Interleukin-10 administration decreases survival in murine recipients of major histocompatibility complex disparate donor bone marrow grafts

Studies in mice and humans have indicated that the predominance of interleukin-4 (IL-4)- and IL-10-producing T-helper type 2 (Th2) cells may serve to downregulate acute graft-versus-host disease (GVHD) reactions, whereas IL-2-producing Th1 cells have been implicated in facilitating acute GVHD. We explored the possibility that the in vivo infusion of IL-10 would inhibit acute GVHD induced by fully allogeneic donor grafts. Unexpectedly, IL-10 infusions resulted in a dose- dependent increase in GVHD-induced mortality. The acceleration of lethal GVHD by IL-10 occurred in irradiated recipients of T-cell- depleted bone marrow (BM) plus 5, 15, or 25 x 10(6) splenocytes but did not influence the post-BM transplantation (post-BMT) survival rate of recipients of BM without splenocytes, suggesting that the IL-10 effects were not due to toxicity. Antimurine IL-10-neutralizing monoclonal antibody injections, administered to diminish endogenous IL-10, reduced GVHD-associated mortality and improved the clinical appearance of the recipients. For BM graft rejection studies, IL-10 was infused into sublethally irradiated recipients of anti-Thy 1.2 + C' T-cell-depleted, fully allogeneic BM grafts. In a short-term (day 7) in vivo assay, IL- 10 infusions significantly inhibited allogeneic (but not syngeneic) BM proliferation in vivo, indicative of increased graft rejection. In long- term chimerism experiments, IL-10 infusions caused a significant increase in early post-BMT mortality caused by a profound anemia typically associated with graft rejection and aplasia. A slightly higher irradiation dose (650 cGy v 600 cGy) eliminated the anemia but did not reverse the graft rejection process associated with IL-10 administration. We conclude that the in vivo infusion of exogenous IL- 10 in recipients of fully allogeneic donor grafts results in accelerated GVHD and graft rejection in the strain combinations tested to date.     

Impact of pretransplant conditioning and donor T cells on chimerism, graft-versus-host disease, graft-versus-leukemia reactivity, and tolerance after bone marrow transplantation

Graft rejection, mixed chimerism, graft-versus-host disease (GVHD), leukemia relapse, and tolerance are interrelated manifestations of immunologic reactivity between donor and host cells that significantly affect survival after allogeneic bone marrow transplantation (BMT). In this report, a mouse model of BMT, in which the donor and host were compatible at the major histocompatibility complex (MHC), was used (1) to examine the interrelationship of pretransplant conditioning and T-cell content of donor BM with regard to lymphoid chimerism and GVHD and (2) to determine how these factors affected graft-versus-leukemia (GVL) reactivity and donor-host-tolerance. AKR (H-2k) host mice were administered optimal or suboptimal total body irradiation (TBI) as pretransplant conditioning followed by administration of BM cells from B10.BR (H-2k) donor mice with or without added spleen cells as a source of T lymphocytes. Transplanted mice were injected with a supralethal dose of AKR leukemia cells 20 and 45 days post-BMT to assess GVL reactivity in vivo. The pretransplant conditioning of the host and T-cell content of the donor marrow affected the extent of donor T-cell chimerism and the severity of GVH disease. GVL reactivity was dependent on transplantation of mature donor T cells and occurred only in complete chimeras. Transplantation of T-cell-deficient BM resulted in the persistence of host T cells, ie, incomplete donor T-cell chimerism, even when lethal TBI was used. Mixed chimerism was associated with a lack of GVL reactivity, despite the fact that similar numbers of donor T cells were present in the spleens of mixed and complete chimeras. In this model, moderate numbers of donor T cells facilitated complete donor T-cell engraftment, caused only mild GVHD, and provided a significant GVL effect without preventing the subsequent development of tolerance after conditioning with suboptimal TBI. In contrast, severe, often lethal, GVHD developed when the dose of TBI was increased, whereas tolerance and no GVH/GVL reactivity developed when the T-cell content of the marrow was decreased.     

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.     

Interleukin-2 in bone marrow transplantation: preclinical studies.

Interleukin-2 (IL-2) promotes the generation and proliferation of killer cells in the peripheral blood and bone marrow (BM) both in vitro and in vivo. When employed in a syngeneic bone marrow transplantation (BMT) setting and followed by IL-2 therapy, murine BM cells activated with IL-2 in vitro (ABM) demonstrate potent graft-versus-leukemia (GVL) and anticytomegalovirus effects. ABM cells retain the capacity to reconstitute the hemopoietic system both in normal and leukemic mice. This therapy does not cause graft-versus-host disease (GVHD). Human ABM cells carry out purging of leukemia without loss of progenitor cell activity in vitro. The purging ability of ABM can be augmented by interleukin-1, interferon, and tumor necrosis factor. IL-2 therapy stimulates the veto suppressor cell activity of T cell-depleted BM, and has reduced GVHD and permitted engraftment of mismatched allogeneic BM in murine models. Future studies should determine the optimum treatment schedules with IL-2 for improving the GVL effect in autologous BMT, and for abolishing GVHD in allogeneic BMT settings.     

Functional comparison of spleen dendritic cells and dendritic cells cultured in vitro from bone marrow precursors

We have compared dendritic cells (DC) isolated from mouse spleen, or generated in vitro from bone marrow (BM) precursors cultured in granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin-4 (IL-4), for the ability to process and present soluble antigen and stimulate major histocompatibility complex (MHC) Class II- restricted T cells. DC from spleen or BM cultures were equally able to stimulate the in vitro proliferation of allogeneic T cells or of antigen-specific T-cell receptor (TCR)-transgenic T cells. Both DC populations also induced comparable levels of IL-2 secretion by a T- cell hybridoma. Therefore, splenic and BM-derived DC express comparable levels of (Antigen + MHC Class II) ligands and/or costimulatory molecules and have comparable ability to stimulate T-cell responses. When presentation of a native protein antigen, rather than peptide, was evaluated, BM-derived DC were at least 50 times better than splenic DC at stimulating the proliferation of TCR-transgenic T cells. The antigen processing ability of the two populations was similar only when splenic DC were used immediately ex vivo. Therefore, unlike spleen DC, BM- derived DC maintain the capacity to process protein antigen for MHC Class II presentation during in vitro culture. Due to these characteristics, BM-derived DC may represent a useful tool in immunotherapy studies, as they combine high T-cell stimulatory properties with the capacity to process and present native antigen.     

Achieving alloengraftment without graft-versus-host disease: approaches using mixed allogeneic bone marrow transplantation

Two opposing immunologically-mediated phenomena currently limit the success of bone marrow transplantation (BMT) in HLA-identical situations and impede the application of this therapeutic modality across MHC barriers. These phenomena are: (1) the response of T cells within the donor marrow allograft to recipient alloantigen, resulting in graft-versus-host disease (GVHD) with its attendant morbidity and mortality; and (2) the response of recipient cells which have survived the ablative conditioning regimen against alloantigen borne by the donor marrow allograft, leading to failure of alloengraftment. While T cell depletion of donor marrow has successfully reduced the incidence of severe GVHD, this reduction has been associated with an increased incidence of failure of alloengraftment. In this communication we review several recent approaches being studied in animal models in our laboratory to avoid such undesirable effects of host-anti-donor and donor-anti-host alloaggression. The first approach is based on the observation that administration of T cell-depleted (TCD) syngeneic bone marrow (BM) appears to limit GVHD while still permitting engraftment by co-administered non-TCD allogeneic BM. This anti-GVH effect of TCD syngeneic marrow can be enhanced by delaying the administration of allogeneic BM by 8 days following whole body irradiation and syngeneic BMT. Evidence that natural suppressor cells derived from syngeneic marrow may be responsible for this phenomenon is reviewed. We also present evidence for the existence of a non-stem cell bone marrow subpopulation, distinct from those T cells which cause GVHD, which is capable of increasing levels of allogeneic chimerism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Graft engineering using ex vivo methods to limit GVHD: fludarabine treatment generates superior GVL effects in allogeneic BMT

OBJECTIVE: To compare the abilities of different ex vivo methods of treating donor lymphocytes to inhibit graft-vs-host disease (GVHD) while preserving graft-vs-leukemia (GVL) activity in murine models of allogeneic bone marrow transplantation. METHODS: Donor/recipient pairs included MHC fully mismatched, MHC haplomismatched, and MiHA mismatched strain combinations. T cell-depleted BM (TCD-BM) was transplanted in combination with untreated, fludarabine-treated, 7.5-Gy gamma-irradiated, or psoralen/UVA (PUVA)-treated splenocytes. GVL activity was studied by adding a lethal number of recipient-type lymphoma cells. Posttransplant survival was determined, and GVHD and GVL activity were assessed by clinical and pathological scoring. Hematopoietic chimerism and donor T-cell expansion were analyzed by flow cytometry of peripheral blood samples at 30 and 60 days posttransplant. RESULTS: Allogeneic splenocytes treated with fludarabine, 7.5 Gy gamma-irradiation, or PUVA had significantly diminished GVHD activity, and all treated donor T cells facilitated engraftment by low-dose TCD-BM. Allogeneic splenocytes treated with fludarabine and, to a lesser extent, PUVA retained GVL activity and contributed more to donor T-cell chimerism compared to gamma-irradiated donor splenocytes. CONCLUSION: Among ex vivo methods of treating donor T cells to limit their proliferative capacity, fludarabine exposure had the greatest differential ability to inhibit the GVHD activity of allogeneic lymphocytes, while preserving their GVL activity and ability to engraft recipients. Thus, ex vivo treatment with fludarabine was superior to gamma-irradiation or PUVA in separating GVL from GVHD activity in murine models of allogeneic bone marrow transplantation.     

Interleukin 18 preserves a perforin-dependent graft-versus-leukemia effect after allogeneic bone marrow transplantation

We have recently shown that early administration of interleukin 18 (IL-18) after bone marrow transplantation (BMT) attenuates acute graft-versus-host disease (GVHD) in a lethally irradiated parent into F1 (B6-->B6D2F1) BMT model. In this study, we investigated whether IL-18 can maintain graft-versus-leukemia (GVL) effect in this context. B6D2F1 mice received transplants of T-cell-depleted (TCD) bone marrow (BM) and splenic T cells from either syngeneic (H2(b/d)) or allogeneic B6 (H2(b)) donors. Recipient mice were treated with recombinant murine IL-18 or the control diluent. Initial studies demonstrated that IL-18 treatment did not affect the proliferative responses or the cytolytic effector functions of T cells after BMT. In subsequent experiments, animals also received host-type P815 mastocytoma cells at the time of BMT. All syngeneic BM transplant recipients died from leukemia by day 18. The allogeneic BM transplant recipients effectively rejected their leukemia regardless of treatment and IL-18 significantly reduced GVHD-related mortality. Examination of the cytotoxic mechanisms with perforin-deficient donor T cells demonstrated that perforin is critical for the GVL effect. Taken together these data demonstrate that IL-18 can attenuate acute GVHD without impairing the in vitro cytolytic function or the in vivo GVL activity after allogeneic BMT.     

The recovery of resistance to alloengraftment following lethal irradiation and administration of T cell-depleted syngeneic bone marrow

Recent studies from this laboratory have shown that unmanipulated, MHC-mismatched allogeneic bone marrow (BM) engrafts and produces complete allogeneic chimerism when administered to recipient mice 8 days following lethal irradiation and reconstitution with T cell-depleted (TCD) syngeneic bone marrow. Host lymphopoietic recovery thus appears to be insufficient by 8 days after irradiation and TCD syngeneic bone marrow transplantation (BMT) to resist alloengraftment. In the present studies we have examined the development of such resistance to alloengraftment by determining the limits of the time period permitting engraftment, and have assessed the role of allogeneic T cells in achieving chimerism after delayed allogeneic bone marrow transplantation. Our results indicate that increasing the delay for more than 8 days following irradiation and TCD syngeneic BMT leads to a rapid loss of the ability to achieve alloengraftment by non-TCD allogeneic bone marrow. Removal of T cells from allogeneic BM inocula administered 8 days after irradiation and TCD syngeneic BMT resulted in loss of the ability to achieve alloengraftment. Repopulation patterns in host spleens following delayed reconstitution suggest that active elimination of engrafted syngeneic lymphohemopoietic elements is necessary to permit engraftment of allogeneic marrow administered after such a delay.     

Irradiated donor leukocytes promote engraftment of allogeneic bone marrow in major histocompatibility complex mismatched recipients without causing graft-versus-host disease.

Graft rejection in allogeneic bone marrow transplantation (BMT) can occur when donor and recipient are mismatched at one or more major histocompatibility complex (MHC) loci. Donor T cells can prevent graft rejection, but may cause fatal graft-versus-host disease (GVHD). We tested whether irradiation of allogeneic donor lymphocytes would preserve their graft-facilitating activity while inhibiting their potential for GVHD. Infusions of irradiated allogeneic T cells did not cause GVHD in MHC-mismatched SJL --> (SJL x C57BL6) F1, C57BL6 --> B10.RIII, and C57BL6 --> B10.BR mouse donor --> recipient BMT pairs. The 60-day survival among MHC-mismatched transplant recipients increased from 2% (BM alone) to up to 75% among recipients of BM plus irradiated allogeneic splenocytes. Optimal results were obtained using 50 x 10(6) to 75 x 10(6) irradiated donor splenocytes administered in multiple injections from day -1 to day +1. Recipients of an equal number of nonirradiated MHC-mismatched donor splenocytes uniformly died of acute GVHD. The graft facilitating activity of the irradiated allogeneic splenocytes was mediated by donor T cells. Irradiation to 7.5 Gy increased nuclear NFkappaB in T cells and their allospecific cytotoxicity. Irradiated T cells survived up to 3 days in the BM of MHC-mismatched recipients without proliferation. Recipients of irradiated allogeneic splenocytes and allogeneic BM had stable donor-derived hematopoiesis without a significant representation of donor splenocytes in the T-cell compartment. Irradiated allogeneic T cells thus represent a form of cellular immunotherapy with time-limited biologic activity in vivo that can facilitate allogeneic BMT without causing GVHD.     

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

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

Dynamics in chimerism of T cells and dendritic cells in relapsed CML patients and the influence on the induction of alloreactivity following donor lymphocyte infusion

Donor lymphocyte infusion (DLI) after allogeneic SCT induces complete remissions in approximately 80% of patients with relapsed CML in chronic phase, but some patients do not respond to DLI. We studied absolute numbers of dendritic cell (DC) subsets and chimerism in T cells and two subsets of blood DCs (myeloid DCs (MDCs) and plasmacytoid DCs (PDCs)) in relation to DLI-induced alloreactivity. Based on T cell and DC chimerism, we identified three groups. Four patients were completely donor chimeric in T cells and DC subsets. These patients had an early stage of relapse, and three of the four patients attained complete molecular remission (CMolR) without significant GVHD. Six patients were completely donor in T cells and mixed chimeric in DC subsets. All patients entered CMolR, but this was associated with GVHD in four and cytopenia in three patients. Five patients had mixed chimerism in T cells and complete recipient chimerism in MDC; only two patients entered CMolR. Our data suggest that the combination of donor T cells and mixed chimerism in DC subsets induces a potent graft-versus-leukemia (GVL) effect in association with GVHD. DLI in patients with an early relapse and donor chimerism in both T cells and DC subsets results in GVL reactivity without GVHD.     

Granulocyte colony-stimulating factor (CSF) but not interleukin-1 (IL- 1), IL-3, and granulocyte-macrophage CSF protect bone marrow progenitor cells from suppression by allosensitized cytotoxic T cells

The major immunological reactions after an allogeneic bone marrow transplantation (BMT) are graft rejection and graft-versus-host disease (GVHD). GVHD can be prevented by T-cell depletion of the allogeneic BM graft, but the beneficial effect of T-cell depletion on the incidence of GVHD is counterbalanced by a higher incidence of graft failure. One option for the prevention of graft rejection after T-cell-depleted BM grafts is the administration of cytokines. Before applying cytokines after an allogeneic BMT, we considered it desirable to learn whether cytokines would alter the susceptibility of donor BM cells to host T cells. An in vitro assay was developed to investigate the role of the cytokines interleukin-1 (IL-1), IL-3, granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage CSF (GM-CSF) on the interaction between allosensitized, cytotoxic-T cells (CTLs) and T-cell- depleted BM cells. CTLs primed against the BM donor suppressed the formation of colonies consisting of granulocytes and macrophages (colony-forming unit GM). Colony formation was not inhibited by CTLs sensitized against a third party. Accordingly, the number of colonies scored in cocultures with CTLs sensitized to third party antigens were designated as 0% inhibition. A 66% inhibition of colony formation was observed for untreated BM cells at an effector:target (E:T) ratio of 1:1. Pretreatment of the BM cells with the cytokines G-CSF, GM-CSF, IL- 1, and IL-3 resulted in a 38% (P = .001), 53%, 66%, and 68% inhibition of colony formation, respectively, at E:T ratios of 1:1. G-CSF reduced the susceptibility of BM cells over a range from 4:1 to 1:16 (E:T ratios). GM-CSF had only significant influence at the lower E:T ratios (1:4 and 1:16). These in vitro data indicate that G-CSF could protect BM cells from killing by allosensitized CTLs and suggest that administration of these cytokines might potentially reduce the susceptibility of T-cell-depleted allogeneic BM grafts to host T-cell- mediated rejection.     

Donor CD8+ T cells facilitate induction of chimerism and tolerance without GVHD in autoimmune NOD mice conditioned with anti-CD3 mAb

Prevention of autoimmune diabetes and induction of islet transplantation tolerance in nonobese diabetic (NOD) mice can be reached by induction of mixed chimerism via bone marrow transplantation (BMT), but this procedure requires total body irradiation (TBI) conditioning of the recipients. The toxicity of radiation and potential for graft-versus-host disease (GVHD) prevents its clinical application. Donor CD8+ T cells play a critical role in facilitation of engraftment but also contribute to induction of GVHD in TBI-conditioned recipients. Here, we showed that high doses of donor CD8+ T cells in combination with bone marrow (BM) cells induced mixed chimerism without GVHD in NOD recipients conditioned with anti-CD3 monoclonal antibody (mAb). The prevention of GVHD in those recipients was associated with low-level production of inflammatory cytokines (ie, tumor necrosis factor alpha [TNF-alpha]), high-level production of anti-inflammatory cytokines (ie, interleukin 4 [IL-4] and IL-10), and confining of the donor CD8+ T-cell expansion to lymphohematopoietic tissues. The chimeric NOD recipients showed donor-specific tolerance and reversal of insulitis. These results demonstrate that donor CD8+ T-cell-mediated facilitation of engraftment can be separated from GVHD in nonirradiated recipients. This regimen may have potential application in the treatment of autoimmune disorders as well as induction of transplantation tolerance.     

Intravenous injection of apoptotic leukocytes enhances bone marrow engraftment across major histocompatibility barriers.

Cross-tolerization of T lymphocytes after apoptotic cell uptake by dendritic cells may be involved in self-tolerance maintenance. Furthermore, immunosuppressive properties are attributed to apoptotic cells. This study evaluated the consequences of apoptotic leukocyte administration in a restrictive engraftment model of murine bone marrow (BM) transplantation. Sublethally irradiated recipients received a limited number of allogeneic BM, with or without irradiated apoptotic leukocytes of different origins. No graft-versus-host disease was observed. Whereas only a low proportion of mice receiving BM cells alone engrafted, addition of apoptotic irradiated leukocytes, independently of the origin (donor, recipient, third-party mice, as well as xenogeneic peripheral blood mononuclear cells), significantly enhanced engraftment. Similar results were obtained after infusion of leukocytes rendered apoptotic by UVB irradiation or by anti-Fas monoclonal antibody stimulation, thus confirming the role of apoptotic cells in engraftment facilitation. Overall, these results suggest that apoptotic leukocytes can nonspecifically facilitate allogeneic BM engraftment. Such a simple approach could be of interest in BM transplantation settings involving an important HLA donor/recipient disparity, a T-cell-depleted graft, or reduced conditioning regimen intensity.     

Clonal heterogeneity of dendritic cells derived from patients with chronic myeloid leukemia and enhancement of their T-cells stimulatory activity by IFN-alpha.

Adoptive immunotherapy in form of donor leukocyte infusions is effective in a significant number of patients with chronic myeloid leukemia (CML) that have relapsed after allogeneic bone marrow transplantation (BMT). However, the therapy is associated with clinically significant side effects such as graft-versus-host disease (GVHD) and bone marrow (BM) hypoplasia that may be avoided through the administration of T cells with specific antileukemic activity. Dendritic cells (DC) functioning as potent antigen presenting cells (APC) may play an important role in the generation of T cells with specificity against CML. We examined a subpopulation of CD1a+/CD14- DC generated in vitro from BM of normal subjects and patients with CML using granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF-alpha) and interleukin-4 (IL-4). These DC derived from both the BM of normal subjects and of patients with CML, differentiated and matured in culture in a similar way. However, DC derived from patients with CML, displayed decreased activity when tested with allogeneic T cells in a mixed lymphocyte reaction (MLR). Addition of interferon-alpha (IFN-alpha) to DC cultures significantly upregulated the expression of major histocompatibility complex (MHC) molecules (class I and class II) and costimulatory molecules (B7.1 and B7.2) on DC from normal donors and CML patients. However, DC grown from CML patients required a higher concentration of IFN-alpha. IFN-alpha also significantly improved the capacity of CML DC to stimulate T-lymphocyte responses. Fluorescence in situ hybridization (FISH) showed that only some CD1a+/CD14- DC derived from BM of patients with CML expressed the bcr/abl fusion gene. Incubation with INF-alpha decreased the proportion of bcr/abl positive DC.     

Hematopoietic reconstitution and prevention of graft-versus-host disease with UVB-irradiated haploidentical murine spleen and marrow cells.

We investigated in a murine model whether UVB irradiation of lymphohemopoietic cells would prevent the development of graft-versus-host disease (GVHD). Preliminary experiments showed that spleen colony (CFU-S) formation by hemopoietic cells was preserved at UVB doses that eliminated lymphocyte proliferation. In a parent into F1 model, UVB irradiation (5 to 15 mJ/cm2) of spleen cells added to normal marrow cells prevented the development of GVHD, whereas all recipients given untreated spleen cells developed GVHD. Syngeneic recipients of marrow exposed to 2.5 to 10 mJ/cm2 of UVB achieved normal hemopoietic reconstitution. Based on these observations, B6D2 F1 (H-2b x H-2d) recipients were given 1,000 cGy of total body irradiation (TBI) followed by transplantation of 5 x 10(6) parental B6 (H-2b) bone marrow cells and 10 x 10(6) B6 spleen cells, either unirradiated or exposed to UVB before infusion. All mice transplanted with cells exposed to 10 or 12.5 mJ/cm2 of UVB survived without GVHD. At 2.5 and 5.0 mJ/cm2, mice showed signs of GVHD, beginning at day 30, and 100% and 80%, respectively, eventually developed chronic GVHD. At 7.5 mJ/cm2, mice had weight loss, from which 60% recovered and survived without GVHD, while 40% died with GVHD. At 15 mJ/cm2, some recipients died from graft failure, while some survived without GVHD. All surviving mice were complete donor-type chimeras. Spleen size and cellularity and in vitro lymphocyte responses correlated inversely with the development of GVHD. Mice without GVHD showed specific tolerance to skin grafts from the second parent strain, while animals with GVHD rejected their skin grafts. Thus, in a murine model UVB irradiation of transplanted hemopoietic stem cells allows for hemopoietic reconstitution and prevents GVHD.     

Significant MLR but not CTL responses against recipient antigens generated in T cells from bone marrow chimeras recovered from acute GVHD

Lethally irradiated AKR mice received BMT from H-2D and minor lymphocyte stimulatory (Mls)-1 disparate B10.A mice. No GVHD signs were detected in AKR recipients of T cell-depleted BM cells (1 x 10(7)) alone ([B10.A --> AKR] T-). When B10.A splenic T cells (1 x 10(5)) were injected in addition to T cell-depleted BM cells ([B10.A --> AKR] T+), overt GVHD was observed. [B10.A --> AKR] T+ chimeras recovered from the GVHD 8 weeks after BMT. In T cells from these [B10.A --> AKR] T+ chimeras, a substantial population of Mls-1a-reactive Vbeta6+ T cells was present, whereas the Vbeta6+ cells were deleted in [B10.A --> AKR] T- chimeras. T cells from [B10.A --> AKR] T+ chimeras showed considerable MLR but no CTL response against AKR cells (split tolerance). Upon stimulation with AKR stimulators or anti-CD3 MoAb, T cells from [B10.A --> AKR] T+ chimeras produced significantly more IL-4 but significantly less IFN-gamma compared with those from [B10.A --> AKR] T- chimeras or unmanipulated B10.A mice. The serum level of IgG1 in [B10.A --> AKR] T+ chimeras was also significantly higher than that in [B10.A --> AKR] T- or B10.A mice. The present findings suggest that the split tolerance observed in BMT chimeras recovered from GVHD is attributable to the Th2 dominant state.     

Abnormal T cell-dependent B-cell responses in SCID mice receiving allogeneic bone marrow in utero. Severe combined immune deficiency

In allogeneic hematopoietic stem cell transplant recipients, restoration of humoral immunity is delayed and can remain impaired for years. In many severe combined immune deficiency (SCID) patients given haploidentical bone marrow (BM), lesions in humoral immunity are exacerbated by poor engraftment of donor B cells. The nature of these defects is important to understand as they render patients susceptible to infection. Previous work in mice suggested that in utero transplantation (IUT) of allogeneic BM might offer several advantages for the correction of primary immune deficiencies. In SCID mice given fully allogeneic BM in utero, the lymphoid compartment was restored with minimal evidence of graft-versus-host disease (GVHD). The present report examines B-cell reconstitution and function in mice that have received allogeneic IUT. Results are compared with those of adult mice given total body irradiation (TBI) followed by transplantation with allogeneic BM. In addition to enumerating the various B-cell subsets present in BM, spleen, and peritoneal cavity (PC), B-cell competence was assessed by challenging mice with T cell-independent (TI) and T cell-dependent (TD) antigens. The results demonstrated that all B-cell subsets in the BM and periphery were restored in allogeneic IUT and TBI mice, as were antibody responses after TI challenge. Upon immunization with TD antigens, however, IUT and TBI mice exhibited suboptimal responses as measured by the capacity to isotype switch and generate germinal center (GC) B cells. Thus, although allogeneic BM transplantation results in complete recovery of the B-cell compartment, certain elements of the humoral response remain defective.     

Allogeneic MHC-mismatched activated natural killer cells administered after bone marrow transplantation provide a strong graft-versus-leukaemia effect in mice

Allogeneic lymphocytes administered with an unmanipulated bone marrow transplant provide a strong antileukaemic effect, the so-called graft-versus-leukaemia (GVL) effect. On the other hand, T-cell-mediated graft-versus-host-disease (GVHD) observed after transplantation of unmanipulated BM graft causes substantial morbidity and mortality. The aim of the present study was to determine the antileukaemic potential of enriched IL-2 activated NK cells administered 2 h after BMT. Balb/c (H-2^d) mice were given a dose of A20 (H-2^d, B-cell leukaemia) cells 2 d prior to lethal total body irradiation (TBI) and transplantation of either syngeneic or allogeneic anti-Thy1.2 (CD90) depleted bone marrow cells. Either syngeneic (Balb/c, H-2^d) or allogeneic (C57BL/6, H-2^b) enriched and IL-2 (200 U/ml for 24 h) activated NK cells were given 2 h after BMT. Injection of A20 leukaemia into normal Balb/c recipients led to death after a median of 14 d. A lethal dose of TBI followed by either syngeneic or allogeneic Thy1.2-depleted BMT resulted in a modest antileukaemic effect. The adoptive transfer of syngeneic enriched and IL-2 preincubated NK cells given at time of BMT exerted a significantly better GVL effect. However, the infusion of allogeneic enriched NK cells resulted in a stronger GVL effect. These results clearly demonstrate that allogeneic NK cells are superior to syngeneic NK cells in their potential to eradicate residual leukaemia cells after BMT without mediating clinical overt GVHD. This experimental setting may offer a strategy for treatment of haematological malignancies in a phase of minimal residual disease.