963 resultados para lymphocyte T CD8
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To modulate alloreactivity after hematopoietic stem cell transplantation, "suicide" gene-modified donor T cells (GMCs) have been administered with an allogeneic T-cell-depleted marrow graft. We previously demonstrated that such GMCs, generated after CD3 activation, retrovirus-mediated transduction, and G418 selection, had an impaired Epstein-Barr virus (EBV) reactivity, likely to result in an altered control of EBV-induced lymphoproliferative disease. To further characterize the antiviral potential of GMCs, we compared the frequencies of cytomegalovirus (CMV)-specific CD8+ T (CMV-T) cells and EBV-specific CD8+ T (EBV-T) cells within GMCs from CMV- and EBV-double seropositive donors. Unlike anti-EBV responses, the anti-CMV responses were not altered by GMC preparation. During the first days of culture, CMV-T cells exhibited a lower level of CD3-induced apoptosis than did EBV-T cells. In addition, the CMV-T cells escaping initial apoptosis subsequently underwent a higher expansion rate than EBV-T cells. The differential early sensitivity to apoptosis could be in relation to the "recent activation" phenotype of EBV-T cells as evidenced by a higher level of CD69 expression. Furthermore, EBV-T cells were found to have a CD45RA-CD27+CCR7- effector memory phenotype, whereas CMV-T cells had a CD45RA+CD27-CCR7- terminal effector phenotype. Such differences could be contributive, because bulk CD8+CD27- cells had a higher expansion than did bulk CD8+CD27+ cells. Overall, ex vivo T-cell culture differentially affects apoptosis, long-term proliferation, and overall survival of CMV-T and EBV-T cells. Such functional differences need to be taken into account when designing cell and/or gene therapy protocols involving ex vivo T-cell manipulation.
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Thse numrise par la Direction des bibliothques de l'Universit de Montral.
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Thse numrise par la Direction des bibliothques de l'Universit de Montral.
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Background: The results of previous studies elsewhere have indicated that GB virus C (GBV-C) infection is frequent in patients infected with the human immunodeficiency virus type 1 (HIV-1) due to similar transmission routes of both viruses. The aim of this study was to determine the prevalence, incidence density and genotypic characteristics of GBV-C in this population. Methodology/Principal Findings: The study population included 233 patients from a cohort primarily comprised of homosexual men recently infected with HIV-1 in Sao Paulo, Brazil. The presence of GBV-C RNA was determined in plasma samples by reverse transcriptase-nested polymerase chain reaction and quantified by real-time PCR. GBV-C genotypes were determined by direct sequencing. HIV viral load, CD4+ T lymphocyte and CD8+ T lymphocyte count were also tested in all patients. The overall prevalence of GBV-C infection was 0.23 (95% CI: 0.18 to 0.29) in the study group. There was no significant difference between patients with and without GBV-C infection and Glycoprotein E2 antibody presence regarding age, sex, HIV-1 viral load, CD4+ and CD8+ T cell counts and treatment with antiretroviral drugs. An inverse correlation was observed between GBV-C and HIV-1 loads at enrollment and after one year. Also, a positive but not significant correlation was observed between GBV-C load and CD4+ T lymphocyte. Phylogenetic analysis of the GBV-C isolates revealed the presence of genotype 1 and genotype 2, these sub classified into subtype 2a and 2b. Conclusion/Significance: GBV-C infection is common in recently HIV -1 infected patients in Sao Paulo, Brazil and the predominant genotype is 2b. This study provides the first report of the GBV-C prevalence at the time of diagnosis of HIV-1 and the incidence density of GBV-C infection in one year.
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Kaposi's sarcoma-associated herpesvirus (KSHV) specific T cell responses and KSHV viremia were analyzed in seven HIV-infected patients with active Kaposi's sarcoma lesions who initiated highly active antiretroviral therapy, and were compared between patients with improved Kaposi's sarcoma and those with progressive Kaposi's sarcoma requiring further systemic chemotherapy. Patients with controlled Kaposi's sarcoma disease demonstrated undetectable Kaposi's sarcoma viremia together with KSHV-specific CD8 T cells secreting interferon-gamma and tumor necrosis factor-alpha, whereas progressors showed increasing viremia with weak or no T-cell responses. These data point toward a potential role of KSHV-specific immunity in the control of AIDS-associated Kaposi's sarcoma.
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Le contrle immunitaire des infections virales est effectu, en grande partie, par les lymphocytes T CD8+ cytotoxiques. Pour y parvenir, les lymphocytes T CD8+ doivent tre en mesure de reconnatre les cellules infectes et de les liminer. Cette reconnaissance des cellules infectes seffectue par linteraction du rcepteur T (TCR) des lymphocytes T CD8+ et des peptides viraux associs au complexe majeur dhistocompatibilit (CMH) de classe I la surface des cellules htes. Cette interaction constitue llment dclencheur permettant llimination de la cellule infecte. On comprend donc toute limportance des mcanismes cellulaires menant la gnration des peptides antigniques partir des protines virales produites au cours dune infection. La vision traditionnelle de cet apprtement protique menant la prsentation dantignes par les molcules du CMH propose deux voies cataboliques distinctes. En effet, il est largement admis que les antignes endognes sont apprts par la voie dite classique de prsentation antignique par les CMH de classe I. Cette voie implique la dgradation des antignes intracellulaires par le protasome dans le cytoplasme, le transport des peptides rsultant de cette dgradation lintrieur du rticulum endoplasmique, leur chargement sur les molcules du CMH de classe I et finalement le transport des complexes peptide-CMH la surface de la cellule o ils pourront activer les lymphocytes T CD8+. Dans la seconde voie impliquant des antignes exognes, le dogme veut que ceux-ci soient apprts par les protases du compartiment endovacuolaire. Les peptides ainsi gnrs sont directement chargs sur les molcules de CMH de classe II lintrieur de ce compartiment. Par la suite, des mcanismes de recyclage vsiculaire assurent le transport des complexes peptide-CMH de classe II la surface de la cellule afin de stimuler les lymphocytes T CD4+. Cependant, cette stricte sgrgation des voies dapprtement antignique a t durement prouve par la capacit des cellules prsentatrices dantignes effectuer lapprtement dantignes exognes et permettre leur prsentation sur des molcules de CMH de classe I. De plus, lidentification rcente de peptides dorigine intracellulaire associs des molcules de CMH de classe II a clairement indiqu la prsence dinteractions entre les deux voies dapprtement antignique permettant de transgresser le dogme pralablement tabli. Lobjectif du travail prsent ici tait de caractriser les voies dapprtement antignique menant la prsentation dantignes viraux par les molcules du CMH de classe I lors dune infection par le virus de lHerps simplex de type I (HSV-1). Dans les rsultats rapports ici, nous dcrivons une nouvelle voie dapprtement antignique rsultant de la formation dautophagosomes dans les cellules infectes. Cette nouvelle voie permet le transfert dantignes viraux vers un compartiment vacuolaire dgradatif dans la phase tardive de linfection par le virus HSV-1. Cette mise en branle dune seconde voie dapprtement antignique permet daugmenter le niveau de prsentation de la glycoprotine B (gB) virale utilise comme modle dans cette tude. De plus, nos rsultats dcrivent la formation dune nouvelle forme dautophagosomes drivs de lenveloppe nuclaire en rponse linfection par le virus HSV-1. Ces nouveaux autophagosomes permettent le transfert dantignes viraux vers un compartiment vacuolaire lytique, action galement assure par les autophagosomes dits classiques. Dans la deuxime partie du travail prsent ici, nous utilisons linfection par le virus HSV-1 et la production de la gB qui en rsulte pour tudier le trafic membranaire permettant le transfert de la gB vers un compartiment vacuolaire dgradatif. Nos rsultats mettent en valeur limportance du rticulum endoplasmique, et des compartiments autophagiques qui en drivent, dans ces mcanismes de transfert antignique permettant damplifier la prsentation antignique de la protine virale gB sur des CMH de classe I via une voie vacuolaire. Lensemble de nos rsultats dmontrent galement une troite collaboration entre la voie classique de prsentation antignique par les CMH de classe I et la voie vacuolaire soulignant, encore une fois, la prsence dinteraction entre les deux voies.
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Les maladies autoimmunes sont des affections chroniques, le plus souvent invalidantes, qui touchent plus de 5% de la population dans les pays dvelopps. Lautoimmunit rsulte de la rupture des mcanismes de tolrance du systme immunitaire vis--vis des autoantignes exprims par les tissus de lorganisme, entranant la destruction dun ou de plusieurs organes-cibles par les lymphocytes T et/ou B. Lhpatite autoimmune et le diabte autoimmun se caractrisent par la destruction slective des hpatocytes et des cellules beta pancratiques, respectivement. De plus en plus darguments suggrent une implication des lymphocytes T CD8+ dans le dclenchement, la progression et la rgulation des rponses associes plusieurs maladies autoimmunes. Dans ce projet, nous avons suivi lvolution de clones de lymphocytes T CD8+ spcifiques un antigne particulier dont le site dexpression diffrait. Pour ce faire, nous avons dvelopp deux nouveaux modles murins double transgniques par croisement entre une ligne de souris exprimant un TCR transgnique spcifique la nucloprotine (NP) du virus de la choriomningite lymphocytaire (LCMV), et une souris exprimant cette NP-LCMV : 1) uniquement dans les hpatocytes (modle dhpatite autoimmune), ou 2) simultanment dans le thymus et le pancras (modle de diabte autoimmun). Lavidit fonctionnelle des lymphocytes T CD8+ spcifiques la NP chez les souris TCR transgniques tait inversement proportionnelle au niveau dexpression du TCR. Le rpertoire lymphocytaire dans le thymus, la rate, les ganglions et le sang priphrique a t caractris pour chacune des lignes de souris double transgniques, de mme que la capacit fonctionnelle et le phnotype (marqueurs dactivation/mmoire) des lymphocytes T CD8+ autoractifs. Chacun des deux nouveaux modles prsents dans cette tude ont montr que les lymphocytes T CD8+ spcifiques la NP sont aptes briser la tolrance centrale et priphrique et provoquer une raction dautoimmunit spontane. Dans le modle dhpatite autoimmune, o lexpression de lautoantigne tait restreinte au foie, la surexpression du TCR transgnique a entran une dltion thymique quasi-totale des lymphocytes T CD8+ spcifiques la NP prvenant le dveloppement dune hpatite spontane. alors quun niveau de TCR comparable celui dune souris de type sauvage a permis une slection positive des lymphocytes autoractifs qui se sont accumuls dans le foie o ils se sont activs pour provoquer une hpatite autoimmune spontane. Dans le modle de diabte autoimmun, o lautoantigne tait exprim dans le pancras et le thymus, les souris des deux lignes double transgniques ont montr une dltion thymique partielle, peu importe le niveau dexpression du TCR. Seuls les mles adultes dveloppaient un diabte spontan et une partie de leurs lymphocytes T CD8+ exprimaient une combinaison particulire de marqueurs dactivation/mmoire (CD44, CD122, PD-1). Cette population lymphocytaire tait absente chez les souris femelles et les mles sains. Ltude de la tolrance des lymphocytes T CD8+ autoractifs dans nos deux nouveaux modles murins double transgniques a permis didentifier des mcanismes alternatifs possiblement impliqus dans la tolrance et lactivation, et de mieux comprendre le rle des lymphocytes T CD8+ autoractifs dans le processus autoimmun menant lhpatite autoimmune et au diabte autoimmun. Ces dcouvertes seront utiles pour dvelopper de nouvelles approches thrapeutiques ciblant les lymphocytes T CD8+ autoractifs.
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La transplantation allognique de cellules souches hmatopotiques (ASCT) est couramment utilise pour traiter diffrents cancers hmatologiques. Malheureusement, leffet bnfique de cette technique est limit par la raction du greffon contre lhte (GVHD) qui demeure la cause principale de mortalit post-greffe. La GVHD endommage diffrents organes et retarde la reconstitution immunitaire des lymphocytes T (LT) ce qui augmente les risques dinfection et de rechute. Le dveloppement de nouveaux traitements permettant dacclrer la reconstitution immunitaire augmenterait donc les chances de survie des patients greffs. Il existe deux faons de rgnrer des LT: via la thymopose qui consiste produire de nouveaux LT, ou par la prolifration homostatique (PH) qui implique lexpansion rapide des LT matures retrouvs dans le greffon. La PH requiert deux signaux essentiels: linterleukine-7 (IL-7) et la prsentation dantignes du soi par les cellules dendritiques (DC) via le complexe majeur dhistocompatibilit (CMH) I pour les LT CD8+ et le CMH II pour les LT CD4+. Dans un contexte dASCT, la chimiothrapie et la GVHD endommagent le thymus rendant la thymopose inefficace. Par consquent, la reconstitution immunitaire repose presque entirement sur la PH des LT. Lobjectif de cette thse tait de comprendre comment la GVHD affecte la reconstitution des LT. Grce un modle murin, nous avons dmontr que la PH des LT CD4+ est absente durant la GVHD et ce, d de faibles niveaux dIL-7 et une diminution du nombre de DC. La perte des DC est en grande partie cause par des niveaux rduits de stromal derived factor-1 (SDF-1) et par labsence de progniteurs de DC dans la moelle osseuse des souris en GVHD. Le traitement des souris en GVHD avec du SDF-1 permet daugmenter le nombre de DC, et lorsquadministr avec lIL-7, amliore significativement la PH des LT CD4+. Contrairement aux LT CD4+, ladministration dIL-7 seule est suffisante pour restaurer la PH des LT CD8+ durant la GVHD et ce, mme en absence des DC. Ces diffrences sexpliquent pour deux raisons : 1) lexpression du CMH I, contrairement au CMH II, nest pas limite aux DC mais est galement exprime par les cellules stromales du receveur ce qui est suffisant pour induire la PH des LT CD8+ et 2) les LT CD8+ rpondent des concentrations plus faibles dIL-7 systmique comparativement aux LT CD4+. En conclusion, lensemble de ces rsultats permettra de mettre en place des tudes translationnelles sur le potentiel thrapeutique du SDF-1 et de lIL-7 dans la reconstitution immunitaire des patients greffs.
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Histoplasmosis is a systemic mycosis endemic in extensive areas of the Americas. The authors report on an urban adult male patient with uncommon oral-cutaneous lesions proven to be histoplasmosis. Additional investigation revealed unnoticed HIV infection with CD4+ cell count of 7/mm3. The treatment was performed with amphotericin B, a 2065 mg total dose followed by itraconazole 200mg/daily plus antiretroviral therapy with apparent cure. Histoplasmosis is an AIDS-defining opportunistic disease process; therefore, its clinical diagnosis must drive full laboratory investigation looking for unnoted HIV-infection. 2013 by Anais Brasileiros de Dermatologia.
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BACKGROUND: The pathogenesis of chronic hepatitis C is still a matter of debate. CD4+ and CD8+ T lymphocytes (TL) are typically observed within the portal and periportal spaces of affected livers, but their functional role in hepatitis C progression has not been fully elucidated. METHODS: CD4+ and CD8+ TL were quantified by immunohistochemistry in portal and periportal spaces of 39 liver biopsies from patients with chronic hepatitis C. They were associated to demographic data, histological parameters, laboratory findings of patients and hepatitis C genotypes. RESULTS: There was high numbers of CD4+ and CD8+ TL from which the density of CD4+ T was higher than CD8+ TL in portal and periportal spaces. CD4+ and CD8+ TL were directly correlated to intensity of interface hepatitis. CD8+ TL correlated to serum enzyme levels. CONCLUSION: The high numbers of CD4+ and CD8+ TL in portal and periportal spaces and their correlation to interface hepatitis suggest that hepatitis C evolution depends on the action of intrahepatic T lymphocytes, lending support to the notion of an immune-mediated mechanism in the pathogenesis of chronic hepatitis C.
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B and T lymphocyte attenuator (BTLA) is a negative regulator of T cell activation, but its function in vivo is not well characterized. Here we show that mice deficient in full-length BTLA or its ligand, herpesvirus entry mediator, had increased number of memory CD8(+) T cells. The memory CD8(+) T cell phenotype resulted from a T cell-intrinsic perturbation of the CD8(+) T cell pool. Naive BTLA-deficient CD8(+) T cells were more efficient than wild-type cells at generating memory in a competitive antigen-specific system. This effect was independent of the initial expansion of the responding antigen-specific T cell population. In addition, BTLA negatively regulated antigen-independent homeostatic expansion of CD4(+) and CD8(+) T cells. These results emphasize two central functions of BTLA in limiting T cell activity in vivo.
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Like most somatic human cells, T lymphocytes have a limited replicative life span. This phenomenon, called senescence, presents a serious barrier to clinical applications that require large numbers of Ag-specific T cells such as adoptive transfer therapy. Ectopic expression of hTERT, the human catalytic subunit of the enzyme telomerase, permits fibroblasts and endothelial cells to avoid senescence and to become immortal. In an attempt to immortalize normal human CD8(+) T lymphocytes, we infected bulk cultures or clones of these cells with a retrovirus transducing an hTERT cDNA clone. More than 90% of transduced cells expressed the transgene, and the cell populations contained high levels of telomerase activity. Measuring the content of total telomere repeats in individual cells (by flowFISH) we found that ectopic hTERT expression reversed the gradual loss of telomeric DNA observed in control populations during long term culture. Telomere length in transduced cells reached the levels observed in freshly isolated normal CD8(+) lymphocytes. Nevertheless, all hTERT-transduced populations stopped to divide at the same time as nontransduced or vector-transduced control cells. When kept in IL-2 the arrested cells remained alive. Our results indicate that hTERT may be required but is not sufficient to immortalize human T lymphocytes.
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Human Ag-specific CD8(+) T lymphocytes are heterogeneous and include functionally distinct populations. In this study, we report that at least two distinct mechanisms control the expansion of circulating naive, memory, and effector CD8(+) T lymphocytes when exposed to mitogen or Ag stimulation. The first one leads to apoptosis and occurs shortly after in vitro stimulation. Susceptibility to cell death is prominent among primed T cell subsets, and it is inversely correlated with the size of the ex vivo Bcl-2(high) population within these subsets. Importantly, the Bcl-2(high) phenotype is associated to the proportion of responsive CD8(+) T cells, independently of their differentiation stage. The second one depends on the expression of newly synthesized cyclin-dependent kinase inhibitor p16(INK4a) that occurs in a significant fraction of T cells that had been actively cycling, leading to their cell cycle arrest upon stimulation. Strikingly, accumulation of p16(INK4a) protein preferentially occurs in naive as opposed to primed derived T lymphocytes and is not related to apoptosis. Significant levels of p16 are readily detectable in a small number of ex vivo CD8(+) T cells. Our observations reveal that activation-induced p16 expression represents an alternative process to apoptosis, limiting the proliferation potential of activated naive derived T lymphocytes.
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The use of synthetic combinatorial peptide libraries in positional scanning format (PS-SCL) has emerged recently as an alternative approach for the identification of peptides recognized by T lymphocytes. The choice of both the PS-SCL used for screening experiments and the method used for data analysis are crucial for implementing this approach. With this aim, we tested the recognition of different PS-SCL by a tyrosinase 368-376-specific CTL clone and analyzed the data obtained with a recently developed biometric data analysis based on a model of independent and additive contribution of individual amino acids to peptide antigen recognition. Mixtures defined with amino acids present at the corresponding positions in the native sequence were among the most active for all of the libraries. Somewhat surprisingly, a higher number of native amino acids were identifiable by using amidated COOH-terminal rather than free COOH-terminal PS-SCL. Also, our data clearly indicate that when using PS-SCL longer than optimal, frame shifts occur frequently and should be taken into account. Biometric analysis of the data obtained with the amidated COOH-terminal nonapeptide library allowed the identification of the native ligand as the sequence with the highest score in a public human protein database. However, the adequacy of the PS-SCL data for the identification for the peptide ligand varied depending on the PS-SCL used. Altogether these results provide insight into the potential of PS-SCL for the identification of CTL-defined tumor-derived antigenic sequences and may significantly implement our ability to interpret the results of these analyses.
