As células dendríticas (DCs) são as principais células apresentadoras de antígeno do sistema imune, e há evidências da participação na tolerância imunológica. Neste estudo avaliamos as alterações ocorridas na população de células CD4+CD25+Foxp3+ após co-cultura de células de linfonodo com BMDCs, na presença de timócitos alogênicos ou singênicos em apoptose. Após cultura na presença de células alogênicas a população de Tregs mostra-se aumentada, e essa expansão é dependente de contato entre a DC e o linfócito T, já que o isolamento das culturas diminuiu a expressão destes marcadores. A internalização de células em apoptose foi induziu caráter tolerogênico nas DCs com baixa expressão de moléculas co-estimuladoras e resistência à maturação por LPS. As células CD4+CD25+ geradas in vitro foram capazes de conter a proliferação de esplenócitos de camundongos BALB/c estimulados por esplenócitos de C57BL/6 irradiados, anti-CD3 e OVA. No ensaio in vivo, as Tregs geradas in vitro também foram capazes de suprimir a proliferação de células CD25- quando transferidas para animais Nude, impedindo também o infiltrado inflamatório no estômago, cólon, fígado e rins, sendo assim capazes de suprimir a resposta imune in vitro e in vivo. / The dendritic cell (DC) plays a very important role in antigen presentation in the immune system and recent articles have shown the involvement in maintaining peripheral tolerance. Here we evaluated the changes in the CD4+CD25+Foxp3+ after co culture of DCs with lymph node cells. BMDCs were pulsed with apoptotic cells and co-cultured with lymph-node cells. Our results show an increase of CD4+CD25+Foxp3+ T cells after co-culture with DCs pulsed with apoptotic cells. Furthermore, the DCs did not change the pattern of co-stimulatory molecules expression due to phagocytosis of syngeneic or allogeneic apoptotic cells and further stimulation with LPS. The CD4+CD25+ cells sorted from the in vitro culture were able to suppress the proliferation of splenocytes in vitro in a specific and non-specific manner. As expected, the co-transfer of CD4+CD25- and CD4+CD25+, both sorted from the in vitro culture, was able to control the cell infiltrates in the target organs and the total cell count in the lymph-nodes. Thus, the Tregs expanded in vitro are able to suppress the immune response in vitro and in vivo assays.

O veneno da subespécie de cascavel Crotalus durissus terrificus (C.d.terrificus) altera a coagulação, tem ação neurotóxica, miotóxica e efeito imunossupressivo. O veneno de C.d.terrificus e a sua fração majoritária, crotoxina (CTX), inibem a resposta celular e humoral, sendo esse efeito independente da indução de morte celular. O objetivo foi investigar os mecanismos envolvidos na imunossupressão exercida pela CTX. A CTX induz a produção de IL-10, TGF-<font face=\"Symbol\">&#946 e prostaglandina E2 (PGE2) pelas células dos camundongos que a receberam. Menor secreção de IFN-<font face=\"Symbol\">&#947 e IL-12 foi observada nas culturas de células de camundongos imunizados e que receberam CTX. A CTX aumenta a expressão da enzima indoleamina 2,3 dioxigenase e a geração de células T reguladoras em camundongos imunizados com OVA e que receberam CTX. A CTX foi capaz de inibir a expressão de CD40, CD80, CD86 e de MHC de classe II em células de camundongos imunizados e nas células dendríticas (DCs) purificadas destes animais. Em culturas de DCs, a CTX induz alta secreção de IL-10, TGF-<font face=\"Symbol\">&#946 e PGE2 e menor de IL-12. / The venom of the rattlesnake Crotalus durissus terrificus (C.d.terrificus) changes the coagulation system and presents neurotoxic, myotoxic and immunosuppressive effect. The venom and its main fraction, crotoxin (CTX) inhibited both the cellular and humoral response. This effect is not due to induction of cell death. The objective was to investigate the immunosuppressive mechanisms of CTX. CTX induces production of IL-10, TGF-<font face=\"Symbol\">&#946 and prostaglandin E2 (PGE2) by cells of mice that received it. Lower secretion of IFN-<font face=\"Symbol\">&#947 and IL-12 was observed in the cultured cells from mice immunized that received CTX. CTX promotes increased expression of the enzyme indoleamine 2,3 dioxygenase and generation of regulatory T cells in mice immunized with OVA and receiving the toxin. CTX was able to inhibit the expression of CD40, CD80, CD86 and MHC II in mice immunized and in dendritic cells (DCs) purified from these animals. In cultures of DCs, CTX increased secretion of IL-10, TGF-<font face=\"Symbol\">&#946 and PGE 2 and lower IL-12.

A identificação e caracterização das células reguladoras (Treg) trouxeram uma nova perspectiva para a indução da tolerância imunológica nos transplantes e um aumento na sobrevida dos enxertos. Uma vez que as células-tronco mesenquimais derivadas de tecido adiposo (ADSC) possuem a capacidade de suprimir uma resposta imune, nos questionamos se as ADSC poderiam melhorar a sobrevida de um enxerto em camundongos C57BL/6, associada à indução de Treg. Nossos resultados mostram que o tratamento com as ADSC aumentou a média de sobrevida do enxerto, com uma melhora na morfologia do tecido transplantado, um aumento na população de linfócitos Treg e na expressão de IFN-g e IL-10, alem de uma inibição da expressão de IL-17 e na proliferação de células T CD4+. Nossos achados sugerem que as ADSC suprimem a resposta imune ao enxerto por meio da indução de Treg, a qual inibe a participação das células Th17, com uma melhora no enxerto. Estes dados ajudam a desenvolver novos aspectos na estratégia terapêutica e possivelmente o uso futuro dessas células na prática clínica. / The identification and characterization de regulatory T cells that can control immune responsiveness to alloantigens opened up opportunities for new therapies in transplantation. After exposure to alloantigens in vivo, antigen-specific immunoregulatory activity is enriched in a population of CD4+ T cells that express high levels of CD25 and Foxp3. Adipose tissue contains one type of mesenchymal stem cells (ADSC) with capacity of suppressing immune response. In this work we propose the correlation of the ADSC cells in ameliorating skin graft survival, and if is associated with Foxp3 expression. Graft survival was enhanced in animals that received ASCs from the donor. Interesting, in the animals treated with ASCs from CBA presented a higher expression of Foxp3+ cells in the lymph-nodes. In treated mice Foxp3 expression was increased and IL-17 were increased in allogeneic group, suggesting a potent inflammatory response inside the graft. So far, these data suggest the ADSCs increase TReg population cells, inhibit IL-17 expression and prolonging skin graft survival.

Law Wai Keung. / Thesis (M.Sc.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 98-108). / Abstracts in English and Chinese. / Abstract --- p.v / 摘要 --- p.viii / Acknowledgement --- p.x / List of Abbreviations --- p.i / Index of tables --- p.xiv / Index of figures --- p.xv / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Literature review --- p.3 / Chapter 2.1 --- Immunosuppression in Organ Transplantation --- p.3 / Chapter 2.2 --- Mechanism of Graft Rejection --- p.4 / Chapter 2.3 --- Conventional immunosuppressive drugs --- p.4 / Chapter 2.3.1 --- Corticosteriod --- p.6 / Chapter 2.3.2 --- Azathioprine --- p.6 / Chapter 2.3.3 --- Polyclonal antilymphocyte globulin and OKT3 --- p.7 / Chapter 2.4 --- Cyclosporine A (CsA) --- p.8 / Chapter 2.4.1 --- Mechanisms of CsA --- p.8 / Chapter 2.4.2 --- Pharmacokinetics of CsA --- p.10 / Chapter 2.4.2.1 --- Absorption --- p.10 / Chapter 2.4.2.2 --- Distribution --- p.11 / Chapter 2.4.2.3 --- Metabolism and elimination --- p.11 / Chapter 2.4.2.4 --- Toxicity --- p.12 / Chapter 2.4.3 --- Therapeutic drug monitoring of CsA --- p.13 / Chapter 2.4.3.1 --- CsA trough monitoring --- p.13 / Chapter 2.4.3.2 --- Full AUC monitoring --- p.15 / Chapter 2.4.3.3 --- Limited sampling strategy --- p.16 / Chapter 2.4.3.4 --- Two-hour post dose CsA level monitoring --- p.20 / Chapter 2.4.4 --- Conventional techniques of measuring cyclosporine concentration --- p.23 / Chapter 2.4.4.1 --- High performance liquid chromatography --- p.23 / Chapter 2.4.4.2 --- Non-specific immunoassays --- p.25 / Chapter 2.4.4.3 --- Specific radioimmunoassays --- p.26 / Chapter 2.4.4.4 --- Specific fluorescent polarization immunoassay --- p.26 / Chapter 2.4.4.5 --- Enzyme multiplied immunoassay technique --- p.28 / Chapter 2.4.4.6 --- Cloned enzyme donor immunoassay --- p.29 / Chapter 2.4.4.7 --- Summary for conventional techniques --- p.29 / Chapter 2.5 --- Liquid chromatography mass spectrometry for CsA measurement --- p.30 / Chapter 2.5.1 --- Main components of MS --- p.31 / Chapter 2.5.1.1 --- Specific interfaces to LC --- p.31 / Chapter 2.5.1.2 --- Mass analyzer --- p.33 / Chapter 2.5.1.3 --- Electron multiplier --- p.36 / Chapter 2.5.2 --- Sample preparation for LC-MS/MS for CsA measurement --- p.36 / Chapter 2.5.2.1 --- Liquid-liquid extraction --- p.37 / Chapter 2.5.2.2 --- Solid phase extraction --- p.38 / Chapter 2.5.2.3 --- Column switching --- p.39 / Chapter 2.5.2.4 --- Dilute and shoot --- p.40 / Chapter 2.5.3 --- LC-MS/MS for CsA measurement --- p.40 / Chapter 2.6 --- Summary --- p.42 / Chapter 3. --- Aim of study --- p.43 / Chapter 4. --- Materials and methods --- p.44 / Chapter 4.1 --- Materials --- p.44 / Chapter 4.1.1 --- Chemicals --- p.44 / Chapter 4.1.2 --- Equipment --- p.44 / Chapter 4.1.3 --- Reagent preparation for CsA analysis --- p.45 / Chapter 4.2 --- Methods --- p.48 / Chapter 4.2.1 --- Immunoassay --- p.48 / Chapter 4.2.2 --- Operation of tandem mass spectrometer --- p.48 / Chapter 4.2.2.1 --- Optimization of cone voltage --- p.50 / Chapter 4.2.2.2 --- Optimization of collision energy --- p.50 / Chapter 4.2.3 --- Optimization of LC-MS/MS --- p.51 / Chapter 4.2.3.1 --- Deproteinization procedures of whole blood --- p.52 / Chapter 4.2.3.2 --- Optimization of mobile phase flow rate --- p.52 / Chapter 4.2.3.3 --- Optimization of source temperature --- p.53 / Chapter 4.2.3.4 --- Optimization of the drying gas flow rate --- p.53 / Chapter 4.2.4 --- Matrix interference on MS/MS response --- p.53 / Chapter 4.2.5 --- Analytical performance of CsA on LC-MS/MS --- p.54 / Chapter 4.2.5.1 --- Linearity study --- p.54 / Chapter 4.2.5.2 --- Precision performance --- p.54 / Chapter 4.2.5.3 --- Accuracy performance --- p.54 / Chapter 4.2.5.4 --- The lowest detection limit of the CsA analysis --- p.55 / Chapter 4.2.5.5 --- Correlation study of the CsA analysis --- p.55 / Chapter 4.3 --- CsA pharmacokinetic studies in Chinese patients --- p.56 / Chapter 4.3.1 --- Determining the time point of CsA correlating better with AUC --- p.56 / Chapter 4.3.1.1 --- Patient and method --- p.56 / Chapter 4.3.1.2 --- Statistical analysis --- p.57 / Chapter 4.3.2 --- "Intra-individual variability of CO, C1 and C2" --- p.57 / Chapter 4.3.2.1 --- Patient and method --- p.57 / Chapter 4.3.2.2 --- Statistical analysis --- p.57 / Chapter 5. --- Results and discussion --- p.59 / Chapter 5.1 --- Optimization of MS parameters --- p.5 9 / Chapter 5.1.1 --- Optimization of cone voltage --- p.61 / Chapter 5.1.2 --- Optimization of collision energy --- p.63 / Chapter 5.2 --- Optimization of LC-MS/MS --- p.63 / Chapter 5.2.1 --- Optimization of mobile phase flow rate --- p.63 / Chapter 5.2.2 --- Optimization of ion source temperature and drying gas flow rate --- p.67 / Chapter 5.3 --- Matrix interference on MS/MS response --- p.69 / Chapter 5.4 --- Analytical performances of CsA on LC-MS/MS method --- p.71 / Chapter 5.4.1 --- Linearity --- p.71 / Chapter 5.4.2 --- Precision performance --- p.71 / Chapter 5.4.3 --- Accuracy performance --- p.72 / Chapter 5.4.4 --- The lowest limit of detection --- p.73 / Chapter 5.4.5 --- Correlation study of the CsA analysis --- p.80 / Chapter 5.5 --- The correlation between CsA at different point and AUCo-6 --- p.84 / Chapter 5.6 --- "Intra-individual variability of CO, C1 and C2" --- p.88 / Chapter 5.7 --- Therapeutic ranges of C2 --- p.90 / Chapter 5.8 --- Practical consideration for C2 measurement by LC-MS/MS method --- p.94 / Chapter 6. --- Conclusions --- p.97 / References --- p.98

Contexto: O tratamento da hepatite autoimune (HAI) composto por prednisona e azatioprina proporciona melhora clínico-laboratorial em até 90% dos pacientes. Entretanto, a remissão completa não é alcançável na maioria dos casos. Cloroquina é um antimalárico utilizado no tratamento de doenças reumatológicas autoimunes e em estudo aberto de manutenção da remissão da HAI foi sugerido menor risco de recidiva da doença com o uso da droga. Objetivos: Avaliar o uso da cloroquina em associação à prednisona no tratamento da HAI em estudo randomizado. Métodos: 57 pacientes com indicação de tratamento da HAI foram randomizados para receber azatioprina ou cloroquina associadas à prednisona, de 2003 a 2012. Para os que mantiveram normalização das transaminases por 18 meses, biópsia hepática foi realizada para avaliação histológica. O desfecho primário foi a remissão completa ao tratamento, composta por remissão bioquímica e histológica da doença. O valor de p < 0,05 foi considerado estatisticamente significativo. Resultados: Não houve diferença entre os grupos quanto às características clínicas, sorológicas, histológicas e de tratamento prévio, ao início do estudo. A idade média foi de 37,2 ± 16,84 anos, 43,8% com fibrose avançada (F3/4) no início do estudo. Não houve diferença estatística na taxa de resposta bioquímica (67% vs. 53,8%, p=0,413) ou histológica (32,2% vs. 15,4%, p=0,21), assim como na dose média de prednisona utilizada. Os pacientes que não atingiram remissão completa no estudo tiveram seguimento com nova terapia. Entre eles, quatro obtiveram remissão histológica com a associação de azatioprina, cloroquina e prednisona. Em relação aos efeitos adversos, houve maior taxa no grupo da cloroquina, porém com tendência a menor prevalência de comorbidades neste grupo. Conclusão: Quando bem toleradas, cloroquina e prednisona proporcionaram resposta completa em pacientes com AIH, sem diferença estatística em relação à terapia padrão. (ClinicalTrials.gov NCT 02463331) / Background: The treatment of autoimmune hepatitis (AIH) with prednisone and azathioprine provides disease remission. However, a complete biochemical and histological response is unreachable in most patients. Chloroquine is an antimalarial drug used for treating rheumatological diseases. It was studied as a single drug for the maintenance of AIH remission in an open study, which suggested a lower risk of relapse in the chloroquine group. Aims: To evaluate a possible role of chloroquine and prednisone for AIH treatment in a randomized study. Methods: 57 AIH adult patients with indication of treatment were enrolled to receive azathioprine or chloroquine, both with varying doses of prednisone, from 2003 to 2012. For those who had maintained biochemical remission for 18 months, liver biopsy was performed to evaluate histological remission. The primary outcome was the achievement of complete response to treatment. A p-value < 0.05 was considered statistically significant. Results: There were no significant differences between the groups concerning clinical, serological, histological, and treatment features at baseline. The average age was 37.2 ± 16.84 years, 43.8% with advanced fibrosis (F3/4) at baseline. There was no statistical differences in biochemical (67.7% vs. 53.8%, p=0.41) or histological response rate (32.26% vs. 15.38%, p = 0.217), as well as in the mean prednisone dose. There was a higher rate of adverse effects in the chloroquine group, but a lower frequency of comorbidities in this group. Conclusion: When well tolerated, chloroquine with prednisone provided a complete therapeutic response in AIH patients with no statistical difference when compared to the standard treatment. (ClinicalTrials.gov NCT 02463331)

Le genre Pneumocystis regroupe des microchampignons atypiques qui colonisent par voie respiratoire les alvéoles pulmonaires de nombreux mammifères. C’est un pathogène opportuniste qui s’avère particulièrement dangereux lorsque le système immunitaire de l’hôte est déficient (VIH, greffés) et dans ce cas il provoque une pneumonie, la pneumocytsose, fatale en absence de traitement. Du fait que les Pneumocystis spp restent des microchampignons non cultivables, il est alors impossible de manipuler directement ses gènes et la seule solution pour étudier leurs fonctions et leurs localisations, demeure leur expression en système hétérologue. Situé dans l'espace alvéolaire, Pneumocystis spp. sont exposés au stress oxydatif générés par les macrophages alvéolaires, les granulocytes neutrophiles ainsi que par les espèces réactives de l'oxygène (EROs) produits par le métabolisme respiratoire. Pour se protéger, ces micro-organismes ont développé un système spécifique de détoxification des EROs incluant les SuperOxyde Dismutases (SOD). Dans notre étude, la carence en MnSOD d'une souche de Saccharomyces cerevisiae (EG110) dépourvue du gène Scsod2 a été complétée par l'introduction d'un plasmide portant une version inductible du gène Sod2 de P. carinii (Pcsod2). Une fois exprimée la PcMnSOD était capable de complémenter le défaut de croissance de la souche EG110 qui a été exposés à la ménadione. En bref, notre étude a montré une bonne complémentation du gène Sod2 de P. carinii chez une levure déficiente en MnSOD à savoir (i) la reprise de la culture en conditions de stress oxydant, (ii) la mise en évidence de la protéine traduite (Western Blot) et (iii) l’adressage mitochondriale de la protéine hétérologue. Selon le degré d’altération du système immunitaire, les infections à P. jirovecii peuvent présenter des tableaux cliniques variés allant de la colonisation à la pneumocystose. Ces infections semblent être en grande partie liées à des déficits majeurs de l’immunité cellulaire se traduisant plus précisément par une diminution du nombre des lymphocytes TCD4 (LTCD4). Notre deuxième objectif était de parvenir à une appréciation quantitative du risque de contamination par P. carinii en fonction du degré d’immunodépression (ID) des rats exposés. Nous avons ainsi développé un modèle animal de transmission naturelle de P. carinii où des rats nude développant une pneumocystose (« rats donneurs ») sont mis en contact direct avec des rats Sprague Dawley Pneumocystis-free (« rats receveurs ») présentant différents niveaux d’ID (dexamethasone). Après 2 semaines de contact, le niveau de colonisation des rats graduellement ID est déterminé soit par comptage après coloration au Bleu de Toluidine O, soit par qPCR. Cette étude a permis tout d’abord de valider notre modèle d’ID graduelle chez le rat ; mais surtout, et pour la première fois dans un modèle expérimentale chez le rat, nous avons montré une relation inverse entre le niveau de colonisation par P. carinii et le taux de LTCD4 ou LTCD8 circulants. Enfin, nous avons réalisé la première étude épidémiologique portant sur Pneumocystis au Liban. Ce projet franco-libanais a été mis en place au vue de l’importance majeure de la colonisation par Pneumocystis chez les patients immunocompétents, en particulier chez les patients atteints de pathologies pulmonaires chroniques obstructives tels que la BPCO où la colonisation par Pneumocystis est considérée comme un facteur aggravant de la maladie. Nos résultats montrent une faible prévalence de colonisation (5.2%) et une prédominance du génotype mtLSU2 chez les patients atteints de pathologies respiratoires au Liban. De plus, dans notre cohorte de patient présentant des pathologies respiratoires variées, la BPCO semble être la seule maladie respiratoire associée à un facteur de risque de colonisation par P. jirovecii. / Pneumocystis is an opportunistic pulmonary fungal pathogen that causes Pneumocystis pneumonia (PcP) in immunocompromised individuals such as patients with HIV infection as well as those without HIV infection who are undergoing immunosuppression as a consequence of chemotherapy or organ transplantation. Pneumocystis colonization in immunocompetent individuals has recently been described by the detection of fungal DNA without signs or symptoms of pneumonia, and accumulating evidences underline its clinical importance. Pneumocystis organisms are airborne transmitted and represent a large group of species of atypical fungi that cannot be continuously grown in culture. Consequently, it is impossible to directly manipulate genes in Pneumocystis species. Located in the alveolar space, Pneumocystis organisms are exposed to oxidative burst from phagocytic alveolar macrophages and neutrophils as well as to reactive oxygen species (ROS) produced by the mitochondrial oxygen metabolism. To counteract this, microorganisms have developed a ROS detoxifying system. This includes superoxide dismutases (SOD). In the present study, the MnSOD deficiency of a Saccharomyces cerevisiae mutant strain was complemented by introducing a plasmid carrying an inducible version of the P. carinii Sod2 gene (Pcsod2). Expression of Pcsod2 revealed that the corresponding MnSOD recombinant protein could complement the growth defect in the mutant yeast strain when cells were exposed to menadione. The mitochondrial localization was confirmed by immuno-colocalization of the P. carinii recombinant MnSOD with the yeast mitochondrial Cox4 protein. These results suggest that Pcsod2 encodes an active MnSOD that is targeted to the mitochondrion. This work increases our understanding of the antioxidant defense mechanisms deployed by the Pneumocystis organisms.The adaptive host response to Pneumocystis infection involves humoral and cellular immune responses working in concert to promote the clearance of infection. Depending on the degree of alteration of the immune system, Pneumocystis infections may have various clinical presentations going from colonization to the most severe form (PcP).These infections appear to be largely related to major deficits in cellular immunity and are more closely reflecting a decrease in the number of CD4 T lymphocytes (LTCD4). Our objective was to achieve a quantitative assessment of the risk of contamination by Pneumocystis depending on the degree of immunosuppression (ID) of the exposed host. Thus, we developed an animal model of natural transmission of P. carinii where rats undergoing gradual ID (dexamethasone) named receivers, are cohoused with nude rats developing PcP, named donors. Following contact between receiver and donor rats, the level of colonization by Pneumocystis of receiver rats is determined by toluidine blue O staining or by qPCR. This study allowed us to validate our gradual ID rat model, in the sense that we were able to maintain the level of circulating LTCD4 and LTCD8 stable. Finally, and for the first time in an experimental rat model, we observed an inverse relationship between the level of colonization by P. carinii and the level of circulating LTCD4 and LTCD8.Finally, we aimed to acquire the first data concerning the prevalence of P. jirovecii in the Lebanese population. This Franco-Lebanese project was set up because the colonization by Pneumocystis is probably of major importance in the public health, especially in susceptible patients such as patients with chronic obstructive pulmonary diseases (COPD) where Pneumocystis is considered as a worsening prognosis factor. Our results show a low prevalence of P. jirovecii colonization (5.2%) and the predominance of mtLSU genotype 2 in patients with respiratory diseases in Lebanon. Moreover, in our cohort of patients with various respiratory diseases, COPD was the only respiratory disease associated with a significant increased risk of P. jirovecii colonization.

Localisé entre l'Epithélium Pigmentaire Rétinien (EPR) et les segments externes des photorécepteurs, l'espace sous-rétinien est une zone immunosuppressive ; régulée par des signaux comme la thrombospondine-1 (TSP-1) ou Fas Ligand (FasL), qui empêchent l'accumulation des phagocytes mononucléés (PMs), en particulier des monocytes inflammatoires. La Dégénérescence Maculaire Liée à l'Age (DMLA) est associée à une rupture de l'immunosuppression de cet espace, et s'accompagne d'une accumulation de PMs ; causant la mort des photorécepteurs, la dédifférenciation de l'EPR et une néovascularisation pathologique. Des études d'associations génétiques ont établi un lien entre la DMLA et un haplotype qui affecte le locus 10q26, qui contient trois gènes : PLEKHA1, ARMS2 et HTRA1. L'haplotype est associé à une augmentation de la transcription de HTRA1 dans les lymphocytes ou les cellules de l'EPR. HTRA1 code pour une sérine protéase qui a une multitude de substrats ; mais le mécanisme par lequel elle pourrait être impliquée dans la pathogenèse de la DMLA reste inconnu. TSP-1 est une glycoprotéine exprimée par l'EPR, les macrophages résidents et inflammatoires. Le domaine C-terminal de TSP-1 contient deux séquences VVM qui peuvent chacune interagir avec un récepteur CD47. Dans cette étude, nous montrons que HTRA1 clive TSP-1 et inhibe l'élimination des PMs régulée par l'interaction entre TSP-1 et CD47 à l'état physiologique, in vitro et in vivo. L'activation pharmacologique de CD47 nous a permis d'annuler les effets pro-inflammatoires de HTRA1 et pourrait représenter un espoir thérapeutique pour le contrôle de la progression de la DMLA chez les patients porteurs de l'haplotype à risque. / Localized between the Retinal Pigment Epithelium (RPE) and the photoreceptors outer segments, the subretinal space is an immunosuppressive zone, mediated by signals such as Thrombospondin-1 (TSP-1), Fas Ligand (FasL) that prevent the accumulation of Mononuclear Phagocytes (MPs) and in particular pathogenic inflammatory monocytes. Age related Macular Degeneration (AMD) is associated with a breakdown of this immunosuppressivity and an accumulation of MPs, which causes photoreceptor degeneration, RPE dedifferentiation and pathological neovascularization. Genome association studies showed a strong link between AMD and a relatively common haplotype of 10q26 locus that contains the PLEKHA1, ARMS2 and HTRA1 genes. The disease haplotype is associated with increased HTRA1 transcription in cell types such as lymphocytes and RPE cells. HTRA1 is a serine protease with a number of substrates, but the mechanism by which it might be involved in AMD pathogenesis is unknown. TSP-1 is a glycoprotein expressed by RPE, resident macrophages and inflammatory macrophages. The C-terminal domain of TSP-1 contains two VVM sequences that can each interact with a CD47 receptor. We show that HTRA1 induced subretinal MP accumulation is dependent on TSP-1 deactivation in an RPE/Mo co-culture model and in a laser induced inflammation model in vivo. This pathogenic effect of HTRA1 was reversible by synthetic CD47 agonists. Our study reveals a comprehensive mechanism how the risk-allele 10q26 participates in the pathogenesis of AMD and opens new therapeutic avenues to restore subretinal immunosuppressivity and inhibit the inflammation-dependent neurodegeneration.

Background: Exposure of skin to UVB radiation (290-320 nm) modulates the immune system, with most studies showing a suppression of Th1-driven immune responses. Investigations into the effects of UVB exposure on allergic respiratory responses have been limited. This study investigated the systemic effects of UVB on Th2-associated immune responses using two different murine models of allergic respiratory inflammation. The mechanism of immune regulation was also examined. Methods and Results: Two murine models of asthma were used: the papain model and the ovalbumin (OVA) model using papain and OVA, respectively, as the allergens. In the papain model, C57BL/6, histamine receptor-1 knockout (H1RKO) and histamine receptor-2 knockout (H2RKO) mice were exposed to a single 4 kJ/m2 dose of UVB (twice a minimal oedemal dose) on shaved dorsal skin three days prior to intranasal sensitisation with papain, a cysteine protease homologue of the house dust mite (Dermatophagoides pteronyssinus) allergen Der p 1. Sensitisation and boost each consisted of five daily intranasal doses of 1 µg papain whilst the challenge consisted of three daily intranasal doses of 100 µg papain. Asthmatic symptoms were assessed 24 h after the final challenge dose. H1RKO mice demonstrated enhanced papain-specific inflammatory responses in the lung-draining lymph nodes (LDLNs) whilst the responses of H2RKO mice closely mimicked those of C57BL/6 mice. UVB irradiation three days before sensitisation reduced in vitro papain-specific proliferation of LDLN cells from C57BL/6 and H1RKO mice but not H2RKO mice 24 h after challenge. The regulatory effect of UVB was transferred by adoptive transfer of 5 x 106 unfractionated LDLN cells from UVB-irradiated, papain-sensitised and -challenged C57BL/6 and H1RKO donor mice into naïve recipients of the corresponding strain that were ii subsequently sensitised and challenged with papain. Additionally, UVB exposure suppressed papain-induced IL-5 and IL-10 production in vitro by LDLN cells from H1RKO mice but not from C57BL/6 mice or H2RKO mice. The results of this study demonstrate systemic immunomodulation of responses to intranasally delivered antigen by UVB irradiation and the induction of regulatory cells in the LDLN following UVB exposure. Furthermore, these results implicate a role for the H2R in UVB-induced suppression of antigen-specific responses in the draining lymph nodes.

IntroducciónEn la actualidad se buscan marcadores para identificar pacientes trasplantados que alcancen cierto grado de tolerancia. El más estudiado recientemente se engloba como células T reguladoras (Tregs), capaces de controlar la respuesta alogénica in vitro y con capacidad tolerogénica en modelos animales. En este trabajo se ha estudiado el comportamiento de Tregs en trasplantados renales y la implicación de procesos inflamatorios y fármacos inmunosupresores más comunes en estos pacientes. Material y MétodosSe midieron las Tregs sanguíneas en los pacientes trasplantados renales mediante citometría de flujo y su función in vitro en cultivos mixtos linfocitarios cada 6 meses post-trasplante hasta los 2 años. Resultados y conclusionesLos pacientes con enfermedad renal terminal presentan un número similar de Tregs que donantes sanos. A los 6 meses del trasplante se observa un descenso de Tregs, recuperándose posteriormente. Se observó una mayor frecuencia de Tregs en los pacientes tratados durante un año con inhibidores de mTOR que los tratados con inhibidores de calcineurina (CNI). Así mismo se observó cómo los niveles sanguíneos de los CNI tenían un efecto deletéreo sobre la función de las Tregs. / IntroductionKidney transplantation has become a therapeutic option choice in patients with chronic renal failure. With the advance of new immunosuppressive agents has been a lower incidence of acute rejection, but still persist long-term problems, largely associated with chronic treatment with immunosuppressive agents. Currently, are looking for markers to identify patients who reach a certain degree of tolerance in order to reduce immunosuppressive load avoiding side effects long term. The most studied biomarker in the last decade includeswith the name of regulatory T cells (Tregs), these cells are able to control allogeneic response in vitro and has tolerogenic capacity demonstrated in many transplant models. Prior to validate this biomarker of transplant tolerance, this work has studied the behavior of Treg cells in renal transplant recipients and their coexistence in the most common inflammatory processes in these patients. In addition, we assess the role of drugs immunosuppressants on these cells.ObjectivesMonitor the levels of Tregs in renal transplant patients and consider the involvement of different events inflammatory on the number of Tregs and to determine the involvement of different immunosuppressive treatments on the number and Tregs function.Material and MethodsThere were two parallel studies, one prospective, in which Treg cells were measured in kidney transplants patients by flow cytometry and theirfunction in vitro by mixed lymphocyte cultures. The samples were collected every 6 months post-transplant until 2 years. In another retrospective study enrolled 64 patients transplantation with a follow-up exceeding one year, dividedin terms of maintenance therapy with calcineurin inhibitors (CNI) or mTOR inhibitors.Results and conclusions At the time prior to transplantation, patients with ESRD have a similar number of Treg cells circulating than healthy donors, excluding retransplantated patients. At 6 months after transplantation there is a dramatic decrease in Treg cell numbers, when the immunosuppressive load is higher. Later the levels of Tregs were recovered. Within the immunosuppressive used in maintenance treatment, there was a higher frequency of Tregs in patients treated for one year with mTOR inhibitors when compared with patients received in the same period calcineurin inhibitors (CNI). Also it was observed that blood levels of the CNI had a deleterious effect on the function of Treg cells.

Epstein-Barr virus (EBV) infects almost all humans and establishes lifelong latency in B cells. Posttransplant lymphoproliferative disorder (PTLD) is a rare but serious complication after transplantation triggered by immunosuppression and often related to EBV infection. The aim of this thesis was to study the role of EBV in relation to clinical and histological features of PTLD, regulatory T cells (Tregs), and donor or recipient origin of PTLD. EBV surveillance after allogeneic hematopoietic stem cell transplantation (allo-HSCT) showed that EBV reactivations were common, but that symptomatic EBV disease (including PTLD) only occurred in the high-risk group (unrelated or mismatched related grafts, reduced-intensity conditioning). A threshold of 1000 copies/ml plasma distinguished EBV disease from asymptomatic reactivations. In a population-based cohort of 135 PTLDs/lymphomas after solid organ transplantation (SOT) almost half were EBV–. EBV+ PTLDs were associated with B cell phenotype, non-germinal center subtype of diffuse large B cell lymphoma (DLBCL), early-onset, graft involvement, antithymocyte globulin treatment, and younger age. EBV– PTLDs were associated with T cell phenotype, bone marrow involvement, and hepatitis C. Most PTLDs displayed few or no intratumoral Tregs with the marker FoxP3, possibly due to heavy immuno­suppres­sion. Half of both FoxP3+ and FoxP3– PTLDs were EBV+. FoxP3+ PTLDs were associated with B cell phenotype and hepatitis C. All PTLDs for which tumor origin could be determined were recipient-derived and half of them were EBV+. Eight of twelve recipient-derived graft PTLDs were disseminated outside the graft. T cell PTLD and hepatitis C were independently associated with inferior overall survival, whereas subtype of DLBCL, FoxP3-expression, and EBV-status did not influence survival. In conclusion, monitoring of EBV DNAemia in high-risk patients after allo-HSCT and pre-emptive therapy is valuable for prevention of PTLD. Use of anti­thymocyte globulin increases the risk for EBV+ PTLDs after allo-HSCT and SOT. With long follow-up time, a large proportion of PLTDs after SOT are EBV– with a different clinical presentation. Tregs are rare in PTLD and do not affect survival. The vast majority of PTLDs after SOT is of recipient origin. Graft PTLDs are more likely recipient-derived if disseminated. EBV-status is not associated with intratumoral Tregs or PTLD of recipient origin.