Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019158 (hepatitis)
 30,205 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous work has shown that stimulation of APCs via CD40 strongly influences the outcome of a CD8 T cell response. In this study, we examined the effect of CD40 ligation on peripheral tolerance induction of self-reactive CD8 T cells in an adoptive transfer model. Naive CD8 T cells from TCR-transgenic (tg) mice specific for the gp33 epitope of lymphocytic choriomeningitis virus were tolerized when transferred into H8-tg mice expressing the gp33 epitope under the control of a MHC class I promoter. However, if the H8 recipient mice were treated with agonistic anti-CD40 Abs, TCR-tg cells vigorously proliferated, and induced destruction of lymphoid organs and hepatitis. Break of peripheral tolerance induction was B cell independent and did not require CD28/B7 interactions. These findings provide further in vivo evidence for the crucial role of the activation state of the APC in peripheral tolerance induction and suggest the need for caution in systemically activating APC via CD40 ligation in the presence of self-reactive T cells.
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PMID:CD40 ligation in the presence of self-reactive CD8 T cells leads to severe immunopathology. 1199 66

CD8(+) T cells infiltrating the CNS control infection by the neurotropic JHM strain of mouse hepatitis virus. Differential susceptibility of infected cell types to clearance by perforin or IFN-gamma uncovered distinct, nonredundant roles for these antiviral mechanisms. To separately evaluate each effector function specifically in the context of CD8(+) T cells, pathogenesis was analyzed in mice deficient in both perforin and IFN-gamma (PKO/GKO) or selectively reconstituted for each function by transfer of CD8(+) T cells. Untreated PKO/GKO mice were unable to control the infection and died of lethal encephalomyelitis within 16 days, despite substantially higher CD8(+) T cell accumulation in the CNS compared with controls. Uncontrolled infection was associated with limited MHC class I up-regulation and an absence of class II expression on microglia, coinciding with decreased CD4(+) T cells in CNS infiltrates. CD8(+) T cells from perforin-deficient and wild-type donors reduced virus replication in PKO/GKO recipients. By contrast, IFN-gamma-deficient donor CD8(+) T cells did not affect virus replication. The inability of perforin-mediated mechanisms to control virus in the absence of IFN-gamma coincided with reduced class I expression. These data not only confirm direct antiviral activity of IFN-gamma within the CNS but also demonstrate IFN-gamma-dependent MHC surface expression to guarantee local T cell effector function in tissues inherently low in MHC expression. The data further imply that IFN-gamma plays a crucial role in pathogenesis by regulating the balance between virus replication in oligodendrocytes, CD8(+) T cell effector function, and demyelination.
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PMID:Perforin-mediated effector function within the central nervous system requires IFN-gamma-mediated MHC up-regulation. 1262 79

We earlier found that a rat monoclonal antibody (mAb) RE2 can induce rapid death of murine activated, but not resting, lymphocytes and lymphocyte cell lines, in a complement-independent manner, a cell death differing from typical apoptosis or necrosis. We here found that this cell death is independent of pathways involving Fas, caspase, and phosphoinositide-3 kinase. With the advantage of producing human B cell line transfectants with stable expression of human/mouse xeno-chimeric MHC class I genes, we found that RE2 epitope resides on the murine class I alpha2 domain. However, the alpha3 domain plays a key role in transducing the death signal, which mediates extensive aggregation of the MHC class I-integrin-actin filament system, giving rise to membrane blebs and pores. In mouse models with T/NKT cell activation-associated fulminant hepatitis, administration of mAb RE2 almost completely inhibited the development of liver cell injuries. Taken collectively, this form of cell death may be involved in homeostatic immune regulation, and induction of this form of cell death using the mAbs may be potentially therapeutic for subjects with immunological diseases mediated by activated lymphocytes.
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PMID:A monoclonal antibody to the alpha2 domain of murine major histocompatibility complex class I that specifically kills activated lymphocytes and blocks liver damage in the concanavalin A hepatitis model. 1288 69

The rhesus macaque ( Macaca mulatta) has become a popular animal model for several human infectious diseases, such as HIV (modeled by SIV infection), hepatitis, and malaria. Investigation of T-cell responses in experimental infectious diseases in rhesus macaques has benefited from an expanding understanding of the diversity of macaque MHC class I heavy chains and the restriction of antigen presentation by macaque class I molecules. Here we add to this understanding with the first nucleotide sequences of M. mulatta beta(2)-microglobulin (beta(2)m) mRNA, including a portion of the 3'-untranslated region (3'UTR). In pairwise comparison, the beta(2)m protein of M. mulatta differs from human and chimpanzee beta(2)m by nine amino-acid substitutions (92% identity), and from Macaca fascicularis by one amino-acid difference in the signal peptide region (99% identity). Allelic variations were identified at one site in the 3'UTR. A structural analysis of human or chimpanzee beta(2)m and M. mulatta beta(2)m suggests that the differences cluster in three solvent-exposed clusters and do not involve contacts with the class I heavy chain. We predict that human and macaque beta(2)m should bind interchangeably with the class I heavy chains of the other species, and show that four M. mulatta class I alleles form cell surface complexes with human beta(2)m. Further, we predict that W6/32 (a monoclonal antibody that recognizes a combined epitope of some class I heavy chains and beta(2)m with a subtle species dependence) should bind similarly human or macaque class I molecules that are bound with beta(2)m of either species, supported by evidence of recognition of both heterologous and homologous complexes of macaque class I heavy chains. Our findings contribute to the growing understanding of rhesus macaque histocompatibility antigens and antigen presentation, and to the phylogeny of beta(2)m in primates.
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PMID:Sequence of beta(2)-microglobulin from rhesus macaque ( Macaca mulatta) includes an allelic variation in the 3'-untranslated region. 1496 20

We measured CD8 T cell clonotypic diversity to three epitopes recognized in C57BL/6 mice infected with mouse hepatitis virus, strain JHM, or lymphocytic choriomeningitis virus. We isolated epitope-specific T cells with an IFN-gamma capture assay or MHC class I/peptide tetramers and identified different clonotypes by Vbeta chain sequence analysis. In agreement with our previous results, the number of different clonotypes responding to all three epitopes fit a log-series distribution. From these distributions, we estimated that >1000 different clonotypes responded to each immunodominant CD8 T cell epitope; the response to a subdominant CD8 T cell epitope was modestly less diverse. These results suggest that T cell response diversity is greater by 1-2 orders of magnitude than predicted previously.
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PMID:Very diverse CD8 T cell clonotypic responses after virus infections. 1497 21

CD4 T cells play an important role in hepatitis B virus (HBV) infection by secretion of Th1 cytokines that down-regulate HBV replication, and by promoting CD8 T cell and B cell responses. We have identified and characterized 10 CD4 T cell epitopes within polymerase and used them to analyze the immunological effects of long-term antiviral therapy as compared with spontaneous recovery from HBV infection. Candidate epitopes were tested for binding to 14 HLA-DR molecules and in IFN-gamma ELISPOT and cytotoxicity assays using peripheral blood lymphocytes from 66 HBV-infected patients and 16 uninfected controls. All 10 epitopes bound with high affinity to the most prevalent HLA-DR Ags, were conserved among HBV genomes, and induced IFN-gamma responses from HBV-specific CD4+ T cells. Several epitopes contained nested MHC class I motifs and stimulated HBV-specific IFN-gamma production and cytotoxicity of CD8+ T cells. HBV polymerase-specific responses were more frequent during acute, self-limited hepatitis and after recovery (12 of 18; 67%) than during chronic hepatitis (16 of 48 (33%); p=0.02). Antiviral therapy of chronic patients restored HBV polymerase and core-specific T cell responses during the first year of treatment, but thereafter, responses decreased and, after 3 years, were no more frequent than in untreated patients. Decreased T cell responsiveness during prolonged therapy was associated with increased prevalence of lamivudine-resistant HBV mutants and increased HBV titers. The data provide a rationale for the combination of antiviral and immunostimulatory therapy. These newly described HBV polymerase epitopes could be a valuable component of a therapeutic vaccine for a large and ethnically diverse patient population.
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PMID:Cellular immune responses to the hepatitis B virus polymerase. 1549 40

Transfer of B6 T cells to major histocompatibility complex (MHC) class I disparate bm1 x B6 F1 mice leads to the development of hepatic graft-versus-host disease (GVHD) characterized by an active hepatitis with portal and lobular inflammation as well as bile duct inflammation and venulitis. The present studies determined the role of tumor necrosis factor (TNF) in hepatic GVHD. B6 responder cells were cultured with irradiated MHC class I disparate bm1 or syngeneic spleen cells (SpC) in the presence or absence of TNF receptor inhibitor [TNFR-immunoglobulin (Ig)]. Recipient bm1 x B6 F1 mice were irradiated (600 cGy) and reconstituted with 5 x 10(6) T cell-depleted B6 bone marrow cells and 1 x 10(7) B6 SpC. Mice were injected with an adenovirus encoding TNFR-Ig [TNF inhibitor-encoding adenovirus (Adv-TNFi)] or beta-galactosidase (Adv-betagal). Severity of liver GVHD was assessed by a composite histopathological score consisting of the sum of scores for venulitis, lobular hepatitis, and bile duct inflammation. Addition of TNFR-Ig reduced cell proliferation in mixed lymphocyte cultures using B6 responder SpC by 71% +/- 12.8% and interferon-gamma responses by 78% +/- 18%. GVHD-induced "wasting disease" was reduced in Adv-TNFi recipients [4.4%+/-5.2% weight loss (n=11)] compared with Adv-betagal recipients [16.1%+/-7.6% weight loss (n=11; P=0.0004)] 9 days post-transplant. Composite histopathological scores and individual venulitis scores were reduced with the addition of Adv-TNFi. Hepatic CD8+ T cells in the recipients of Adv-TNFi were reduced as compared with recipients of Adv-betagal. In conclusion, Adv-TNFi reduces MHC class I disparate alloproliferative responses and hepatic GVHD.
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PMID:The role of TNF in hepatic histopathological manifestations and hepatic CD8+ T cell alloresponses in murine MHC class I disparate GVHD. 1608 94

West Nile virus causes febrile illness in humans with a proportion of cases progressing to meningoencephalitis, encephalitis, hepatitis, and death. Isolates of the virus fall into two genetic lineages, with differences in neuroinvasiveness for mice occurring between strains within both lineages. We used DNA microarrays to compare gene expression in mice infected peripherally with seven lineage 1 and 2 strains confirmed to be of either high or low neuroinvasiveness in mice and associated with severe or benign infection in humans and birds. The 4 strains with highest neuroinvasiveness induced increased expression of 47 genes in the brain, 111 genes in the liver, and 70 genes in the spleen, relative to the 3 least neuroinvasive strains. Genes involved in interferon signaling pathways, protein degradation, T-cell recruitment, MHC class I and II antigen presentation, and apoptosis were identified that may have both pathogenic and protective effects, but increased expression of certain acute proteins, central nervous system specific proteins and proteins associated with T-cell hepatitis, implicate mechanisms related to exalted virulence.
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PMID:Gene expression in mice infected with West Nile virus strains of different neurovirulence. 1612 13

NKT cells are a subset of regulatory lymphocytes characterized by co-expression of the NK cell receptor-CD161 and an invariant TCR-alpha chain (Valpha14-Jalpha28). They are most abundant in the liver, spleen, and bone marrow. NKT lymphocytes have been implicated in the regulation of autoimmune processes in both mice and humans. Activation of NKT lymphocytes leads to rapid amplification of either IFNgamma or IL4, endowing these cells with the capability to mediate both pro-inflammatory and anti-inflammatory immune responses. Activation of this subset of cells is associated with significant liver damage in the Concanavalin A immune mediated hepatitis model. Administration of CD1d ligand has a protective role in collagen-induced arthritis in mice. Disease amelioration was associated with a shift in the immune balance from a pathological Th1 type response towards a protective Th2 type response. In humans, patients with SLE, scleroderma, diabetes, multiple sclerosis, and rheumatoid arthritis have lower numbers of peripheral NKT cells. NKT lymphocytes promote tumor rejection in experimental models of tumor immunotherapy. In contrast, NKT lymphocyte-related anti-tumor activity is associated with pro-inflammatory Th1-type immune responses. NKT cells were shown to have a role in suppression of hepatocellular carcinoma (HCC) via immune regulation towards tumor derived antigens, and adoptive transfer of dendritic cells pulsed ex vivo with the same antigens. NKT lymphocytes are activated by interaction of their TCR with glycolipids presented by CD1d, a nonpolymorphic, MHC class I-like molecule expressed by antigen presenting cells, and also by hepatocytes. Several possible ligands for NKT cells have recently been suggested including CD1d bound Glucocerebroside. Glucocerebroside (GC, beta-glucosylceramide), a naturally occurring glycolipid, is a metabolic intermediate in the anabolic and catabolic pathways of complex glycosphingolipids. Its synthesis from ceramide is catalyzed by the enzyme glucosylceramide synthase. Inherited deficiency of glucocerebrosidase, a lysosomal hydrolase, results in Gaucher's disease. Patients with Gaucher's disease have altered humoral and cellular immune profiles and increased peripheral blood NKT lymphocytes. CD1d-bound glucocerebroside does not activate NKT cells directly, and may inhibit activation of NKT cells by alpha-GalCer. On the other hand, glucosylceramide-synthase deficiency was shown to lead to defective ligand presentation by CD1d, with secondary inhibition of NKT cell activation. Recent studies have suggested that a number of glycolipids, including GC, have an immune modulatory effect in several immune mediated disorders. The ability to alter NKT lymphocyte function in various settings and the potential application of natural glycolipids for treatment are discussed.
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PMID:Glycolipids as immune modulatory tools. 1710 Jun 36

Cytotoxic T lymphocyte escape occurs in many human infections, as well as mice infected with the JHM strain of mouse hepatitis virus, which exhibit CTL escape variants with mutations in a single epitope from the spike glycoprotein (S510). In all CTL epitopes prone to escape, only a subset of all potential variants is generally detected, even though many of the changes that are not selected would result in evasion of the T cell response. It is postulated that these unselected mutations significantly impair virus fitness. To define more precisely the basis for this preferential selection, we combine x-ray crystallographic studies of the MHC class I (D(b))/S510 complexes with viral reverse genetics to identify a prominent TCR contact residue (tryptophan at position 4) prone to escape mutations. The data show that a mutation that is commonly detected in chronically infected mice (tryptophan to arginine) potently disrupts the topology of the complex, explaining its selection. However, other mutations at this residue, which also abrogate the CTL response, are never selected in vivo even though they do not compromise virus fitness in acutely infected animals or induce a significant de novo CTL response. Thus, while structural analyses of the S510/D(b) complex provide a strong basis for why some CTL escape variants are selected, our results also show that factors other than effects on virus fitness limit the diversification of CD8 T cell epitopes.
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PMID:Structural and biological basis of CTL escape in coronavirus-infected mice. 1832 1


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