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Biomedical subjects

B R Blazar

Publications and source records attributed to B R Blazar.

At least 19 recordsLinked to original sources
PubMed2007

Fludarabine vs cladribine plus busulfan and low-dose TBI as reduced intensity conditioning for allogeneic hematopoietic stem cell transplantation: a prospective randomized trial.

Purine analogs are often used for conditioning preceding allogeneic hematopoietic stem cell transplantation (HCT). We prospectively tested fludarabine (Flu) 40 mg/m(2)/day x 5 days vs cladribine (Clad) 10 mg/m(2)/day x 5 days plus oral busulfan (1 mg/kg q6 h x 2 days) and total body irradiation 200 cGy in 32 recipients of matched sibling and unrelated donor (URD) HCT. Patients were similar in age (median 52 years), diagnosis, extensive pre-HCT therapy (56 vs 63%), and high-risk disease status (81 vs 93%). Neutrophil engraftment was prompt (median 11 vs 12 days), but early graft failure using Clad halted randomization. Platelet recovery was prompt (median Flu 18 vs Clad 24 days). Graft-versus-host disease (GVHD) after Flu vs Clad was similar; (acute grade II/IV 56 vs 69%, P=0.26; chronic 50 vs 31%, P=0.27). Nonrelapse mortality (Flu 25 vs Clad 38%, P=0.47) and progression-free survival at 3 years were similar as well. Multivariate analyses showed slightly, but not significantly lower relative risk (RR) of neutrophil engraftment with Clad (RR 0.6 (95% CI 0.2-1.3) P=0.16) and with URD RR 0.4 (0.2-1.0) P=0.04). Older patients with advanced hematologic malignancies achieve satisfactory outcomes using either of these reduced intensity conditioning regimens.

Adult↗
PubMed2003

IL-2-based immunotherapy after autologous transplantation for lymphoma and breast cancer induces immune activation and cytokine release: a phase I/II trial.

We determined the safety, immune activating effects, and potential efficacy of i.v. infusion of ex vivo interleukin-2 (IL-2) activated natural killer (NK) cells (part I) or IL-2 boluses (part II) during daily s.c. IL-2 administration following hematopoietic recovery from autologous transplantation. In all, 57 patients with relapsed lymphoma (n=29) or metastatic breast cancer (n=28) were enrolled. In part I of the study, 34 patients were enrolled at three dose levels of ex vivo IL-2-activated NK cells. Lymphaphereses were performed on days 28 and 42 of s.c. IL-2 administration. Following overnight ex vivo IL-2 activation of the pheresis product, the cells were reinfused the following day. In part II, 23 patients were enrolled at three dose levels of supplemental i.v. IL-2 bolus infusions, given on days 28 and 35 during s.c. IL-2 administration. Toxicities were generally mild, and no patient required hospitalization. Lytic function was markedly enhanced for fresh peripheral blood mononuclear cells (PBMNCs) obtained 1 day postinfusion of either IL-2-activated cells or IL-2 boluses. IL-2 boluses transiently increased the levels of IL-6, IFN-gamma, TNF-alpha and IL1-beta, with increases in IL-6 and IFN-gamma being dose dependent. A total of 37 patients (19 patients with lymphoma, 18 with breast cancer) treated with an optimum dose of post-transplant immunotherapy (defined as having received 1.75 x 10(6) IU/m(2)/day of s.c. IL-2 plus at least one of the planned ex vivo IL-2-activated cell infusions/IL-2 boluses) could be matched with controls from the Autologous Blood and Marrow Transplant Registry database. The matched-pairs analysis demonstrated no improvement in disease outcomes of survival and relapse. We conclude that IL-2-activated cells/IL-2 boluses can be safely administered, generate PBMNCs with enhanced cytotoxicity against NK-resistant targets, and increase cytokine levels. With this dose and schedule of administration of IL-2, no improvement in patient disease outcomes was noted. Alternative strategies will be needed to exploit the immunotherapeutic potential of IL-2-activated NK cells.

Adult↗
PubMed2001

Homeostatic expansion occurs independently of costimulatory signals.

Naive T cells undergo homeostatic proliferation in lymphopenic mice, a process that involves TCR recognition of specific self peptide/MHC complexes. Since costimulation signals regulate the T cell response to foreign Ags, we asked whether they also regulate homeostatic expansion. We report in this study that homeostatic expansion of CD4 and CD8 T cells occurs independently of costimulation signals mediated through CD28/B7, CD40L/CD40, or 4-1BB/4-1BBL interactions. Using DO11.10 TCR transgenic T cells, we confirmed that CD28 expression was dispensable for homeostatic expansion, and showed that the presence of endogenous CD4(+)CD25(+) regulatory cells did not detectably influence homeostatic expansion. The implications of these findings with respect to regulation of T cell homeostasis and autoimmunity are discussed.

4-1BB Ligand↗
PubMed2001

Regulation of glutathione redox status in lung and liver by conditioning regimens and keratinocyte growth factor in murine allogeneic bone marrow transplantation.

BACKGROUND: Reactive oxygen species (ROS) and glutathione (GSH) depletion contribute to organ injury after bone marrow transplantation (BMT). Keratinocyte growth factor (KGF) ameliorates graft-versus-host disease (GVHD)-associated organ injury in murine BMT models. METHODS: B10.BR mice received total body irradiation (TBI; day -1) +/- cyclophosphamide (Cy; 120 mg/kg/day i.p., days -3 and -2), then were transplanted on day 0 with C57BL/6 bone marrow + spleen cells as a source of GVHD-causing T cells. KGF (5 mg/kg/day subcutaneously [s.c.]) or saline was given on days -6, -5, and -4. Lung and liver GSH and oxidized GSH disulfide (GSSG) levels were measured on days 0 and 5 and glutathione redox potential (Eh) calculated. Organ malondialdehyde (MDA) was determined on day 5 as an index of ROS-mediated lipid peroxidation. RESULTS: In lung, TBI+BMT oxidized GSH Eh and increased MDA. Cy further oxidized lung GSH Eh. In liver, neither BMT regimen altered GSH redox status or MDA. KGF prevented the decrease in lung GSH after TBI+Cy and decreased lung MDA after both TBI and TBI+Cy. KGF increased liver GSH levels and GSH Eh after TBI and GSH Eh after TBI+Cy. CONCLUSIONS: In murine allogeneic BMT, TBI oxidizes the lung GSH redox pool and Cy exacerbates this response by 5 days post-BMT. In contrast, liver GSH redox status is maintained under these experimental conditions. KGF treatment attenuates the Cy-induced decrease in lung GSH, decreases post-BMT lung lipid peroxidation, and improves liver GSH redox indices. KGF may have a therapeutic role to prevent or attenuate GSH depletion and ROS-mediated organ injury in BMT.

Animals↗
PubMed2001

Treatment of steroid-refractory acute graft-versus-host disease with anti-CD147 monoclonal antibody ABX-CBL.

ABX-CBL, an immunoglobulin M murine monoclonal antibody, recognizes CD147 and initiates cell killing through complement-mediated lysis. In a dose-finding trial, 27 patients with steroid-refractory acute graft-versus-host disease (GVHD) received ABX-CBL at 0.01 (presumed no effect dose), 0.1, 0.2, or 0.3 mg/kg per day, and an additional 32 patients were given ABX-CBL at 0.2 or 0.15 mg/kg per day. All patients had undergone allogeneic transplantation for malignant or nonmalignant disorders and received GVHD prophylaxis, generally with methotrexate- and cyclosporine-containing regimens. None responded to methylprednisolone, given for a minimum of 3 days. ABX-CBL was started 20 to 236 (median, 47) days after transplantation; it was given for 7 consecutive days and was followed by 2 infusions per week for 2 more weeks. Among 51 patients evaluable for efficacy, 26 (51%) responded, including 13 with complete responses (CR) and 13 with partial responses (PR). CR lasting 14 days or longer or PR lasting 7 days or longer occurred in 21 (41%; 8 CR, 13 PR) patients, including 19 of 43 (44%) patients who received 0.1 to 0.3 mg/kg ABX-CBL and 2 of 8 (25%) patients given 0.01 mg/kg per day. Myalgias at doses 0.2 mg/kg or greater were dose limiting and resolved without sequelae. Causes of death included organ failure, progressive GVHD, and infection. No death was attributed to ABX-CBL. At 6 months after the initiation of ABX-CBL therapy, 26 (44%) patients were surviving. These results are encouraging. Further studies on the use of ABX-CBL in the management of GVHD are warranted.

Acute Disease↗
PubMed2001

CD47 (integrin-associated protein) engagement of dendritic cell and macrophage counterreceptors is required to prevent the clearance of donor lymphohematopoietic cells.

Integrin-associated protein (CD47) is a broadly expressed protein that costimulates T cells, facilitates leukocyte migration, and inhibits macrophage scavenger function. To determine the role of CD47 in regulating alloresponses, CD47(+/+) or CD47(-/-) T cells were infused into irradiated or nonconditioned major histocompatibility complex disparate recipients. Graft-versus-host disease lethality was markedly reduced with CD47(-/-) T cells. Donor CD47(-/-) T cells failed to engraft in immunodeficient allogeneic recipients. CD47(-/-) marrow was unable to reconstitute heavily irradiated allogeneic or congenic immune-deficient CD47(+/+) recipients. These data suggested that CD47(-/-) T cells and marrow cells were cleared by the innate immune system. To address this hypothesis, dye-labeled CD47(-/-) and CD47(+/+) lymphocytes or marrow cells were infused in vivo and clearance was followed. Dye-labeled CD47(-/-) cells were engulfed by splenic dendritic cells and macrophages resulting in the clearance of virtually all CD47(-/-) lymphohematopoietic cells within 1 day after infusion. Host phagocyte-depleted CD47(+/+) recipients partially accepted allogeneic CD47(-/-) T cells. Thus, dendritic cells and macrophages clear lymphohematopoietic cells that have downregulated CD47 density. CD47 expression may be a critical indicator for determining whether lymphohematopoietic cells will survive or be cleared.

Animals↗
PubMed2001

Synthetic unmethylated cytosine-phosphate-guanosine oligodeoxynucleotides are potent stimulators of antileukemia responses in naive and bone marrow transplant recipients.

Immunostimulatory cytosine-phophate-guanosine (CpG)--containing motifs in bacterial DNA are potent immune system activators. Depending on the bases flanking the CpG motif and on the DNA backbone, CpG oligodeoxynucleotides (ODNs) can induce relatively more B-cell activation or relatively more natural killer (NK)--cell activation. To evaluate their antitumor activities, an NK-optimized ODN (1585) and 2 B-cell--optimized ODNs (1826 and 2006) were compared for their ability to protect naive mice against a lethal acute myelogenous leukemia (AML) challenge. CpG 2006, but not CpG 1585, administered 2 days before the AML challenge, allowed mice to survive more than 100 times a lethal tumor dose. Cell depletion studies showed that protection did not require T or B cells but depended on NK cells and also on an NK-independent mechanism. CpG 2006 protected against AML challenge in both syngeneic and allogeneic bone marrow transplant (BMT) recipients at both early and late time points after transplantation. Although CpG 1585 had no protective effect on its own, it showed a striking synergy with CpG 2006 to induce prolonged survival to AML challenge in allogeneic recipients of T-cell-depleted marrow grafts, exceeding the survival benefit of donor lymphocyte infusion (DLI). When combined with DLI, a synergistic effect was observed in recipients of CpG2006 or 2006 + 1585 with 88% of mice surviving long-term. These data are the first to indicate that the systemic administration of CpG ODNs is a potent means of inducing therapeutic anti-AML innate immune responses in naive and BMT recipients. (Blood. 2001;98:1217-1225)

Animals↗
PubMed2001

Requirements for the promotion of allogeneic engraftment by anti-CD154 (anti-CD40L) monoclonal antibody under nonmyeloablative conditions.

The promotion of alloengraftment in the absence of global immune suppression and multiorgan toxicity is a major goal of transplantation. It is demonstrated that the infusion of a single modest bone marrow dosage in 200 cGy-irradiated recipients treated with anti-CD154 (anti-CD40L) monoclonal antibody (mAb) resulted in chimerism levels of 48%. Reducing irradiation to 100 or 50 cGy permitted 24% and 10% chimerism, respectively. In contrast, pan-T-cell depletion resulted in only transient engraftment in 200 cGy-irradiated recipients. Host CD4(+) cells were essential for alloengraftment as depletion of CD4(+) cells abrogated engraftment in anti-CD154-treated recipients. Strikingly, the depletion of CD8(+) cells did not further enhance engraftment in anti-CD154 mAb-treated recipients in a model in which rejection is mediated by both CD4(+) and CD8(+) T cells. However, anti-CD154 mAb did facilitate engraftment in a model in which only CD8(+) T cells mediate rejection. Furthermore, CD154 deletional mice irradiated with 200 cGy irradiation were not tolerant of grafts, suggesting that engraftment promotion by anti-CD154 mAb may not simply be the result of CD154:CD40 blockade. Together, these data suggest that a CD4(+) regulatory T cell may be induced by anti-CD154 mAb. In contrast to anti-CD154 mAb, anti-B7 mAb did not promote donor engraftment. Additionally, the administration of either anti-CD28 mAb or anti-CD152 (anti-CTLA-4) mAb or the use of CD28 deletional recipients abrogated engraftment in anti-CD154 mAb-treated mice, suggesting that balanced CD28/CD152:B7 interactions are required for the engraftment-promoting capacity of anti-CD154 mAb. These data have important ramifications for the design of clinical nonmyeloablative regimens based on anti-CD154 mAb administration.

Animals↗
PubMed2001

CD4(+)CD25(+) immune regulatory cells are required for induction of tolerance to alloantigen via costimulatory blockade.

Immune regulatory CD4(+)CD25(+) cells play a vital role in the induction and maintenance of self-tolerance and are essential for T cell homeostasis and the prevention of autoimmunity. Induction of tolerance to allogeneic donor grafts is a clinically desirable goal in bone marrow and solid organ transplantation. To determine whether CD4(+)CD25(+) cells regulate T cell responses to alloantigen and are critical for tolerance induction, murine CD4(+) T cells were tolerized to alloantigen via ex vivo CD40 ligand (CD40L)/CD40 or CD28/cytotoxic T lymphocyte-associated antigen 4/B7 blockade resulting in secondary mixed leukocyte reaction hyporesponsiveness and tolerance to alloantigen in vivo. CD4(+)CD25(+) T cells were found to be potent regulators of alloresponses. Depletion of CD4(+)CD25(+) T cells from the CD4(+) responder population completely abrogated ex vivo tolerance induction to alloantigen as measured by intact responses to alloantigen restimulation in vitro and in vivo. Addback of CD4(+)CD25(+) T cells to CD4(+)CD25(-) cultures restored tolerance induction. These data are the first to indicate that CD4(+)CD25(+) cells are essential for the induction of tolerance to alloantigen and have important implications for tolerance-inducing strategies targeted at T cell costimulatory pathways.

Abatacept↗
PubMed2001

Augmentation of antitumor effects by NK cell inhibitory receptor blockade in vitro and in vivo.

Subsets of natural killer (NK) cells are characterized by the expression of inhibitory and/or stimulatory receptors specific for major histocompatibility complex (MHC) class I determinants. In mice, these include the Ly49 family of molecules. One mechanism by which tumor cells may evade NK cell killing is by expressing the appropriate MHC class I and binding inhibitory Ly49 receptors. Therefore, the question of whether blocking the interaction between the Ly49 inhibitory receptors on NK and MHC class I cells on tumor cells augments antitumor activity was investigated. Blockade of Ly49C and I inhibitory receptors using F(ab')(2) fragments of the 5E6 monoclonal antibody (mAb) resulted in increased cytotoxicity against syngeneic tumors and decreased tumor cell growth in vitro. The effect of 5E6 F(ab')(2) was specific for the MHC of the tumor, as the use of F(ab')(2) of the mAb against Ly49G2 failed to increase NK activity. Treatment of leukemia-bearing mice with 5E6 F(ab')(2) fragments or adoptive transfer of NK cells treated ex vivo with the F(ab')(2) resulted in significant increases in survival. These results demonstrate that blockade of NK inhibitory receptors enhances antitumor activity both in vitro and in vivo, suggesting that NK inhibitory receptors can be responsible for diminishing antitumor responses. Therefore, strategies to block inhibitory receptors may be of potential use in increasing the efficacy of immunotherapy. (Blood. 2001;97:3132-3137)

Animals↗
PubMed2001

Factors affecting thymic function after allogeneic hematopoietic stem cell transplantation.

Hematopoietic stem cell transplantation (HSCT) is followed by profound immunodeficiency. Thymic function is necessary for de novo generation of T cells after HSCT. Circulating CD45RA(+) naive T-cell levels are predictive of antigen-specific T-cell responses in the absence of graft-versus-host disease (GVHD). These T cells may not represent recent thymic emigrants, since naive T cells may maintain this phenotype if not antigen-activated. To accurately measure thymic output after HSCT and determine the factors that influence thymic function, T-cell receptor excision circles (TRECs) were examined in CD4(+) and CD8(+) cells from a cross-section of patients following HSCT. TREC levels rose weeks after HSCT and could be detected in patients 6 years after HSCT. TREC levels correlated with the frequency of phenotypically naive T cells, indicating that such cells were not expanded progeny of naive T cells present in the donor graft. Chronic GVHD was the most important factor that predicted low TREC levels even years after HSCT. Patients with a history of resolved GVHD had decreased numbers of TREC, compared with those with no GVHD. Because few adults had no history of GVHD, it was not possible to determine whether age alone inversely correlated with TREC levels. Recipients of cord blood grafts had no evidence of decreased TREC induced by immunosuppressive prophylaxis drugs. Compared with unrelated donor grafts, recipients of matched sibling grafts had higher TREC levels. Collectively, these data suggest that thymopoiesis is inhibited by GVHD. Larger studies will be needed to determine the independent contributions of age and preparative regimen to post-transplant thymopoietic capacity.

Adolescent↗
PubMed2001

In vitro tumor-pulsed or in vivo Flt3 ligand-generated dendritic cells provide protection against acute myelogenous leukemia in nontransplanted or syngeneic bone marrow-transplanted mice.

To determine whether immune stimulation could reduce acute myelogenous leukemia (AML) lethality, dendritic cells (DCs) were pulsed with AML antigens and used as vaccines or generated in vivo by Flt3 ligand (Flt3L), a potent stimulator of DC and natural killer (NK) cell generation. Mice were then challenged with AML cells. The total number of splenic anti-AML cytotoxic T-lymphocyte precursors (CTLPs) present at the time of challenge was increased 1.9-fold and 16.4-fold by Flt3L or DC tumor vaccines, respectively. As compared with the 0% survival of controls, 63% or more of recipients of pulsed DCs or Flt3L survived long term. Mice given AML cells prior to DC vaccines or Flt3L had only a slight survival advantage versus non-treated controls. NK cells or NK cells and T cells were found to be involved in the antitumor responses of Flt3L or DCs, respectively. DC vaccines lead to long-term memory responses but Flt3L does not. Syngeneic bone marrow transplantation (BMT) recipients were analyzed beginning 2 months post-BMT. In contrast to the uniform lethality in BMT controls given AML cells, recipients of either Flt3L or DC vaccines had a significant increase in survival. The total number of splenic anti-AML CTLPs at the time of AML challenge in BMT controls was 40% of concurrently analyzed non-BMT controls. Flt3L or DC vaccines increased the total anti-AML CTLPs 1.4-fold and 6.8-fold, respectively. Neither approach was successful when initiated after AML challenge. It was concluded that DC vaccines and Flt3L administration can enhance an AML response in non-transplanted or syngeneic BMT mice but only when initiated prior to AML progression.

Adjuvants, Immunologic↗
PubMed2001

Gastrointestinal cells of IL-7 receptor null mice exhibit increased sensitivity to irradiation.

IL-7 is a critical cytokine in the development of T and B cells but little is known about its activity on nonhematopoietic cells. An unexpected finding was noted in allogeneic bone marrow transplant studies using IL-7 receptor null (IL-7R alpha(-/-)) mice as recipients. These mice exhibited a significantly greater weight loss after total body irradiation compared with wild type, IL-7R alpha(+/+), mice. Pathological assessment indicated greater intestinal crypt damage in IL-7R alpha(-/-) recipients, suggesting these mice may be predisposed to gut destruction. Therefore, we determined the effect of the conditioning itself on the intestinal tract of these mice. IL-7R alpha(-/-) mice and IL-7R alpha(+/+) mice were irradiated and examined for lesions and apoptosis within the small intestine. In moribund animals, IL-7R alpha(-/-) mice had extensive damage in the small intestine, including marked ablation of the crypts and extreme shortening of villi following 1500 cGy total body irradiation. In contrast, by 8 days after irradiation, the small intestines of IL-7R alpha(+/+) mice had regenerated as distinguished by normal villus length and hyperplastic crypts. Following 750 cGy irradiation, IL-7R alpha(-/-) mice had a higher proportion of apoptotic cells in the crypts and an accompanying increase in the pro-apoptotic protein Bak was expressed in intestinal epithelial cells. These results demonstrate the increased radiosensitivity of intestinal stem cells within the crypts in IL-7R alpha(-/-) mice and a role for IL-7 in the protection of radiation-induced apoptosis in these same cells. This study describes a novel role of IL-7 in nonhematopoietic tissues.

Animals↗
PubMed2001

Ligation of 4-1BB (CDw137) regulates graft-versus-host disease, graft-versus-leukemia, and graft rejection in allogeneic bone marrow transplant recipients.

4-1BB is expressed on activated CD4(+) and CD8(+) T cells; its ligand, 4-1BB ligand is expressed on APCs. Despite expression on both T cell subpopulations, 4-1BB has been reported to predominantly affect CD8(+) T cell responses. By quantifying graft-vs-host disease alloresponses in vivo, we demonstrate that both CD4(+) and CD8(+) T cell-mediated alloresponses are regulated by 4-1BB/4-1BB ligand interactions to approximately the same extent. 4-1BB receptor-facilitated CD4(+) T cell-mediated alloresponses were partly CD28 independent. In two distinct marrow graft rejection systems, host CD8(+) and CD4(+) T cells each separately contributed to host anti-donor T cell-mediated allograft rejection. alpha 4-1BB mAb increased the graft-vs-leukemia effect of a suboptimal number of donor splenocytes given later post bone marrow transplantation by bolstering allogeneic responses resulting in leukemia elimination. In summary, 4-1BB ligation is a potent regulator of CD4(+) and CD8(+) T cell-mediated allogeneic responses in vivo. Modifying the ligation of 4-1BB represents a new approach to altering the graft-vs-host disease and graft-vs-leukemia effects of allogeneic T cells post bone marrow transplantation.

4-1BB Ligand↗
PubMed2001

Altered T-cell receptor + CD28-mediated signaling and blocked cell cycle progression in interleukin 10 and transforming growth factor-beta-treated alloreactive T cells that do not induce graft-versus-host disease.

The induction of anergy in T cells, although widely accepted as critical for the maintenance of tolerance, is still poorly understood at the molecular level. Recent evidence demonstrates that in addition to blockade of costimulation using monoclonal antibodies (mAbs) directed against cell surface determinants, treatment of mixed lymphocyte reaction (MLR) cultures with interleukin 10 (IL-10) and transforming growth factor-beta (TGF-beta) results in induction of tolerance, rendering alloreactive murine CD4(+) T cells incapable of inducing graft-versus-host disease (GVHD) after in vivo transfer to histoincompatible recipients. The present study, using these cells prior to adoptive transfer, determined that IL-10 + TGF-beta-tolerant CD4(+) T cells exhibit an altered pattern of T-cell receptor (TCR) + CD28-mediated signaling and are incapable of progressing out of the G(1) phase of the cell cycle during stimulation with HLA class II disparate antigen-presenting cells. TGFbeta + IL-10-tolerant cells were incapable of phosphorylating TCR-zeta, or activating ZAP-70, Ras, and MAPK, similarly to T-cell tolerized by blockade of B7/CD28 and CD40/CD40L pathways. Moreover, these cells were incapable of clonal expansion due to defective synthesis of cyclin D3 and cyclin A, and defective activation of cyclin-dependent kinase (cdk)4, cdk6, and cdk2. These cells also exhibited defective down-regulation of p27(kip1) cdk inhibitor and lack of cyclin D2-cdk4 activation, Rb hyperphosphorylation, and progression to the S phase of the cell cycle. These data link anergy-specific proximal biochemical alterations and the downstream nuclear pathways that control T-cell expansion and provide a biochemical profile of IL-10 + TGF-beta-tolerant alloreactive T cells that do not induce GVHD when transferred into MHC class II disparate recipients in vivo.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Antibodies to CD40 induce a lethal cytokine cascade after syngeneic bone marrow transplantation.

CD40 stimulation, by either antibody or ligand, has been shown to inhibit the growth of a variety of neoplastic cells, both in vivo and in vitro. In this study, we assessed the effects of CD40 stimulation using a murine agonistic CD40 monoclonal antibody (MoAb) (FGK115) or a soluble recombinant murine CD40 ligand (srmCD40L) in both lethally irradiated and nonirradiated BALB/c mice. Toxicity after CD40 stimulation was not observed in nonirradiated animals receiving up to 100 microg of the agonist anti-CD40 MoAb. However, as little as 10 microg of the agonistic anti-CD40 MoAb induced acute toxicity resulting in 100% morbidity of lethally irradiated animals by 4 days after irradiation. Histological evaluation of animals receiving anti-CD40 MoAb revealed severe intestinal lesions with disruption of the villi, goblet cell depletion, and crypt hyperplasia of the small intestine, colon, and cecum. Delaying the administration of anti-CD40 MoAb or reducing the amount of irradiation given resulted in increased survival and less severe lesions. Analysis of serum cytokine levels in lethally irradiated mice receiving agonistic anti-CD40 showed a marked increase of interferon (IFN)-gamma. Lethally irradiated IFN-gamma knockout mice given the agonistic anti-CD40 MoAb demonstrated significant increases in survival and minimal gut lesions compared with wild-type mice receiving the same regimen, suggesting that IFN-gamma plays a major role in this toxic reaction. These results indicate that CD40 stimulation using agonistic antibodies following lethal irradiation leads to a fatal, cytokine-induced disease affecting the intestine.

Animals↗
PubMed2001

Flt3 ligand (FL) treatment of murine donors does not modify graft-versus-host disease (GVHD) but FL treatment of recipients post-bone marrow transplantation accelerates GVHD lethality.

Flt3 ligand (FL) is a hematopoietic cytokine that has been shown to facilitate the expansion of dendritic cells (DCs) and the generation of antitumor immune responses. In addition, the use of FL in mobilizing peripheral blood progenitor cells is being investigated. In the present study, we sought to quantify the influence of FL-treated donor cells on graft-versus-host disease (GVHD). FL treatment resulted in a marked expansion in the absolute number of myeloid- and lymphoid-related DCs and a reduction in the proportion of donor splenic T cells. Irradiated recipients who were given splenocytes from FL-treated donors had reduced GVHD lethality compared with controls due to the infusion of fewer mature T cells. Highly purified T cells from FL-treated donors produced comparable in vitro alloresponses and there was no evidence of a skewing toward T-helper type 1 (interleukin [IL]-2, interferon-gamma) or T-helper type 2 (IL-4, IL-10) cytokine production. The GVHD lethality associated with purified T cells obtained from FL-treated or control donors was comparable. In contrast, FL treatment of recipients resulted in a significant increase in GVHD lethality. Increased lethality was observed even when the infusions of allogeneic T cells and FL were delayed until 3 weeks post-bone marrow transplantation (BMT). Our data indicate that FL treatment of donors does not increase GVHD risk, but treatment of recipients increases GVH lethality even if FL treatment is delayed until later post-BMT.

Animals↗