymus independent. Suppressor function can be abolished by lethal physicochemical procedures including formaldehyde fixation, multiple freeze-thawing, and heating to 56 degrees C, and it cannot be conferred by supernatants of TLI-suppressed MLR suspensions. Suppression cannot be overcome by adding various cell factors including T cell growth factor (TCGF) and lymphocyte-activating factor (LAF), nor is it affected by a prostaglandin inhibitor. Equally potent radioresistant suppressive activity is documented by co-culturing cells derived from other sources enriched in large, immature hematopoietic cells, including fetal liver cells and bone marrow cells obtained from normal and congenitally athymic mice. The presence of a large cell population and MLR suppressor function is also documented in the spleens of mice treated with single dose or fractionated doses of lethal whole body irradiation, followed by reconstitution with bone marrow cells obtained from normal mice. The data suggest that MLR suppressor cells, which are large, immature and predominantly radioresistant, can be induced after a short and well-tolerated TLI regimen.

Demonstration and characterization of virus released by murine B cell leukemia cells (BCL1)

LPS-stimulated leukemia cells derived from BALB/c mice bearing transplantable B-lymphocytic leukemia (BCL1) which arose spontaneously in a female BALB/c mouse, contained viral particles as suggested by electron microscopy as well as by tissue cultures using the XC assay. Some cell free extracts prepared from BCL1 cells were capable of transforming normal B-lymphocytes when inoculated into untreated syngeneic recipients. Cytogenetic analysis of spleen cells obtained from a splenomegalic male mouse neonatally inoculated with cell-free extract indicated that the tumor cells had a male karyotype with 42 chromosomes as compared to 37 chromosomes and a female karyotype in original BCL1 cells, thus excluding the possibility of tumor propagation by transplantation of intact BCL1 cells. These findings suggest viral involvement in the etiology of BCL1.

Suppression and elimination of BCL1 leukemia by allogeneic bone marrow transplantation

Mice carrying the B cell leukemia (BCL1)+ were successfully treated by total lymphoid irradiation (TLI), cyclophosphamide, and allogeneic bone marrow (BM) transplantation. Long-term survivors were examined for residual BCL1 cells and for the ability to transfer adoptively graft vs. leukemia (GVL) activity. Residual BCL1 cells could not be detected in the allogeneic BM chimeras (greater than 14 to 16 months) with the use of indirect immunofluorescent staining with anti-idiotype antibody. However, residual tumor cells were present in 50% of the "cured" chimeric mice since adoptive transfer of 10(6) spleen cells from 50% of the treated chimeric mice caused leukemia in BALB/c recipients. In order to determine whether leukemia had been prevented in the "cured" chimeras by a persistent cell-mediated mechanism, BALB/c mice were injected with 10(6) spleen cells from the "cured" BM chimeras together with a dose of 10(2) or 5 x 10(5) BCL1 cells. Onset of leukemia was delayed or completely abolished in a significant proportion of recipients receiving the cell mixtures, suggesting the presence of anti-tumor immunity in the cured mice. The data suggest that a persistent active immune mechanism may be responsible, in part, for the significant antileukemic effects observed in mice tolerant to donor alloantigens.

Suppression and elimination of BCL1 leukemia by allogeneic bone marrow transplantation

Mice carrying the B cell leukemia (BCL1)+ were successfully treated by total lymphoid irradiation (TLI), cyclophosphamide, and allogeneic bone marrow (BM) transplantation. Long-term survivors were examined for residual BCL1 cells and for the ability to transfer adoptively graft vs. leukemia (GVL) activity. Residual BCL1 cells could not be detected in the allogeneic BM chimeras (greater than 14 to 16 months) with the use of indirect immunofluorescent staining with anti-idiotype antibody. However, residual tumor cells were present in 50% of the "cured" chimeric mice since adoptive transfer of 10(6) spleen cells from 50% of the treated chimeric mice caused leukemia in BALB/c recipients. In order to determine whether leukemia had been prevented in the "cured" chimeras by a persistent cell-mediated mechanism, BALB/c mice were injected with 10(6) spleen cells from the "cured" BM chimeras together with a dose of 10(2) or 5 x 10(5) BCL1 cells. Onset of leukemia was delayed or completely abolished in a significant proportion of recipients receiving the cell mixtures, suggesting the presence of anti-tumor immunity in the cured mice. The data suggest that a persistent active immune mechanism may be responsible, in part, for the significant antileukemic effects observed in mice tolerant to donor alloantigens.

Long-term enzyme replacement therapy in beta-glucuronidase--deficient mice by allogeneic bone marrow transplantation

Enzyme replacement therapy was successfully accomplished in beta-Glu-deficient C3H/HeJ mice after transplantation of BM cells obtained from normal BALB/c donors. Marrow recipients were prepared for transplantation by fractionated TLI. Enzyme activity increased from 20.5 +/- 7.0 nmol/mg of protein per hour to 180 +/- 30.2 in the liver (p less than 0.001) and from 8.2 +/- 2.0 to 17.5 +/- 5.0 nmol/ml/hr in the plasma (p less than 0.05) at 50 days after marrow infusion. Normal enzyme activity was maintained in treated mice for at least 100 days after marrow transplantation, as documented by repeated liver biopsies and examination of plasma samples. The marrow donors and the recipients were fully histoincompatible. Both immunologic rejection of the marrow allograft and GVHD were prevented by the prior conditioning of the recipients with TLI, resulting in bilateral transplantation tolerance of host vs. graft and graft vs. host. The data suggest that allogeneic BM transplantation may provide a possible therapeutic approach for certain enzyme deficiency syndromes.

Ultrastructural, cell membrane, and cytogenetic characteristics of B-cell leukemia, a murine model of chronic lymphocytic leukemia

A murine model of a spontaneous, transplantable BALB/c B-cell leukemia (BCL1) is described. Extreme leukemia and splenomegaly develop in H-2d-compatible recipients of tumor cells. Tumor cells are medium to large lymphocytes that can be transformed into plasmacytoid cells following in vitro stimulation with lipopolysaccharide. Karyotypic analysis of transformed tumor cells reveals 36 chromosomes with several monosomies and 7 markers chromosomes. The ultrastructure of the tumor cells was studied using transmission and scanning electron microscopy. Although the appearance of tumor cells seems normal by morphological criteria, an impaired capping ability was documented using the fluorescein-conjugated concanavalin A-binding test. Impaired capping ability was documented before leukemia was overt as early as 1 to 3 days following inoculation of tumor cells. The B-cell leukemia (BCL1) provides a useful murine model for the study of various aspects of human bone marrow-derived malignant disorders.