Regulatory T cells (Tregs) suppress effector immune responses and have been implicated in promoting chronic viral infections. Their role during influenza infection and vaccination, however, is still unclear. Influenza is a major public health concern, claiming over 49,000 lives annually in the U.S. alone. Vaccination is the best approach for preventing disease but frequent mutations of immunogenic epitopes requires a new vaccine to be formulated and administered annually. This poses a challenge for vaccine manufacturing and may strain patient compliance. A universal influenza vaccine, which targets the highly conserved extracellular domain of the influenza matrix protein 2 (M2e), may circumvent this problem by generating cross-protective immunity. In this study, we tested the efficacy of the M2e universal vaccine in the ferret, and determined whether vaccination induces a Treg response after influenza infection. We found that vaccination promotes the development of M2e specific IgM and IgG antibodies after boosting. Upon challenge with A/Memphis H1N1, vaccinated ferrets exhibited a lower body temperature and reduced virus titer compared to non-vaccinated animals. Together these findings suggest that the M2e vaccine protects ferrets against influenza infection. In order to determine whether Tregs increase after vaccination in ferrets, we had to first clone and characterize genes involved with Treg phenotype and function including CD25, Foxp3, and IL-10. The reciprocal nature between Tregs and Th17 cells and their involvement during influenza infection prompted us to also clone ferret IL-17F. Using these sequences, we designed a qRT-PCR array to measure the expression of Foxp3, IL-10, and IL-17F in ferret tissue. We also identified cross-reactive antibodies against ferret CD8, CD25, and Foxp3 for use in FACS, western blot, and ICC. Using these tools, we found that vaccination significantly increased the expression of Foxp3 in the spleen. An increased percentage of Foxp3+ lymphocytes was detected in both the PBMCs and splenocytes of immunized animals. In contrast, IL-10 and IL-17F expression decreased significantly in both immunized and non-immunized ferrets compared with naïve animals. These studies suggest that the M2e influenza vaccine induces a regulatory T cell response in ferrets and protects against influenza infection. / acase@tulane.edu

CD4+CD25+FoxP3+ regulatory T cells (Treg) possess the capacity to modulate both adaptive and innate immunity. Due to their suppressive nature, Treg cells have been studied and tested in a variety of scenarios in an attempt to ameliorate undesired immune responses. While graft versus host disease (GVHD) has in fact emerged as the first clinical application for human Treg cells (Riley et al. 2009), equally important are issues concerning hematopoietic engraftment and immune reconstitution. Currently, little is known about the effect(s) that regulatory T cells may exert outside the immune system in this context. Based on cytokine effector molecules they can produce we hypothesized that Treg cells could regulate hematopoietic phenomena. The studies portrayed in this dissertation demonstrate that Treg cells can differentially affect the colony forming activity of myeloid and erythroid progenitor cells. In-vitro as well as in-vivo findings demonstrate the ability of Tregs to inhibit and augment the differentiation of primitive and intermediate myeloid (interleukin (IL)-3 driven) and late erythroid (erythropoietin driven) hematopoietic progenitor cells, respectively. The inhibitory and enhancing affects appeared to be mediated by independent pathways, the former requiring cell-cell contact, major histocompatibility complex (MHC) class II expression on marrow cells and involving transforming growth factor beta (TGF-beta), whereas the latter required interleukin (IL)-9 and was not contact dependent. Strikingly, we observed that in addition to regulating hematopoietic activity in normal primary BM cells, Tregs were also capable of suppressing colony forming activity by the myelogenous leukemia cell line NFS-60. Furthermore, studies involving endogenous Treg manipulations in-situ (i.e. depletion of these cells) resulted in elevated overall myeloid colony activity (CFU-IL3) and diminished colony numbers of erythroid precursors (CFU-E) in recipients following BMT. Consistent with these results, it was found that upon co-transplant with limiting numbers of bone marrow cells, exogenously added Treg cells exert in-vivo regulation of myeloid and erythroid CFU activity during the initial weeks post-transplantation. This regulation of hematopoietic activity by freshly generated Tregs upon transplantation led to the elaboration of a second hypothesis; following lethal total body irradiation (TBI) the host microenvironment facilitates regulatory T cell activation/effector function. Substantial evidence has accumulated in support of this hypothesis, for example we demonstrate up-regulation of surface molecules such as GARP and CD150/SLAM, which have been previously reported as indicators of Treg activation following TCR signaling and co-stimulation, occurs in donor (reporter) Treg populations. Acquisition of an activated phenotype and hence of effector/modulatory function is consistent with the previous in-vivo observations, indicating that both recipient and donor Treg cells can influence hematopoietic progenitor cell activity post-transplant. Finally, the present studies may be of great relevance in the emerging field of Treg cell based immunotherapy for prevention and/or treatment of HSCT complications.

Globalement, un tiers de la population mondiale est infectée par Mycobacterium tuberculosis, l'agent infectieux de la tuberculose (TB). Fort heureusement, seuls 5 à 10 % des individus infectés développent un jour une TB active. Les individus non malades restent cependant infectés à vie, on parle d'infection latente. Chaque année, 8-10 millions nouveaux cas de tuberculose active sont recensés et M. tuberculosis est responsable de 1,5 à 2 millions de décès. Depuis plus d'une décennie, M. tuberculosis s'est étroitement associé à l'infection par le virus de l'immunodéficience humaine. Cette alliance néfaste représente une importante menace pour les pays en voie de développement, car ces 2 pathogènes déciment les forces vives de ces populations. Il faut malheureusement rajouter à ce triste tableau une fréquence grandissante de souches multi-résistantes, voire extensivement multi-résistantes. Face à ces souches, les avancées thérapeutiques du siècle dernier sont pratiquement réduites à néant. Considérant ces données, il est désormais crucial d'améliorer nos outils de dépistage de l'infection latente, de diagnostic de la maladie active, de prévention (vaccins) et de traitement. Pour atteindre ces objectifs, une des pistes est la caractérisation détaillée des réponses immunitaires. En comparant les réponses immunitaires des sujets infectés de manière latente à celles liées à la maladie active, nous pourrons peut-être comprendre certains mécanismes de protection. L'étude des réponses immunitaires induites par la « Heparin-Binding-Hemagglutinin » (HBHA) s'est faite dans cet objectif. La HBHA est une adhésine exprimée par le complexe M. tuberculosis. Elle est impliquée dans la dissémination extrapulmonaire du bacille et constitue donc un facteur de virulence. Par ailleurs, une vaccination de souris par seulement 3 doses de 5 µg de HBHA suffit à protéger de l'infection avec une efficacité comparable à celle du vaccin BCG. Chez l'homme, les sujets sains mais infectés développent d'importantes sécrétions d'interféron-gamma (IFN-γ) en réponse à cet antigène, alors que la majorité des patients tuberculeux ne le font pas. Cette différence est importante pour comprendre une des raisons d'échappement de M. tuberculosis au contrôle immunitaire. La HBHA est une protéine méthylée et la méthylation s’avère essentielle pour ses propriétés immunoprotectrices. Nos travaux présentés ici se sont axés sur deux éléments de la réponse immunitaire à la HBHA chez l'homme : d'une part, l'exploitation de la réponse périphérique d'IFN-γ à la HBHA comme outil de dépistage de l'infection latente et, d'autre part, l'étude des raisons de la faible sécrétion d'IFN-γ spécifique de la HBHA lors de la maladie active. L'évaluation de la sécrétion périphérique d'IFN-γ en réponse à la HBHA a permis de démontrer rétrospectivement que celle-ci permet de détecter plus de 90 % des sujets réagissant positivement à l'injection intradermique de tuberculine. De manière intéressante, l'utilisation d'un test commercial, le QuantiFERON TB Gold IT (QFT-IT) n'a permis de détecter que la moitié des sujets infectés sains. De notre point de vue, le QFT-IT ne peut être recommandé seul pour le dépistage systématique de l'infection latente par M. tuberculosis. De manière parallèle, un test de stimulation basé uniquement sur la sécrétion d’IFN-γ suite à une stimulation à l'ESAT-6, composant du QFT-IT, n'a pas permis d'augmenter la sensibilité, ni d'ajouter une plus-value au test basé sur la HBHA. A l'instar de l'intradermoréaction à la tuberculine, le dépistage de la maladie active reste décevant que ce soit par l'utilisation de la HBHA ou de l'ESAT-6. La TB active est caractérisée par une basse sécrétion périphérique d'IFN-γ en réponse à la stimulation par la HBHA. Cette faible sécrétion est cependant réversible, puisque un traitement efficace permet d'atteindre des taux d'IFN-γ significativement plus élevés. Ceci nous démontre qu'il s'agit d'une suppression associée à la phase active de l'infection. Nous avons d'abord évalué l'importance de la modulation de la sécrétion d'IFN-γ en réponse à la HBHA par 2 cytokines immunomodulatrices, l'interleukine-10 (IL-10) et le Transforming-Growth-Factor-Beta (TGF-ß). De manière intéressante, alors que ces 2 cytokines sont associées à l'infection par M. tuberculosis, la HBHA n'est inductrice ni d'IL-10, ni de TGF-ß. Les lymphocytes T régulateurs (Treg) expriment 2 marqueurs d'intérêt : le CD25, composant du récepteur à l'IL-2, et Foxp3, un gène régulateur majeur des cellules Treg. Ces cellules sont décrites comme suppressives de réponses immunitaires déclenchées par des antigènes du Soi et du non-Soi. Nous avons montré que la proportion de lymphocytes Treg périphériques est augmentée en cas de TB active. Par ailleurs, nous avons également démontré que ces cellules suppriment la sécrétion d'IFN-γ et la prolifération induite par la HBHA après stimulation des cellules mononucléées sanguines périphériques de patients tuberculeux in vitro. Cependant, la réponse anti-HBHA des patients tuberculeux, qui est démasquée par la déplétion des lymphocytes Treg, n'est pas dirigée contre des épitopes protecteurs. En effet, la méthylation n'influence pas leur sécrétion d'IFN-γ. De ce point de vue, les lymphocytes Treg sont impliqués dans la maladie tuberculeuse et influencent négativement les réponses dirigées contre un antigène protecteur. Cependant, il semble que la TB active soit également associée à une ignorance d'épitopes protecteurs. Enfin, nous avons également démontré qu'il était possible d'induire des lymphocytes Treg au départ de cellules sanguines périphériques de sujets infectés sains. En effet, la stimulation in vitro des cellules sanguines périphériques en présence de BCG et de TGF-ß est un moyen rapide pour induire l'apparition de lymphocytes Treg fonctionnels in vitro. Ceci nous interroge quant aux rôles des lymphocytes Treg dans la pathogenèse de la maladie. En effet, un excès de TGF-ß circulant est observé dans certaines conditions cliniques à haut-risque de TB post-primaire. De ce point de vue, les lymphocytes Treg pourraient être des acteurs déterminant dans la perte du contrôle à long terme de l'infection et, par là, pourraient être des cibles thérapeutiques d'intérêts lors de l'infection par M. tuberculosis. /Mycobacterium tuberculosis is the causative agent of tuberculosis (TB). It is estimated approximately one third of the World’s population is infected with M. tuberculosis. Fortunately, only 5 to 10 % of the infected individuals will develop the disease throughout their life. However, the other healthy infected individuals remain infected for life: this is the latent TB infection (LTBI). Every year, 8 to 10 million new cases of TB are recorded globally, and about 2 to 3 million of people die from the disease. During the last several decades the co-infection of M. tuberculosis and the human immunodeficiency virus have worsened the picture. This dreadful association currently affects mostly the poorest people of the World. Unfortunately, bad news never stands alone. We now witness increasing emergence of multi-drug-resistant and even of extensively-multi-drug-resistant M. tuberculosis strains. Against these strains current therapeutics are virtually useless. The development of new tools for prevention (vaccines), diagnostics and treatment is crucial. In order to fulfill these objectives, detailed studies on the immune responses is one of the main tracks to explore. Indeed, the comparison of immune responses in LTBI subjects with those in TB patients may provide some clues to understand immune mechanisms of protection. Studies of the immune responses that are specific to Heparin-Binding-Hemagglutinin (HBHA) may be one of these clues. HBHA is an adhesin, which is expressed by the micro-organisms of the M. tuberculosis complex. It largely contributes to the extrapulmonary dissemination of the tubercle bacilli. Hence, HBHA may be qualified as an important virulence factor. Furthermore, vaccination of mice with three doses of only 5 µg HBHA each affords the same level of protection as vaccination with BCG. In humans, peripheral blood mononuclear cells (PBMC) from LTBI subjects secrete significant levels of IFN-γ in response to HBHA, whereas PBMC from TB patients do not. This discrepancy may be a cornerstone in the understanding of some of the mechanisms underlying the immune escape mediated by M. tuberculosis. HBHA is a methylated protein, and the methylation is crucial for its immuno-protective properties. This work focused on 2 major issues of the HBHA-specific immune response in humans: the use of the peripheral IFN-γ secretion in response to HBHA as a diagnostic tool for LTBI and the analysis of the underlying mechanisms to the low IFN-γ secretion during active TB. In our study, the measurement of HBHA-specific IFN-γ secretion resulted in the detection of more than 90 % of the tuberculin-skin-test (TST) positive LTBI. Strikingly, the QuantiFERON TB Gold IT (QFT-IT), a commercial test, failed to identify those LTBI subjects in more than 50 % of the cases. Therefore, we cannot recommend the use of QFT-IT alone instead of the TST for the detection of LTBI. Similarly, a test relying on the detection of IFN-γ secretion upon ESAT-6 stimulation, one of the antigens used in the QFT-IT, was not sufficiently sensitive for the LTBI detection, nor did it improve the sensitivity or the specificity of the HBHA-based test. In contrast to the diagnosis of LTBI, the tests based on HBHA- or ESAT-6-induced IFN-γ secretions displayed poor sensitivity for the diagnosis of active TB. During active TB, the HBHA-specific IFN-γ secretion in the periphery is low. However, this weak secretion is reversible upon effective treatment, as the IFN-γ response to HBHA is increased after completion of chemotherapy. This is strongly suggestive of an immune suppression during active disease. Therefore, we have first evaluated the role of two immunomodulatory cytokines, interleukin-10 (IL-10) and Transforming-Growth-Factor-Beta (TGF-ß), in the suppression of the HBHA-specific IFN-γ secretion. We found that neutralization of neither IL-10 nor TGF-ß with specific antibodies induced HBHA-specific IFN-γ secretion by PBMC of TB patients in vitro. In contrast, depletion of regulatory T cells (Treg) that express 2 major markers, CD25, a constituent of the IL-2 receptor, and Foxp3, a master regulatory gene, resulted in increased HBHA-specific IFN-γ secretion by the PBMC of TB patients. These cells are known to be involved in the suppression of immune responses to both Self and non-Self antigens. We further show that the size of the peripheral Treg cell population increases during active disease. In addition to suppressing the HBHA-specific IFN-γ secretion these cells suppress T cell proliferation in response to HBHA in vitro. However, even after depletion of the Treg cells, the uncovered HBHA-specific immune responses are not directed to the methylated epitopes during TB disease. Finally, we show that Treg cells can be induced (or expanded) from the PBMC of LTBI subjects. Stimulation of those PBMC with BCG in the presence of TGF-ß resulted in a quick appearance of functional Treg cells in vitro. This observation strongly suggests a role of Treg cells in the pathogenesis of TB, in particular in the progression of latency to reactivation. Interestingly, excessive concentration of TGF-ß, associated with various clinical conditions, is high risk factor for post-primary TB. Thus, Treg cells may result in the loss of immune control against latent M. tuberculosis infection. Therefore, Treg cells may represent potential therapeutic targets during M. tuberculosis infection.

<p>Naturally occurring CD4+CD25+Foxp3+ regulatory T cells (TReg) are a cell lineage that develops in the thymus and exits to the periphery, where they represent 5-10% of the peripheral CD4+ T cell population. Phenotypically, they are characterized by the expression of the cell surface markers CD25, as known as the IL-2 receptor alpha chain, glucocorticoid-induced tumor necrosis factor receptor (GITR), and cytotoxic T-lymphocyte antigen-4 (CTLA-4), as well as forkhead box P3 (Foxp3), a transcription factor considered to be the most specific TReg marker. Functionally, TReg cells are defined by their ability to suppress the activation of multiple cell types including CD4+ and CD8+ T cells, B cells, natural killer (NK) cells, and dendritic cells (DCs). Suppression can be achieved by the production of immunosuppressive cytokines or direct cell-to-cell contact, with these mechanisms directly affecting suppressed cells or indirectly affecting them by modulating antigen presenting cells (APCs). The suppressive abilities of TReg cells are crucial in maintaining dominant tolerance--the active, trans-acting suppression of the immune system for the prevention of autoimmune diseases. In addition to preventing autoimmune diseases, studies have also demonstrated critical roles for TReg cells in down-modulating anti-tumor immunity, suppressing allergic diseases, such as asthma, and achieving transplant tolerance. Recent studies have also demonstrated roles for TReg cells during pathogen infection, which will be the focus of this thesis.</p><p>Studies examining TReg cells during infection have largely focused on chronic infection models. These studies have shown that TReg cells can affect responses to pathogens in various ways that can be beneficial or detrimental for either the host or the invading pathogen. In some infections, TReg cells downregulation effector responses, which can lead to pathogen persistence and, in some cases, concomitant immunity. TReg cell-mediated suppression can also reduce immunopathology at sites of infection, which can occur as a result of a vigorous anti-pathogen immune response. </p><p>In contrast to chronic infection, how TReg cells behave and function following acute infections remains largely unknown as, to date, very few studies have been conducted. Current work with acute infection models has indicated that TReg cells affect immune responses in some acute infection models, but not in all. Furthermore, the results of these studies have implicated that current approaches to examine TReg cells during acute infection by depleting the total TReg cell repertoire, as opposed to targeting pathogen-specific TReg cells, may not be ideal. Finally, it is unclear what happens to activated TReg cells following the resolution of infection. </p><p>Due to the lack of knowledge about the role of pathogen-specific TReg cells during acute infection, we sought to employ a different approach to address some of the outstanding questions in the field. Here, we utilized CD4+ non-TReg and TReg cells from T cell receptor (TCR) transgenic mice that recognize a pathogen-specific epitope found in three different models of acute viral infection: recombinant vaccinia virus, recombinant adenovirus, and influenza. Using this model system, we were able to track pathogen-specific TReg cells following acute viral infection to determine their kinetics during the course of infection, as well as their influence on CD4+ non-TReg cells during different times after infection. We also employed major histocompatibility complex (MHC) Class II tetramer technology to track the fate of endogenous pathogen-specific TReg cells following infection with influenza. </p><p>Using these models systems, we show that pathogen-specific TReg cells can be activated and expand upon acute viral infections in vivo. The activated TReg cells then contract to form a "memory" pool after resolution of the infection. These "memory" TReg cells expand rapidly upon a secondary challenge, secrete large amounts of IL-10, and suppress excessive immunopathology, which is elicited by the expansion of non-TReg cells, via an IL-10-dependent mechanism. The work presented in this thesis reveals a previously unknown "memory" TReg cell population that develops after acute viral infections and may help design effective strategies to circumvent excessive immunopathology.</p> / Dissertation

The long-term success of transplantation is limited by the need for immunosuppression; thus, tolerance induction is an important therapeutic goal. A 16-day treatment with rapamycin in mice led to indefinite graft survival of fully mismatched cardiac allografts, whereas untreated hearts were rejected after 8-10 days. Specific tolerance was confirmed through subsequent skin grafts and in vitro lymphocyte assays that showed recipient mice remained immunocompetent towards 3rd party antigens but were impaired in responding to donor antigens. Mechanisms that account for this tolerant state were then investigated. Splenic CD8+CD44+ memory T-cells were reduced in tolerant mice but had increased frequencies of the CD62LLO population. CD4+CD25+Foxp3+ regulatory T-cells were increased in tolerant mice. Through multiplex PCR, 4 regulatory T-cell related genes were found up-regulated and 2 proinflammatory genes were down-regulated in accepted hearts. This expression pattern may serve as a putative biomarker of tolerance in patients undergoing transplantation.

The long-term success of transplantation is limited by the need for immunosuppression; thus, tolerance induction is an important therapeutic goal. A 16-day treatment with rapamycin in mice led to indefinite graft survival of fully mismatched cardiac allografts, whereas untreated hearts were rejected after 8-10 days. Specific tolerance was confirmed through subsequent skin grafts and in vitro lymphocyte assays that showed recipient mice remained immunocompetent towards 3rd party antigens but were impaired in responding to donor antigens. Mechanisms that account for this tolerant state were then investigated. Splenic CD8+CD44+ memory T-cells were reduced in tolerant mice but had increased frequencies of the CD62LLO population. CD4+CD25+Foxp3+ regulatory T-cells were increased in tolerant mice. Through multiplex PCR, 4 regulatory T-cell related genes were found up-regulated and 2 proinflammatory genes were down-regulated in accepted hearts. This expression pattern may serve as a putative biomarker of tolerance in patients undergoing transplantation.

Universidade Federal do Cearà / A hansenÃase à uma doenÃa crÃnica causada pelo Mycobacterium leprae, que representa um importante problema de saÃde pÃblica mundial, especialmente no estado do CearÃ, Brasil. A incidÃncia nos menores de 15 anos de idade reflete a endemicidade da regiÃo e a dificuldade no seu controle. A doenÃa apresenta um espectro variado de manifestaÃÃes clÃnicas que està relacionado a resposta imune desenvolvida pelo indivÃduo, com as respostas Th1 e Th2 relacionadas com as formas paucibacilar e multibacilar, respectivamente. CÃlulas T regulatÃrias (Tregs) tÃm recebido atenÃÃo especial na literatura e tÃm sido relacionadas com o desenvolvimento de infecÃÃes crÃnicas, entretanto seu papel na hansenÃase nos menores de 15 anos ainda nÃo foi elucidado. Esse trabalho teve por objetivo avaliar a freqÃÃncia das Tregs CD4+CD25+FOXP3high, CD8+CD25+FOXP3high, CD4+CD25highFOXP3+ e CD8+CD25highFOXP3+ em pacientes com hansenÃase e contatos intradomiciliares, ambos menores de 15 anos. CÃlulas mononucelares de sangue perifÃrico foram cultivadas por 72 horas com ativadores (anti-CD3 e anti-CD28) e/ou com M.leprae total sonicado. ApÃs cultura, a frequÃncia das Tregs foi identificada por citometria de fluxo. Observamos maior freqÃÃncia de cÃlulas CD4+CD25+FOXP3high em pacientes do que em contatos,nÃo havendo diferenÃas entre eles com relaÃÃo Ãs outras populaÃÃes avaliadas. Os pacientes multibacilares apresentaram maior freqÃÃncia de cÃlulas CD4+CD25+FOXP3high e CD8+CD25+FOXP3high do que os contatos. Apenas nesses pacientes, as cÃlulas CD4+CD25+FOXP3high foram negativamente correlacionadas com linfÃcitos CD4+ e CD8+ nÃo-regulatÃrios e as cÃlulas CD8+CD25+FOXP3high com linfÃcitos CD4+ nÃo-regulatÃrios. A maior frequÃncia de Tregs com elevada expressÃo de FOXP3 nos menores de 15 anos com hansenÃase multibacilar, bem como sua correlaÃÃo inversa com a frequÃncia de linfÃcitos nÃo regulatÃrios nesses pacientes sugere a participaÃÃo dessas cÃlulas na perpetuaÃÃo da infecÃÃo pelo M. leprae. / Leprosy is a chronic disease caused by Mycobacterium leprae, which represents an important health problem worldwide, especially in CearÃ, Brazil. The incidence in under-15-year-olds reflects the endemicity of the region and the difficulty in its control. The disease presents a wide spectrum of clinical manifestations that reflects the immune response developed, with Th1 and Th2 responses related to the paucibacillary and multibacillary (MB) forms, respectively. Regulatory T cells(Tregs) cells have received special attention in the literature and have been associated with development of chronic infections, however its role in leprosy in children under-15-years-old has not yet been elucidated. This study aimed to evaluate the frequency of CD4+CD25+FOXP3high, CD8+CD25+FOXP3high, CD4+CD25highFOXP3+ and CD8+CD25highFOXP3+ Treg cells in patients with leprosy and household contacts(HHC), both under 15 years. Peripheral blood mononucelares cells were cultured for 72 hours with activators(anti-CD3 and anti-CD28) and/or with M.leprae total sonicated. After culture, Treg cells were identified by flow cytometry. We found a greater frequency of CD4+CD25+FOXP3high cells in patients than in HHC, where there were no differences in the other cell populations evaluated. The multibacillary patients had a higher frequency of CD4+CD25+FOXP3high and CD8+CD25+FOXP3high cells compared to HHC. Only these patients, CD4+CD25+FOXP3high cells were negatively correlated with CD4+ and CD8+ non-Treg lymphocytes , and CD8+CD25+FOXP3high cells with CD4+ non-Treg lymphocytes. The greater frequency of Tregs with high expression of FOXP3 in individuals with multibacillary leprosy under-15-years-old and its inverse correlation with the frequency of non-regulatory lymphocytes in these patients suggests the involvement of these cells in the perpetuation of M. leprae infection.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21020号 / 医博第4366号 / 新制||医||1028(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 椛島 健治, 教授 三森 経世, 教授 小柳 義夫 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Regulatory T cells (Treg) are essential for the induction and maintenance of immunological tolerance to self and foreign antigens. The development of allergic asthma is mediated by T helper cell type-2 (Th2) inflammatory mechanisms and may also involve, based on murine and human studies of allergic asthma, compromised Treg immune regulation. Our overall objective was to more thoroughly elucidate the biology of Treg in allergic asthma, and to better understand their potential as a treatment for the disease. Initially, we characterized three different Treg phenotypes based on frequency and functional capacity. We showed both quantitative and functional heterogeneity in circulating Treg. Quantitative variability was also observed in circulating, but not airway, Treg when comparisons were made between healthy controls and asthmatic subjects. These findings emphasize the need for clear definitions of Treg phenotypes, and that interpretation of their frequency and function in health and disease needs to be phenotype-specific. Next, we assessed the Treg response in mild allergic asthmatic isolated early responders and dual responders after allergen inhalation challenge. We observed a reduced frequency of airway Treg after allergen challenge in DR, but not IER, associated with a smaller ratio of Treg to CD4+ cells. These data suggest that Treg to T effector cell (Teff) balance is important in the regulation of late asthmatic responses. Lastly, we evaluated the effects of two novel monoclonal anti-asthma therapies on circulating Treg after allergen inhalation challenge. We demonstrated that neither anti-OX40L nor anti-TSLP therapy altered circulating Treg frequency, while anti-TSLP, but not anti-OX40L, was effective in attenuating allergen-induced airway responses. These observations demonstrate the need for further investigation into the effects of anti-asthma therapies on Treg as well as the development of novel therapies aimed at manipulating Treg in order to better control immune responses. The findings of this thesis enhance our understanding of Treg in allergic asthma. Treg, utilized as stand-alone or adjunct therapy, may provide a novel therapy in the treatment of allergic asthma. / Thesis / Doctor of Philosophy (PhD)

No description available.