Engraftment of Severe Combined Immune Deficient Mice Receiving Allogeneic Bone Marrow Via In Utero or Postnatal Transfer

Although in utero transplantation (IUT) has been shown to beeffective in treating human severe combined immune deficiency (SCID), the relative merit of IUT as compared withpostnatal bone marrow transplantation (BMT) for SCID is unknown.Therefore, comparative studies were undertaken in mice to determine theengraftment outcome in these two settings. Because T-cell depletion(TCD) reduces graft-versus-host disease (GVHD) severity but compromisesalloengraftment, studies were performed with TCD or non-TCD BM and GVHDrisk was assessed using a tissue scoring system and by the adoptivetransfer of splenocytes from engrafted mice into secondary recipients. Non-SCID recipients received pre-BMT irradiation to simulate those circumstances in which conditioning is required for alloengraftment. IUT recipients of non-TCD and especially TCD BM cells in general hadhigher levels of donor T-cell and myeloid peripheral blood (PB)engraftment than nonconditioned SCID recipients. Increased TCD ornon-TCD BM cell numbers in adult SCID recipients resulted in similarlevels of PB engraftment as IUT recipients. However, under theseconditions, mean GVHD scores were higher than in IUT recipients. Themajority of adoptive transfer recipients of splenocytes from IUTrecipients were GVHD-free, consistent with the in vitro evidence oftolerance to host alloantigens. Total body irradiation (TBI)-treatedmice that had the highest engraftment had evidence of thymic damage asdenoted by a higher proportion of thymic and splenic T cells with amemory phenotype as compared with IUT recipients. IUT mice had vigorousthymic reconstitution by 3 weeks of age. Our data indicate that IUT hasa number of advantages as compared with postnatal BMT. Future studiesexamining the fine specificity of immunoreconstitution in IUT versuspostnatal BMT are indicated.     

Circulating erythropoietin levels after bone marrow transplantation: inappropriate response to anemia in allogeneic transplants.

We studied 24 recipients of autologous bone marrow transplantation (ABMT) or allogeneic BMT (BMT) to determine whether impaired erythropoietin (Epo) response to anemia could delay full erythropoietic recovery. Observed Epo levels were compared with predicted levels based on the relationship between Epo and hematocrit in 125 control subjects. Circulating Epo levels were normal during conditioning and the early posttransplant period. Between days 21 and 180, Epo levels remained normal in ABMT patients but were inappropriately low for the degree of anemia in BMT patients. Median time to full erythropoietic engraftment was longer in BMT than in ABMT recipients. Circulating Epo returned to appropriate levels after day 180, except in patients with active cytomegalovirus infection. We conclude that impaired Epo response to anemia can contribute to delayed erythropoietic recovery after allogenic BMT. Renal toxicity of ciclosporin, interaction between host and donor marrow, and cytomegalovirus infection might play a role. This study could support the use of recombinant human Epo to accelerate erythropoietic engraftment after 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.     

Partial chimerism after T-cell-depleted allogeneic bone marrow transplantation in leukemic HLA-matched patients: a cytogenetic documentation

We evaluated serially by cytogenetics the blood and marrow chimerism of 38 leukemic recipients of HLA-matched bone marrow transplants (BMT) who were prepared by high doses of alkylating agents and fractionated total- body irradiation (2.2 Gy X 5). Donor or host mitoses were identified by examination of sex chromosomes in 32 patients or by evaluation of the polymorphism of other chromosomes after specific banding in six patients. Twenty-four patients were recipients of untreated BMT, and 14 were recipients of T-cell-depleted BMT. In the 24 patients who received untreated BMT, all showed successful engraftment, and only three had a transient mixed chimera. In the 14 recipients of T-cell-depleted BMTs, four rejected their grafts, and seven had mixed chimeras; these mixed chimeras were more frequent in blood lymphocytes than in marrow cells and could be detected up to 26 months after BMT. This high frequency of partial chimerism after T-cell-depleted BMT by comparison with a control group suggests that the donor's T cells play an important role in the eradication of host residual hematopoiesis after allogeneic BMT.     

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.     

Immunoglobulin E levels following allogeneic, autologous, and syngeneic bone marrow transplantation: an indirect association between hyperproduction and acute graft-v-host disease in allogeneic BMT

Markedly elevated serum IgE levels have been noted following allogeneic bone marrow transplantation (BMT) and have been correlated with graft-v- host disease (GVHD) in several studies. To investigate this phenomenon, we measured serum IgE levels in 387 allogeneic, 143 autologous, and 21 syngeneic BMT recipients before and at intervals after BMT. As a population, allogeneic BMT recipients displayed a biphasic elevation in IgE levels, with peak levels occurring either early (days 15 to 19) or late (days 80 to 89) posttransplant. Only in individuals in whom peak levels occurred early did IgE level correlate with liver disease, histological changes, and overall clinical stage of GVHD. The association of IgE elevation and GVHD does not appear to be direct since recipients of syngeneic (monozygotic twin) grafts had the highest incidence of IgE hyperresponsiveness as well as the highest absolute IgE levels. Similarly, 22 recipients of autologous marrow not treated with 4-hydroperoxycyclophosphamide had elevated IgE levels comparable to those seen in allogeneic graft recipients. We hypothesize that augmented IgE synthesis and its subsequent resolution is the natural consequence of immune reconstitution in the presence of potentially reaginic agents such as antibiotics and infectious agents. As such, IgE hyperresponsiveness in syngeneic graft recipients may reflect the maturational sequence of IgE regulatory elements in the absence of interference by GVHD, GVHD therapy, or minor histocompatibility disparities. The cell populations required for IgE response (T cells, B cells, and antigen-presenting cells) may be reconstituted in advance of the regulatory elements that limit IgE production in healthy subjects. Although this temporal relationship does not appear to hold in allogeneic BMT, the balance between positive and negative factors, which determines the rates of IgE synthesis and catabolism, may be altered by GVHD, infection, and liver dysfunction acting alone or in combination.     

Interleukin 2 prevents graft-versus-host disease while preserving the graft-versus-leukemia effect of allogeneic T cells.

We have recently demonstrated that interleukin 2 (IL-2), when administered in high doses for several days beginning on the day of allogeneic bone marrow transplantation (BMT), markedly diminishes graft-versus-host disease (GVHD) mortality in lethally irradiated mice. An optimal anti-GVHD effect was attained by coadministering T-cell-depleted (TCD) syngeneic marrow. We demonstrate here that the full graft-versus-leukemia effect of allogeneic T lymphocytes is obtained even when GVHD is markedly diminished by the coadministration of IL-2 and TCD syngeneic marrow. This methodology represents an approach to the treatment of leukemia in which the beneficial effects of allogeneic T cells can be exploited while their major deleterious effect, GVHD, is avoided. These results may thus have an impact on the clinical use of BMT for the treatment of hematologic malignancies.     

Administration of interleukin-7 after allogeneic bone marrow transplantation improves immune reconstitution without aggravating graft-versus-host disease

Prolonged immunodeficiency after allogeneic bone marrow transplantation (BMT) causes significant morbidity and mortality from infection. This study examined in murine models the effects of interleukin-7 (IL-7) given to young and middle-aged (9-month-old) recipients of major histocompatibility complex (MHC)-matched or -mismatched allogeneic BMT. Although administration of IL-7 from day 0 to 14 after syngeneic BMT promoted lymphoid reconstitution, this regimen was ineffective after allogeneic BMT. However, IL-7 administration from day 14 (or 21) to 27 after allogeneic BMT accelerated restoration of the major lymphoid cell populations even in middle-aged recipients. This regimen significantly expanded donor-derived thymocytes and peripheral T cells, B-lineage cells in bone marrow and spleen, splenic natural killer (NK) cells, NK T cells, and monocytes and macrophages. Interestingly, although recipients treated with IL-7 had significant increases in CD4(+) and CD8(+) memory T-cell populations, increases in naive T cells were less profound. Most notable, however, were the observations that IL-7 treatment did not exacerbate graft-versus-host disease (GVHD) in recipients of an MHC-matched BMT, and would ameliorate GVHD in recipients of a MHC-mismatched BMT. Nonetheless, graft-versus-leukemia (GVL) activity (measured against 32Dp210 leukemia) remained intact. Although activated and memory CD4(+) and CD8(+) T cells normally express high levels of IL-7 receptor (IL-7R, CD127), activated and memory alloreactive donor-derived T cells from recipients of allogeneic BMT expressed little IL-7R. This might explain the failure of IL-7 administration to exacerbate GVHD. In conclusion, posttransplant IL-7 administration to recipients of an allogeneic BMT enhances lymphoid reconstitution without aggravating GVHD while preserving GVL.     

Growth factor treatment prior to low-dose total body irradiation increases donor cell engraftment after bone marrow transplantation in mice

Low-toxicity conditioning regimens prior to bone marrow transplantation (BMT) are widely explored. We developed a new protocol using hematopoietic growth factors prior to low-dose total body irradiation (TBI) in recipients of autologous transplants to establish high levels of long-term donor cell engraftment. We hypothesized that treatment of recipient mice with growth factors would selectively deplete stem cells, resulting in successful long-term donor cell engraftment after transplantation. Recipient mice were treated for 1 or 7 days with growth factors (stem cell factor [SCF] plus interleukin 11 [IL-11], SCF plus Flt-3 ligand [FL], or granulocyte colony-stimulating factor [G-CSF]) prior to low-dose TBI (4 Gy). Donor cell chimerism was measured after transplantation of congenic bone marrow cells. High levels of donor cell engraftment were observed in recipients pretreated for 7 days with SCF plus IL-11 or SCF plus FL. Although 1-day pretreatments with these cytokines initially resulted in reduced donor cell engraftment, a continuous increase in time was observed, finally resulting in highly significantly increased levels of donor cell contribution. In contrast, G-CSF treatment showed no beneficial effects on long-term engraftment. In vitro stem cell assays demonstrated the effect of cytokine treatment on stem cell numbers. Donor cell engraftment and number of remaining recipient stem cells after TBI were strongly inversely correlated, except for groups treated for 1 day with SCF plus IL-11 or SCF plus FL. We conclude that long-term donor cell engraftment can be strongly augmented by treatment of recipient mice prior to low-dose TBI with hematopoietic growth factors that act on primitive cells.     

Promotion of murine marrow alloengraftment and hematopoietic recovery across the major histocompatibility barrier by administration of recombinant human interleukin-1 alpha.

Irradiated C57BL/6 (H-2b) recipients of T-cell-depleted (TCD) BALB/c (H-2d) bone marrow (BM) and recombinant interleukin-1 alpha (IL-1 alpha) (1 microgram/d) had a significantly (P less than or equal to .006) higher 100-day actuarial survival rate, accelerated hematopoietic recovery, and higher levels of alloengraftment than a group of transplanted control mice treated identically, but given phosphate-buffered saline (PBS). To elucidate the mechanisms involved with IL-1 alpha-induced promotion of alloengraftment and hematopoietic recovery, we performed sequential splenic FACS studies on transplanted mice and secondary transfer studies in syngeneic mice given IL-1 alpha or PBS. Splenic phenotyping showed that recipients of IL-1 alpha had a higher proportion of donor granulocytes (52% v 19%) as compared with PBS controls as early as 7 days after bone marrow transplantation (BMT). On day 11 post-BMT, recipients of IL-1 alpha had a more than fourfold increase in splenocyte number, which included a higher percentage (90% v 59%) of donor cells, especially donor granulocytes (52% vs 32%), and a sevenfold increase in donor T cells as compared with controls. Host T-cell numbers were not affected. Taken together, these data suggest that IL-1 alpha stimulated bipotential (myeloid and lymphoid) donor cell engraftment. In a syngeneic BMT system, administration of IL-1 alpha resulted in a higher incidence of survival when recipients were transplanted with BM cells, indicating that IL-1 alpha administration probably either expanded or potentiated engraftment of a committed progenitor cell pool. Secondary transfer experiments using marrow from IL-1 alpha-treated mice showed that the number of day 12 colony-forming unit-spleen (CFU-S) cells was unaltered compared with untreated control mice, suggesting that more primitive, albeit committed, hematopoietic progenitor cells were not affected. We also examined the potential additive effects of IL-1 alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF) administered in combination (for 14 days). Mice receiving a suboptimal amount of IL-1 alpha along with GM-CSF had significantly higher levels of donor alloengraftment (92%) with superior hematopoietic recovery, as compared with mice receiving either IL-1 alpha (57%) or GM-CSF (18%) alone.     

Interleukin-1 administration before lethal irradiation and allogeneic bone marrow transplantation: early transient increase of peripheral granulocytes and successful engraftment with accelerated leukocyte, erythrocyte, and platelet recovery

Administration of interleukin-1 beta (IL-1 beta) before a lethal irradiation with or without allogeneic bone marrow transplantation (BMT) protects greater than 90% of the irradiated mice. To approach the mechanisms responsible for the radioprotective effect of IL-1, we examined the effects of IL-1 pretreatment on engraftment and kinetics of peripheral blood, spleen, and marrow cell reconstitution after irradiation and BMT. Although the BMT was not necessary for the survival of the IL-1-pretreated lethally irradiated mice, allogeneic marrow did engraft in these mice as evaluated in the spleen and marrow 2 months after BMT. IL-1 pretreatment significantly accelerated hematopoietic recovery versus transplanted saline-treated controls with a pronounced enhancement of peripheral leukocyte, platelet, and erythrocyte recovery. Leukocyte recovery in IL-1-pretreated mice was unique in that IL-1 first induced an early transient (maximum at day 7) increase of peripheral granulocytes before accelerating leukocyte recovery after day 11. IL-1 pretreatment also significantly enhanced marrow cell recovery after allogeneic BMT with an eightfold increase in marrow cellularity from day 4 to 11 versus control transplanted mice. When lethal irradiation was not followed by allogeneic BMT. IL-1 pretreatment also affected the peripheral reconstitution of leukocytes, platelets, and erythrocytes. Interestingly, in the absence of BMT, IL-1 also induced an early circulation of peripheral granulocytes. Overall, our data demonstrate that a single administration of IL-1 before lethal irradiation and allogeneic BMT can induce an early transient increase of circulating granulocytes, followed by an accelerated multilineage recovery and long-term allogeneic engraftment.     

Addition of a second, different allogeneic graft accelerates white cell and platelet engraftment after T-cell-depleted bone marrow transplantation

Significant delays in engraftment and lymphoid recovery are the 2 major challenges in cord blood transplantation. The cause for this delay is presumed to be the low numbers of hematopoietic precursors found in one unit of cord blood. One approach to increase the stem cell doses could be to combine cord blood units from different donors differing at the major histocompatibility complex (MHC). As a first step toward this goal, the kinetics of hematologic engraftment and immune reconstitution were compared between 1 unit (2.5 x 10(6) cells) of T-cell-depleted bone marrow cells from a single donor (C57BL/6 [H2(b)] or SJL/J [H2(s)]) and 2 units from different donors (C57BL/6 + SJL/J) after transplantation into lethally irradiated (8.5 Gy) BALB/c recipients (H2(d)). Addition of T-cell-depleted bone marrow from an MHC-mismatched allogeneic donor doubled the white blood counts compared with recipients of one single unit on days +10 and +14. Similar effects were also observed on platelets. The beneficial effect of additional cells on peripheral T-cell counts were first observed on day +14. Cells both from donors (C57BL/6 and/or SJL/J) and recipients (BALB/c) contributed to myeloid and lymphoid reconstitution. The chimeras containing cells from 3 strains of mice were able to mount a recall immune response. Our data suggest that combining stem cells from MHC-mismatched allogeneic donors is feasible, that it has beneficial effects on myeloid engraftment and T-cell phenotypic recovery, and that the long-term stable mixed chimeras are immunologically normal following T-cell-depleted bone marrow transplantation.     

Quantitation of mafosfamide-resistant pre-colony-forming units in allogeneic bone marrow transplantation: relationship with rate of engraftment and evidence for long-lasting reduction in stem cell numbers

Current assays of human committed-stem cells are of limited value in predicting the rate of engraftment or in assessing the integrity of the stem cell pool after allogeneic bone marrow (BM) transplantation (BMT). We have used a limiting dilution assay of mafosfamide-resistant progenitors (pre-colony-forming units [CFU]), which are ancestral to committed progenitors such as CFU-granulocyte-macrophage (GM) to analyze the kinetics of myeloid engraftment after BMT and to assess the size of the stem cell pool at intervals up to 66 months thereafter. In 24 patients transplanted for chronic myeloid leukemia in chronic phase (eight with matched unrelated donors and 16 with sibling donors), the rate of neutrophil engraftment correlated strongly with the number of pre-CFU transfused per kilogram recipient body weight (r = .7, P < .005) but not with CFU-GM per kilogram or nucleated cells per kilogram. In 25 patients studied 6 to 66 months after allogeneic BMT, the mean number of pre-CFU in the marrow was 3.1/10(5) mononuclear cells (MNC) (median, 3.47; range, 0.4 to 23.3), compared with 24.7/10(5) MNC (median, 27.3; range, 4.2 to 180) in 25 normal subjects. CFU-GM were also reduced in these patients, but with considerable overlap into the normal range (mean +/- SD: 54 +/- 45.6 per 10(5) MNC; normal, 129 +/- 61.6). Low pre-CFU but not low CFU-GM levels were associated with reduced peripheral blood white blood cell counts in post-BMT patients. Pre-CFU and CFU-GM levels were not related to the interval posttransplant and remained low for up to 66 months. We conclude that the pre-CFU assay measures a population of stem/progenitor cells that are important in the kinetics of engraftment after allogeneic BMT. Our data suggest that pre-CFU levels may remain low for some years after BMT in humans.     

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)     

Immature reticulocytes as an early predictor of engraftment in autologous and allogeneic bone marrow transplantation

The purpose of this study was to evaluate reticulocyte parameters by means of flow cytometric reticulocyte counting in a group of patients who had undergone autologous and allogeneic bone marrow transplantation (BMT). The pattern of reticulocyte response and the predictive value of absolute neutrophil count (ANC), platelet count, number of CD34+ cell infused and graft source for reticulocyte response were studied. We compared absolute reticulocyte count (RetAbs), mean fluorescence index (MFI) and mean reticulocyte volume/mean corpuscular volume (MRV/MCV) ratio with conventional criteria (ANC and platelet count) in 22 allogeneic and 20 autologous BMT recipients. An abrupt increase in MRV/MCV ratio or a rise in MFI value were the earliest signs of erythropoietic recovery following allogeneic transplantation (63.6 and 22.8% of cases, respectively). In 13.6% of the cases, both parameters were observed simultaneously. All but three autologous transplant recipients showed changes in reticulocyte parameters earlier than ANC recovery. Granulocyte recovery and peripheral blood progenitor cells (PBPC) graft were predictive variables for RetAbs response in allogeneic transplant recipients. In the autologous group, predictive variables for RetAbs response were a high number of CD34+ infused cells and platelet recovery. An increase in the immature reticulocyte population is the earliest sign of haematopoietic recovery following BMT.     

The development of cellular immunity to Epstein-Barr virus after allogeneic bone marrow transplantation

Epstein-Barr virus-induced lymphoproliferative disease (EBV-LPD) is a potentially lethal complication during the first 6 months after allogeneic bone marrow transplantation (BMT). To determine whether deficiencies of EBV-specific cellular immunity contribute to EBV-LPD susceptibility and distinguish patients at risk, we performed limiting dilution analysis to quantify anti-EBV cytotoxic T-lymphocyte precursor (CTLp) frequencies in 26 recipients of unmodified or T-cell-depleted (TCD) grafts from EBV-seropositive donors. At 3 months post-BMT (n = 26), only five patients had EBV CTLp frequencies in the range of seropositive normal controls, irrespective of the type of transplant administered. By 6 months post-BMT, 9 of 13 patients tested had EBV CTLp frequencies within the normal range. The time period in which these patients had deficient cellular immunity to EBV corresponds to the period in which we have observed EBV-LPD in most prior patients. One patient with a low EBV CTLp frequency at 4 months post-BMT developed an EBV-LPD. Within 2 weeks of receiving an infusion of donor peripheral blood mononuclear cells (PBMC) providing less than 1,200 EBV- specific cytotoxic T-cell precursors, populations of EBV-specific CTL in the circulation were restored to levels detected in normal seropositive adults. Concurrently, the patient achieved a regression of the EBV-LPD, which has been sustained without further therapy. These studies indicate that recipients of both unmodified and TCD marrow grafts have profound deficiencies of EBV-specific T cell-mediated immunity early posttransplant, and that the period of risk for EBV-LPD closely corresponds to this interval of severe deficiency. Treatment of one patient with EBV-LPD with marrow donor-derived PBMC induced a rapid expansion of EBV-specific cytotoxic T-cell populations that occurred contemporaneously with the clinical regression of disease.     

Interleukin-15 enhances immune reconstitution after allogeneic bone marrow transplantation

Interleukin-15 (IL-15) is a gamma-common cytokine that plays an important role in the development, survival, and proliferation of natural killer (NK), NK T, and CD8+ T-cells. We administered IL-15 to recipients of an allogeneic bone marrow transplantation (allo BMT) to determine its effects on immune reconstitution. Posttransplantation IL-15 administration significantly increased donor-derived CD8+ T (mostly CD122(+)CD44(+)CD8+ T-cells), NK, and NK T-cells at day +28 in young and old recipients of allo BMT. This was associated with enhanced T-cell and NK-cell function. IL-15 stimulated homeostatic proliferation of donor CD8+ T-cells in recipients of carboxyfluorescein diacetate succinimidyl ester-labeled donor T-cell infusions. Posttransplantation IL-15 administration also resulted in a decrease in apoptotic CD8+ T-cells, an increase in Bcl-2-expressing CD8+ T-cells, and an increase in the fraction of Ki67+ proliferative NK and CD8+ T-cells in recipients of allo BMT. IL-15 did not exacerbate graft-versus-host disease (GVHD) in recipients of T-cell-depleted BMT but could aggravate GVHD in some cases in recipients of a T-cell-repleted BMT. Finally, we found that IL-15 administration could enhance graft-versus-leukemia activity. In conclusion, IL-15 can be administered safely to recipients of a T-cell-depleted allo BMT to enhance CD8+ T, NK, and NK T-cell reconstitution.     

A comparison of murine T-cell-depleted adult bone marrow and full-term fetal blood cells in hematopoietic engraftment and immune reconstitution.

Umbilical cord blood has been increasingly used as a source of hematopoietic stem cells. A major area of concern for the use of cord blood transplantation is the delay in myeloid and lymphoid recovery. To directly compare myeloid and lymphoid recovery using an animal model of bone marrow and cord blood as sources of stem cells, hematopoietic engraftment and immune recovery were studied following infusion of T-cell-depleted adult bone marrow or full-term fetal blood cells, as a model of cord blood in a murine allogeneic transplantation model (C57BL/6 [H-2(b)] --> BALB/c [H-2(d)]). Allogeneic full-term fetal blood has poorer radioprotective capacity but greater long-term engraftment potential on a cell-to-cell basis compared with T-cell-depleted bone marrow. Allogeneic full-term fetal blood recipients had decreased absolute numbers of T, B, and dendritic cells compared with bone marrow recipients. Splenic T cells in allogeneic full-term fetal blood recipients proliferated poorly, were unable to generate cytotoxic effectors against third-party alloantigens in vitro, and failed to generate alloantigen-specific cytotoxic antibodies in vivo. In addition, reconstituting T cells in fetal blood recipients had decreased mouse T-cell receptor delta single-joint excision circles compared with bone marrow recipients. At a per-cell level, B cells from fetal blood recipients did not proliferate as well as those found in bone marrow recipients. These results suggest that full-term fetal blood can engraft allogeneic hosts across the major histocompatibility barrier with slower hematopoietic engraftment and impaired immune reconstitution.     

Autologous and allogeneic bone marrow transplantation for poor prognosis patients with B-cell chronic lymphocytic leukemia

Twenty patients with poor prognosis B-cell chronic lymphocytic leukemia (B-CLL) underwent uniform high-dose chemoradiotherapy followed by rescue with multiple monoclonal antibody-purged autologous bone marrow (BM) (12 patients) or T-cell-depleted allogeneic BM from HLA-identical siblings (8 patients) in a pilot study to assess the feasibility of BM transplantation (BMT) in this disease. All had poor prognosis disease by either staging, BM pattern, tumor doubling time criteria, or cytogenetics. All patients achieved remission criteria (defined as < or = 2 adenopathy, absence of splenomegaly, < or = 20% of the intertrabecular space involved on BM biopsy) before BMT. Despite the use of fludarabine, a median of three treatment regimens were required to achieve BMT eligibility. After BMT, all patients achieved complete hematologic engraftment. Toxicities were not significantly different between autologous versus allogeneic BMT. Two toxic deaths were observed. Of 19 evaluable patients, 17 clinical complete clinical remissions (89%) were observed, with 2 patients (1 allogeneic and 1 autologous) exhibiting persistent BM disease. Complete clinical remissions were documented at the phenotypic and molecular level for the majority of patients in whom dual fluorescence for CD5 and CD20 (15 of 15; 100%) and Ig gene rearrangements (11 of 14; 79%) were performed. Although long-term follow-up is needed to assess any potential impact on the disease-free and overall survival of these patients, this study shows the feasibility of using high-dose chemoradiotherapy and BMT in patients with poor prognosis B-CLL.     

Syngeneic and allogeneic bone marrow engraftment after total body irradiation: dependence on dose, dose rate, and fractionation

Murine bone marrow chimera models were used to assess the efficacy of host total body irradiation (TBI) given at different doses, dose rates, and fractionation schemes in providing for engraftment of syngeneic and allogeneic bone marrow. B6-Hbbd congenic and LP mice, respectively, were used as donors (10(7) bone marrow cells) for syngeneic and allogenic (H-2 compatible) transplantation in standard B6 recipients. Stable marrow chimerism was determined from host and donor stem cell-derived hemoglobin phenotypes (Hbbs and Hbbd) on gel electrophoresis at 3 months posttransplant. Partial engraftment of syngeneic marrow was seen at single doses as low as 2 Gy, with the donor component increasing steadily with increasing TBI dose to a level of 100% at 7 Gy. Immunologic resistance of the host appeared to prevent allogeneic engraftment until 5.5 Gy. A very steep radiation dose response was then observed so that the level of chimerism with 6 Gy and above became comparable with syngeneic engraftment. Low dose rate (5 cGy minute-1) and fractionated TBI required higher total doses for equivalent engraftment (radiation dose-sparing) in both syngeneic and allogenic bone marrow transplantation. This displacement in the dose-response curve on fractionation was seen with interfraction intervals of 3 and 6 hours. A further dose-sparing effect was observed on extending the interval to 18 and 24 hours, but only for allogeneic transplantation, and may therefore be related to recovery of immune-mediated graft resistance. The involvement of multiple target cell populations in determining allogenic engraftment rendered the application of the linear-quadratic model for radiation cell survival problematic in this case. The recovery in dose when low dose rate and 6-hour interfraction intervals were applied in either syngeneic or allogeneic BMT is consistent with appreciable sub-lethal damage repair in the primitive self-renewing stem cell population of the host marrow. These results contrast with the poor repair capacity of the 11-day spleen colony-forming units (CFUs) population after fractionated irradiation and support the notion that ablation of early stem cells in the pre-CFUs compartment is essential for long-term marrow engraftment.