Donor and recipient plasma follistatin levels are associated with acute GvHD in Blood and Marrow Transplant Clinical Trials Network 0402

Follistatin is an angiogenic factor elevated in the circulation after allogeneic hematopoietic cell transplantation (HCT). Elevations in follistatin plasma concentrations are associated with the onset of and poor survival after acute graft versus host disease (aGVHD). Using data from the Blood and Marrow Transplant Clinical Trials Network 0402 study (n=247), we sought to further quantify the longitudinal associations between plasma follistatin levels in transplant recipients, as well as baseline HCT donor follistatin levels, and allogeneic HCT outcomes. Higher recipient baseline follistatin levels were predictive of development of aGVHD (P=0.04). High donor follistatin levels were also associated with the incidence of aGVHD (P<0.01). Elevated follistatin levels on day 28 were associated with the onset of grade II–IV aGVHD prior to day 28, higher one-year non-relapse mortality, (NRM), and lower overall survival (OS). In multivariate analyses, individuals with follistatin levels >1088 pg/mL at day 28 had a four-fold increased risk for NRM (RR=4.3, 95% CI 1.9–9.9, P<0.01) and a nearly three-fold increased overall risk for mortality (RR=2.8, 95% CI 1.5–5.2, P<0.01). Given the multiple roles of follistatin in tissue inflammation and repair, and the confirmation that this biomarker is predictive of important HCT outcomes, the pathobiology of these relationships need further study.

L-selectin is dispensable for T regulatory cell function postallogeneic bone marrow transplantation

In murine models, the adoptive transfer of CD4(+) /CD25(+) regulatory T cells (T(regs) ) inhibited graft-versus-host disease (GvHD). Previous work has indicated a critical role for the adhesion molecule L-selectin (CD62L) in the function of T(regs) in preventing GvHD. Here we examined the capacity of naive wild-type (WT), CD62L(-/-) and ex vivo expanded CD62L(Lo) T(regs) to inhibit acute GvHD. Surprisingly, we found that CD62L(-/-) T(regs) were potent suppressors of GvHD, whereas CD62L(Lo) T(regs) were unable to inhibit disease despite being functionally competent to suppress allo T cell responses in vitro. Concomitant with improved outcomes, WT and CD62L(-/-) T(regs) significantly reduced liver pathology and systemic pro-inflammatory cytokine production, although CD62L(-/-) T(regs) were less effective in reducing lung pathology. While accumulation of CD62L(-/-) T(regs) in GvHD target organs was equivalent to WT T(regs) , CD62L(-/-) T(regs) did not migrate as well as WT T(regs) to peripheral lymph nodes (PLNs) over the first 2 weeks posttransplantation. This work demonstrated that CD62L was dispensable for T(reg) -mediated protection from GvHD.

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.

Preclinical studies targeting normal and leukemic hematopoietic cells with Yttrium-90-labeled anti-CD45 antibody in vitro and in vivo in nude mice

A study was undertaken to investigate the suitability of using a high affinity (Kd = 1.1 nM) anti-CD45 monoclonal antibody for delivering the high energy beta-particle emitting isotope (90)Y to lymphohematopoietic target cells in vivo. The antibody, AHN-12, recognized the tyrosine phosphatase CD45 expressed on the surface of normal and malignant hematopoietic cells and studies showed that it reacted with both CD45-expressing normal peripheral blood cells and leukemia cells from patients. The antibody was readily labeled with (90)Y using the highly stable chelate 1B4M-DTPA and the radioimmunoconjugate was designated (90)Y-anti-CD45. The agent selectively bound to CD45(+) B cell line Daudi, but not CD45(-) control cells and significantly (p = 0.007) more bound to Daudi tumors growing in athymic nude mice than did a control non-reactive antibody. Moreover, biodistribution data correlated well to an anti-Daudi effect observed against established tumors in nude mice. The effect was dose dependent and irreversible with the best results in mice receiving a single dose of 137 microCi (90)Y-anti-CD45. These mice displayed a significantly (p < 0.0095) better anti-tumor effect than a control (90)Y-labeled antibody and survived over 135 days with no evidence of tumor. Histology studies showed no significant injury to kidney, liver, or small intestine even at 254 microCi, the highest dose tested. Because radiolabeled anti-CD45 antibody can be used to deliver radiation selectively to lymphohematopoietic tissue, these data indicate that this agent may be used to improve treatment of hematopoietic malignancies, particularly leukemia and lymphoma, when combined with hematopoietic stem cell transplantation in a future clinical trial.

Intercellular adhesion molecule-I (ICAM-I, CD54) deficiency segregates the unique pathophysiological requirements for generating idiopathic pneumonia syndrome (IPS) versus graft-versus-host disease following allogeneic murine bone marrow transplantation

Following allogeneic bone marrow transplantation (alloBMT), idiopathic pneumonia syndrome (IPS) and graft-versus-host disease (GVHD) caused by donor cell alloreactivity remain major obstacles to a successful outcome. Intercellular adhesion molecule-1 (ICAM-1) is an adhesion molecule that is involved in regulating lymphohematopoietic cell migration and facilitating T-cell responses. To determine whether ICAM-1 expression in the host would affect IPS or GVHD tissue injury responses, ICAM-1(-/-) mice were compared with ICAM-1(+/+) controls. ICAM-1(-/-) recipients did not exhibit the manifestations of IPS injury such as an increase in lung weights nor decreased lung function. The influx of T cells, macrophages, and neutrophils was dramatically dampened as was the production of the inflammatory cytokines interferon-gamma and tumor necrosis factor alpha and the chemokines monocyte chemotactic protein 1, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and lymphotactin, normally upregulated in the lung during IPS. In contrast, systemic levels of these mediators were unaffected and GVHD-induced lesions in the liver and colon did not differ in severity regardless of ICAM-1 expression. GVHD-mediated mortality was accelerated in ICAM-1(-/-) recipients at doses of allogeneic spleen cells that are otherwise not uniformally lethal. These data implicate ICAM-1 as playing a critical role in the generation of IPS; therefore, ICAM-1 may be a discerning element, segregating IPS from GVHD injury post-alloBMT.

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.

Effects of oxidant stress on inflammation and survival of iNOS knockout mice after marrow transplantation

In a model of idiopathic pneumonia syndrome after bone marrow transplantation (BMT), injection of allogeneic T cells induces nitric oxide (.NO), and the addition of cyclophosphamide (Cy) generates superoxide (O.) and a tissue-damaging nitrating oxidant. We hypothesized that.NO and O. balance are major determinants of post-BMT survival and inflammation. Inducible nitric oxide synthase (iNOS) deletional mutant mice (-/-) given donor bone marrow and spleen T cells (BMS) exhibited improved survival compared with matched BMS controls. Bronchoalveolar lavage fluids obtained on day 7 post-BMT from iNOS(-/-) BMS mice contained less tumor necrosis factor-alpha and interferon-gamma, indicating that.NO stimulated the production of proinflammatory cytokines. However, despite suppressed inflammation and decreased nitrotyrosine staining, iNOS(-/-) mice given both donor T cells and Cy (BMS + Cy) died earlier than iNOS-sufficient BMS + Cy mice. Alveolar macrophages from iNOS(-/-) BMS + Cy mice did not produce.NO but persisted to generate strong oxidants as assessed by the oxidation of the intracellular fluorescent probe 2',7'-dichlorofluorescin. We concluded that.NO amplifies T cell-dependent inflammation and addition of Cy exacerbates.NO-dependent mortality. However, the lack of.NO during Cy-induced oxidant stress decreases survival of T cell-recipient mice, most likely by generation of.NO-independent toxic oxidants.

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.

Human surfactant protein a suppresses T cell-dependent inflammation and attenuates the manifestations of idiopathic pneumonia syndrome in mice

We have previously shown an association between growth factor-induced upregulation of surfactant protein (SP)-A and suppression of alveolar inflammation in our murine model of donor T cell-dependent lung dysfunction after bone-marrow transplantation, referred to as idiopathic pneumonia syndrome (IPS). We hypothesized that SP-A protects the lung in vivo from IPS injury by downregulation of alveolar inflammation. Human SP-A (100 microg), purified by n-butanol extraction or preparative isoelectric focusing, was transtracheally instilled on Day 4 after BMT during a time of in vivo donor T-cell activation. At 48 h after treatment, immunohistochemical staining of lung sections showed that SP-A did not alter T cell- dependent cellular infiltration. However, macrophages from SP-A-instilled mice were less injured and spontaneously produced less tumor necrosis factor-alpha than did cells from buffer-instilled mice. Although exogenous SP-A did not significantly alter bronchoalveolar lavage fluid (BALF) high levels of total protein (TP), an inverse correlation between BALF SP-A and TP concentrations (r = -0.65; P = 0.02) was observed in SP-A-treated but not in buffer-instilled mice. The only difference between the effects of the two sources of SP-A was that butanol-extracted SP-A, but not isoelectric focusing-purified SP-A, suppressed the interferon-gamma/nitric oxide pathway. We conclude that SP-A downregulates T cell-dependent alveolar inflammation by multiple pathways leading to decreased IPS injury.

Abnormalities of bone marrow mesenchymal cells in multiple myeloma patients

BACKGROUND

The importance of the bone marrow microenvironment in multiple myeloma is receiving increasing attention. Recent studies have suggested the importance of cytokine production and cell-cell contact by bone marrow stromal cells in the survival of myeloma cells.

METHODS

In the current study, the authors examined bone marrow mesenchymal progenitor cell (MPC) cultures derived from eight multiple myeloma patients (mean age, 58 years) and nine normal donors (mean age, 61 years), with emphasis on cell surface antigens, cytokine, and growth factor expression.

RESULTS

The authors have found, based on analysis of cellular receptors, growth factors, and cytokine expression, that myeloma MPCs are phenotypically and functionally distinguishable from normal donor MPCs. Immunofluorescence analysis of MPC monolayers shows that myeloma MPC cultures expressed reduced cell surface vascular cell adhesion molecule-1 and fibronectin, in contrast with the strong expression found on normal donor MPCs. Furthermore, a subset of myeloma MPCs strongly express intracellular receptor for hyaluronan-mediated motility, whereas normal MPCs do not. Cytokine expression in bone marrow MPC cultures was examined by reverse transcription-polymerase chain reaction and enzyme linked immunosorbent assay. Bone marrow MPCs constitutively express interleukin (IL)-1beta, IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage (GM)-CSF, stem cell factor (SCF), and tumor necrosis factor (TNF)-alpha. In comparison to normal MPCs, multiple myeloma MPCs express increased basal levels of IL-1beta and TNF-alpha. In vitro exposure of MPC cultures to dexamethasone resulted in the down-regulation of IL-6, G-CSF, and GM-CSF in both normal and myeloma MPC cultures. However, dexamethasone treatment significantly increased expression of SCF-1 in myeloma MPCs.

CONCLUSIONS

In myeloma, bone marrow stromal cells provide paracrine factors, through cytokine production and cell-cell contact, which play a role in plasma cell growth and survival. The authors' data indicate differences in bone marrow MPCs, which may be biologically relevant to the growth and survival of myeloma plasma cells.

Abnormalities of bone marrow mesenchymal cells in multiple myeloma patients

BACKGROUND

The importance of the bone marrow microenvironment in multiple myeloma is receiving increasing attention. Recent studies have suggested the importance of cytokine production and cell-cell contact by bone marrow stromal cells in the survival of myeloma cells.

METHODS

In the current study, the authors examined bone marrow mesenchymal progenitor cell (MPC) cultures derived from eight multiple myeloma patients (mean age, 58 years) and nine normal donors (mean age, 61 years), with emphasis on cell surface antigens, cytokine, and growth factor expression.

RESULTS

The authors have found, based on analysis of cellular receptors, growth factors, and cytokine expression, that myeloma MPCs are phenotypically and functionally distinguishable from normal donor MPCs. Immunofluorescence analysis of MPC monolayers shows that myeloma MPC cultures expressed reduced cell surface vascular cell adhesion molecule-1 and fibronectin, in contrast with the strong expression found on normal donor MPCs. Furthermore, a subset of myeloma MPCs strongly express intracellular receptor for hyaluronan-mediated motility, whereas normal MPCs do not. Cytokine expression in bone marrow MPC cultures was examined by reverse transcription-polymerase chain reaction and enzyme linked immunosorbent assay. Bone marrow MPCs constitutively express interleukin (IL)-1beta, IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage (GM)-CSF, stem cell factor (SCF), and tumor necrosis factor (TNF)-alpha. In comparison to normal MPCs, multiple myeloma MPCs express increased basal levels of IL-1beta and TNF-alpha. In vitro exposure of MPC cultures to dexamethasone resulted in the down-regulation of IL-6, G-CSF, and GM-CSF in both normal and myeloma MPC cultures. However, dexamethasone treatment significantly increased expression of SCF-1 in myeloma MPCs.

CONCLUSIONS

In myeloma, bone marrow stromal cells provide paracrine factors, through cytokine production and cell-cell contact, which play a role in plasma cell growth and survival. The authors' data indicate differences in bone marrow MPCs, which may be biologically relevant to the growth and survival of myeloma plasma cells.

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.

Visualization of immunotoxin-mediated tumor cell death in vivo

We present a novel methodology to visualize tumor cells directly in a whole mouse. This technique combines immunohistochemistry with whole mouse sectioning. It lets one see the exact distribution of tumor cells throughout an animal and how effectively these cells are eliminated by cancer therapeutics. We used this technique to assess the efficacy of a T cell-specific immunotoxin in a severe combined immunodeficient mouse model of human T-cell leukemia. Severe combined immunodeficient mice were injected with one of two human T-cell acute lymphoblastic leukemia cell lines (Molt 3 and Molt 13) and were either left untreated or were treated with DA7, an immunotoxin specific for the T cell-associated antigen CD7. Mice were sacrificed after tumor cell injection and immunotoxin therapy, whole mouse cross-sections were prepared, and tumor cells in the sections were visualized by immunohistochemistry. No tumor cells were detected in DA7-treated mice injected with Molt 3, consistent with the long-term survival of this group and the sensitivity of Molt 3 to DA7 in vitro. In contrast, DA7 treatment did not visibly eliminate tumor cells in mice challenged with Molt 13, nor did it result in their long-term survival. Furthermore, tumor cells were detected in areas that may have otherwise been overlooked, and their distribution differed from that of mice injected with Molt 13 alone. These analyses indicate that whole mouse sectioning will be a valuable tool for assessing residual disease in the preclinical evaluation of cancer therapeutics.

A phase I clinical, pharmacological, and biological trial of interleukin 6 plus granulocyte-colony stimulating factor after ifosfamide, carboplatin, and etoposide in children with recurrent/refractory solid tumors: enhanced hematological responses but a high incidence of grade III/IV constitutional toxicities

A Phase I trial was conducted to determine the safety, biological activity, and hematopoietic recovery by the combination of interleukin 6 (IL-6) and granulocyte-colony stimulating factor (G-CSF) after myelosuppressive chemotherapy in children. Patients <22 years of age at diagnosis with either recurrent or refractory solid tumors received ifosfamide 1,800 mg/m2/day x 5 days, carboplatin 400 mg/m2/ day x 2 days, and etoposide 100 mg/m2/day x 5 days, followed by daily s.c. G-CSF (5 microg/kg/day) and IL-6 (2.5, 3.75, or 5.0 microg/kg/day). Pharmacokinetic, proinflammatory mediator levels, hematopoietic colony assays, and cytokine receptor expression studies were performed during course one. Nineteen patients were evaluable for toxicity and received IL-6 at doses of 2.5 (n = 8), 3.75 (n = 5), or 5.0 (n = 6) microg/kg/day. Dose-limiting constitutional toxicity occurred in two of six patients at 5.0 microg/kg/day, two of five patients at 3.75 microg/kg/day, and two of eight patients at 2.5 microg/kg/day. The maximum tolerated dose (MTD) exceeded the lowest dose tested. Because of lack of drug availability, an MTD was not established. The maximum concentration of IL-6 (2.5 microg/kg/day) was 0.799 +/- 1.055 ng/ml (mean +/- SD). During the first course, the median time to absolute neutrophil count > or = 1,000/mm3 and platelets > or = 100,000 mm3 was estimated at 19 and 23 days, respectively. Peripheral blood progenitor cells expressing receptors to IL-3, IL-6, and G-CSF increased significantly over baseline (P < 0.05). After the first dose of IL-6, IFN-gamma levels were abnormal in 13 patients, and IL-1beta levels were abnormal in 10 patients. IL-6 has a high incidence of constitutional toxicity and a lower MTD in children compared with adults. In vivo use of IL-6 in children after chemotherapy remains limited. However, IL-6 may be more optimally investigated in children under ex vivo conditions.

Keratinocyte growth factor facilitates alloengraftment and ameliorates graft-versus-host disease in mice by a mechanism independent of repair of conditioning-induced tissue injury

We have previously shown that pretreatment of mice with keratinocyte growth factor (KGF), an epithelial tissue repair factor, can ameliorate graft-versus-host disease (GVHD) after intensive chemoradiotherapeutic conditioning and allogeneic bone marrow transplantation (BMT). To determine whether this effect was dependent on a KGF-mediated mechanism affecting repair of conditioning-induced epithelial cell injury, we studied GVHD in the absence of conditioning using BALB/c severe combined immune-deficient (SCID) recipients given C57BL/6 T cells. KGF (5 mg/kg per day, subcutaneously) given either before or after T-cell transfer enhanced body weights and extended survival. KGF-treated recipients had elevated serum levels of the Th2 cytokine interleukin 13 (IL-13) on day 6 after T-cell transfer concomitant with reduced levels of the inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interferon gamma (IFN-gamma). A 3-day KGF pretreatment also depressed the secondary in vitro mixed lymphocyte response (MLR) of C57BL/6 splenocytes taken 7 days after in vivo alloimmunization with irradiated BALB/c spleen cells. To determine whether KGF would inhibit host-antidonor-mediated BM rejection, pan-T-cell-depleted BALB/c BM cells were infused into sublethally irradiated C57BL/6 mice and administered KGF either before or before and after BMT. Surprisingly, all KGF schedules tested actually resulted in enhanced alloengraftment. The presence of KGF receptor on donor antihost alloreactive T cells could not be detected by binding studies with radiolabeled KGF, reverse transcriptase-polymerase chain reaction, and Western blotting. Therefore, the mechanism of action of KGF on inhibiting T-cell-mediated immune effects may not be due to a direct effect of KGF on T cells. These studies demonstrate that KGF, by mechanisms independent of repair of conditioning-induced injury, has great potential as an anti-GVHD therapeutic agent with the added benefit of inhibiting the rejection of pan-T-cell-depleted donor BM allografts. (Blood. 2000;96:4350-4356)

Cyclophosphamide prevents systemic keratinocyte growth factor-induced up-regulation of surfactant protein A after allogeneic transplant in mice

We reported that systemic keratinocyte growth factor (KGF) given before bone marrow transplantation (BMT) prevents allogeneic T cell-dependent lung inflammation assessed on Day 7 post-BMT, but the antiinflammatory effects of KGF were impaired in mice injected with both T cells and conditioning regimen of cyclophosphamide (Cy). Intratracheal KGF is known to stimulate the expression of surfactant protein A (SP-A), an oxidant-sensitive T cell immunomodulator produced by alveolar type II cells. We hypothesized that systemic KGF up-regulates SP-A after allogeneic BMT, and the addition of Cy may interfere with the ability of KGF to enhance SP-A production. The subcutaneous administration of recombinant human KGF (5 mg/kg on Days -6, -5, and -4 pre-BMT) increased SP-A protein and mRNA in allogeneic T cell-recipient irradiated mice measured on Day 7 post-BMT. In contrast, the same KGF treatment in irradiated mice given T cells and Cy failed to up-regulate SP-A mRNA and protein expression. In mixed lymphocyte reaction experiments designed to simulate the in vivo model, the addition of human SP-A (5-50 microg) to alloactivated T cells suppressed the production of interleukin-2 in a dose-dependent fashion. We conclude that the systemic pre-BMT injection of KGF in recipients of allogeneic T cells up-regulates SP-A, which may contribute to the early antiinflammatory effects of KGF. The protective KGF-mediated SP-A production is abolished in mice given alloreactive T cells plus Cy.

T-lymphocyte production of macrophage inflammatory protein-1alpha is critical to the recruitment of CD8(+) T cells to the liver, lung, and spleen during graft-versus-host disease

To investigate the mechanism by which macrophage inflammatory protein-1alpha (MIP-1alpha) affects graft-versus-host disease (GVHD), the expression and function of MIP-1alpha in 2 murine models of GVHD were evaluated. In irradiated class I and class II disparate recipients, the expression of messenger RNA (mRNA) and protein for MIP-1alpha was significantly increased in GVHD target organs after transfer of allogeneic lymphocytes compared to syngeneic lymphocytes. When lymphocytes unable to make MIP-1alpha were transferred, there was a decrease in the production of MIP-1alpha in the liver, lung, and spleen of bm1 (B6.C-H2(bm1)/By) and bm12 (B6.C-H2(bm12)/KhEg) recipients compared to the transfer of wild-type splenocytes. At day 6 there was a 4-fold decrease in the number of transferred CD8(+) T cells in the lung and approximately a 2-fold decrease in the number of CD8(+) T cells in the liver and spleen in bm1 recipients after transfer of MIP-1alpha-deficient (MIP-1alpha(-/-)) splenocytes compared to wild-type (MIP-1alpha(+/+)) splenocytes. These differences persisted for 13 days after splenocyte transfer. In contrast, the number of donor CD4(+) T cells found in the liver and lung was significantly increased after the transfer of MIP-1alpha(-/-) compared to wild-type splenocytes in bm12 recipients from day 6 through day 10. Thus, the transfer of allogeneic T cells was associated with the enhanced expression of MIP-1alpha in both a class I and class II mismatch setting. However, the increased expression only led to enhanced recruitment of CD8(+), but not CD4(+), donor T cells. Production of MIP-1alpha by donor T cells is important in the occurrence of GVHD and functions in a tissue-dependent fashion.

Induction of monocyte- and T-cell-attracting chemokines in the lung during the generation of idiopathic pneumonia syndrome following allogeneic murine bone marrow transplantation

Idiopathic pneumonia syndrome (IPS) is a significant complication following bone marrow transplantation (BMT). We have developed a murine model in which severe IPS is induced by pre-BMT conditioning and allogeneic T cells and is characterized by the recruitment of host monocytes and donor T cells into the lung by day 7 post-BMT. Chemokines regulate cellular recruitment and the migration of cells into inflammatory lesions. In this study, we examined the profiles of chemokines produced locally in the lung (parenchyma and bronchoalveolar lavage fluid) and systemically (serum) during the generation of IPS in the peri-BMT period. Protein and messenger RNA (mRNA) levels of CC chemokines (monocyte/lymphocyte attractants), especially monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, RANTES (regulated upon activation normal T-cell expressed and secreted), and C10, were preferentially induced in the lung by day 7 postallogeneic BMT. In addition, there was an increase in mRNA for IP-10 (a monocyte and Th1-cell chemoattractant). The CXC chemokines MIP-2 and KC, known neutrophil attractants, were moderately elevated. For the most part, these increases in chemokines were dependent on the coinfusion of allogeneic T cells with the BM inoculum. Ribonuclease protection assay and in situ hybridization analyses post-BMT showed that the lung was a major producer of MCP-1, a potent inducer of monocyte chemotaxis. Increases in MCP-1 levels in the lung preceded host APC influx whereas MIP-1alpha levels accompanied donor T-cell infiltration. In summary, we have shown that monocyte- and T-cell-attracting chemokines are associated with monocyte and T-cell recruitment during IPS.

Molecular modification of a recombinant anti-CD3epsilon-directed immunotoxin by inducing terminal cysteine bridging enhances anti-GVHD efficacy and reduces organ toxicity in a lethal murine model

Immunotoxin (IT) therapy shows potential for selectively eliminating GVHD-causing T cells in vivo, but the field has been hampered by toxicity. Previously, we showed that a genetically engineered IT consisting of a single-chain protein, including the anti-CD3sFv spliced to a portion of diphtheria-toxin (DT(390)) has anti-GVHD effects, but pronounced organ toxicity common to this class of agent. A recombinant DT(390) anti-CD3sFv protein previously shown to have anti-GVHD activity was modified to reduce its filtration into kidney by genetically inserting a cysteine residue downstream of the sFv moiety at the c-terminus of the protein. This modification produced an intermolecular disulfide bridge, resulting in a bivalent, rather than a monovalent IT, termed SS2, that selectively inhibited T-cell proliferation in vitro. Although monomer and SS2 were similar in in vitro activity, SS2 had a superior therapeutic index in vivo with at least 8-fold more being tolerated with reduced kidney toxicity. Most importantly, in a lethal model of GVHD, 40 microg SS2 given for 1 day, protected 100% of the mice from lethal GVHD for 3 months, whereas the maximum tolerated dose (MTD) of monomer protected only 33%. To our knowledge, this is the first time disulfide bonded ITs have been created in this way and this simple molecular modification may address several problems in the IT field because it (1) markedly increased efficacy curing mice of GVHD after a single daily treatment, (2) markedly decreased organ toxicity, (3) increased the tolerated dosage, and (4) created a therapeutic window where none existed before.

KGF pretreatment decreases B7 and granzyme B expression and hastens repair in lungs of mice after allogeneic BMT

We investigated keratinocyte growth factor (KGF) as a pretreatment therapy for idiopathic pneumonia syndrome (IPS) generated as a result of lung damage and allogeneic T cell-dependent inflammatory events occurring in the early peri-bone marrow (BM) transplant (BMT) period. B10.BR (H2(k)) recipient mice were transplanted with C57BL/6 (H2(b)) BM with spleen cells after lethal irradiation with and without cyclophosphamide conditioning with and without subcutaneous KGF pretreatment. KGF-pretreated mice had fewer injured alveolar type II (ATII) cells at the time of BMT and exhibited ATII cell hyperplasia at day 3 post-BMT. The composition of infiltrating cells on day 7 post-BMT was not altered by KGF pretreatment, but the frequencies of cells expressing the T-cell costimulatory molecules B7.1 and B7.2 and mRNA for the cytolysin granzyme B (usually increased in IPS) were decreased by KGF. Sera from KGF-treated mice had increases in the Th2 cytokines interleukin (IL)-4, IL-6, and IL-13 4 days after cessation of KGF administration (i.e., at the time of BMT). These data suggest that KGF hinders IPS by two modes: 1) stimulation of alveolar epithelialization and 2) attenuation of immune-mediated injury as a consequence of failure to upregulate cytolytic molecules and B7 ligand expression and the induction of anti-inflammatory Th2 cytokines in situ.

Thrombopoietic cytokines in relation to platelet recovery after bone marrow transplantation

In order to evaluate the importance of different thrombopoietic stimulatory cytokines in accelerating platelet recovery after bone marrow transplantation (BMT), we assayed serial plasma concentrations of three cytokines, thrombopoietin (TPO), interleukin-6 (IL-6), and IL-11 through the course of platelet nadir and recovery after BMT. Both mean TPO and IL-6 levels showed a marked rise and later fall preceding or coincident with the platelet nadir and recovery, suggesting their potential role as circulating regulators or stimulators of thrombopoiesis. In contrast, IL-11 levels remained remarkably constant through the whole course suggesting that this cytokine, though capable of stimulating thrombopoiesis, does not serve as a circulating regulator of platelet production. Additionally, we assayed the levels of these three cytokines following initial platelet transfusion to assess the capacity of transfused platelets to adsorb these thrombopoietic cytokines from the plasma and reduce their circulating levels, thus potentially modifying their availability for stimulating megakaryocyte proliferation. No consistent falls in TPO, IL-6 or IL-11 levels were observed following the initial two platelet transfusions. These data support the importance of circulating TPO and IL-6 as hormones capable of stimulating platelet production. Their physiologic relevance as in vivo regulators of thrombopoiesis and clinical utility for therapy of thrombocytopenia need further investigation.

Retroviral immunotoxin gene therapy of acute myelogenous leukemia in mice using cytotoxic T cells transduced with an interleukin 4/diphtheria toxin gene

The potential benefit of immunotoxin (IT) for cancer therapy has mostly been limited by the fact that only a small portion of injected dose ever reaches the cancer target. Thus, we set out to determine whether antigen-specific CTLs would be suitable vehicles to deliver IT to the site of cancer cells in vivo. A retroviral vector was constructed for gene therapy with (interleukin 4) IL-4 positioned downstream of its 20-amino-acid leader sequence that permitted cotranslational protein synthesis of IT along with truncated diphtheria toxin (DT). IL-4 was chosen as a ligand based on the expression of IL-4 receptor (IL-4R) on most acute myeloid leukemia cases. The first-time expression and secretion of a cytokine/DT fusion toxin was accomplished in mammalian NIH.3T3 cells, and then a retroviral vector was assembled. The retroviral IT was used to transiently transduce T15, a CD8+ CTL T cell line that specifically recognized C1498 (a lethal murine acute myeloid leukemia cell line). Transduced T15 T cells expressed intracellular DT and IL-4 as determined by immunofluorescence. Secreted IT supernatants collected from T15 had enzymatic activity and killed IL-4R+ C1498 cells, but not IL-4R- EL4 cells. Intravenous injection of transduced T15, but not nontransduced T15, into mice with s.c. tumors significantly inhibited tumor growth. In contrast, systemic therapy with a bacterial preparation of the same IL-4 IT given at its maximum tolerated dose did not protect. Retroviral IT-treated mice showed no sign of the renal or hepatic toxicity that is common to this class of IT. Together, these data indicate that retroviral IT may solve problems relating to systemic IT therapy by delivering reagent more directly to the site of cancer in vivo and may impart new anticancer defense mechanisms to antigen-specific T cells.

Analysis of the requirements for the induction of CD4+ T cell alloantigen hyporesponsiveness by ex vivo anti-CD40 ligand antibody

A major goal of the transplant field is to selectively tolerize only those donor T cells recognizing host alloantigen and mediating graft-vs-host disease (GVHD). Recently, we described an ex vivo approach in which the blockade of the CD40 ligand (CD40L):CD40 costimulatory pathway in bulk MLR cultures induces donor CD4+ T cells to become specifically tolerant to MHC class II-disparate alloantigenic-bearing stimulators, resulting in a profound reduction in GVHD generation in vivo. In studies presented in this work, we investigated the ex vivo requirements for tolerance induction. We found that CD4+ T cells become profoundly more hyporesponsive to alloantigen restimulation with prolonged culture duration such that 7 to 10 but not 4 days is needed to achieve maximum alloantigen hyporesponsiveness as assessed in secondary MLR cultures and GVHD generation. By day 7, both primed and tolerized cells had substantially increased blastogenesis and CD25 expression. Primed but not tolerized cells substantially down-regulated L-selectin expression, indicating that the tolerized cells do not become fully Ag experienced. Both Th1 and Th2 cytokine production is severely impaired by CD40L:CD40 blockade. Analysis of culture supernatants and results from IL-4 and IL-10 knockout mice indicated that GVHD prevention was not mediated by a skewing toward a Th2 phenotype. The addition of IL-4 to the cultures as a survival factor precluded the induction of tolerance in the anti-CD40L-cultured cells. These data provide further impetus for the ex vivo use of anti-CD40L mAb to block GVHD generation.

Induction of CD4+ T cell alloantigen-specific hyporesponsiveness by IL-10 and TGF-beta

Induction and maintenance of Ag-specific tolerance are pivotal for immune homeostasis, prevention of autoimmune disorders, and the goal of transplantation. Recent studies suggest that certain cytokines, notably IL-10 and TGF-beta, may play a role in down-regulating immune functions. To further examine the role of cytokines in Ag-specific hyporesponsiveness, murine CD4+ T cells were exposed ex vivo to alloantigen-bearing stimulators in the presence of exogenous IL-10 and/or TGF-beta. Primary but not secondary alloantigen proliferative responses were inhibited by IL-10 alone. However, the combined addition of IL-10 + TGF-beta markedly induced alloantigen hyporesponsiveness in both primary and secondary MLR cultures. Alloantigen-specific hyporesponsiveness was observed also under conditions in which nominal Ag responses were intact. In adoptive transfer experiments, IL-10 + TGF-beta-treated CD4+ T cells, but not T cells treated with either cytokine alone, were markedly impaired in inducing graft-vs-host disease alloresponses to MHC class II disparate recipients. These data provide the first formal evidence that IL-10 and TGF-beta have at least an additive effect in inducing alloantigen-specific tolerance, and that in vitro cytokines can be exploited to suppress CD4+ T cell-mediated Ag-specific responses in vivo.

Targeting myeloid leukemia with a DT(390)-mIL-3 fusion immunotoxin: ex vivo and in vivo studies in mice

The IL-3 receptor was expressed on a high frequency of myeloid leukemia cells and also on hematopoietic and vascular cells. We previously showed that a recombinant IL-3 fusion immunotoxin (DT(390)IL-3) expressed by splicing the murine IL-3 gene to a truncated diphtheria toxin (DT(390)) gene selectively killed IL-3R(+) expressing cells and was not uniformly toxic to uncommitted BM progenitor cells (Chan,C.-H., Blazar,B.R., Greenfield,L., Kreitman,R.J. and Vallera,D.A., 1996, Blood, 88, 1445-1456). Thus, we explored the feasibility of using DT(390)IL-3 as an anti-leukemia agent. DT(390)IL-3 was toxic when administered to mice at doses as low as 0.1 microg/day. The dose limiting toxicity appeared to be related to platelet and bleeding effects of the fusion toxin. Because of these effects, DT(390)IL-3 was studied ex vivo as a means of purging contaminating leukemia cells from BM grafts in a murine autologous BM transplantation. In this setting, as few as 1000 IL-3R-expressing, bcr/abl transformed myeloid 32Dp210 leukemia cells were lethal. An optimal purging interval of 10 nM/l for 8 h eliminated leukemia cells from 32Dp210/BM mixtures given to lethally irradiated (8 Gy) C3H/HeJ syngeneic mice. Mice given treated grafts containing BM and a lethal dose of 32Dp210 cells survived over 100 days while mice given untreated grafts did not survive (P < 0.00001). DT(390)IL-3 may prove highly useful for ex vivo purging of lethal malignant leukemia cells from autologous BM grafts.

Interactions of keratinocyte growth factor with a nitrating species after marrow transplantation in mice

We reported that allogeneic T cells given to irradiated mice at the time of marrow transplantation stimulated tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and nitric oxide (. NO) production in the lung, and the addition of cyclophosphamide (known to stimulate superoxide production) favored the generation of a nitrating species. Although keratinocyte growth factor (KGF) prevents experimental lung injury by promoting epithelial repair, its effects on the production of inflammatory mediators has not been studied. KGF given before transplantation inhibited the T cell-induced increase in bronchoalveolar lavage fluid protein, TNF-alpha, IFN-gamma, and nitrite levels measured on day 7 after transplantation without modifying cellular infiltration or proinflammatory cytokines and inducible. NO synthase mRNA. KGF also suppressed. NO production by alveolar macrophages obtained from mice injected with T cells. In contrast, the same schedule of KGF failed to prevent permeability edema or suppress TNF-alpha, IFN-gamma, and. NO production in mice injected with both T cells and cyclophosphamide. Because only epithelial cells respond to KGF, these data are consistent with the production of an epithelial cell-derived mediator capable of downregulating macrophage function. However, the presence of a nitrating agent impairs KGF-derived responses.

High levels of peroxynitrite are generated in the lungs of irradiated mice given cyclophosphamide and allogeneic T cells. A potential mechanism of injury after marrow transplantation

In a murine bone-marrow transplant (BMT) model designed to determine risk factors for lung dysfunction in irradiated mice, we reported that cyclophosphamide (Cy)-induced injury and lethality depended on the infusion of donor spleen T cells. In the study reported here, we hypothesized that alveolar macrophage (AM)-derived reactive oxygen/nitrogen species are associated with lung dysfunction caused by allogeneic T cells, which stimulate nitric oxide (.NO) production, and by Cy, which stimulates superoxide production.NO reacts with superoxide to form peroxynitrite, a tissue-damaging oxidant. On Day 7 after allogeneic BMT, bronchoalveolar lavage fluid (BALF) obtained from mice injected with T cells contained increased levels of nitrite, which was associated with increased lactate dehydrogenase and protein levels, both of which are indices of lung injury. The injury was most severe in mice receiving both T cells and Cy. Messenger RNA (mRNA) for inducible nitric oxide synthase was detected only in murine lungs injected with T cells +/- Cy. AMs obtained on Day 7 after BMT from mice receiving T cells +/- Cy spontaneously generated between 20 and 40 microM nitrite in culture, versus < 2 microM generated by macrophages obtained from mice undergoing BMT but not receiving T cells. The level of 3-nitrotyrosine, the stable byproduct of the reaction of peroxynitrite with tyrosine residues, was increased in the BALF proteins of mice injected with both T cells and Cy. We conclude that allogeneic T cells stimulate macrophage-derived.NO, and that the addition of Cy favors peroxynitrite formation. Peroxynitrite generation clarifies the dependence of Cy-induced lung injury and lethality on the presence of allogeneic T cells.

Opposing roles of CD28:B7 and CTLA-4:B7 pathways in regulating in vivo alloresponses in murine recipients of MHC disparate T cells

Blockade with B7 antagonists interferes with CD28:B7 and CTLA-4:B7 interactions, which may have opposing effects. We have examined the roles of CD28:B7 and CTLA-4:B7 on in vivo alloresponses. A critical role of B7:CD28 was demonstrated by markedly compromised expansion of CD28-deficient T cells and diminished graft-versus-host disease lethality of limited numbers of purified CD4+ or CD8+ T cells. When high numbers of T cells were infused, the requirement for CD28:B7 interaction was lessened. In lethally irradiated recipients, anti-CTLA-4 mAb enhanced in vivo donor T cell expansion, but did not affect, on a per cell basis, anti-host proliferative or CTL responses of donor T cells. Graft-versus-host lethality was accelerated by anti-CTLA-4 mAb infusion given early post-bone marrow transplantation (BMT), mostly in a CD28-dependent fashion. Donor T cells obtained from anti-CTLA-4 mAb-treated recipients were skewed toward a Th2 phenotype. Enhanced T cell expansion in mAb-treated recipients was strikingly advantageous in the graft-versus-leukemia effects of delayed donor lymphocyte infusion. In two different systems, anti-CTLA-4 mAb enhanced the rejection of allogeneic T cell-depleted marrow infused into sublethally irradiated recipients. We conclude that blockade of the selective CD28-B7 interactions early post-BMT, which preserve CTLA-4:B7 interactions, would be preferable to blocking both pathways. For later post-BMT, the selective blockade of CTLA-4:B7 interactions provides a potent and previously unidentified means for augmenting the GVL effect of delayed donor lymphocyte infusion.

Cutting edge: sustained expansion of CD8+ T cells requires CD154 expression by Th cells in acute graft versus host disease

Brief treatment with alphaCD154 Ab has been shown to prevent acute graft versus host disease (aGvHD). We extend these data to show that in the absence of CD154 function, donor T cells are unable to expand or generate high level anti-host CTL activity. Using transgenic (Tg) alloreactive CD8+ T cells adoptively transferred into allogeneic recipients, we show that short-term expansion of the CD8+ Tg T cells occurred in the absence of Th cells, and this short-term expansion could be facilitated with an agonistic alphaCD40. While CD40 agonism could enhance short-term expansion, sustained expansion of CD8+ Tg T cells required bona fide CD154-expressing CD4+ alloreactive Th cells. While CD154 was necessary for CD8+ Tg T cell sustained expansion, IL-2 was also implicated as essential. These observations suggest alphaCD154 therapy in GvHD is effective because the treatment causes an abortive CD8 alloresponse leading to the exhaustion or deletion of alloreactive CD8+ clones preventing the development of disease.

A critical role for CD48 antigen in regulating alloengraftment and lymphohematopoietic recovery after bone marrow transplantation

The binding of CD2, present on T cells, to its counterreceptor CD48 facilitates adhesion, signaling, alloantigen-induced cytokine production, and cytotoxic T-lymphocyte responses. Because these T-cell functions have been implicated in graft-versus-host disease (GVHD) pathogenesis, we have analyzed the effects of the CD2:CD48 pathway on GVHD mediated by CD4(+) and CD8(+) T cells infused into sublethally irradiated recipients. CD4(+) T-cell-mediated, and to a lesser extent, CD8(+) T-cell-mediated GVHD was inhibited by CD2 + 48 monoclonal antibody (MoAb) infusion. To assess the effects of combined MoAb infusion on alloengraftment, two different alloengraftment bone marrow transplantation (BMT) models were used. In both, MoAb infusion markedly inhibited alloengraftment and hematopoietic recovery post-BMT. To determine if the adverse effects on lymphohematopoiesis in the allogeneic BMT recipients were caused by an immune or nonimmune mechanism, studies were performed in congenic BMT recipients to preclude an immune mechanism as the cause for delayed recovery post-BMT. MoAb infusion resulted in impaired lymphohematopoietic recovery in congenic BMT recipients and markedly reduced day 12 colony-forming unit-spleen formation in syngeneic BMT recipients, consistent with a nonimmune mediated mechanism. Because the spleen is a site of early hematopoietic recovery post-BMT, studies were performed using adult splenectomized syngeneic BMT recipients. MoAb infusion delayed recovery in both nonsplenectomized and splenectomized recipients post-BMT, indicating that the delayed hematopoietic recovery was not the consequence of an abnormal homing pattern of hematopoietic progenitors to the spleen early post-BMT. CD48 MoAb was necessary and sufficient for the inhibition of GVHD lethality and delayed lymphohematopoietic effects of the combined MoAb regimen. CD48 MoAb was found to induce a profound modulation of CD48 antigen expression on BM cells, suggesting that the CD48 antigen may have an important function in hematopoiesis in the BM compartment. Taken together, these data provide evidence that the CD48 antigen plays a critical role in regulating hematopoiesis in post-BMT.

Interleukin-10 dose-dependent regulation of CD4+ and CD8+ T cell-mediated graft-versus-host disease

BACKGROUND

Endogenous interleukin (IL)-10 production has been associated with the lack of graft-versus-host disease (GVHD) in human recipients of MHC-disparate donor grafts. Paradoxically, we have shown that the exogenous administration of high doses (30 microg/dose) of IL-10 to murine recipients of MHC-disparate grafts accelerates GVHD lethality.

METHODS

The effects of IL-10 on GVHD mediated by either CD4+ or CD8+ T cells was examined in studies involving exogenous IL-10 administration or the infusion of T cells from IL-10-deficient (-/-) donor mice. The role of interferon (IFN)-gamma on IL-10-induced GVHD acceleration was studied using IFN-gamma-deficient (-/-) donor mice or neutralizing monoclonal antibody.

RESULTS

IL-10 was found to have a dose-dependent effect on the GVHD lethality mediated by either CD4+ or CD8+ T cells. High doses of exogenous IL-10 accelerated GVHD lethality. IFN-gamma release was not responsible for the IL-10 facilitation of GVHD lethality. Paradoxically, low doses of IL-10 protected mice against GVHD lethality. The GVHD protective effect of the bioavailability of small amounts of IL-10 was confirmed by demonstrating that the infusion of T cells from IL-10 -/- donors accelerated GVHD lethality.

CONCLUSIONS

The results suggest that IL-10 has a dose-dependent effect on the GVHD lethality mediated by CD4+ or CD8+ T cells, such that high doses accelerate lethality, while low amounts of bioavailable IL-10 are protective.

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 be effective in treating human severe combined immune deficiency (SCID), the relative merit of IUT as compared with postnatal bone marrow transplantation (BMT) for SCID is unknown. Therefore, comparative studies were undertaken in mice to determine the engraftment outcome in these two settings. Because T-cell depletion (TCD) reduces graft-versus-host disease (GVHD) severity but compromises alloengraftment, studies were performed with TCD or non-TCD BM and GVHD risk was assessed using a tissue scoring system and by the adoptive transfer 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 had higher levels of donor T-cell and myeloid peripheral blood (PB) engraftment than nonconditioned SCID recipients. Increased TCD or non-TCD BM cell numbers in adult SCID recipients resulted in similar levels of PB engraftment as IUT recipients. However, under these conditions, mean GVHD scores were higher than in IUT recipients. The majority of adoptive transfer recipients of splenocytes from IUT recipients were GVHD-free, consistent with the in vitro evidence of tolerance to host alloantigens. Total body irradiation (TBI)-treated mice that had the highest engraftment had evidence of thymic damage as denoted by a higher proportion of thymic and splenic T cells with a memory phenotype as compared with IUT recipients. IUT mice had vigorous thymic reconstitution by 3 weeks of age. Our data indicate that IUT has a number of advantages as compared with postnatal BMT. Future studies examining the fine specificity of immunoreconstitution in IUT versus postnatal BMT are indicated.

Keratinocyte growth factor administered before conditioning ameliorates graft-versus-host disease after allogeneic bone marrow transplantation in mice

Keratinocyte growth factor (KGF) is important in tissue repair and wound healing and its administration can abrogate chemical- and radiation-induced tissue damage in rodents. We investigated KGF as a therapeutic agent for the prevention of graft-versus-host disease (GVHD)-induced tissue damage, morbidity, and mortality in an established murine allogeneic bone marrow transplantation (BMT) model. B10.BR (H2(k)) recipient mice were lethally irradiated and transplanted with C57BL/6 (H2(b)) bone marrow (BM) with spleen cells (BMS) as a source of GVHD-causing T cells. KGF-treated mice (5 mg/kg/d subcutaneously days -6, -5, and -4 pre-BMT) receiving BMS exhibited better survival than those not receiving KGF (P =.0027). Cyclophosphamide (Cy), a common component of total body irradiation (TBI)-containing regimens, was administered to other cohorts of mice at a dose of 120 mg/kg/d intraperitoneally on days -3 and -2 before BMT. KGF-treated mice again exhibited a better survival rate than those not receiving KGF (P =.00086). However, KGF-treated recipients receiving TBI or Cy/TBI BMS were not GVHD-free, as shown by lower body weights compared with BM groups. GVHD target tissues were assessed histologically during a 38-day post-BMT observation period. KGF ameliorated GVHD-induced tissue damage in the liver, skin, and lung (completely in some recipients) and moderately so in the spleen, colon, and ileum, even with Cy conditioning. These studies demonstrate that KGF administration, completed before conditioning, has potential as an anti-GVHD therapeutic agent.

Genetic and immunological parameters governing in vivo susceptibility/resistance to retrovirally induced murine malignant histiocytosis

Malignant histiocytosis sarcoma virus (MHSV) arose as a recombinant of c-Harvey-ras murine sarcoma virus (Ha-MuSV) and Friend mink cell focus-forming virus (F-MCFV). It is a defective acute transforming retrovirus that, along with Friend murine leukemia helper virus (F-MuLV), induces malignant histiocytosis (MH) in susceptible adult mice. We have assessed the in vivo susceptibility to MHSV in inbred homozygous, F1 hybrid, congenic, and recombinant inbred (RI) mice. We have shown that: (1) in vivo resistance to MHSV is multigenic, regulated by MHC and non-MHC genes in a different fashion than with F-MCFV, F-MuLV, or Ha-MuSV; (2) using BXD RI mice, the resistance phenotype is linked with 95.8% probability to two linked loci, Pmv-9 and Iapls3-14, on chromosome 13 (homologous to the area of human chromosome 5 for which a chromosomal break point at position 5q35 is associated with human MH); and (3) CD4+ T cells are critical for MHSV resistance.

Rapamycin inhibits the generation of graft-versus-host disease- and graft-versus-leukemia-causing T cells by interfering with the production of Th1 or Th1 cytotoxic cytokines

Rapamycin (RAPA), an inhibitor of cytokine responses, is under investigation in humans for graft-vs-host disease (GVHD) prevention. The mechanisms responsible for GVHD prevention are unknown. We show that RAPA is more effective in inhibiting CD8+ or TCR gammadelta+ than CD4+ T cell-mediated murine GVHD. To determine how RAPA inhibited GVHD, thoracic duct lymphocytes (TDL) were isolated from recipients of allogeneic donor grafts. Compared with controls, RAPA-treated recipients had a marked decrease in donor TDL T cell number between days 5 and 24 posttransplant. CD8+ T cell expansion was preferentially inhibited. RAPA inhibited Th1 or Th1 cytotoxic (Tc1) cytokines, but not Th2 or Tc2, cell generation. In situ mRNA hybridization also showed that TDL T cells from RAPA-treated mice had a lower frequency of granzyme B+ cells, indicating that RAPA inhibited the generation of CTL capable of mediating cytolysis through the release of granzyme B. In another system, RAPA was found to inhibit the GVL response of delayed donor lymphocyte infusions. Since CD8+ T cells are the primary effectors in this system, these data suggest that RAPA directly interfered with GVL effector cell expansion or function. We conclude that RAPA is effective in inhibiting Th1 or Tc1 cytokine production and CD8+ and TCRgammadelta+ T cell-mediated GVHD, but abrogates GVL.

Anti-CD3 epsilon F(ab')2 fragments inhibit T cell expansion in vivo during graft-versus-host disease or the primary immune response to nominal antigen

This study was undertaken to distinguish between several mechanisms responsible for graft-vs-host disease (GVHD) protection in anti-CD3epsilonF(ab')2 fragment (Fr)-treated recipients: TCR down-modulation, deletion, failure of expansion, or anergy induction. To quantify alloreactive T cell expansion and function, thoracic duct lymphocytes (TDL) were analyzed. Sixfold fewer donor TDL T cells were recoverable from anti-CD3epsilonF(ab')2 Fr as compared with irrelevant F(ab')2 Fr-treated recipients at the time of peak T cell expansion in vivo. Kinetic analysis revealed that donor T cell expansion was inhibited and not simply delayed by anti-CD3epsilonF(ab')2 Fr. Similar proportions of TDL T cells in irrelevant and anti-CD3epsilonF(ab')2 Fr were undergoing apoptosis. Although TCR modulation was observed, donor TDL T cells had intact anti-host alloresponses as compared with irrelevant F(ab')2 Fr-treated recipients. Because donor CD4+ T cells are primarily responsible for GVHD in this model, an adoptive transfer system was used in which the function and kinetics of expansion of OVA-specific CD4+ TCR transgenic cells could be physically tracked. Relevant Fr severely blunted CD4+ TCR transgenic T cell clonal expansion after OVA administration. Nonviable transgenic and nontransgenic T cells were proportionally similar in OVA-pulsed recipients, regardless of whether relevant or irrelevant F(ab')2 Fr were given. After discontinuing Fr, transgenic T cells were found to have intact in vitro OVA-specific responses. Our current and previous results suggest that reduced donor T cell expansion and T cell depletion both contribute to GVHD protection by anti-CD3epsilonF(ab')2 Fr. These data have implications for designing therapeutic approaches directed toward TCR targeting in humans.