Downregulation of L3T4+ cytotoxic T lymphocytes by interleukin-2.

Proliferation of activated cytotoxic T lymphocytes (CTLs) that recognize foreign histocompatibility antigens is induced by interleukin-2, a potent immunoregulatory molecule originally described as T cell growth factor. Interleukin-2 (IL-2) is widely used to isolate and induce clonal expansion of CTLs for functional studies in vitro and in vivo. However, in studies with CTLs specific for class I and class II histocompatibility antigens, IL-2 rapidly downregulated the lytic activity of some class II-specific CTLs in a time- and dose-dependent manner. Lytic activity of L3T4+ CTLs specific for the murine class II antigen I-Ek was repeatedly up- and downregulated in vitro by alternate exposure to specific (alloantigen) and nonspecific (recombinant IL-2) signals, respectively. These results demonstrate that some CTLs modulate their functional property (cytolysis) while undergoing IL-2-driven cell proliferation without loss of antigen specificity or ability to revert to a lytic phenotype.

Low-dose chemotherapy as a prelude to intensive treatment of spontaneous leukemia-lymphoma in AKR mice.

Groups of AKR mice bearing spontaneous leukemia-lymphoma were treated with five different combinations of chemotherapy or chemoradiotherapy. Each treatment combination was given in two sequences--high dose first and low dose last, or low dose first and high dose last--administered over 6-7 days. When the initial treatment was a high dose of chemotherapy, radiotherapy, or chemoradiotherapy, mortality in the first 24 hours exceeded 40%, and at least 70% of the mice in each group were dead within 2 weeks. When low-dose chemotherapy was given first, mortality in the first 24 hours was minimal but, most significantly, no deaths occurred in the 24 hours after subsequent high-dose treatment. In the most successful group (100 mg cyclophosphamide/kg on day 0, and 250 mg cyclophosphamide/kg and 400 R total-body X-irradiation on day 7), the median survival time increased significantly as compared with the median survival time among mice given the same regimen in reverse sequence (p less than 0.001) or among untreated control mice (p less than 0.01). With this regimen, survival 60 days after the last treatment was 47%. No mouse survived 30 days when the sequence of treatments was reversed. From these results, we conclude that chemotherapeutic and chemoradiotherapeutic regimens for AKR spontaneous leukemia-lymphoma should be designed so that low, minimally lethal doses precede higher doses.

Graft versus leukemia. VI. Adoptive immunotherapy in combination with chemoradiotherapy for spontaneous leukemia-lymphoma in AKR mice.

A three-step treatment plan incorporating adoptive immunotherapy and chemoradiotherapy was used to treat AKR (H-2k) mice bearing spontaneous leukemia-lymphoma (SLL). 1) Leukemic mice were treated with chemoradiotherapy for immunosuppression and leukemia cytoreduction. 2) To introduce a graft-versus-leukemia reaction against residual malignant cells, the immunosuppressed AKR mice were given immunocompetent cells from H-2 mismatched DBA/2 (H-2d) donors. 3) To "rescue" the AKR hosts from incipient graft-versus-host disease, the mismatched DBA/2 cells were killed with combination chemotherapy, and cells from allogeneic H-2 matched RF (H-2k) donors were administered to restore hematopoiesis. Leukemic AKR mice thus treated had significant prolongation of their median survival time and a higher 60-day survival rate post treatment than did untreated controls, chemoradiotherapy controls, or control mice that received chemoradiotherapy plus cells from syngeneic donors. Therefore, adoptive immunotherapy may be useful as an adjunct to conventional therapy for treatment of SLL in AKR mice.

Partially matched bone marrow transplantation in patients with myelodysplastic syndromes.

Six patients with a myelodysplastic syndrome (MDS) were treated with bone marrow transplantation (BMT) using partially-matched related (3) or unrelated (3) donors. Patients' ages ranged from 7 to 31 years (median, 10 years). Bone marrow karyotype abnormalities were present in five patients included four with monosomy 7 and one with trisomy 8. One patient was in complete remission before transplant; the remaining five had excess of blasts or were undergoing leukemic transformation. Donor, and recipient were mismatched at the DR locus (2), A locus (2), B locus (1), or A and B loci (1). Conditioning included busulfan, cytarabine, cyclophosphamide, methylprednisolone, and total body irradiation. Cyclosporine was started on day -1. Marrows were T-cell depleted using a monoclonal antibody (MoAb) (CD3) and normal rabbit serum. Four patients engrafted routinely. One patient died of aspergillosis before engraftment (day 12) and one patient failed to engraft on first attempt, but engrafted following additional preparation. Median time to neutrophils greater than 500/microL and platelets greater than 25,000/microL were 16 and 19 days, respectively. Acute graft-v-host disease (GVHD) was less than or equal to grade II in all patients. One patient died with recurrent disease (day 257). One patient died at day 515 of pancreatitis and respiratory failure. Three patients are alive and disease-free at 240, 395, and 560 days post-BMT including two patients with unrelated donors. Partially matched T-depleted bone marrow from related or unrelated donors may be effective, and possibly curative therapy for patients with MDS who lack a histocompatibility locus antigen (HLA)-identical sibling donor.

Regulation of lymphokine-activated killer activity in T-replete and T-cell-depleted human bone marrow by interleukin 4.

Donor-derived lymphokine-activated killer (LAK) cells appear to play a role in mediating an antileukemia effect in recipients of both T-replete and T-cell-depleted (TCD) bone marrow transplants. LAK activity, however, is subject to regulation by cytokines other than interleukin 2 (IL-2). The purpose of this study was to examine the effect of interleukin 4 (IL-4) on the induction of LAK activity in both T-replete and TCD bone marrow. IL-4 inhibited the induction of LAK activity in a time- and dose-dependent manner in both T-replete and TCD bone marrow cultures, although there appeared to be a differential effect, suggesting that T and non-T LAK precursors have different thresholds of sensitivity to IL-4. Single-cell cytotoxicity assays indicated that IL-4 did not inhibit binding of LAK effectors to targets but did reduce the frequency of lytic conjugates. Kinetic analysis techniques demonstrated that IL-4 decreased the maximal rate of target cell lysis by IL-2-activated LAK precursors and inhibited the rate of lytic programming. These data indicate that IL-4 is able to regulate the induction of LAK activity in both T-replete and TCD bone marrow and may play a role in modulating the generation of effector cells with potential antileukemia reactivity in vivo.

Graft versus leukemia. VIII. Selective reduction in antihost reactivity without loss of antileukemic reactivity by treatment of donor mice with lipopolysaccharide.

Spleen and lymph node cells from DBA/2 (H-2d) donor mice treated with multiple injections of bacterial lipopolysaccharide (LPS) were tested in vivo for reactivity against normal tissues of host AKR (H-2k) mice against an AKR long-passage, acute lymphoblastic leukemia (BW5147). LPS treatment of donor mice resulted in a reduction in graft-versus-host (GVH) reactivity without loss of graft-versus-leukemia (GVL) reactivity. Immunocompetent cells from LPS treated DBA/2 donors were effective when used for adoptive immunotherapy (in combination with chemoradiotherapy) of BW5147 leukemia. GVH associated mortality decreased as the dose of spleen cells from LPS treated histoincompatible donors was increased as much as four times the number necessary to eliminate leukemia. The mechanism by which LPS reduced GVH reactivity without eliminating GVL reactivity is unclear; however, it does not appear to be the result of a dilution in the number of GVH reactive cells by nonlymphoid elements in the donor spleen nor of the adjuvant effects of LPS on resistance to bacterial infections.

Mitigation of graft-versus-host disease in mice by treatment of donors with bacterial endotoxin.

Treatment of DBA/2 (H-2d) mice with bacterial endotoxin prior to transplantation of their spleen and lymph node cells into immunosuppressed AKR (H-2k) mice prevented acute mortality from graft-versus-host (GVH) disease. AKR mice that received immunocompetent cells from untreated DBA/2 mice had a median survival time (MST) of 13 days. In contrast, AKR mice that received immunocompetent cells from endotoxin-treated DBA/2 donors had an MST of 54 days. Endotoxin treatment of AKR recipients was not essential for preventing mortality from acute GVH disease. Chimerism was proved by demonstrating that the lymphoid cells of long-term surviving AKR mice had the characteristics of DBA/2 lymphoid cells as measured by their response in mixed leukocyte culture (MLC) tests. Spleen cells from endotoxin-treated DBA/2 mice were able to stimulate, and to be stimulated by, AKR spleen cells in MLC assays. Furthermore, spleen cells from endotoxin-treated DBA/2 mice did not suppress the responses of DBA/2 or AKR spleen cells in 'three-party' MLC tests.

Immunological evaluation of pediatric cancer patients receiving recombinant interleukin-2 in a phase I trial.

Immunological evaluations were performed on 14 pediatric cancer patients who received human recombinant interleukin-2 (rIL-2) as a bolus intravenous infusion every 8 h for 5 consecutive days in a phase I trial. Three-to-four patients were treated at dose levels of 10, 30, 60, and 100 x 10(3) Cetus U/kg. Six of the patients had stage D neuroblastoma; the remainder had other solid tumors or leukemias. Infusion of rIL-2 was associated with a rapid margination of IL-2-responsive cells followed by demargination and heightened proliferative and cytotoxic activity after therapy was completed. The predominant phenotypic change in circulating peripheral blood mononuclear cells (PBMC) was an increase in CD2 expression by CD56+ natural killer (NK) cells. Appearance of CD2+ CD56+ cells in the circulation correlated with increased lymphokine-activated killer (LAK) cell activity as defined by the ability to kill NK-resistant Daudi tumor cells in vitro. Sustained LAK activity appeared to be dependent on the bioavailability of rIL-2 in vivo as well as in vitro. After rIL-2 therapy, PBMC that were highly responsive to rIL-2 (activated and "poised" LAK cells) persisted for at least 72 h. In the patients tested, increased lysis of autologous and/or allogeneic, histologically similar tumor cell lines was also observed after therapy. The immunoenhancing effects of rIL-2 occurred even at the lower doses used in this study. However, an objective tumor response was not observed in any of the patients.

Allogeneic bone marrow chimerism in germ-free mice. IV. Therapy of "Hodgkin's-like" reticulum cell sarcoma in SJL mice.

"Hodgkin's-like reticulum cell sarcoma develops spontaneously in most SJL mice. Germ-free and conventional SJL mice bearing advanced reticulum cell sarcoma were treated with X-irradiation and transplantation of bone marrow from SJL or C3H/He donors. The 120-day survival rate of germ-free mice receiving allogeneic bone marrow (70%) exceeded that of all control groups; more importantly, germ-free mice that survived more than 4 months after treatment with allogeneic cells had no evidence of neoplastic lesions when killed. The germ-free environment effectively prevented graft-versus-host disease that was lethal to conventional mice. The results of these experiments offer additional evidence that bone marrow transplantation can be used as a therapeutic tool for spontaneous murine neoplasms.

A decrease in graft-vs.-host disease without loss of graft-vs.-leukemia reactivity after MHC-matched bone marrow transplantation by selective depletion of donor NK cells in vivo.

It is thought that natural killer cells may play a role in graft-vs.-host reactions after allogeneic bone marrow transplantation, but the use of NK cell-specific reagents has been limited. In this report, an NK allele-specific monoclonal antibody, anti-NK 1.1, was used to study the impact of in vivo donor NK cell depletion on GVH disease, graft-vs.-leukemia (GVL) reactivity and donor T cell chimerism after allogeneic murine BMT. AKR/J (H-2k) recipient mice were preconditioned with suboptimal irradiation (9 Gy = LD50) and transplanted with major histocompatibility complex-matched B10.BR (H-2k) BM cells with or without added spleen cells as a source of T cells. The addition of increasing numbers of spleen cells to the BM inoculum produced GVHD of varying intensities. The beneficial effect of NK depletion on GVHD was dependent on the intensity of the GVH reaction. Donor NK cell depletion had no effect on the survival of mice with severe GVHD after MHC-matched BMT (B10.BR into AKR) or after MHC-mismatched BMT (B10.BR into DBA/2; H-2k into H-2d). However, donor NK depletion increased survival of AKR hosts given sufficient B10.BR splenic T cells to induce mild-to-moderate GVHD. Ex vivo depletion of donor CD8+ T cells also reduced GVH-associated mortality, but the use of both CD8 and NK depletion offered no improvement over either alone, suggesting an interaction between CD8+ and NK 1.1+ cells. In contrast to CD8 depletion, donor NK depletion did not compromise the rapid and complete establishment of donor T cell chimerism nor the ability of chimeras to mount an effective GVL reaction. Thus, elimination of donor NK cells provides an alternate strategy for reducing GVHD without loss of GVL reactivity following MHC-matched allogeneic BMT.

Manipulation of graft-versus-host disease for a graft-versus-leukemia effect after allogeneic bone marrow transplantation in AKR mice with spontaneous leukemia/lymphoma.

Graft-versus-host (GVH) disease can result in a beneficial graft-versus leukemia (GVL) effect after bone marrow transplantation in patients with malignant disease. In this report, we used bacteria-free AKR (H-2k) mice bearing advanced spontaneous T cell leukemia/lymphoma as a moel to evaluate the GVH and GVL effects of bone marrow transplantation using fully incompatible SJL (H-2s) donors. A therapeutic GVL effect, accompanied by increased leukemia-free survival, was obtained only when 0.5 X 10(6) allogeneic lymphocytes (lymph node cells) were added to the marrow inoculum. Transplantation of allogeneic bone marrow without added lymph node cells (or use of syngeneic cells) resulted in a significant increase in leukemia relapse; increasing the dose of allogeneic lymph node cells to 2.0 X 10(6) resulted in significantly higher GVH-associated mortality. Survival and therapeutic benefits were obtained only when the intensity of the GVH reaction was carefully controlled by manipulation of alloreactive lymphocytes present in the marrow. These results suggest, indirectly, that T cell depletion may abolish any GVL effect of marrow transplantation, even if the donor is mismatched with the host at the major histocompatibility complex. The frequency in the spleen of cytotoxic T lymphocytes (CTL) reactive against host alloantigens was estimated using limiting-dilution microcytotoxicity assays at various times after transplantation of allogeneic bone marrow with and without added lymph node cells. The average frequency of CTL was highest in mice that were given marrow plus lymph node cells and tested within the first four weeks after transplantation. The level of CTL activity measured in vitro was dependent on the dose of lymphocytes injected and correlated with both the GVL and GVH effects in vivo. Down-regulation of CTL activity against host, but not third-party, alloantigens in vitro was observed under limiting dilution assay conditions, leading to the suggestion that host-specific regulatory cells may be present in these allogeneic bone marrow chimeras.

Reactivity of in-vitro-expanded alloimmune cytotoxic T lymphocytes and Qa-1-specific cytotoxic T lymphocytes against AKR leukemia in vivo.

The ability of alloimmune spleen cells expanded in mixed leukocyte culture (MLC) and cloned cytotoxic T lymphocytes (CTL) to kill H-2-compatible leukemia in vivo was evaluated. In comparison with fresh alloimmune spleen cells, MLC-expanded cells had a significantly higher frequency of CTL reactive against leukemia targets in vitro. However, the reactivity of MLC-expanded cells against first-passage spontaneous AKR (H-2k) leukemia in vivo was significantly less than when an equivalent number of fresh alloimmune spleen cells was injected. Comparable antileukemia reactivity was observed in vivo only when the inoculum of MLC-expanded cells was 2-3-fold higher than that of fresh spleen cells. This relative ineffectiveness was attributed to the altered migration pattern of cultured cells in vivo. IL-2-dependent cloned CTL, specific for a normal lymphocyte antigen (Qa-1b) also present on leukemia cells, were derived from MLC-expanded cultures and tested in vivo. For cloned CTL, as with MLC-expanded cells, eradication of AKR leukemia in vivo was associated with the tissue distribution pattern of the injected effector cells. That is, an effective antileukemia reaction was achieved only in tissues in which effector and target proximity was maintained. Qa-1b-specific cloned CTL did not interfere with engraftment of autologous or allogeneic bone marrow in lethally irradiated host mice, nor did they cause any clinically evident graft-versus-host disease. These findings suggest that cloned CTL specific for a normal cell surface antigen with limited host tissue distribution, but present on tumor cells, could be used for adoptive immunotherapy, provided CTL and tumor cell proximity can be attained.

Preservation of lymphokine-activated killer activity following T cell depletion of human bone marrow.

T cell depletion has decreased the incidence and severity of graft-versus-host disease following transplantation of allogeneic bone marrow. In the treatment of leukemia, decreased GVHD has often been associated with diminished antileukemia or graft-versus-leukemia (GVL) reactivity resulting in higher relapse rates. However, we have not seen a loss of the GVL effect following transplantation of marrow grafts depleted of CD3+ T cells. This suggests that non-T-cell effectors may play a role in preventing leukemic relapse. To study whether natural killer and lymphokine-activated killer (LAK) activity in BM was compromised by T cell depletion, the effect of T-cell-specific monoclonal antibodies against CD3 and CD6 determinants alone, or in combination, on the generation and expansion of NK/LAK cells was examined in vitro and compared to the effect of T depletion on mitogen-driven T cell proliferation. Limiting dilution analysis revealed that T depletion with CD3 and/or CD6 specific antibodies significantly reduced the number of proliferating T lymphocytes but did not significantly affect the frequency of cells able to expand and mediate LAK activity. Bone marrow, depleted of CD3+ or CD6+ T cells, generated levels of LAK activity equivalent to non-T-cell-depleted bone marrow following long-term culture in recombinant interleukin 2. CD3- NKH-1+ cells were the predominant population in rIL-2 expanded marrow cultures prior to transplant and in the peripheral blood of patients who had received a CD3-depleted marrow graft 21-65 days earlier. These studies show that it is possible to selectively reduce GVH-reactive T cells in allogeneic bone marrow while retaining non-T-effector cells with potential to mediate an antileukemia effect in vivo.

Transplantation of hematopoietic and lymphoid cells in mice.

CBA mice were exposed to a supralethal dose of whole body X-irradiation and recieved transplants of graded, small doses of bone marrow, fetal liver, or fetal liver plus fetal thymus cells obtained from H-2 matched C58 or H-2 mismatched A donors. Survival at 20 days was used to evaluate the ability of the transplants to restore hematopoiesis following the acute radiation injury. In the higher dose ranges of 6 X 10(7) and 1.2 X 10(8) cells/kg body weight, the fetal cells were as effective as adult bone marrow in both the matched and mismatched strain combinations. Survival at 100 days was used to evaluate the severity of chronic graft-versus-host disease produced by each of the transplants. In the higher dose ranges, cells from fetal donors promoted higher long-term survival rates than did comparable doses of bone marrow cells in both the matched and mismatched strain combinations. In some experimental groups, the addition of fetal thymus cells to fetal liver cells resulted in higher short-term and long-term survival rates than did fetal liver alone, but this was inconsistent and generally fell short of statistical significance. The most important finding was that cells from mismatched unrelated fetal donors (using a cell dose per kilogram body weight comparable to the number of fetal liver and thymus cells which would be obtainable from one human fetus at 14 weeks of embryonation) promoted higher long-term survival rates than did bone marrow transplants from matched unrelated donors.

Migration patterns and functional activity of cloned cytotoxic T lymphocytes in syngeneic and allogeneic mice.

The quantitative distribution of cytolytic T lymphocytes (CTL) generated in mixed leukocyte culture (MLC) and an interleukin-2 (IL-2)-dependent, CTL clone (WRL-A3) was investigated in various tissues of irradiated syngeneic and allogeneic mice. In addition, the ability of the WRL-A3 CTL clone to remain viable and retain antigen specificity following in vivo passage was evaluated. Injection i.v. of 51Cr-labeled cultured CTL resulted in: (1) extensive deposition of cells in the lungs with significantly more lymphocytes being recovered in allogeneic as compared with syngeneic lung tissue; (2) minimal accumulation in spleen with more in syngeneic than in allogeneic tissue; and (3) no localization in blood, femurs, thymus, or lymph nodes. The migration rate of cultured CTL exiting the lung during the first 4 hr was markedly faster in syngeneic than in allogeneic recipients and was directly associated with the distribution of these cells in other tissues at 24 hr. The WRL-A3 CTL clone recovered from irradiated syngeneic and allogeneic lung tissue at 1, 3, 6, 8, and 13 days after i.v. injection remained viable, even though no exogenous IL-2 was administered to the recipient mice. The recovered cells proliferated when recultured with IL-2, and retained their antigen specificity for Qed-1b target cells after in vivo passage. These findings indicate that restricted and undesirable tissue distribution, rather than impaired viability or loss of antigenic specificity, is the major obstacle to successful use of cultured CTL for adoptive immunotherapy of disseminated cancer.

Contribution of CD4+ and CD8+ T cells to graft-versus-host disease and graft-versus-leukemia reactivity after transplantation of MHC-compatible bone marrow.

A murine model of allogeneic bone marrow (BM) transplantation was used to determine the relative importance of CD4+ and CD8+ T cells in establishing donor T cell chimerism and in the development of graft-versus-host (GVH) and graft-versus-leukemia (GVL) reactivity. Mature donor T cells were essential for complete chimerism when host mice (AKR, H-2k) were conditioned with suboptimal irradiation (9 Gy = LD50). Transplantation of donor BM (B10.BR, H-2k) resulted in mixed chimerism, whereas mice given BM containing additional T cells developed into complete and stable chimeras. Depletion of T cell subsets was associated with an increase in the frequency of mixed chimerism. The incidence of lethal GVHD was dependent on the number of T cells added to the BM inoculum. Ex vivo depletion of CD4+ T cells eliminated GVH-associated mortality. Removal of CD8+ T cells had no effect on overall survival. In contrast to the GVH results, removal of either CD4+ or CD8+ T cells compromised GVL reactivity, indicating that an optimal GVL response required both CD4+ and CD8+ T cells. T cell-subset depletion did not interfere with the induction of donor-host tolerance in these chimeras and may have facilitated its development. The loss of GVH/GVL effector cells as a result of T cell depletion and the development of donor-host tolerance may act synergistically to prevent or suppress GVH and GVL reactivity.

Delayed infusion of normal donor cells after MHC-matched bone marrow transplantation provides an antileukemia reaction without graft-versus-host disease.

When allogeneic BMT is used for the treatment of leukemia, depletion of T cells from the donor BM to avoid GVHD may be accompanied by persistence of host cells and post-transplant relapse. In this report, a murine model of MHC-compatible BMT was used to show that delayed infusion of immunocompetent donor cells early after T cell-deficient BMT eliminated residual host cells and provided an antileukemic effect without causing lethal GVHD. AKR (H-2k) recipient mice were pre-conditioned with 9 Gy total body irradiation (LD50) and transplanted with 10(7) BM cells from MHC-matched B10.BR donors. These mice did not develop GVHD and became stable, long-term mixed (donor-host) T cell chimeras. In this model, mixed or incomplete donor T cell chimerism was associated with decreased GVL reactivity. AKR hosts that were transplanted with B10.BR bone marrow admixed with 3 x 10(7) B10.BR spleen cells (as a source of T cells) became complete donor T cell chimeras, but they developed severe and lethal GVHD. However, when the infusion of donor spleen cells was delayed until 21 days after BMT, few mice exhibited any clinical signs of GVHD, and > 95% of the mice became long-term survivors. The infused spleen cells eliminated residual host T cells by 21 days after infusion, and most chimeras were able to resist a supralethal challenge with AKR leukemia/lymphoma cells. Thus, post-transplant adoptive immunotherapy with normal mononuclear cells from the marrow donor may be an effective way to eliminate residual disease or treat leukemia relapse after BMT without causing significant GVHD.

The graft-versus-leukemia effect of post-transplant donor leukocyte infusion.

Tumor relapse remains a major obstacle to the success of allogeneic bone marrow transplantation (BMT) as a treatment for leukemia. Due to limited treatment options, the outlook for most patients that relapse following allogeneic BMT has been poor. The infusion of normal immunocompetent leukocytes from the original marrow donor has become a promising new option for treating/preventing leukemia relapse in allogeneic BMT recipients. This form of treatment has often been referred to as donor leukocyte infusion (DLI) therapy. Our laboratory is using murine models of allogeneic BMT to address important unresolved issues regarding DLI therapy in an effort to make the treatment more effective. These include identification of the antileukemic effector cells, augmentation of the antileukemic effect, and understanding why graft-versus-host-disease (GVHD) is less severe than anticipated. This article reviews our work in murine models of DLI and introduces our current working hypotheses concerning DLI therapy.

Alloimmunization: induction of antileukemic reactivity without modification of anti-host reactivity in H-2-compatible mice.

Transplanted immunocompetent cells from CBA (H-2k) mice immunized against individual or pooled lymphoid cells from various allogeneic strains resulted in the elimination of widely disseminated leukemia cells in AKR (H-2k) host mice as measured in a GVL bioassay. In most cases, alloimmunization resulted in reactivity against AKR-L comparable to that observed when CBA donors were specifically immunized with irradiated AKR-L cells. Cells from unimmunized or isoimmunized CBA mice had no detectable GVL reactivity. Alloimmunization caused no increase in the mild GVH reactivity of unimmunized or isoimmunized CBA lymphoid cells transplanted into lethally irradiated nonleukemic AKR hosts; whereas, specific immunization with AKR-LX cells resulted in significantly increased GVH-related mortality.

Graft-versus-leukemia for AKR spontaneous leukemia-lymphoma.

Adoptive immunotherapy in the form of a transient graft of mismatched DBA/2 BM + LN cells was used in combination with several chemoradiotherapy regimens to treat AKR mice bearing advanced SLL. Leukemic mice treated in this manner had a significant prolongation of their MST and significantly higher survival rates 60 and 90 days posttreatment than corresponding control groups. Syngeneic- or allogeneic-matched cells did not provide substantial GVL effect. An inverse relationship that influenced survival was observed between the radiation dose and the dose of GVL effector cells used to treat leukemic AKR mice in the treatment model. Recurrence leukemia remains a major problem.