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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
151

The impact of HLA-driven escape mutation on viral replicative capacity and immune control in HIV infection

Tsai, Ming-Han Chloe January 2017 (has links)
Despite the introduction of antiretroviral therapy, the HIV/HIV epidemic remains an unsolved global health problem. Amongst all the host defence mechanisms, HLA class I molecules have shown the strongest genetic association with delayed disease progression, in particular HLA-B alleles. Numerous studies have shown that the HLAmediated CD8+ T cell responses play a central role in the immune control of HIV. Yet our understanding of HLA-mediated immune control of HIV remains incomplete, even when considering the best-defined epitopes restricted by the protective HLA alleles at a population level. The studies I have conducted and describe herein focus on two well-charaterised protective HLA-B molecules, HLA-B*81:01 and HLA-B*27:05; a third protective molecule, HLA-B*52:01, that has not been well-studied hitherto; and finally the most prevalent HLAB allele in many Asian populations such as Taiwan, HLA-B*40:01, which has an apparently neutral effect on viral replication. This thesis is centred on the Gag-specific immune response, since previous studies have shown the benefits of CD8+ T-cell responses targeting this conserved and immunogenic region of the HIV proteome, in particular the p24 capsid protein. I have investigated here HLA footprints driven by CD8+ T-cell pressure on HIV that are evident in the viral sequences of individuals expressing these HLA molecules. These footprints include novel escape and putative compensatory mutations. The impact of these variants on viral replicative capacity (VRC) and on HIV disease outcome clinical outcomes was examined via fitness assays. These studies identified several escape mutations that effectively cripple HIV. The distinct compensatory pathways available to the virus to mitigate the fitness cost of particular escape mutations were evaluated. In the course of these analyses I have demonstrated the critical influence of the viral backbone, including HIV clade, in combination with particular viral variants, on VRC. Computational modelling analysis has been applied to facilitate understanding of the mechanism by which certain mutants affect the stability of interactions between HLA and viral capsid protein. This thesis offers novel insights into immune control of the key HIV subtypes – B- and C-clade – and of the most severely affected populations – in Africa (South Africa) and Asia (India and Taiwan) – within the global epidemic. This work helps to better define the viral mutation landscape that is essential both for future vaccines designed to corner the virus, and for successful HIV cure strategies.
152

HLA-DRB3/4/5 Matching Improves Outcome of Unrelated Hematopoietic Stem Cell Transplantation

Tsamadou, Chrysanthi, Engelhardt, Daphne, Platzbecker, Uwe, Sala, Elisa, Valerius, Thomas, Wagner-Drouet, Eva, Wulf, Gerald, Kröger, Nicolaus, Murawski, Niels, Einsele, Hermann, Schaefer-Eckart, Kerstin, Freitag, Sebastian, Caspar, Jochen, Kaufmann, Martin, Dürholt, Mareike, Hertenstein, Bernd, Klein, Stefan, Ringhoffer, Mark, Frank, Sandra, Neuchel, Christine, Schrezenmeier, Hubert, Mytilineos, Joannis, Fuerst, Daniel 04 April 2023 (has links)
The HLA-DRB3/4/5 loci are closely linked to the HLA-DRB1 gene. Mismatches in these loci occur with a frequency of about 8%–12% in otherwise 10/10 HLA-matched transplant pairs. There is preliminary evidence that these disparities may associate with increased acute graft-versus-host disease (GvHD) rates. The aim of this study was to analyze a large cohort of German patients and their donors for HLA-DRB3/4/5 compatibility and to correlate the HLA-DRB3/4/5 matching status with the outcome of unrelated hematopoietic stem cell transplantation (uHSCT). To this end, 3,410 patients and their respective donors were HLA-DRB3/4/5 and HLA-DPB1 typed by amplicon-based nextgeneration sequencing (NGS). All patients included received their first allogeneic transplant for malignant hematologic diseases between 2000 and 2014. Mismatches in the antigen recognition domain (ARD) of HLA-DRB3/4/5 genes were correlated with clinical outcome. HLA-DRB3/4/5 incompatibility was seen in 12.5% (n = 296) and 17.8% (n = 185) of the 10/10 and 9/10 HLA-matched cases, respectively. HLA-DRB3/4/5 mismatches in the ARD associated with a worse overall survival (OS), as shown in univariate (5-year OS: 46.1% vs. 39.8%, log-rank p = 0.038) and multivariate analyses [hazard ratio (HR) 1.25, 95% CI 1.02–1.54, p = 0.034] in the otherwise 10/10 HLAmatched subgroup. The worse outcome was mainly driven by a significantly higher nonrelapse mortality (HR 1.35, 95% CI 1.05–1.73, p = 0.017). In the 9/10 HLA-matched cases, the effect was not statistically significant. Our study results suggest that mismatches within the ARD of HLA-DRB3/4/5 genes significantly impact the outcome of otherwise fully matched uHSCT and support their consideration upon donor selection in the future.
153

HLA-DRB3/4/5 Matching Improves Outcome of Unrelated Hematopoietic Stem Cell Transplantation

Tsamadou, Chrysanthi, Engelhardt, Daphne, Platzbecker, Uwe, Sala, Elisa, Valerius, Thomas, Wagner-Drouet, Eva, Wulf, Gerald, Kröger, Nicolaus, Murawski, Niels, Einsele, Herrmann, Schaefer-Eckart, Kerstin, Freitag, Sebastian, Caspar, Jochen, Kaufmann, Martin, Dürholt, Mareike, Herstenstein, Bernd, Klein, Stefan, Ringhoffer, Mark, Frank, Sandra, Neuchel, Christine, Schrezenmeier, Hubert, Mytilineos, Joannis, Fuerst, Daniel 24 March 2023 (has links)
The HLA-DRB3/4/5 loci are closely linked to the HLA-DRB1 gene. Mismatches in these loci occur with a frequency of about 8%–12% in otherwise 10/10 HLA-matched transplant pairs. There is preliminary evidence that these disparities may associate with increased acute graft-versus-host disease (GvHD) rates. The aim of this study was to analyze a large cohort of German patients and their donors for HLA-DRB3/4/5 compatibility and to correlate the HLA-DRB3/4/5 matching status with the outcome of unrelated hematopoietic stem cell transplantation (uHSCT). To this end, 3,410 patients and their respective donors were HLA-DRB3/4/5 and HLA-DPB1 typed by amplicon-based nextgeneration sequencing (NGS). All patients included received their first allogeneic transplant for malignant hematologic diseases between 2000 and 2014. Mismatches in the antigen recognition domain (ARD) of HLA-DRB3/4/5 genes were correlated with clinical outcome. HLA-DRB3/4/5 incompatibility was seen in 12.5% (n = 296) and 17.8% (n = 185) of the 10/10 and 9/10 HLA-matched cases, respectively. HLA-DRB3/4/5 mismatches in the ARD associated with a worse overall survival (OS), as shown in univariate (5-year OS: 46.1% vs. 39.8%, log-rank p = 0.038) and multivariate analyses [hazard ratio (HR) 1.25, 95% CI 1.02–1.54, p = 0.034] in the otherwise 10/10 HLAmatched subgroup. The worse outcome was mainly driven by a significantly higher nonrelapse mortality (HR 1.35, 95% CI 1.05–1.73, p = 0.017). In the 9/10 HLA-matched cases, the effect was not statistically significant. Our study results suggest that mismatches within the ARD of HLA-DRB3/4/5 genes significantly impact the outcome of otherwise fully matched uHSCT and support their consideration upon donor selection in the future.
154

Epigenetická regulace genů HLA II. třídy a jejich role u autoimunitních onemocnění. / Epigenetic regulation of HLA class II genes and their role in autoimmune diseases.

Čepek, Pavel January 2012 (has links)
Abstract Background: Type 1 diabetes (T1D) is a multifactorial autoimmune disease. Its incidence in Europe is continuously rising. The highest T1D risk is associated with HLA (human leukocyte antigen) class II genes. HLA class II molecules play a key role in regulation of immune response. They contribute to the selection of T cell repertoire by presenting antigenic peptides to the CD4+ T lymphocytes. HLA class II expression is controlled by regulatory module that is situated 150 - 300 base pairs upstream of the transcription- initiation site in all HLA class II genes. Polymorphisms in this region are linked to some autoimmune diseases. There were identified several promoter alleles (named QAP) in the HLA DQA1 gene promoter region. Most of the polymorphisms appear to be conserved within haplotype. Individual QAP alleles may have a different promoter strength by which they influence expression of HLA DQA1 gene alleles. Promoter strength can be modulated by DNA methylation. Aims:Our aim was to define methylation profile of HLA DQA1 promoters and determine the mRNA expression of individual alleles of HLA DQA1 gene in T1D patients. The mRNA expression level of HLA DQA1 gene alleles was determined using quantitative PCR. Methods: 30 diabetic pacients (age range 21 to 76 years), were included in this pilot...
155

Cytomégalovirus : réponse des lymphocytes T γδ et impact sur le développement tumoral / Cytomegalovirus : response of γδ T cells and impact on tumor development

Massara, Layal 01 October 2018 (has links)
Le cytomégalovirus (CMV), un β-herpes virus, est considéré comme un modèle d'immuno-évasion virale. Il s'agit d'un agent pathogène opportuniste fréquent chez les patients immunodéprimés et une cause majeure de malformations congénitales lors de l'acquisition in utero. Le CMV code pour des protéines (i) qui empêchent la présentation de l'antigène aux lymphocytes T αβ notamment par l'inhibition de l'expression des molécules HLA-I et (ii) qui suppriment les fonctions des cellules NK en imitant ou en régulant à la baisse les ligands des récepteurs NK (NKR). Ces mécanismes d'évasion ne devraient pas affecter les lymphocytes T γδ dont la reconnaissance antigénique est indépendante du HLA-I, et d’ailleurs leur réponse au CMV a été largement rapportée dans de nombreux contextes physiopathologiques. Notre objectif était de comprendre comment les mécanismes d’immuno-évasion du CMV affectent la réponse des lymphocytes T γδ. Nous avons utilisé des adénovirus recombinants exprimant chacun des quatre gènes du CMV impliqués dans l’inhibition de l’expression du HLA-I, et un mutant du HCMV déficient pour ces 4 gènes (CMV-∆US). Nous avons observé une induction de l'expression de HLA-I par l'adénovirus control, et une inhibition par US2, US3 et US11. Lors de l'utilisation de CMV-∆US, les cellules infectées exprimaient beaucoup plus de HLA-I que les cellules infectées par CMV-WT. De façon intéressante et à l’opposé des lymphocytes T αβ, les lymphocytes T γδ produisent plus d'IFNy en présence de fibroblastes infectés par le CMV-WT, qu’avec des fibroblastes infectés par CMV-∆US. Ces résultats indiquent que les molécules HLA-I régulent les lymphocytes T γδ grâce à des mécanismes qui sont en cours d'investigation dans notre équipe. Les processus d'échappement immunitaire développés par le CMV pourraient ainsi favoriser la réponse des lymphocytes T γδ par rapport à celle des lymphocytes T αβ et expliquer le rôle important des cellules T γδ dans le contrôle du virus chez les individus immunodéprimés. D'autre part, les acides nucléiques et les protéines du HCMV ont été trouvés dans les tissus tumoraux, mais la relation précise entre le HCMV et le cancer reste un sujet de débat. La plupart du temps, HCMV est décrit comme un virus oncomodulateur avec un rôle pro-tumoral. Notre objectif était d'utiliser le modèle de la souris pour tester in vivo l'impact de CMV de souris (MCMV) sur la croissance des cellules tumorales. Nous avons observé que MCMV pourrait inhiber la croissance de tumeurs sous-cutanées de côlon MC38 chez les souris immunodéficientes. Encore plus surprenant lorsque l'on considère la spécificité d’espèce des CMV, l'infection par le MCMV inhibe de la même façon la croissance des cellules cancéreuses du côlon humain HT29, qui n’est pas affectée par le HCMV. In vitro, les protéines MCMV précoces (IE-1) sont détectées dans des cellules cancéreuses humaines et murines après l'infection. Cependant, peu de cellules cancéreuses sont retrouvées positives pour le MCMV dans les tumeurs HT29 prélevées sur des souris infectées par le MCMV. De manière surprenante, le MCMV inhibe la prolifération des cellules cancéreuses de côlon humain contrairement au HCMV. De plus, la transcription de l'interféron β humain est induite après une infection par le MCMV. Cette induction n'a pas été observée après l'infection par le HCMV. En conclusion, nos données suggèrent un potentiel effet anti-tumoral de MCMV sur les cellules cancéreuses du côlon humain (HT29), qui pourrait être au moins partiellement médiée par l'interféron β. Ces résultats ouvrent la voie à l'utilisation potentielle du MCMV en tant que traitement du cancer du côlon humain. / Cytomegalovirus (CMV), a Beta Herpes virus, is considered as a paradigm for viral evasion.It is an important opportunistic pathogen in immunocompromised patients and a major cause of congenital birth defects when acquired in utero. CMV encodes molecules to prevent antigen presentation to αβ T cells through inhibition of MHC Class I expression and to suppress NK cell functions by mimicking or down-regulating ligands of NK receptors (NKR). These evasion mechanisms are not expected to affect γδ T cells and, as a matter of fact, their response to CMV has been widely reported in many different physiopathological contexts as well as in CMV-seropositive healthy donors (Dechanet et al, 1999)( Scheper, 2013). Our aim was to understand how CMV induce γδ T cell response. We used recombinant adenoviruses expressing each of the four US genes, and a mutant HCMV deleted for these 4 genes (CMV-DUS). We observed an induction of HLA-I expression by the control adenovirus, and an inhibition by US2, US3 and US11. When using CMV-DUS, infected cells expressed much more native HLA-I than CMV-WT infected cells. Interestingly and in sharp contrast to αβ T cells, γδ T cell were activated to produce IFNg when cultured with fibroblasts infected with CMV-WT, but not when fibroblasts were infected with CMV-DUS. These results indicate that HLA-I molecules regulate γδ T cells through mechanisms that are under investigation in our team. The immune escape processes developed by CMV could thus promote γδ over αβ T cell response and explain the important response of γδ T cells to the virus in immunosuppressed individuals.
156

Avaliação da expressão das isoformas da molécula HLA-G e do perfil da resposta imune em pacientes com lúpus eritematoso sistêmico juvenil (LESJ) / Evaluation of the expression of isoforms of HLA-G molecule and the profile of the immune response in patients with juvenile systemic lupus erythematosus (SLE)

Santos, Rossana Suelle Nascimento January 2015 (has links)
Made available in DSpace on 2016-05-19T13:08:22Z (GMT). No. of bitstreams: 2 204.pdf: 1337649 bytes, checksum: 244b0e0500a3148923b324ca08b898bf (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2015 / Fundação Oswaldo Cruz. Centro de Pesquisas Aggeu Magalhães. Recife, PE, Brasil / O lúpus eritematoso sistêmico juvenil (LESJ) é uma doença inflamatória crônica causada pela produção de autoanticorpos, que reconhecem como estranhos antígenos próprios do organismo, e possuem alta morbidade e mortalidade em relação à doença no adulto. Em sua patogênese estão envolvidos fatores ambientais, hormonais, imunológicos e genéticos. Estudos de associação genética demonstraram que a susceptibilidade ao lúpus é poligênica, e entre os genes envolvidos está o HLA-G que é responsável pela regulação da resposta imune. No estudo, foi analisada a expressão de isoforma da molécula HLA-G e observamos o perfil de resposta imune em pacientes com lúpus eritematoso sistêmico juvenil. Os pacientes que participaram do estudo foram selecionados no serviço de Reumatologia do Hospital das Clínicas e foi coletado sangue periférico de 10 pacientes no momento ativo e inativo do LESJ. O estudo comparou a expressão do mRNA do HLA-G5, IL-10 e TNF, os níveis plasmáticos de sHLA-G e citocinas Th1, Th2 e Th17 entre os grupos com a doença ativa, inativa e o grupo de crianças saudáveis aplicando os testes de Mann-Whitney U e Kruskal-Wallis. Os resultados mostraram que pacientes com LESJ ativo apresentaram níveis elevados das citocinas IL-10 (p=0,004) e IL-6 (p=0,011), além de apresentarem expressão de mRNA do TNF mais elevada em relação ao grupo inativo (p0,05). Mesmo com número reduzido, foi possível caracterizar que houve mudança do perfil de citocinas durante a ativação do LESJ, e a relação dessa ativação com a expressão de HLA-G solúvel, além de servir como base para proposta de um modelo de regulação imunológica, que poderá ser validado em futuros experimentos
157

The Complex Genetics of Multiple Sclerosis : A preliminary study of MS-associated SNPs prior to a larger genotyping project

Söderholm, Simon January 2016 (has links)
Biomedical research have been revolutionized by recent technological advances, both in the fields of molecular biology and computer science, turning the biomolecular and genetic research into “big data science”. One of the main objectives have been to improve our understanding of complex human diseases. Among those diseases, multiple sclerosis (MS) is considered as one of the most common. MS is a chronic autoimmune disease that cause inflammation and damage to the central nervous system. In this study, a set of bioinformatics analyses have been conducted on SNP data, as an initial step to gain more information prior to an upcoming genotyping project. The results showed extensive regulatory properties for the 761 selected SNPs, which is consistent with current scientific knowledge, and also identified another 332 SNPs in linkage to these. However, during the study some issues have also been identified, which need to be addressed going forward.
158

Characterization of a monoclonal antibody reactive against major histocompatibility complex class II antigens

葉德俊, Yip, Tak-chun, Timothy. January 1992 (has links)
published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy
159

Ciblage exosomal et effet de HLA-DM sur la présentation antigénique par le complexe majeur d'histocompatibilité de classe II

Côté, Marie-Hélène 04 1900 (has links)
Les molécules du complexe majeur d'histocompatibilité de classe II (CMH II) sont exprimées exclusivement à la surface des cellules présentatrices d'antigènes et servent à stimuler les cellules CD4+ initiant une réponse immunitaire. Le chargement peptidique sur HLA-DR se produit dans les endosomes tardifs et les lysosomes sous l'action de HLA-DM. Cette molécule de classe II non-classique enlève les fragments peptidiques de la chaîne invariante (Ii) restés associés aux molécules de classe II (CLIP) et édite leur répertoire d'antigènes présentés. En utilisant une forme mutante de HLA-DM (HLA-DMy) qui s'accumule à la surface plasmique, nous avons observé que HLA-DMy augmente les chargements de peptides exogènes et aussi la réponse des cellules T en comparaison avec HLA-DM sauvage. Il a été démontré que des molécules chimiques, comme le n-propanol, pouvait avoir le même effet que HLA-DM en remplaçant les peptides associés aux molécules de classe II de la surface cellulaire. De plus, HLA-DMy et le n-propanol ont présenté un effet additif sur la présentation de peptides exogènes. Certaines protéines de la voie endocytique, comme HLA-DR, HLA-DM, HLA-DO et Ii sont ciblés aux compartiments multivésiculaires (MVB) et peuvent être ciblées aux exosomes. Suite à une fusion entre les MVB et la membrane plasmique, les exosomes sont relâchés dans le milieu extracellulaire. Nous avons déterminé que le motif tyrosine de HLA-DMβ et son interaction avec HLA-DR n'affectaient pas le ciblage aux exosomes, sauf la molécule HLA-DO. Cette étude nous a permis de démontrer que HLA-DMy augmente la quantité de peptides exogènes chargés sur les CPA et que HLA-DM et HLA-DMy sont incorporés dans les exosomes. / Major histocompatibility class II (MHC II) molecules are expressed exclusively on the surface of antigen presenting cells and serve to stimulate CD4+ cells to initiate an immune response. Peptide loading on MHC II molecules occurs in late endosomal and lysosomal compartments by the catalytic action of HLA-DM. This non-classical class II molecule removes class-II-associated invariant-chain peptide (CLIP) from class II molecules and edits their repertoire of antigenic peptides loaded. Using a mutant form of HLA-DM (HLA-DMy) that is targeted to the plasma membrane, we observed in the case of HLA-DMy, there is an increase of the loading of exogenous peptides and also significantly increased T cell response in comparison with HLA-DM wild-type. It was found that some chemical molecules, like n-propanol, could mimic the effect of HLA-DM by removing peptides from cell surface class II molecules. Interestingly, HLA-DMy and n-propanol seem to have an additive effect on the exogenous peptide loading. Some proteins of the endosomal pathway, like HLA-DR, HLA-DM, HLA-DO and Ii are targeted to microvesicules-containing compartments called MVB and they can be introduced into exosomes. Following the fusion between MVB and plasma membrane, exosomes are released in extracellular environment. We have determined that tyrosine motif of HLA-DMβ and interaction with HLA-DR does not affect HLA-DM targeting to exosomes, except for the HLA-DO molecule. In conclusion, we showed that HLA-DMy increases the quantity and the quality of exogenous peptides loading on APC and HLA-DM and HLA-DMy are incorporated to exosomes.
160

Funktionelle Analyse der Antigen- und Superantigenpräsentation durch MHC-Klasse-II-Moleküle der LEW-Ratte / Functional analysis of antigen and superantigen presentation by LEW rat MHC class II molecules

Dlaske, Henry January 2008 (has links) (PDF)
In der vorliegenden Arbeit wurde die Präsentationsfunktion der LEW-Ratten-MHC-Klasse-II-Moleküle RT1B und RT1D für verschiedene Super- und Peptidantigene sowie die Generierung gemischter MHC-Klasse-II-Isotypen in der LEW-Ratte untersucht. Sag sind Proteine bakterieller und viraler Herkunft und führen nach Bindung an MHC-Klasse-II-Moleküle durch Interaktion mit dem TZR-Vb-Teil zu einer von der TZR-Spezifität unabhängigen Aktivierung von T-Zellen, die bis zu 30 % der Gesamt-T-Zellpopulation eines Organismus erfassen kann. Die dadurch bedingte Mediatorenfreisetzung aus T- oder konsekutiv aktivierten Zellen ist einerseits für die Entwicklung bestimmter akuter Krankheitsbilder wie des toxischen Schocksyndroms, Gastroenteritiden u. a. verantwortlich, kann aber auch potentiell zu einer Aktivierung autoreaktiver T-Zellen und der Entstehung von Autoimmunkrankheiten beitragen. Zur Untersuchung der LEW-MHC-Klasse-II-Charakteristika wurden zunächst mittels retroviralen Gentransfers RT1B- und RT1D-Gene in L929-Zellen übertragen und die Oberflächenexpression durch die mAK Ox6 und 14-4-4S nachgewiesen. Anschließend erfolgte der Nachweis einer Sag-Präsentation durch Stimulation des LEW-Vb8.2-TZH 53/4 durch die bakteriellen Sag SEB, SEC1-3, MAS und YPM und von aus Lymphknoten isolierten LEW-T-Zellen durch SEC1, MAS und YPM, die beide mit der durch eine HLA-DR1-positive Zelllinie getragenen Aktivierung verglichen wurden. Beide Experimente ergaben für die Sag des primär humanpathogen Staph. aureus eine weitaus stärkere Reaktivität in Anwesenheit humaner gegenüber LEW-MHC-Klasse-II-Molekülen bei RT1B-dominierter Antwort innerhalb der präsentatorischen Rattenmoleküle. Für SEB ergaben sich zusätzlich Hinweise auf eine MHC-Klasse-II-unabhängige Aktivierung. Das von Yersinia pseudotuberculosis produzierte Sag YPM wurde ebenfalls wesentlich besser von humanen als LEW-MHC-Klasse-II-Molekülen präsentiert, zeigte allerdings nur geringe Unterschiede zwischen RT1B und RT1D. Für das aus Nagern isolierte Sag von Mykoplasma arthritidis MAS konnte eine präferentielle Bindung an RT1D mit HLA-DR1-ähnlicher Stimulationskapazität nachgewiesen werden. Darüber hinaus wurden die generierten Zelllinien auf Präsentation der definierten Antigene L.casein und gpMBP gegenüber reaktiven TZH getestet. Dabei konnte die RT1D-restringierte Antwort von Klon19 auf L.casein und die RT1B-restringierte Antwort von 53/4 auf gpMBP bestätigt werden. Ebenfalls wurden die erstellten Transfektanten mit einem viralen Sag der Maus, dem vSag7-Gen des mtv7, transfiziert und auf Stimulation des TZH RG17 und von LEW-Lymphozyten getestet. Dabei zeigte sich eine geringe Reaktivität gegenüber den erstellten Transfektanten, die RT1B-dominiert war. Gleichzeitig ergaben sich in der Auswertung Hinweise für einen vSag7-Transfer von MHC-Klasse-II-negativen Produzenten auf MHC-Klasse-II-positive Rattenzellen, die durch weitere Experimente inklusive eines In-vivo-Tests bestätigt werden konnten. In der Generierung gemischter Isotypen aus MHC-Klasse-II-Einzelkettengenen der LEW-Ratte konnte gezeigt werde, dass die Übertragung der RT1DaBb-Genkombination mit Hilfe eines retroviralen Gentransfers auf P80- und L929-Zellen nicht zu einer sicher detektierbaren Oberflächenexpression führte, auch nicht bei Koübertragung der invarianten Kette der Maus. Durch einen Western Blot unter reduzierenden Bedingungen konnte eine bezüglich Molekulargewicht und Quantität zu einem regulären RT1B-Molekül differente RT1Bb-Einzelkette in der Kombination RT1DaBb nachgewiesen werden. / In the work at hand the presenting function of LEW rat MHC class II molecules RT1B and RT1D for various superantigens and antigens as well as the generation of mixed MHC class II isotypes in the LEW rat have been investigated. Superantigens are proteins of bacterial and viral origin, which lead to a TCR-specificity-independent activation of up to 30 % of the individual's T-cell population by interacting with the Vb part of the T-cell receptor after having bound to an MHC class II molecule. The release of mediators by T- and consecutively activated cells causes on the one hand development of acute diseases like toxic shock syndrome, gastroenteritis and other, but can also potentially activate autoreactive T-cells and lead to autoimmune diseases. In order to examine characteristics of LEW MHC class II molecules, first RT1B and RT1D chain genes were transferred into L929 cells via a retroviral transfection system and surface expression was demonstrated by using the monoclonal antibodies Ox6 and 14-4-4S. Successively, superantigen presentation was verified by stimulation of the LEW Vb8.2+ T-cell hybridoma 53/4 by bacterial superantigens SEB, SEC1-3, MAS and YPM and of LEW T-cells isolated from lymph nodes by SEC1, MAS and YPM. Both results were compared to activation in context of an HLA-DR1+ cell line. Experiments showed a much higher reactivity for the superantigens of human pathogen staph. aureus in presence of human versus LEW MHC class II molecules and an RT1B dominated answer amongst LEW presentatory molecules. Additionally, clues for MHC class II independent activation were found in case of SEB. The superantigen of yersinia pseudotuberculosis YPM was also much better presented by human than LEW MHC class II molecules while showing little differences between RT1B and RT1D. MAS bound preferentially to RT1D and equal stimulative capacity compared to HLA-DR1 could be detected. Accessorily, generated cell lines were analysed for presentation of peptide antigens L.casein and gpMBP towards reactive T-cell hybridomas, in which RT1D-restricted answer of Klon19 to L.casein and RT1B-restricted answer of 53/4 to gpMBP could be confirmed. Also generated cell lines were transfected with a viral mouse superantigen, the vsag7 gene of mtv7, and tested for stimulation of the RG17 T-cell hybridoma and LEW lymphocytes. Low reactivity towards transfected cell lines was detected, which was dominated by RT1B. Additionally, evidence for a transfer of vsag7 from MHC class II- producers to MHC class II+ rat cells could be found, which was enhanced by additional experiments including in vivo testing. Attempting to create mixed isotypes consisting of LEW rat MHC class II chains, it was demonstrated, that transferring the gene combination RT1DaBb via retroviral gene transfer into P80 and L929 cell lines resulted in no certain surface expression, also not under cotransfection of these cells with mouse invariant chain. Using western blot method under reducing conditions, a RT1Bb single chain different to the one of the regular RT1B molecule concerning molecular weight and quantitiy could be detected in the combination RT1DaBb.

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