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R B Levy

Publications and source records attributed to R B Levy.

At least 19 recordsLinked to original sources
PubMed2006

MiHA reactive CD4 and CD8 T-cells effect resistance to hematopoietic engraftment following reduced intensity conditioning.

Reduced intensity conditioning (RIC) prior to allogeneic hematopoietic cell transplantation (HCT) has shown promise in lowering the incidence of post-transplant complications including infection and graft-versus-host disease. T-cell-mediated graft rejection, however, remains a crucial factor in determining how 'mild' a level of immunosuppression can be administered. Understanding the kinetics of resistance responses as well as the role of CD4+ and CD8+ T cells underlies the development of protocols to circumvent resistance and support hematopoietic engraftment. In these studies, a major histocompatibility complex (MHC)-matched/minor histocompatibility antigen (MiHA) disparate RIC HCT model was developed in which resistance against donor hematopoietic progenitors as well as mature peripheral blood cells could be assessed. Interestingly, resistance was diminished in the absence of either host CD4+ or CD8+ T cells. However, its impairment was more severe in CD4-/- mice where resistance was not detected. Host CD4+ T cells were required for optimal expansion of specific (H60) T-cell receptor (TCR) expressing host anti-donor MiHA reactive CD8+ T cells following HCT. These observations demonstrate a critical role for host CD4+ T cells in resistance against MiHA disparate HCT. This RIC HCT resistance model will be useful for the analysis of the barrier to engraftment mediated by host T cells and the development of strategies to support engraftment.

Animals↗
PubMed2001

Major histocompatibility complex-mismatched allogeneic bone marrow transplantation using perforin and/or Fas ligand double-defective CD4(+) donor T cells: involvement of cytotoxic function by donor lymphocytes prior to graft-versus-host disease pathogenesis.

Experimental allogeneic bone marrow transplantation (BMT) models using cytotoxic single-deficient (perforin/granzyme or Fas ligand [FasL]) and cytotoxic double-deficient (cdd) CD4(+) donor T cells have previously demonstrated roles for both effector pathways in graft-versus-host disease (GVHD). In the present study, the role of CD4-mediated antihost cytotoxicity in a GVH response is further examined across a complete major histocompatibility complex class I/II mismatch. As predicted, a double cytotoxic deficiency resulted in a clear delay in GVH-associated weight loss, clinical changes, and mortality. Interestingly, analysis of donor T-cell presence in 5.5-Gy recipients soon after BMT demonstrated that the double cytotoxic deficiency resulted in a marked decrease in donor CD4 numbers. Transplantation of singularly perforin- or FasL-deficient donor CD4(+) T cells demonstrated that the absence of FasL was responsible for the markedly diminished CD4 number in recipient lymph nodes and spleens soon after BMT. However, increasing recipient total body irradiation conditioning (11.0 Gy) abrogated the decrease in FasL-defective B6-cdd and B6-gld CD4 numbers. Thus, the decrease was not a result of inherent CD4 defects, but was probably attributable to host resistance. Consistent with these observations, transplantation into 11.0-Gy recipients resulted in identical GVH lethality by equal numbers of B6 wild-type, B6-cdd, and B6-gld CD4(+) T-cell inoculum. In total, the findings indicate that aggressive host conditioning lessens the requirement for donor CD4(+) cytotoxic function in GVH responses soon after BMT. The present results thus support the notion of a role for cytotoxic effector function in donor CD4(+) T cells prior to GVH-induced tissue injury.

Animals↗
PubMed2000

Cytotoxically impaired transplant recipients can efficiently resist major histocompatibility complex--matched bone marrow allografts.

High rates of allograft rejection using T cell--depleted marrow or after transplantations into multiply transfused recipients have been reported. Together with current approaches to diminish host preparative immunosuppression before stem cell transplant, issues regarding the cells and effector pathways involved in resistance to progenitor cell presence in recipients are of increasing interest. The present investigation addressed questions concerning the contribution of cytotoxic effector mechanisms used by host cells involved in resistance to progenitor cell engraftment. A murine model was developed in which short-term resistance against major histocompatibility complex (MHC)-matched allogeneic T cell--depleted marrow was examined using a sensitive in vitro assay to detect progenitor cell presence by colony formation in vitro. Resistance was found to be dependent on previous priming to donor nonMHC antigens and could be transferred by a CD3+NK1.1- population. The resistance mechanism explicitly discriminated between donor and syngeneic progenitors after mixed marrow transplantation. Interestingly, the resistance was not impaired in animals unable to mediate cell-mediated cytotoxicity involving perforin-dependent or CD95L-dependent pathways. These results indicate that either cytotoxic effector pathway alone is sufficient to effect marrow allograft resistance or that non-perforin and CD95L effector mechanisms are responsible for barrier activity. The findings are discussed with respect to previous studies concerning T-cell involvement in resistance to MHC and hematopoietic histoincompatible-mismatched marrow grafts.

Animals↗
PubMed1998

Monoclonal antibodies to the common gamma-chain as cytokine receptor antagonists in vivo: effect on intrathymic and intestinal intraepithelial T lymphocyte development.

Mice lacking a functional gamma c subunit of cytokine receptors exhibit profound defects in the development of multiple lymphoid lineages. To investigate the role of gamma c-dependent cytokines in T cell development, the phenotype of developing T cells was compared in interleukin (IL)-7Ralpha-deficient mice and anti-gamma c mAb-treated chimeric mice reconstituted with adult bone marrow cells or subsets of pro-T cells. These studies indicate that gamma c contributes to T cell development at multiple stages of pro-T cell maturation and that IL-7/IL-7R is the primary cytokine for thymic-dependent T cell development. However, our data also implicate other gamma c-dependent cytokines during thymic T cell development. By contrast, substantial intestinal intraepithelial lymphocytes (IEL) development was observed in the intestinal intraepithelium in both types of mice. Analysis of IL-7Ralpha-deficient mice indicates that the IL-7/IL-7R system is critical only for the development of TCR gammadelta+ IEL. However, the inhibitory activity of the anti-deltac mAb in the chimeric mouse model suggests that additional gamma cutilizing cytokines regulate the development of the remaining subsets of IEL.

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PubMed1998

Cytokine and cytotoxic pathways of NK cell rejection of class I-deficient bone marrow grafts: influence of mouse colony environment.

Mouse NK cells may use both cytokine, e.g. IFN-gamma, tumor necrosis factor (TNF)-alpha and IL-12, and cytotoxic, e.g. perforin and Fas-FasL, pathways to reject incompatible bone marrow cell (BMC) grafts. To begin a dissection of these two major pathways, mice bearing deletional mutations of IFN-gamma, TNF-RI/II or perforin, or mice treated with mAb to IL-12, IFN-gamma or NK1.1 were irradiated and challenged with class I-deficient BMC grafts, a system in which only NK cells are the effector cells. Proliferation of the donor-derived cells was judged in terms of splenic incorporation of [125I]iododeoxyuridine 5 or 7 days after cell transfer. All of these mice maintained in a specific pathogen-free (s.p.f.) environment were able to reject the BMC, except those treated with anti-NK1.1 mAb. However, perforin deficient mice maintained in a conventional breeding facility failed to reject class I (Tap-1)-deficient marrow cells. Transfer of mice from the pathogen-free to the conventional facility resulted in a slow and incomplete loss of the ability to reject marrow cells. Thus, the breeding colony environment can elicit otherwise undetectable defects in the rejection ability of perforin-deficient NK cells. This report will hopefully alert those investigators who have only studied immune gene knockout mice in s.p.f. facilities and found no significant abnormalities.

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PubMed1997

Graft-versus-host-disease-associated lymphoid hypoplasia and B cell dysfunction is dependent upon donor T cell-mediated Fas-ligand function, but not perforin function.

Allogeneic bone marrow transplant recipients often exhibit a graft-versus-host-disease (GVHD)-associated immune deficiency that can be prolonged and lead to life-threatening infections. We have examined the role of donor T cell-mediated cytotoxic function in the development of GVHD-associated immune deficiency. A major histocompatibility complex-matched model of allogeneic bone marrow transplantation was employed in which lethally irradiated C3H.SW mice received a nonlethal dose of T cells from either perforin-deficient (B6-perforin 0/0), Fas-ligand (FasL)-defective (B6-gld), or normal (B6) allogeneic donor mice. T cell-depleted marrow from B6-Ly-5.1 congenic donor mice was transplanted along with the donor T cell populations to determine the effects of donor T cell-mediated cytotoxicity on engraftment. Our results demonstrate that recipients of perforin-deficient or normal allogeneic T cells exhibit profound lymphoid hypoplasia and severely reduced splenic proliferative responses to lipopolysaccharide in vitro. In contrast, GVHD-associated lymphoid hypoplasia is dramatically reduced and in vitro B cell function is intact in recipients of FasL-defective allogeneic T cells. Engraftment of myeloid and erythroid lineage cells occurs irrespective of donor T cell cytotoxic function. Although recipients of perforin-deficient or normal allogeneic T cells exhibited hematopoietic engraftment exclusively of donor origin, recipients of FasL-defective donor T cells exhibited significant mixed chimerism (Ly-5.1/Ly-5.2). Because only marrow of donor origin was transplanted, this finding suggests that Fas-mediated antirecipient cytotoxicity is required for clearance of residual hematopoietic stem cells of host origin that persist following lethal irradiation.

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PubMed1996

The role of cell-mediated cytotoxicity in acute GVHD after MHC-matched allogeneic bone marrow transplantation in mice.

The role of cell-mediated cytotoxicity in the complex pathophysiology of graft-versus-host disease (GVHD) has remained poorly defined for several decades. We transplanted T cells from Fas-ligand (FasL)-defective and perforin-deficient mutant donor mice into lethally irradiated MHC-matched allogeneic recipient mice to characterize the role of cell-mediated cytotoxicity in GVHD. Although recipients of allogeneic FasL-defective donor T cells underwent severe GVHD-associated cachexia, they exhibited only minimal signs of hepatic and cutaneous GVHD pathology. Recipients of perforin-deficient allogeneic donor T cells developed signs of acute GVHD, but the time of onset was significantly delayed. These findings demonstrate that Fas-mediated anti-recipient cytotoxicity may be critical for the development of hepatic and cutaneous GVHD, but is not required for GVHD-associated cachexia. In addition, perforin-mediated anti-recipient cytotoxicity appears to play an important role in the kinetics of GVHD pathophysiology, but is not required for GVHD-associated tissue damage.

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PubMed1996

Concurrent MCMV infection augments donor antihost-specific activity and alters clinical outcome following experimental allogenic bone marrow transplantation.

The present studies were undertaken to examine whether concurrent MCMV infection during allogeneic bone marrow transplantation (BMT) could alter the developing donor-host immune interactions and affect the overall outcome of the transplant. In order to determine the effect of MCMV on antihost activity arising following an allogeneic BMT, specific donor antihost cytotoxicity was examined. The results demonstrated that concurrent virus infection in mice receiving a BMT from donors either H2-matched and non-MHC-mismatched or mismatched at both MHC and non-MHC transplantation loci, augmented antihost cytotoxic activity mediated by CD8+ T cells assayed directly from the recipient's spleen 10-14 days posttransplant. Notably, allogenic BMT recipients receiving either lethal or nonlethal numbers of donor T cells and inoculated with MCMV exhibited more rapid and profound weight loss compared with uninfected allogeneic and syngeneic BMT recipients. Concurrent virus presence also resulted in a markedly increased incidence of mortality in allogeneic BMT recipients of nonlethal numbers of T cells. We conclude from these findings that when virus is present early after allogeneic BMT, the resulting interactions can potentiate T cell-mediated donor-antirecipient--i.e., graft vs. host-reactivity. In total, the results support the notion that pathogens could complicate allogeneic BMT by contributing to the development of graft vs. host disease.

Animals↗
PubMed1996

1,25-dihydroxyvitamin D3 stimulates phagocytosis but suppresses HLA-DR and CD13 antigen expression in human mononuclear phagocytes.

This study investigated the regulatory activity of 1,25-dihydroxyvitamin D3 (1,25-[OH]2D3) on phagocytic cells obtained from normal human peripheral blood. Flow cytometric analysis enabled identification of two discrete populations of cells, one predominantly monocytes ("monocyte" gate) and one containing primarily lymphoid and other cell types ("lymphoid" gate). The monocyte-associated antigens CD13 and CD33 were highly expressed by cells in this monocyte gate and used to monitor this population. Following 5 days of culture, cells in the monocyte gate manifested high phagocytic activity as determined by ingestion of fluorescent carboxylmicrospheres and exhibited high expression of class II HLA-DR products. 1,25-(OH)2D3 profoundly upregulated phagocytic activity while downregulating HLA-DR antigen expression on the cells in the monocyte gate. Moreover, 1,25-(OH)2D3 also reduced cell surface CD13 expression on the cells with low but not high phagocytic activity in this gate. Proportional activities by the 1,24-(OH)2D3 and 24,25-(OH)2D3 metabolites indicated the regulatory effects are likely mediated by the 1,25-(OH)2D3 receptor (VDR). Prostaglandin E2 (PGE2), a known modulator of monocyte/macrophage activity also markedly inhibited HLA-DR expression while enhancing the phagocytic activity of cells in the monocyte gate. In contrast to 1,25-(OH)2D3, PGE2 clearly upregulated CD13 expression in cells with high phagocyte activity. Since indomethacin, an inhibitor of PGE2 synthesis, failed to reverse the 1,25-(OH)2D3 induced inhibitory effect on HLA-DR expression, this effect is apparently not mediated through endogenous PGE2 synthesis. Based on these findings we speculate that 1,25-(OH)2D3 may be capable of acting as both an upregulating agent during natural immunity via the enhancement of phagocytosis by monocyte/macrophage populations and as a "downregulator" during acquired immune responses via an inhibitory effect on MHC class II antigen expression by professional antigen-presenting cells.

CD13 Antigens↗
PubMed1995

Blockade of T- and B-lymphocyte development by antibody to the gamma c subunit of the receptors for interleukins 2, 4, and 7.

Cytokines are important regulators of hematopoesis. Mutations in gamma c, which is a subunit shared by the receptors for interleukin (IL) 2, IL-4, and IL-7, have been causally associated with human X chromosome-linked severe combined immunodeficiency disease. This finding indicates a mandatory role for cytokine receptor signaling at one or more stages of lymphocyte development. To evaluate the cellular level at which gamma c is critical for lymphopoiesis, the effect of monoclonal antibodies to gamma c on the capacity of syngeneic bone marrow cells to reconstitute the hematopoietic compartment of lethally irradiated recipient mice was examined. We show that monoclonal antibody to gamma c blocked lymphocyte development at or before the appearance of pro-B cells and prior to or at the seeding of the thymus by precursor cells while erythromyeloid cell development was normal. These results suggest that one level of lymphocyte development that requires gamma c is a point in hematopoietic cell differentiation near the divergence of lymphopoiesis and erythromyelopoesis.

Animals↗
PubMed1995

Transgenic control of perforin gene expression. Functional evidence for two separate control regions.

Perforin is a pore-forming effector molecule of CTL and NK cells. To characterize perforin gene expression and its transcriptional control mechanisms in vivo, expression of a cell surface tag, i.e., human CD4, was driven by 5.1 kb of the murine perforin 5' flanking and promoter region in transgenic mice. Six out of seven transgenic lines expressed the perforin-tag hybrid gene at low to intermediate levels, depending on the integration site. Tissues not yet reported to contain perforin-expressing lymphocytes were identified. Transgene expression occurred in all cells that physiologically are able to express perforin, i.e., in T cells and NK cells, and in some T cells that normally may express little or no perforin. At the whole organ level, significant amounts of transgenic mRNA and endogenous perforin mRNA were co-expressed in the lymphoid organs, as well as in the lung, the ileum, the oviduct/uterus, and the bone marrow. At the single cell level, the perforin tag was present on NK cells and on CD8+, as well as on CD4+ T cells. Also targeted were Thy-1.2+ gamma delta T cells, but not Thy1.2- gamma delta T cells, B cells, nor monocytes. During thymic T cell development, transgene expression occurred in double negative (CD4-CD8-) thymocytes and was detected at all subsequent stages, but exceeded the expression levels of the endogenous gene in the thymus. In conclusion, the analyzed perforin 5' flanking and promoter region contains important cis-acting sequences that restrict perforin expression to T cells and NK cells, and therefore provides a unique tool for manipulating T cell and/or NK cell-mediated immune responses in transgenic mice. On the other hand, the normal control of perforin gene expression involves at least one additional negative control mechanism that was not mediated by the transgenic promoter and upstream region. This control restricts perforin gene expression in thymically developing T cells and in most resting peripheral T cells, but can be released upon T cell activation.

Animals↗
PubMed1995

IL-7 drives donor T cell proliferation and can costimulate cytokine secretion after MHC-matched allogeneic bone marrow transplantation.

Transplantation of MHC-matched, allogeneic B10.D2 bone marrow plus T cells into BALB/c recipients ultimately results in chronic graft-vs-host disease (GVHD) and mortality 8 to 12 wk post-transplant. We have identified IL-7-specific mRNA in the spleens of BALB/c bone marrow transplantation (BMT) recipients during the first week post-transplant. The response by T cells from B10.D2-->BALB/c BMT recipients to stimulation with IL-7 in vitro during the early period after transplant was then examined. The findings indicated that within the first week post-transplant, spleen cells removed from recipients injected with allogeneic, but not syngeneic, T cells proliferated vigorously to rIL-7. Both IL-2-dependent and -independent components were identified. Depletion of responding cells before culture with anti-Thy-1.2 Ab virtually eliminated this response. We conclude that transplant of allogeneic T cells is required for the observed IL-7 response, and moreover, such cells proliferate after exposure to this cytokine in vitro. To determine whether IL-7 could have a functional effect on donor T cells, the production of IFN-gamma by T cells from allogeneic BMT recipients stimulated with anti-T cell receptor (i.e., anti-V beta) Ab was examined. IL-7 was demonstrated to enhance IFN-gamma production by donor T cells postallogeneic BMT. These results suggest that a cytokine presumably produced in the host for the physiologic function of hematologic reconstitution is playing an additional role during the early events after allogeneic BMT mediated via the expansion and augmented cytokine production by donor T cells.

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