Biomedical subjects

H Yagita

Publications and source records attributed to H Yagita.

At least 19 recordsLinked to original sources

PubMed1999

IL-18 up-regulates perforin-mediated NK activity without increasing perforin messenger RNA expression by binding to constitutively expressed IL-18 receptor.

IL-18 is a powerful inducer of IFN-gamma production, particularly in collaboration with IL-12. IL-18, like IL-12, also augments NK activity. Here we investigated the molecular mechanism underlying the up-regulation of killing activity of NK cells by IL-18. IL-18, like IL-12, dose dependently enhanced NK activity of splenocytes. This action was further enhanced by costimulation with IL-12. Treatment with anti-IL-2R Ab did not affect IL-18- and/or IL-12-augmented NK activity, and splenocytes from IFN-gamma-deficient mice showed enhanced NK activity following stimulation with IL-12 and/or IL-18. Splenocytes from the mice deficient in both IL-12 and IL-18 normally responded to IL-18 and/or IL-12 with facilitated NK activity, suggesting that functional NK cells develop in the absence of IL-12 and IL-18. IL-18R, as well as IL-12R mRNA, was constitutively expressed in splenocytes from SCID mice, which lack T cells and B cells but have intact NK cells, and in those from IL-12 and IL-18 double knockout mice. NK cells isolated from SCID splenocytes expressed IL-18R on their surface. IL-18, in contrast to IL-12, did not enhance mRNA expression of perforin, a key molecule for exocytosis-mediated cytotoxicity. However, pretreatment with concanamycin A completely inhibited this IL-18- and/or IL-12-augmented NK activity. Furthermore, IL-18, like IL-12, failed to enhance NK activity of splenocytes from perforin-deficient mice. These data suggested that NK cells develop and express IL-12R and IL-18R in the absence of IL-12 or IL-18, and that both IL-18 and IL-12 directly and independently augment perforin-mediated cytotoxic activity of NK cells.

Animals↗

PubMed1999

CD44 variants but not CD44s cooperate with beta1-containing integrins to permit cells to bind to osteopontin independently of arginine-glycine-aspartic acid, thereby stimulating cell motility and chemotaxis.

The expression of osteopontin (OPN), CD44 variants, and integrins has been correlated with tumorigenesis and metastasis. Here we show that these proteins cooperate to enhance cell motility. First, we demonstrate that several different CD44 variants bind to OPN in an arginine-glycineaspartic acid-independent manner, but that the standard form of CD44 does not. These CD44 variants bind to both the amino- and COOH-terminal portions of OPN independently of the arginine-glycine-aspartic acid sequence, suggesting that multiple domains on OPN can be bound by the CD44 variants. Antibodies directed against the integrin beta1 subunit are able to inhibit this binding. The binding of CD44 variants to OPN is significantly augmented by both anti-CD44s and anti-CD44v antibodies. This augmentation by anti-CD44 antibodies is OPN specific and, again, can be blocked by anti-beta1 antibodies. Finally, we show that OPN binding by CD44 variants/beta1-containing integrins promotes cell spreading, motility, and chemotactic behavior.

Animals↗

PubMed1998

Functional cooperation of cyclin C and c-Myc in mediating homotypic cell adhesion via very late antigen-4 activation and vascular cell adhesion molecule-1 induction.

Very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1) are a pair of adhesion molecules mediating cell-cell interaction. The binding activity of each depends on its surface expression, yet integrin activity can also be modulated through inside-out signaling. However, the specific intracellular molecules involved in modulating integrin VLA-4 activation via inside-out signaling or in regulating VCAM-1 expression are poorly understood. We show here that constitutive coexpression of cyclin C and c-Myc in hematopoietic BAF-B03 cells induces homotypic cell adhesion, which results from enhanced VLA-4 ligand-binding activity and induced expression of VCAM-1. Furthermore, regulation of cell adhesion appears to be a feature unique to cyclin C, but not other G1 cyclins, E and D3, and its regulatory function is independent of CDK8 kinase activity. Our results provide a novel role for cyclin C and c-Myc in the regulation of cell adhesion through distinct mechanisms.

Animals↗

PubMed1998

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.

Animals↗

PubMed1998

Suppressive effect on Theiler's murine encephalomyelitis virus-induced demyelinating disease by the administration of anti-IL-12 antibody.

We examined the role of IL-12, a cytokine critical to the evolution of cellular responses, in the development of Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD). Treatment with mAbs to IL-12, especially during the effector phase, resulted in significant suppression of the development of this disease both clinically and histologically. In mice treated with these mAbs, the production of inflammatory and Th1-derived cytokines such as TNF-alpha and IFN-gamma in the spleen cells was decreased, and that of Th2-derived cytokines such as IL-4 and IL-10 was increased. The delayed type hypersensitivity and T cell proliferative response specific for TMEV were decreased by this treatment. These data suggest that IL-12 is critically involved in the pathogenesis of TMEV-IDD and that Abs to IL-12 could be a novel therapeutic approach in the clinical treatment of demyelinating diseases such as human multiple sclerosis.

Animals↗

PubMed1998

Chemotactic activity of soluble Fas ligand against phagocytes.

A recombinant soluble form of human Fas ligand (sFasL) was tested for its chemotactic activity against human and mouse polymorphonuclear neutrophils (PMN) by the Boyden chamber method. sFasL exhibited a potent chemotactic activity against both human and mouse PMN and HL-60 cells when differentiated into neutrophils or monocytes. A neutralizing anti-FasL mAb abolished the chemotactic activity, while control mAb did not. Ligation of Fas by either IgM- or IgG-type anti-Fas mAb also induced PMN migration. PMN derived from lpr mice that express few Fas molecules did not respond to sFasL. In contrast, those derived from lpr(cg) mice that express Fas molecules with a mutated death domain normally responded to sFasL chemotaxis. These results directly indicated a chemotactic activity of sFasL against PMN and suggest a novel signaling function of Fas, which appears to be independent of the death domain-mediated apoptosis.

Animals↗

PubMed1998

Identification of rat OX40 ligand by molecular cloning.

OX40 (CD134) is a member of the tumor necrosis factor (TNF) receptor superfamily first identified as a rat T cell activation marker. In the present study, we identified the rat ligand for OX40 (OX40L) by molecular cloning. Rat OX40L cDNA was cloned from a HTLV-1-transformed rat T cell line by cross-hybridization with mouse OX40L cDNA. The predicted rat OX40L polypeptide is composed of 199 amino acids, showing 80.9 and 43.3% homology to mouse and human OX40L, respectively. Expression of rat OX40L mRNA was found in HTLV-1-transformed rat T cell lines. Expression of OX40L on the cell surface of these HTLV-1-transformed rat T cell lines was also demonstrated by flow cytometric analysis with a soluble fusion protein composed of the extracellular region of the Fc portion of human IgG (OX40-Ig). To explore the function of rat OX40L, we generated cDNA transfectants stably expressing rat OX40L. The rat OX40L transfectants exhibited a potent costimulatory activity for proliferation and IL-2 production of anti-CD3-stimulated rat T cells. These results indicated that rat OX40L can provide an efficient costimulation for rat T cells and that it may be involved in HTLV-1-associated pathologies in the rat system as has been suggested in the human system.

Amino Acid Sequence↗

PubMed1998

Tenascin suppresses CD3-mediated T cell activation.

Tenascin (TN) is an extracellular matrix protein which interferes with fibronectin (FN)-dependent cell attachment and activation as a natural antagonist to FN action. In this study, we examined the inhibitory effect of TN on T cell proliferation induced by immobilized anti-CD3 Ab combined with various costimulators in a serum-free condition. Consistent with previous studies, human T cell activation induced by anti-CD3 plus FN was completely inhibited by the addition of TN. Interestingly, TN could interfere with T cell proliferations costimulated by various very late activation antigen (VLA) integrin/ligand interactions such as VLA-4/FN, VLA-5/FN and VLA-6/laminin. Furthermore, lymphocyte function-associated antigen 1 (LFA-1)-, CD2- and CD28-costimulated T cell activation were also inhibited by TN, while TN could not affect the phorbol ester-stimulated T cell proliferation. Collectively, TN inhibits anti-CD3-induced T cell proliferation irrespectively of costimulatory molecules, suggesting that TN acts as a generally immunosuppressive extracellular matrix protein which potentially interferes with T cell receptor/CD3-mediated T cell activation.

CD3 Complex↗

PubMed1998

Expression of costimulatory molecule CD40 in murine heart with acute myocarditis and reduction of inflammation by treatment with anti-CD40L/B7-1 monoclonal antibodies.

Evidence has accumulated that antigen-specific T cells infiltrate the heart and play an important role in the pathogenesis of viral myocarditis. Costimulatory molecules such as B7s and CD40 expressed on antigen-presenting cells are known to play a critical role for antigen-specific T-cell activation to occur. To investigate the role for a costimulatory molecule, CD40, in the development of acute viral myocarditis, we first analyzed the expression of CD40 in the hearts of mice with acute viral myocarditis induced by Coxsackievirus B3. We also evaluated the induction of CD40 in cultured cardiac myocytes treated with interferon gamma in vitro. Second, we analyzed the cytokine production by cultured cardiac myocytes by stimulation with anti-CD40 monoclonal antibody (mAb) in vitro. Third, we examined the effects of in vivo administration of anti-CD40L/B7-1 mAbs on the development of acute viral myocarditis. We found that Coxsackievirus B3-induced murine acute myocarditis results in enhanced expression of CD40 on cardiac myocytes. The expression of CD40 on cardiac myocytes could be induced by interferon gamma in vitro. We also found that the production of interleukin-6 by cardiac myocytes was stimulated with anti-CD40 mAb and that in vivo anti-CD40L/B7-1 mAb treatment significantly decreased the myocardial inflammation. Our findings strongly suggest that CD40 plays an important role in the development of acute viral myocarditis and raise the possibility of immunotherapy with anti-CD40L/B7-1 mAbs to prevent T cell-mediated myocardial damage in viral myocarditis.

Animals↗

PubMed1998

Antitumor effect of CD40 ligand: elicitation of local and systemic antitumor responses by IL-12 and B7.

The interaction between CD40 ligand (CD40L, CD154) and its receptor CD40 has been implicated in the establishment of cell-mediated immunity as well as humoral immune responses. To examine the role of CD40L in eliciting antitumor immunity, we introduced murine CD40L gene into P815 mastocytoma (CD40L-P815). CD40L-P815 cells underwent prompt rejection when inoculated s.c. into syngenic DBA/2 mice or athymic BALB/c nu/nu mice, which was mediated by NK cells and dependent on endogenous IL-12. The primary rejection of CD40L-P815 cells in DBA/2 mice elicited CD8+ T cell-mediated protective and systemic immunity against parental tumor cells, which was induced by CD4+ T cells and endogenous B7. These results indicated a potent antitumor effect of CD40L that is mediated by potentiation of host Ag-presenting cell functions, and introduction of CD40L will be useful as a new strategy of immuno-gene therapy against tumors.

Animals↗

PubMed1998

Fas/FasL interaction is not involved in apoptosis of activated CD4+ T cells upon HIV-1 infection in vitro.

In HIV-1-infected individuals, Fas expression and Fas/FasL-mediated apoptosis of mature T cells are known to increase compared with those in normal individuals. To elucidate a relation between acute HIV-1 infection and the regulation of Fas/FasL system upon T-cell activation, resting CD4+ T cells were acutely infected or uninfected with HIV-1 and subsequently activated by phorbol myristate acetate and ionomycin (PMA/IM). Four days after infection, when HIV-1 env gp120 is expressed in more than one half of activated T cells, Fas/FasL expression was analyzed by flow cytometry, and apoptosis-inducing activity of these activated primary CD4+ T cells on Fas+ Jurkat cells was examined. The level of Fas or FasL expression was not altered during acute HIV-1 infection. The enhanced apoptosis-inducing activity upon HIV-1 infection was observed in some individuals, but its activity was not Fas/FasL-mediated. These results indicate that HIV-1 infection is not necessarily associated with either upregulation of Fas/FasL expression or Fas/FasL-mediated apoptosis.

Antibodies, Monoclonal↗

PubMed1998

In vivo analysis of Fas/FasL interactions in HIV-infected patients.

Recent insights into the pharmacological control of HIV replication and the molecular mechanisms of peripheral T cells homeostasis allowed us to investigate in vivo the mechanisms mediating T cell depletion in HIV-infected patients. Before the initiation of highly active antiretroviral therapy (HAART), a high degree of lymphoid tissue apoptosis is present, which is reduced upon HAART initiation (P < 0.001) and directly correlates with reduction of viral load and increases of peripheral T lymphocytes (P < 0.01). Because Fas/FasL interactions play a key role in peripheral T lymphocyte homeostasis, we investigated the susceptibility to Fas-mediated apoptosis in peripheral T lymphocytes and of FasL expression in lymphoid tissue before and during HAART. High levels of Fas-susceptibility found in peripheral CD4 T lymphocytes before HAART were significantly reduced after HAART, coinciding with decreases in viral load (P = 0.018) and increases in peripheral CD4 T lymphocyte counts (P < 0.01). However, the increased FasL expression in the lymphoid tissue of HIV-infected individuals was not reduced after HAART. These results demonstrate that lymphoid tissue apoptosis directly correlates with viral load and peripheral T lymphocyte numbers, and suggest that HIV-induced susceptibility to Fas-dependent apoptosis may play a key role in the regulation of T cell homeostasis in HIV-infected individuals.

Anti-HIV Agents↗

PubMed1998

Involvement of Fas-mediated apoptosis in the hematopoietic progenitor cells of graft-versus-host reaction-associated myelosuppression.

The influence of graft-versus-host (GVH) reaction on the host hematopoietic cells clinically manifests itself both as adverse reactions in transfusion-associated GVH disease (GVHD) and as a therapeutic graft-versus-leukemia (GVL) effect in either donor lymphocytes transfusion (DLT) or allogeneic bone marrow (BM) transplantation. We examined the effect of GVH reaction on the host hematopoiesis in the murine parent-into-F1 (P1 --> F1) model of GVHD. The systemic transfer of 5 x 10(7) of C57BL/6 (B6) splenocytes into (B6xDBA/2)F1 mice (BDF1), which results in acute GVHD, reduced the peripheral blood cell counts, the number of BM cells, and colony-forming unit-granulocyte macrophage (CFU-GM), whereas the injection of 10(8) of DBA/2 cells into BDF1, which results in chronic GVHD, did not affect hematopoiesis 2 weeks after the transfer. To clarify the mechanism of such myelosuppression, we examined the Fas expression in both hematopoietic progenitor cells as well as whole BM cells. The Fas expressions in each fraction significantly increased in BDF1 mice 2 weeks after the induction of acute GVHD, whereas no such effects were observed in the BDF1 mice with chronic GVHD. Furthermore, when such BM cells were incubated with anti-Fas antibody (Jo2), which induces apoptosis through Fas, the fraction of apoptotic cells increased and the number of CFU-GM decreased significantly. The in vivo administration of neutralizing anti-FasL antibody into BDF1 mice receiving with B6 spleen cells thus protected the host mice from BM failure. These results indicate that the functional expression of Fas on hematopoietic cells plays an essential role in the myelosuppressive effect of GVHD.

Animals↗

PubMed1998

Differential involvement of a Fas-CPP32-like protease pathway in apoptosis of TCR/CD9-costimulated, naive T cells and TCR-restimulated, activated T cells.

Our previous study showed that CD9 costimulation of TCR-triggered naive T cells elicits activation ([3H]TdR incorporation) that is similar to CD28 costimulation; however, unlike CD28 costimulation, CD9 costimulation results in apoptosis of these previously activated T cells. Here, we investigated whether the apoptosis occurring after TCR/CD9 stimulation is associated with a death pathway involving Fas stimulation and Fas-mediated caspase activation as observed in activation-induced cell death (AICD). In contrast to AICD, the apoptosis resulting from TCR/CD9 stimulation in C57BL/6 T cells was independent of Fas, because this form of apoptosis was not prevented by anti-Fas ligand mAb and was also induced in MRL/lpr T cells. AICD was observed at 12 h after the restimulation of activated T cells with anti-CD3 and reached a peak level at 24 h after this restimulation. CPP32-like protease activity was detected during AICD. Although TCR/CD9 stimulation-associated apoptosis was observed at 24 h after the stimulation of naive T cells and reached a peak level at 36 h after this stimulation, CPP32-like protease activity in these T cells was only marginal at all time points. Nevertheless, both forms of apoptosis were prevented similarly by two different peptide-based caspase inhibitors. These results indicate that the apoptosis that follows the T cell activation which is induced as a result of CD9 costimulation does not involve a Fas-CPP32-like protease pathway, but suggest that different caspase members are likely to be critical in this form of apoptosis.

Animals↗

PubMed1998

The expression of Fas Ligand by macrophages and its upregulation by human immunodeficiency virus infection.

Fas/Fas Ligand (FasL) interactions play a significant role in peripheral T lymphocyte homeostasis and in certain pathological states characterized by T cell depletion. In this study, we demonstrate that antigen-presenting cells such as monocyte-derived human macrophages (MDM) but not monocyte-derived dendritic cells express basal levels of FasL. HIV infection of MDM increases FasL protein expression independent of posttranslational mechanisms, thus highlighting the virus-induced transcriptional upregulation of FasL. The in vitro relevance of these observations is confirmed in human lymphoid tissue. FasL protein expression is constitutive and restricted to tissue macrophages and not dendritic cells. Moreover, a significant increase in macrophage-associated FasL is observed in lymphoid tissue from HIV (+) individuals (P < 0.001), which is further supported by increased levels of FasL mRNA using in situ hybridization. The degree of FasL protein expression in vivo correlates with the degree of tissue apoptosis (r = 0.761, P < 0. 001), which is significantly increased in tissue from HIV-infected patients (P < 0.001). These results identify human tissue macrophages as a relevant source for FasL expression in vitro and in vivo and highlight the potential role of FasL expression in the immunopathogenesis of HIV infection.

Apoptosis↗

PubMed1998

Differential effects of anti-Fas ligand and anti-tumor necrosis factor alpha antibodies on acute graft-versus-host disease pathologies.

Both tumor necrosis factor alpha (TNFalpha) and Fas ligand (FasL) have been implicated in the pathogenesis of graft-versus-host disease (GVHD). In this study, we examined the ameliorating effects of neutralizing anti-FasL and/or anti-TNFalpha monoclonal antibody (MoAb) in a lethal acute GVHD model in mice. Whereas the treatment with either anti-FasL or anti-TNFalpha MoAb alone significantly delayed the mortality and improved the body weight, a complete protection was achieved by the administration of both MoAbs. Pathological examination indicated differential effects of anti-FasL or anti-TNFalpha MoAb on GVHD-associated pathologies. Hepatic lesion was improved by anti-FasL but not anti-TNFalpha MoAb. In contrast, intestinal lesion was improved by anti-TNFalpha but not anti-FasL MoAb. Cutaneous and splenic lesions were improved by either MoAb. The combination of both MoAbs improved all these lesions. These results indicate that FasL and TNFalpha differentially contribute to the GVHD pathologies and a complete protection from mortality can be achieved by neutralization of both FasL and TNFalpha.

Animals↗

PubMed1998

Two types of anti-TL (thymus leukemia) CTL clones with distinct target specificities: differences in cytotoxic mechanisms and accessory molecule requirements.

TCRalphabeta CTL clones recognizing mouse thymus leukemia (TL) Ags were established and categorized into two groups: those killing any TL+ target cells (type I) and those killing only TL+ Con A blasts (type II). Cold target inhibition assays showed that the antigenic determinant(s) recognized by type II clones are expressed not only on TL+ Con A blasts but also on other TL+ target cells. The relation of the target specificity to the killing machinery and the accessory molecules involved in cytotoxicity were therefore analyzed using four representative clones selected from each type. Of the target cells tested, Fas was only expressed on Con A blasts, indicating that Fas ligand (FasL)-dependent cytotoxicity is limited to such cells. All four type II and one of four type I clones expressed FasL on the surface, while both types contained perforin in the cytoplasm. Blocking studies using neutralizing anti-FasL mAbs and concanamycin A (CMA), a selective inhibitor of the perforin pathway, suggested that type I clones kill target cells by way of perforin, while type II clones kill TL+ Con A blasts through FasL together with perforin. For their cytotoxicity, type I CTLs require a signal through CD8, while type II require LFA-1/ICAM-1 interactions. Type II clones also need a co-stimulatory signal through an unknown molecule for perforin-dependent cytotoxicity. These results taken together suggest that the difference in the target specificity of anti-TL CTL clones is due to variation in the killing machineries and the dependence on accessory molecules.

Animals↗

PubMed1998

CD27, a member of the tumor necrosis factor receptor superfamily, activates NF-kappaB and stress-activated protein kinase/c-Jun N-terminal kinase via TRAF2, TRAF5, and NF-kappaB-inducing kinase.

CD27 is a member of the tumor necrosis factor (TNF) receptor superfamily and is expressed on T, B, and NK cells. The signal via CD27 plays pivotal roles in T-T and T-B cell interactions. Here we demonstrate that overexpression of CD27 activates NF-kappaB and stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK). Deletion analysis of the cytoplasmic domain of CD27 revealed that the C-terminal PIQEDYR motif was indispensable for both NF-kappaB and SAPK/JNK activation and was also required for the interaction with TNF receptor-associated factor (TRAF) 2 and TRAF5, both of which have been implicated in NF-kappaB activation by members of the TNF-R superfamily. Co-transfection of a dominant negative TRAF2 or TRAF5 blocked NF-kappaB and SAPK/JNK activation induced by CD27. Recently, a TRAF2-interacting kinase has been identified, termed NF-kappaB-inducing kinase (NIK). A kinase-inactive mutant NIK blocked CD27-, TRAF2-, and TRAF5-mediated NF-kappaB and SAPK/JNK activation. These results indicate that TRAF2 and TRAF5 are involved in NF-kappaB and SAPK/JNK activation by CD27, and NIK is a common downstream kinase of TRAF2 and TRAF5 for NF-kappaB and SAPK/JNK activation.

Calcium-Calmodulin-Dependent Protein Kinases↗