Les méthodes de vaccination actuelles contre l’influenza, axées sur la réponse à anticorps dirigée contre des antigènes hautement variables, nécessitent la production d’un vaccin pour chaque nouvelle souche. Le défi est maintenant de stimuler simultanément une réponse cellulaire pan-spécifique ciblant des antigènes conservés du virus, tel que la protéine de la matrice (M1) ou la nucléoprotéine (NP). Or, la présentation antigénique de ces protéines est peu définie chez l’humain. Nous avons analysé la présentation endogène par les complexes majeurs d’histocompatibilité de classes (CMH)-I et -II de M1 et de NP. Ainsi, les protéines M1 et NP ont été exprimées dans des cellules présentatrices d’antigènes (CPAs). Notamment, des épitopes de M1 et de NP endogènes peuvent être présentées par CMH-I et -II, ce qui résulte en une activation respectivement de lymphocytes T CD8+ et CD4+ précédemment isolés. Étant donné l’importance des lymphocytes T CD4+ dans la réponse cellulaire, nous avons cloné M1 ou NP en fusion avec des séquences de la protéine gp100 permettant la mobilisation vers les compartiments du CMH-II sans affecter la présentation par CMH-I. Des CPAs exprimant de façon endogène ces constructions modifiées ou sauvages ont ensuite été utilisées pour stimuler in vitro des lymphocytes T humains dont la qualité a été évaluée selon la production de cytokines et la présence de molécules de surface (ELISA ou marquage de cytokines intracellulaire). Nous avons observé une expansion de lymphocytes T CD8+ et CD4+ effecteurs spécifiques sécrétant diverses cytokines pro-inflammatoires (IFN-γ, TNF, MIP-1β) dans des proportions comparables avec une présentation par CMH-II basale ou améliorée. Cette qualité indépendante du niveau de présentation endogène par CMH-II de M1 et de NP des lymphocytes T CD4+ et CD8+ suggère que cette présentation est suffisante à court terme. En outre, la présentation endogène de M1 et NP a permis de stimuler des lymphocytes T spécifiques à des épitopes conservés du virus, tel qu’identifié à l’aide une méthode d’identification originale basée sur des segments d’ARNm, « mRNA PCR-based epitope chase (mPEC) ». Ensemble, ces nouvelles connaissances sur la présentation antigénique de M1 et de NP pourraient servir à établir de nouvelles stratégies vaccinales pan-spécifiques contre l’influenza. / New vaccines targeting hyper-variable influenza determinants must be prepared against every new strain. The challenge is now to develop influenza vaccines also eliciting a strong and sustained cytotoxic response against highly-conserved determinants such as the matrix (M1) and nuclear (NP) proteins. However, their antigenic presentation properties in humans are less defined. We, therefore, analyzed major histocompatibility complex class (MHC)-I and -II presentation of endogenously processed M1 and NP in human antigen presenting cells (APCs). To do so, we used APCs endogenously-expressing the M1 and NP proteins. M1 and NP epitopes can be presented by MHC-I and -II, which results in the activation of previously-isolated antigen-specific CD8+ and CD4+ T lymphocytes. Considering the importance of CD4+ T lymphocytes in the cellular immune response, we cloned M1 and NP proteins in fusion with gp100 MHC-II enhancing sequences, which do not disrupt MHC-I presentation. APCs expressing MHC-II-enhanced or wild type constructs were used to stimulate human T lymphocytes in vitro and quality of antigen presentation was evaluated on the basis of cytokine production and cell surface molecule expression (ELISA or intracellular cytokine staining). We expanded antigen-specific effector CD8+ and CD4+ T lymphocytes which secreted pro-inflammatory cytokines (IFN-γ, TNF and MIP-1β) to similar extents both with and without MHC-II enhancement. The quality of CD4+ and CD8+ T lymphocytes generated independent of the level of M1 and NP endogenous MHCII presentation suggests that this presentation is sufficient for short-term T lymphocyte stimulation. Thus, endogenous expression of M1 and NP have stimulated T lymphocytes specific to conserved influenza epitopes, as determined by an original identification technique based on mRNA segments called mRNA PCR-based epitope chase (mPEC). Overall, these new insights about T lymphocytes expanded following MHC-I and -II presentation of endogenous M1 and NP could prove useful for new complementary heterosubtypic vaccination strategies.

La sclérose en plaques (SEP) est une maladie inflammatoire du système nerveux central (SNC) caractérisée par une infiltration périvasculaire de cellules mononucléaires, telles que les lymphocytes T CD4+ et CD8+, les lymphocytes B ainsi que les cellules myéloïdes qui comprend les monocytes, les macrophages et les cellules dendritiques (DCs). Ce phénomène d’infiltration est dû à une fragilisation de la barrière hémato-encéphalique (BHE). L’entrée des cellules immunitaires au SNC va mener à la destruction de la gaine de myéline et donc à l’apparition de plaques de démyélinisation. Ainsi, nous avons émis l’hypothèse que la migration des divers sous-types de cellules immunitaires du sang périphérique à travers la BHE est contrôlée par des mécanismes moléculaires distincts et spécifiques à chaque type cellulaire. Afin de répondre à cette hypothèse, quatre différentes études ont été mises sur pieds. En premier lieu, nous démontrons un effet bénéfique des statines sur la BHE en SEP, en diminuant la migration des lymphocytes T et des monocytes, et en diminuant la diffusion de marqueurs moléculaire soluble. Ce phénomène s’opère via la suppression du processus d’isoprenylation, et en empêchant probablement la contraction des cellules endothéliales de la BHE. De plus, nous démontrons que les monocytes qui migrent au SNC en condition inflammé sont en mesures de se différencier en DCs et d’induire une réponse inflammatoire de la part des lymphocytes T CD4+. La migration des monocytes à travers la BHE est contrôlée par une nouvelle molécule d’adhérence nommée Ninjurin-1. Le blocage de Ninjurin-1 conduit à une inhibition spécifique de la migration des monocytes in vitro, ainsi qu’à une amélioration des signes cliniques du modèle animal de la SEP, soit l’encéphalomyélite auto-immune expérimentale (EAE). Finalement, nous démontrons que la migration des lymphocytes T CD8+ au SNC s’effectue via l’intégrine alpha-4. De plus, la majorité des lymphocytes T CD8+ que l’on retrouve dans le liquide céphalo-rachidien de patients SEP, dans le SNC de souris EAE ainsi que dans le SNC de souris infectée au virus de l’hépatite murine portent un phénotype effecteur mémoire. Ces données pourraient expliquer l’émergence de leucoencéphalopathie multifocale progressive observée chez certains patients SEP traités au natalizumab, un anticorps dirigé contre l’intégrine alpha-4. En conclusion, notre étude a permis de démontrer l’importance des monocytes provenant de la périphérie dans le processus inflammatoire prenant part au SNC en SEP. L’inhibition d’entrée de ces cellules pourrait s’avérer bénéfique en SEP tout en permettant l’immuno-surveillance du cerveau, ce que l’anti-alpha-4 intégrine ne permet pas. Les statines pourraient s’avérer une autre option intéressante puisqu’elles agissent sur les processus inflammatoires impliqués dans la SEP. / Multiple sclerosis (MS) is an immune-mediated disorder of the central nervous system (CNS) characterized by multifocal areas of leukocyte infiltration and demyelination associated with a breakdown of the blood-brain barrier (BBB). Typically, demyelination is centered around perivascular accumulation of CD4+ and CD8+ T lymphocytes, monocytes, macrophages and dendritic cells (DCs) that arise from migration of peripheral blood immune cells across the CNS microvascular endothelium. We have thus suggested that the migration across the BBB of immune cells subsets from the blood is controlled by molecular mechanism specific for each cell type. To answer this hypothesize, we have performed four different studies. We first show a beneficial effect of statins on the BBB, restricting the migration of lymphocytes and monocytes as well as the diffusion of soluble molecular tracers. This phenomenon is mediated through abrogation of isoprenylation processes that is probably inhibiting the ability of endothelial cells of the BBB to contract. We also show that CD14+ monocytes migrate across the inflamed human blood BBB and differentiate into DCs in response to BBB-secreted TGF-beta and GM-CSF. These DCs then promote the proliferation and expansion of inflammatory CD4+ T lymphocytes. We demonstrate that the migration of monocytes is controlled by a new adhesion molecule called Ninjurin-1. Ninjurin-1 neutralization specifically abrogated the adhesion and migration of human monocytes across endothelial cells of the BBB, without affecting lymphocyte recruitment. Moreover, Ninjurin-1 blockade reduced clinical disease activity and histopathological indices of experimental allergic encephalomyelitis (EAE). Finally we show that migration of CD8+ T lymphocytes across BBB is dependent on alpha-4 integrin. Also, the majority of CD8+ T lymphocytes found in the cerebrospinal fluid of MS patients, and in the CNS of EAE mice as well as the CNS of mouse infected with hepatitis virus are showing an effector memory phenotype. These data could explain the numerous cases of progressive multifocal leukoencephalopathy seen in natalizumab treated MS patients. In conclusion, our study unveils an important role of peripheral monocytes in MS. The inhibition of migration of these cells to the CNS could be a beneficial therapy since it would allow immune surveillance of the brain. The statins could also be a very interesting option since these molecules would reduce the inflammatory processes involved in MS.

Introduction: L’activation des cellules stellaires hépatiques (CSHs) est un point clé du processus de fibrose hépatique. Les lymphocytes T CD4+ intra-hépatiques sont une source majeure de cytokines anti-inflammatoires comme l’IL-10 et pro-inflammatoire (IL-17A), hépatoprotectrice (IL-22) produites par les Th17. Les Th17 sont impliqués dans de nombreuses pathologies inflammatoires mais l’effet de ces cellules sur les CSHs n’est pas encore élucidé. Objectif: Comprendre le rôle des cytokines de type Th17 dans le processus d’activation des CSHs. Méthodes: La lignée de CSHs humaine LX2 a été stimulée par l’IL-17A ou l’IL-22 puis comparée à des cellules traitées par le TGF-b et le tampon phosphate salin (PBS). L’activation des CSHs a été évaluée en examinant les molécules profibrotique alpha-smooth muscle actin (a-SMA), collagène de type I (COL1A1) et inhibiteur produits par les tissus des métalloprotéases matricielles I (TIMP-I) par q-PCR. L’expression protéique a été validée par immunobuvardage ou coloration au rouge de picro Sirius. L’expression membranaire de l’IL-10Rb, du TGF-b-RII et de l’IL-17RA a été mesurée par cytométrie en flux. Résultats: L’IL-17A et l’IL-22 n’activent pas les cellules LX2, car aucune induction d’a-SMA, de COL1A1 et de TIMP-I n’a été observée. Cependant, l’IL-17A et l’IL-22 sensibilisent les CSHs à l’action du TGF-b, tel que démontré par une forte expression et production d’a-SMA, collagène type I et TIMP-I. L’IL-17A, mais pas l’IL-22, induit la surexpression à la surface cellulaire du TGF-b-RII et inhibe partiellement la baisse d’expression du TGF--RII après stimulation au TGF-b. Conclusion: Nos résultats démontrent une fonction pro-fibrotique de l’IL-17A et de l’IL-22, car les deux cytokines sensibilisent les CSHs à l’action du TGF-b. L’IL-17A agit via la surexpression et la stabilisation du TGF-b-RII tandis que l’IL-22 agit probablement par des mécanismes intracellulaires. / Background: Activated hepatic stellate cells (HSCs) are key initiators of the fibrogenic process. Intrahepatic CD4+ T cells are major producers of hepatoprotective cytokines such as IL-10 produced by regulatory T cells (Tregs) or inflammatory and regulatory cytokines like IL-17 and IL-22 produced by Th17 cells. Th17 cells have been implicated in various conditions or liver damage but the mechanism of action of Th17 cytokines on HSC is still poorly understood. Aims: To understand the role of the different Th17 cytokines (IL17-A and IL-22) in modulating HSC activation. Methods: The HSC line LX2 was stimulated with increasing doses of IL-17A or IL-22, and compared to TGF-b and PBS-treated cells. Activation of HSCs was evaluated by examining the expression of the pro-fibrotic molecules alpha-smooth muscle actin (a-SMA), collagen type I (COL1A1) and tissue inhibitor of matrix metalloproteinase I (TIMP-I) by q-PCR. Protein expression was validated by either western blot or picro Sirius red stain. Cell surface expression of the cytokine receptors IL-10Rb, TGF-b-RII and IL-17RA was evaluated by flow cytometry. Results: IL-17A and IL-22 alone did not induce LX2 activation, as no induction of a-SMA, COL1A1 and TIMP-I was observed. However, both IL-17A and IL-22 sensitized HSCs to the action of suboptimal doses of TGF-b, confirmed by strong a-SMA, collagen type I and TIMP-I gene expression and protein production. IL-17A but not IL-22 upregulated TGF-b-RII cell surface expression and partially inhibited TGF-b-RII downmodulation upon TGF-b stimulation. Conclusion: Our results demonstrated a pro-fibrotic function for IL-17A and IL-22, as both cytokines sensitize HSC to the action of TGF-b. IL-17A acts through upregulation and stabilization of the TGF-b-RII while IL-22 probably acts through an intracellular mechanism.

Thesis (Ph. D.)--Uniformed Services University of the Health Sciences, 2005. / Typescript (photocopy).

Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 182-199.

Cytotoxic T-lymphocytes (CTLs) are important components of the adaptive immune system and function by scanning the intracellular environment so as to detect and de-stroy infected cells. CTL responses play a major role in controlling virus-infected cells such as in HIV or influenza and cells infected with intracellular bacteria such as in tuberculosis. To do so they require the antigens to be presented to them, which is fulfilled by the major histocompatibility complex (MHC), commonly known as human leukocyte antigen or HLA molecules in humans. Recognition of antigenic peptides to Class-1 HLA molecules is a prerequisite for triggering CTL immune responses. Individuals differ significantly in their ability to respond to an infection. Among the factors that govern the outcome of an infection, HLA polymorphism in the host is one of the most important. Despite a large body of work on HLA molecules, much remains to be understood about the relationship between HLA diversity and disease susceptibility. High complexity arises due to HLA allele polymorphism, extensive antigen cross-presentability, and host-pathogen heterogeneity. A given allele can recognize a number of different peptides from various pathogens and a given peptide can also bind to a number of different individuals. Thus, given the plurality in peptide-allele pairs and the large number of alleles, understanding the differences in recognition profiles and the implications that follow for disease susceptibilities require mathematical modelling and computational analysis. The main objectives of the thesis were to understand heterogeneity in antigen presentation by HLA molecules at different scales and how that heterogeneity translates to variations in disease susceptibilities and finally the disease dynamics in different populations. Towards this goal, first the variations in HLA alleles need to be characterized systematically and their recognition properties understood. A structure-based classification of all known HLA class-1 alleles was therefore attempted. In the process, it was also of interest to see if understanding of sub-structures at the binding grooves of HLA molecules could help in high confidence prediction of epitopes for different alleles. Next, the goal was to understand how HLA heterogeneity affect disease susceptibilities and disease spread in populations. This was studied at two different levels. Firstly, modelling the HLA genotypes and CTL responses in different populations and assessing how they recognized epitopes from a given virus. The second approach involved modelling the disease dynamics given the predicted susceptibilities in different populations. Influenza H1N1 infection was used as a case study. The specific objectives addressed are: (a) To develop a classification scheme for all known HLA class-1 alleles that can explain epitope recognition profiles and further to dissect the physic-chemical features responsible for differences in peptide specificities, (b) A statistical model has been derived from a large dataset of HLA-peptide complexes. The derived model was used to identify the interdependencies of residues at different peptide and thereby, rationalize the HLA class-I allele binding specificity at a greater detail, (c) To understand the effect of HLA heterogeneity on CTL mediated disease response. A model of HLA genotypes for different populations was required for this, which was constructed and used for estimating disease response to H1N1 via the prediction of epi-topes and (d) To model disease dynamics in different populations with the knowledge of the CTL response-grouping and to evaluate the effect of heterogeneity on different vaccination strategies. Each of the four objectives listed above are described subsequently in chapters 2 to 5, followed by Chapter 6 which summarises the findings from the thesis and presents future directions. Chapter 1 presents an introduction to the importance of the function of HLA molecules, describes structural bioinformatics as a discipline and the methods that are available for it. The chapter also describes different mathematical modelling strategies available to study host immune responses. Chapter 2 describes a novel method for structure-based hierarchical classification of HLA alleles. Presently, more than 2000 HLA class-I alleles are reported, and they vary only across peptide-binding grooves. The polymorphism they exhibit, enables them to bind to a wide range of peptide antigens from diverse sources. HLA molecules and peptides present a complex molecular recognition pattern due to multiplicity in their associations. Thus, a powerful grouping scheme that not only provides an insightful classification, but is also capable of dissecting the physicochemical basis of recognition specificity is necessary to address this complexity. The study reports a hierarchical classification of 2010 class-I alleles by using a systematic divisive clustering method. All-pair distances of alleles were obtained by comparing binding pockets in the structural models. By varying the similarity thresholds, a multilevel classification with 7 supergroups was derived, each further categorized to yield a total of 72 groups. An independent clustering scheme based only on the similarities in their epitope pools correlated highly with pocket-based clustering. Physicochemical feature combinations that best explains the basis for the observed clustering are identified. Mutual information calculated for the set of peptide ligands enables identification of binding site residues that contribute to peptide specificity. The grouping of HLA molecules achieved here will be useful for rational vaccine design, understanding disease susceptibilities and predicting risk of organ transplants. The results are presented in an interactive web- server http://proline.iisc.ernet.in/hlaclassify. In Chapter 3, the knowledge of structural features responsible for generating peptide recognition specificities are first analysed and then utilized for predicting T-cell epi-topes for any class-1 HLA allele. Since identification of epitopes is critical and central to many of the questions in immunology, a study of several HLA-peptide complexes is carried out at the structural level and factors are identified that discriminate good binder peptides from those that do not. T-cell epitopes serve as molecular keys to initiate adaptive immune responses. Identification of T-cell epitopes is also a key step in rational vaccine design. Most available methods are driven by informatics, critically dependent on experimentally obtained training data. Analysis of the training set from IEDB for several alleles indicate that sampling of the peptide space is extremely sparse covering only a tiny fraction of all possible nonamer space, and also heavily skewed, thus restricting the range of epitope prediction. A new epitope prediction method is therefore developed. The method has four distinct modules, (a) structural modelling, estimating statistical pair-potentials and constraint derivation, (b) implicit modelling and interaction profiling, (c) binding affinity prediction through feature representation and (d) use of graphical models to extract peptide sequence signatures to predict epitopes for HLA class I alleles . HLaffy is a novel and efficient epitope prediction method that predicts epitopes for any HLA Class-1 allele, by estimating binding strengths of peptide-HLA complexes which is achieved through learning pair-potentials important for peptide binding. It stands on the strength of mechanistic understanding of HLA-peptide recognition and provides an estimate of the total ligand space for each allele. The method is made accessible through a webserver http://proline.biochem.iisc.ernet.in/HLaffy. In chapter 4, the effect of genetic heterogeneity on disease susceptibilities are investigated. Individuals differ significantly in their ability to respond to an infection. Among the factors that govern the outcome of an infection, HLA polymorphism in the host is one of the most important. Despite a large body of work on HLA molecules, much remains to be understood about how host HLA diversity affects disease susceptibilities. High complexity due to polymorphism, extensive cross-presentability among HLA alleles, host and pathogen heterogeneity, demands for an investigation through computational approaches. Host heterogeneity in a population is modelled through a molecular systems approach starting with mining ‘big data’ from literature. The in-sights derived through this is used to investigate the effect of heterogeneity in a population in terms of the impact it makes on recognizing a pathogen. A case study of influenza virus H1N1 infection is presented. For this, a comprehensive CTL immunome is defined by taking a consensus prediction by three distinct methods. Next, HLA genotypes are constructed for different populations using a probabilistic method. Epidemic incidences in general are observed to correlate with poor CTL response in populations. From this study, it is seen that large populations can be classified into a small number of groups called response-types, specific to a given viral strain. Individuals of a response type are expected to exhibit similar CTL responses. Extent of CTL responses varies significantly across different populations and increases with increase in genetic heterogeneity. Overall, the study presents a conceptual advance towards understanding how genetic heterogeneity influences disease susceptibility in individuals and in populations. Lists of top-ranking epitopes and proteins are also derived, ranked on the basis of conservation, antigenic cross-reactivity and population coverage, which pro- vide ready short-lists for rational vaccine design (flutope). Next, in Chapter 5, the effect of genetic heterogeneity on disease dynamics has been investigated. A mathematical framework has been developed to incorporate the heterogeneity information in the form of response-types described in the previous chap-ter. The spread of a disease in a population is a complex process, controlled by various factors, ranging from molecular level recognition events to socio-economic causes. The ‘response-typing’ described in the previous chapter allows identification of distinct groups of individuals, each with a different extent of susceptibility to a given strain of the virus. 3 different approaches are used for modelling: (i) an SIR model where different response types are considered as partitions of each S, I and R compartment. Initially SIR models are developed, such that the S compartment is sub-divided into further groups based on the ‘response-types’ obtained in the previous chapter. This analysis shows an effect in infection sweep time, i.e., how long the infection stays in the population. A stochastic model incorporates the environmental noise due to random variation in population influx, due to birth, death or migration. The system is observed to show higher stability in the presence of genetic heterogeneity. As the contagion spreads only through direct host to host contact. The topology of the contact network, plays major role in deciding the extent of disease dynamics. An agent based computational framework has been developed for modelling disease spread by considering spatial distribution of the agents, their movement patterns and resulting contact probabilities. The agent-based model (ABM) incorporates the temporal patterns of contacts. The ABM is based on a city block model and captures movement of individuals parametrically. A new concept of system ‘characteristic time’ has been introduced in context of a time-evolving network. ‘Characteristic time’ is the minimum time required to ensure, every individual is connected to all other individuals, in the time aggregated contact network. For any given temporal system, disease time must exceed ‘characteristic time’ in order to spread throughout the population. Shorter ‘characteristic time’ of the system is suggestive of faster spread of the disease. A disease spread network is constructed which shows how the disease spreads from one infected individual to others in the city, given the contact rules and their relative susceptibilities to that viral strain. A high degree of population heterogeneity is seen to results in longer disease residence time. Susceptible individuals preferentially get infected first thereby exposing more susceptible individuals to the disease. Vaccination strategies are derived from the model, which indicates that vaccinating only 20% of the agents, who are hub nodes or highly central nodes and who also have a high degree to susceptible agents, lead to high levels of herd immunity and can confer protection to the rest of the population. Overall, the thesis has provided biologically meaningful classification of all known HLA class-1 alleles and has unravelled the physico-chemical basis for their peptide recognition specificities. The thesis also presents a new algorithm for estimating pep-tide binding affinities and consequently predicting epitopes for all alleles. Finally the thesis presents a conceptual advance in relating HLA diversity to disease susceptibilities and explains how different populations can respond differently to a given infection. A case study with the influenza H1N1 virus identified populations who are most susceptible and those who are least susceptible, in the process identifying important epitopes and responder alleles, providing important pointers for vaccine design. The influence of heterogeneity and response-typing on disease dynamics is also presented for influenza H1N1 infection, which has led to the rational identification of effective vaccination strategies. The methods and concepts developed here are fairly generic and can be adapted easily for studying other infectious diseases as well. Three new web-resources, a) HLAclassify, b) HLaffy and c) Flutope have been developed, which host pre-computed results as well as allow interactive querying to an user to perform analysis with a specific allele, peptide or a pathogenic genome sequence.

No description available.

The prevalence of diabetes is approaching epidemic proportions worldwide. There is currently no cure for type 1 diabetes, and successful treatment requires constant monitoring of blood sugars and use of exogenous insulin to prevent hyperglycemia. Diabetes will be curable when pancreatic β-islet cells can be transplanted into diabetes patients without requiring long-term immunosuppression. This will require learning more about the induction of functional tolerance, a state that maintains the competence of the immune system to most antigens but protects graft-specific antigens from immune rejection, permitting transplantation. One known mechanism of peripheral tolerance is T cell anergy, a phenotype of hypo-reponsiveness in CD4+ T cells. The focus of this thesis is a description of factors shown to be specific to the induction and maintenance of T cell anergy, whose loss reverses the anergic phenotype, restoring the ability of the cells to proliferate in response to antigen. The first of these is Egr-2, a zinc-finger transcription factor, whose presence is required for the induction of anergy induced in T cell clones by TCR stimulation in the absence of costimulation. Egr-2 is shown to be important to anergy induction but not anergy maintenance. In contrast, a negative costimulation receptor, PD-1, is shown to be necessary for the maintenance of anergy. It is possible that learning more about the genetic factors that orchestrate T cell anergy will prove useful in the development of tolerance-based protocols for organ and tissue transplantation without the use of long-term immunosuppression.

No description available.

O transplante de células-tronco hematopoiéticas tem sido a melhor opção terapêutica para muitas doenças. Seu sucesso, no entanto, depende de alguns fatores que influenciam a taxa de mortalidade. A doença do enxerto-contra-hospedeiro é uma causa de mortalidade. Apresenta duas formas, a aguda e a crônica, e ambas têm linfócitos T na patofisiologia. Outra causa são as infecções, cujos patógenos variam conforme o tempo de recuperação do sistema imune. O presente estudo avaliou a recuperação linfoide T com base no timo e distinção das subpopulações e citocinas nos pacientes que desenvolveram doença do enxerto-contra-hospedeiro crônica no primeiro ano de transplante. Os pacientes foram alocados no Hospital de Transplante Amaral Carvalho (Jaú/SP) e tinham entre 18 e 60 anos de idade. No pré-transplante, foram comparados com indivíduos saudáveis, pareados em idade. Após o transplante, todos os pacientes foram acompanhados por um ano e seis meses, para observação de possíveis eventos de doença do enxerto-contra-hospedeiro e/ou infecções. A análise laboratorial foi feita com o sangue do paciente, sendo a primeira antes do transplante, seguidas por mais quatro, com intervalos de três meses. Tais avaliações laboratoriais tinham por objetivos caracterizar a função tímica por quantificação de sjTREC; as subpopulações de linfócitos T, por citometria de fluxo e a análise de citocinas, por Luminex. Foram estudados 172 indivíduos, sendo 75 do transplante alogênico, 43 do transplante autólogo, além de 54 pessoas saudáveis. Nossos resultados mostraram que os pacientes apresentaram função tímica diminuída antes mesmo da realização do transplante. A função tímica enfraquecida foi um fator de risco para doença do enxerto-contrahospedeiro crônica e a recuperação do sistema imune foi melhor nos pacientes que não apresentaram doença do enxerto-contra-hospedeiro crônica após um ano do transplante. No entanto, a função tímica não foi diferente entre os pacientes que faleceram e os que estão vivos. No geral, não houve distinção quanto à apresentação das subpopulações de linfócitos T e à produção de citocinas entre os pacientes submetidos ao transplante alogênico que desenvolveram doença do enxerto-contra-hospedeiro crônica, relativamente aos demais pacientes. Com o tempo, foi observada a recuperação gradual do compartimento linfoide T e diminuição na incidência de infecções. A taxa de infecções não influenciou a apresentação das subpopulações de linfócitos T e a produção de citocinas nos pacientes que desenvolveram doença do enxerto-contrahospedeiro crônica em relação aos demais pacientes. Como conclusão, a função tímica apresentou-se deteriorada antes da realização do transplante, porém não foi determinante para que houvesse piora na evolução clínica após o transplante. Os pacientes que desenvolveram doença do enxerto-contra-hospedeiro crônica, independentemente da incidência de infecções, apresentaram semelhança no perfil das subpopulações de linfócitos T e das citocinas, quando comparados aos demais / Hematopoietic stem cell transplantation has been the best therapeutic option for many diseases. Its success depends on some factors that influence the mortality rate. Graftversus- host disease is one cause of mortality. It has two forms, acute and chronic, and both have T lymphocytes in their pathophysiology. Other causes are infections, whose pathogens vary according to immune system recovery time. The present study evaluated the lymphoid T recuperation through the thymus and the differentiation of subpopulations and cytokines in patients who developed chronic graft-versus-host disease at the first year of transplantation. The patients were allocated at Hospital de Transplantes Amaral Carvalho (Jaú/SP). They were between 18 and 60 years old. At pre-transplant phase, patients were compared to healthy individuals, age-matched. After transplantation, they were all assisted for one year and six months, so that graft-versushost disease\'s and infections\' events could be observed. The laboratory analysis was done by blood sample; the first occurred before the transplant, followed by four more, every three months. Laboratory examinations were performed to characterize thymic function by quantification of sjTREC; T lymphocyte subpopulations, by flow cytometry, and cytokine analysis, by Luminex. A total of 172 individuals were studied: 75 allogeneic transplant patients, 43 autologous transplant patients and 54 healthy persons. Our results showed that patients presented thymic function impaired even before the transplant. The weakening of the thymic function was a risk factor for chronic graft-versus-host disease and immune system recovery was better in patients who did not develop chronic graft-versus-host disease after one year of transplantation. However, the thymic function was not different between patients who died and those who remained alive. In general, there was no distinction of the presentation of T lymphocyte subpopulations and cytokines production among patients who underwent allogeneic transplant and developed chronic graft-versus-host disease, in comparison to the other patients. Over time, a gradual recovery of the T lymphoid compartment and a decrease in the infections incidence were observed. The infection rate did not influence the presentation of the T lymphocyte subpopulations and the production of cytokines in patients who developed chronic graft-versus-host disease in comparison to the other patients. In conclusion, the thymic function was impaired before transplantation, but it was not relevant for clinical evolution worsening after transplantation. Patients who developed chronic graft-versus-host disease, regardless of the incidence of infections, showed similar profile of T lymphocytes subpopulations and cytokines, relatively to other patients