<p><strong>INTRODUCTION: </strong>Pre-clinical and clinical data strongly support the feasibility of employing immunotherapy as a strategy to treat cancer.</p> <p><strong>METHODS: </strong>Using the B16F10 murine melanoma model, we have been investigating mechanisms of T cell-mediated antitumor immunity following immunization with dopachrome tautomerase (DCT), a melanoma-associated antigen.</p> <p><strong>RESULTS: </strong>In <strong>Chapter 2</strong>, we uncovered an interesting dichotomy whereby DCT-specific CD4⁺ T cell-mediated tumor protection and autoimmunity are dependent on IL-4/STAT-6 and IFN-g/STAT-4, respectively. Our data also revealed that this phenomenon is extrinsic of CD4⁺ T cell polarization.</p> <p>To gain further insight into the targets recognized by CD4⁺ T cells, we conducted in <strong>Chapter 3</strong> extensive CD4⁺ T cell epitope mapping experiments using overlapping peptide libraries. Interestingly, while we were able to identify “helper” epitopes within DCT that were required for maximal CD8⁺ T cell expansion, we were unable to identify “effector” epitopes responsible for tumor rejection. Further examination of the requirements for the generation of CD4⁺ T cell effector epitopes showed that post-translational modifications of the protein were involved.</p> <p>In <strong>Chapter 4</strong>, we investigated the modest efficacy afforded by DCT immunization in the context of established B16F10 melanomas. Using intratumoral transcriptional analysis, we demonstrated that the vaccine rapidly promoted an IFN-g-dependent immunosuppressive state inside the tumor. Concurrent treatment with the immunomodulatory antibodies anti-4-1BB and anti-PD-1 effectively counteracted this tumor immunosuppression, resulting in complete regression of tumors and long-term survival in 70% of the mice.</p> <p><strong>CONCLUSIONS: </strong>The research described in this thesis sheds new light into the mechanisms by which vaccine-mediated CD4⁺ T cell responses participate to tumor rejection and autoimmunity. Moreover, our findings indicate that cancer vaccine-induced tumor immunosuppression significantly limits tumor regression, emphasizing the requirement of combinatorial approaches for successful cancer immunotherapy. Overall, our research offers new insight for future vaccine development.</p> / Doctor of Philosophy (Medical Science)

<p>Antibodies have the ability to influence the antibody response against the very antigen they are specific for, in a process called antibody feedback regulation. Depending on the nature of the antigen, the antibody response can be either enhanced or almost completely inhibited. This thesis focuses on the underlying mechanisms of antibody feedback regulation <i>in vivo</i>. </p><p>Antigen-specific IgG can inhibit the antibody response to a particulate antigen. Based on its ability to inhibit B cell activation, the inhibitory FcγRIIB (low affinity receptor for IgG) has been suggested to be involved. Here we show that although FcγRIIB is required for efficient suppression<i> in vitro, </i>it is not required <i>in vivo</i>. Therefore, even though FcγRIIB can inhibit antibody responses, other mechanisms (such as epitope masking and enhanced antigen clearance) play a more dominant role<i> in vivo</i>.</p><p>The antibody response to soluble antigen is greatly enhanced when it is introduced to the immune system in complex with antigen-specific IgG or IgE. We found that FcγRIIB attenuates the magnitude of IgG-mediated enhancement. In mice lacking FcγRIIB, IgG enhanced the antibody response much more efficiently than in normal mice.</p><p>Since B cells require CD4⁺ T cell help in order to become antibody-producing cells, we examined the CD4⁺ T cell response to immune complexes <i>in vivo</i>. Using an adoptive transfer strategy with transgenic ovalbumin (OVA)-specific CD4⁺T cells, we could show that the enhanced OVA-specific IgG response to IgG2a/OVA and IgE/OVA complexes was preceded by a potent OVA-specific CD4⁺ T cell response. IgG2a-mediated enhancement was dependent on activating Fcγ receptors, whereas IgE-mediated enhancement was dependent on CD23, the low affinity receptor for IgE. We identified CD23⁺ B cells as the responsible effector cells for IgE-mediated enhancement<i> in vivo</i>. Taken together, these results show that Fc receptor-mediated antigen presentation is a major mechanism underlying antibody feedback enhancement. </p>

Antibodies have the ability to influence the antibody response against the very antigen they are specific for, in a process called antibody feedback regulation. Depending on the nature of the antigen, the antibody response can be either enhanced or almost completely inhibited. This thesis focuses on the underlying mechanisms of antibody feedback regulation in vivo. Antigen-specific IgG can inhibit the antibody response to a particulate antigen. Based on its ability to inhibit B cell activation, the inhibitory FcγRIIB (low affinity receptor for IgG) has been suggested to be involved. Here we show that although FcγRIIB is required for efficient suppression in vitro, it is not required in vivo. Therefore, even though FcγRIIB can inhibit antibody responses, other mechanisms (such as epitope masking and enhanced antigen clearance) play a more dominant role in vivo. The antibody response to soluble antigen is greatly enhanced when it is introduced to the immune system in complex with antigen-specific IgG or IgE. We found that FcγRIIB attenuates the magnitude of IgG-mediated enhancement. In mice lacking FcγRIIB, IgG enhanced the antibody response much more efficiently than in normal mice. Since B cells require CD4+ T cell help in order to become antibody-producing cells, we examined the CD4+ T cell response to immune complexes in vivo. Using an adoptive transfer strategy with transgenic ovalbumin (OVA)-specific CD4+T cells, we could show that the enhanced OVA-specific IgG response to IgG2a/OVA and IgE/OVA complexes was preceded by a potent OVA-specific CD4+ T cell response. IgG2a-mediated enhancement was dependent on activating Fcγ receptors, whereas IgE-mediated enhancement was dependent on CD23, the low affinity receptor for IgE. We identified CD23+ B cells as the responsible effector cells for IgE-mediated enhancement in vivo. Taken together, these results show that Fc receptor-mediated antigen presentation is a major mechanism underlying antibody feedback enhancement.

Es ist davon auszugehen, dass Fehlfunktionen im Immunsystem mit der Ausprä-gung des Krankheitsbildes der aggressiven Parodontitis im Zusammenhang ste-hen. In dieser Arbeit sollen anhand klinischer, immunologischer und mikrobiologischer Untersuchungen ein immunologisches Risikoprofil bei Patienten mit aggressiver Parodontitis erschlossen, gegebenenfalls Unterschiede zur moderaten chronischen Parodontitis beleuchtet und explorativ Zusammenhänge zwischen immunologischen und mikrobiologischen Befunden eruiert werden. Es wurden geeignete Patienten und gesunde Probanden laut Ethikvotum rekrutiert. Die immunologischen Untersuchungen erfolgten an PBMCs unter Verwendung durchflusszytometrischer Methoden und mittels ELISpot-Assay. Mikrobiologische Untersuchungen subgingivaler Plaque wurden als klassische Kultur und 16S rRNA-Sequenzierung durchgeführt. Immundefekterkrankungen konnten bei allen Individuen ausgeschlossen werden. Im Gruppenvergleich wurde eine erhöhte Stimulierbarkeit der PBMCs von Patienten mit moderater chronischer Parodontitis bezüglich ihrer IL-1β-Freisetzung bei Inkubation mit LPS festgestellt. Des Weiteren wies diese Patientengruppe einen vergleichsweise höheren Anteil an Gedächtnis-B-Zellen auf. In der mikrobiologischen Untersuchung konnten bekannte parodontopathogene Spezies nachgewiesen und Prevotella denticola als bislang nicht explizit erwähntes Pathogen mit aggressiver Parodontitis assoziiert werden. Unsere Untersuchung weisen auf Zusammenhänge zwischen immunologischen und mikrobiologischen Befunde bezüglich einiger parodontopathogener Bakterien, wie Prevotella oralis, und Stimulierbarkeit der IL-1β-Freisetzung, B-Zelldifferenzierung und T-Zellverhältnis hin.

Respiratory syncytial virus (RSV) is the most common cause of acute lower respiratory tract infection in young children worldwide, accounting for an estimated 33.8 million cases of respiratory disease, over 3 million of which require hospitalization, and between 66,000 and 199,000 deaths in this susceptible population. Additionally, severe RSV infection early in life is associated with an increased risk of wheeze and other airway disorders later in life. Despite this, there is currently no vaccine or economically reasonable prophylactic regimen to prevent infection. While disease is typically more severe in infancy RSV can infect throughout the lifespan repeatedly as the body does not develop protective immunity during primary or subsequent infection. The mechanisms behind this incomplete immunity are unclear. RSV has been reported to infect numerous extra-epithelial cell types. Interestingly, viral infection in human mesenchymal stem cells (MSCs) has been reported, but the consequences are poorly understood. MSCs are an immune regulatory cell population present in nearly every organ including the nasal mucosa and the lung. They play a role in regulating immune responses and mediating tissue repair. In the following studies we sought to determine whether RSV infection of MSCs enhances their immune regulatory functions and contributes to RSV-associated lung disease. RSV was shown to replicate in human MSCs by fluorescence microscopy, plaque assay, and expression of RSV transcripts. RSV-infected MSCs showed differentially altered expression of cytokines and chemokines such as IL-1β, IL-6, IL-8 and SDF-1 compared to normal human bronchial epithelial cells. Notably, RSV-infected MSCs exhibited significantly increased expression of IFN-β (~100-fold) and indoleamine-2,3-dioxygenase (IDO) (~70-fold) compared with mock-infected MSCs. IDO was identified in cytosolic protein of infected cells by Western blots and enzymatic activity was detected by tryptophan catabolism assay. Treatment of PBMCs with culture supernatants from RSV-infected MSCs reduced their proliferation in a dose dependent manner. This effect on PBMC activation was reversed by treatment of MSCs with the IDO inhibitors 1-methyltryptophan and vitamin K3 during RSV infection. We also demonstrated the pathway leading to IDO expression in RSV infected MSCs. Neutralizing IFN-β prevented IDO expression and activity indicating its role as a viral response factor perhaps “high jacked” by the virus in immune escape. Treatment of MSCs with an endosomal TLR, but not a RIG-I, inhibitor prevented IFN-β and IDO expression. Additionally, TLR3/dsRNA complex inhibitor was able to block IFN-β stimulation, while a TLR7/8/9 inhibitory ODN did not, suggesting that endosomal TLR3 detection of RSV dsRNA was leading to IFN-β and IDO expression. Together, these findings indicate that RSV infection of MSCs triggers their immune regulatory function via TLR3 recognition of dsRNA, upregulating IFN-β expression and IDO activity, ultimately affecting immune cell proliferation. This finding may account for the lack of protective RSV immunity and consequent repeated infections throughout one's lifetime.

Due to high incidence, medical and socioeconomic burden and impact on individual quality of life and productivity, allergic disorders are a crucial issue for 21st century immunology. Much still remains to be elucidated, particularly regarding the very early processes in allergy development. In order to introduce timely, effective preventive measures, novel, more reliable predictive factors of allergy risk also need to be established. Dysregulation of proper balance between the branches of immune response, particularly unwarranted dominance of Th2, is the underlying cause of allergy. After birth, new immune balance needs to be established to prepare the neonate for adequate reactivity towards newly encountered environmental stimuli. Regulatory T cells (Treg) play a central role in finely setting this balance and inducing tolerance towards harmless environmental antigens, including allergens. Interactions with external factors, most importantly microbiota, modulate this process during the early postnatal "window of opportunity." Analysis of cord blood Treg of children of allergic mothers uncovered decreased presence of function-associated surface markers and lower production of IL-10. Furthermore, decreased proportion of Helios- induced Treg was observed in children with higher risk of allergy....

No description available.

O diabetes mellitus do tipo 1 (DM1) é uma doença autoimune caracterizada pela destruição seletiva de células pancreáticas produtoras de insulina. Existem diversas formas de tratamento do DM1, tais como administração de insulina, imunossupressores, transplantes de pâncreas ou de ilhotas pancreáticas, porém todos se mostram ineficientes em algum aspecto. Recentemente, uma nova classe de medicamentos, os inibidores da enzima dipeptidil peptidase 4 (iDPP-4), demonstrou eficiência terapêutica e segurança no tratamento de pacientes com diabetes mellitus do tipo 2 devido ao aumento do hormônio peptídeo-1 semelhante ao glucagon (GLP-1, do inglês glucagon-like peptide-1). Além disso, o uso de inibidores de DPP-4 em modelos experimentais de DM1 demonstrou proteção das células pancreáticas contra apoptose, estimulação de neogênese de ilhotas pancreáticas e melhora do controle homeostático da glicose. Esse presente projeto teve como objetivo avaliar o perfil imunológico e endocrinológico da administração do inibidor de DPP-4 (MK0431) em DM1 experimental quimicamente induzido por estreptozotocina em camundongos C57Bl/6. Os animais diabéticos foram tratados com ração controle ou ração contendo inibidor de DPP-4 (4g MK0431/Kg de ração) ad libitum durante 30 e 90 dias. Durante o tratamento os animais tiveram glicemia, peso e teste de tolerância oral à glicose avaliados. Ao final do tratamento, os animais foram eutanasiados e o sangue, baço, timo, linfonodos pancreáticos e pâncreas foram coletados. Após 30 dias de tratamento com inibidor, foi observado um aumento do hormônio GLP-1 no soro, além de um padrão imunológico favorável. Dentre os mecanismos imunológicos, foi possível observar um aumento de células T reguladoras (CD4+CD25+Foxp3+) no baço e uma diminuição da citocina IFN- no homogenato pancreático. Após 90 dias de tratamento com inibidor, também foi detectado um aumento de insulina e GLP-1 séricos e uma diminuição nos níveis glicêmicos dos animais tratados. Observou-se uma redução no padrão inflamatório no microambiente pancreático, caracterizado pela diminuição das citocinas TNF- e IFN- no homogenato pancreático e por uma redução da freqüência de macrófagos CD11b+ nos linfonodos pancreáticos. Os resultados obtidos neste projeto contribuíram para validar a eficácia terapêutica da administração de inibidor de DPP-4 no tratamento do DM1 experimental, bem como os mecanismos imunológicos e endocrinológicos envolvidos. Sem a ocorrência de efeitos tóxicos relevantes, o uso de inibidores de DPP-4 pode se tornar uma alternativa terapêutica para o tratamento do DM1 em humanos, que constitui uma doença crônica associada à baixa qualidade de vida em longo prazo e necessidade de tratamento de alto custo. / Davanso, M.R. Immunoendocrinological analyses after administration of dipeptidyl-peptidase-4 inhibitor on experimental type 1 diabetes. 2012. 105p. Thesis (Masters Degree) School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, 2012. Type 1 Diabetes Mellitus (DM1) is an autoimmune disease characterized by the selective destruction of the insulin-producing pancreatic cells. Several forms of treatment for DM1 are current known such as insulin administration, immunosuppressors, pancreas or pancreatic islets transplantation, however, they all are inefficient in some aspect. Recently, a new class of drugs, the dipeptidyl-peptidase-4 inhibitors (iDPP-4) showed therapeutic efficacy and safety in the treatment with type 2 diabetes mellitus patients due to an increase in the glucagon-like peptide-1 (GLP-1). In addition, the use of DPP-4 inhibitors in experimental models of DM1 has demonstrated a protection of pancreatic cells against apoptosis, stimulation of pancreatic islets neogenesis and improvement in the glucose homeostatic control. This project evaluated the immunological and endocrinological profile of the DPP-4 (MK0431) inhibitor administration in experimental chemically induced DM1 by streptozotocin in C57BI/6 mice. The diabetic animals were treated with either a normal chow diet or diet containing DPP-4 inhibitor (4g MK0431/Kg of diet) ad libitum during 30 and 90 days. During the treatment the animals were evaluated regarding glycemia, weight, and oral glucose tolerance test. At the end of the treatment, the animals were killed and the blood, spleen, thymus, pancreatic lymph nodes and pancreas were collected. After 30 days of treatment with inhibitor, it was observed an increase in the hormone GLP-1 in the serum, besides a favorable immunological pattern. Among the immunologic mechanisms, it was possible to observe an increase in the regulator T cells (CD4+CD25+Foxp3+) of the spleen and a decrease in the cytokine IFN- in the pancreatic homogenate. After 90 days of treatment with inhibitor, it was also noticed an increase in the insulin and serum GLP-1 levels as well as a decrease in the glycemic levels in the treated animals. It was observed a reduction in the inflammatory pattern in the pancreatic microenvironment characterized by a decrease in the cytokines TNF- and IFN- in the pancreatic homogenate and by a reduction in the frequency of CD11b+ macrophages in the pancreatic lymph nodes. The results obtained in this project contributed to validate the therapeutic efficacy of the DPP-4 inhibitor administration in the treatment of experimental DM1, as well as the immunological and endocrinological mechanisms involved. Without the occurrence of relevant toxic effects, the use of DPP-4 inhibitors may become a therapeutic alternative for the treatment of DM1 in humans, which constitutes a chronic disease associated to low life quality and need for high cost treatment.

<p>Circulating immune complexes play an important role in the modulation of antibody responses and in the pathogenesis of immune diseases. This thesis deals with the <i>in vivo </i>regulatory properties of antibodies and their specific Fc receptors.</p><p>The immunosuppressive function of IgG is used clinically, to prevent rhesus-negative women from becoming sensitized to rhesus-positive erythrocytes from the fetus. The mechanism behind this regulation is poorly understood but involvement of a receptor for IgG, FcγRII, has been suggested. It is shown in this thesis that IgG and also IgE induce immunosuppression against sheep erythrocytes to a similar extent both in mice lacking all the known Fc receptors as in wild-type animals. These findings imply that antibody-mediated suppression of humoral responses against particulate antigens is Fc-independent and that the major operating mechanism is masking of epitopes.</p><p>Immunization with soluble antigens in complex with specific IgG leads to an augmentation of antibody production. The cellular mechanism behind this control is examined here and it is found that the capture of IgG2a immune complexes by a bone marrow-derived cell expressing FcγRI (and FcγRIII) is essential. An analysis of the ability of IgG3 to mediate this regulation indicated that, in contrast, this subclass of IgG augments antibody responses independently of FcγRI (and FcγRIII). These findings suggest that distinct mechanisms mediate the enhancing effect of different subclasses of antibodies.</p><p>Finally, the contribution of FcγRIII was studied in the development of collagen-induced arthritis (CIA), an animal model for rheumatoid arthritis in humans. It was discovered that while DBA/1 wild-type control mice frequently developed severe CIA, with high incidence, FcγRIII-deficient mice were almost completely protected, indicating a crucial role for FcγRIII in CIA.</p><p>The results presented here help to understand how immune complexes regulate immune responses <i>in vivo</i> and show that Fc receptors for IgG, if involved, could be new targets for the treatment of immune complex-related disorders.</p>

Circulating immune complexes play an important role in the modulation of antibody responses and in the pathogenesis of immune diseases. This thesis deals with the in vivo regulatory properties of antibodies and their specific Fc receptors. The immunosuppressive function of IgG is used clinically, to prevent rhesus-negative women from becoming sensitized to rhesus-positive erythrocytes from the fetus. The mechanism behind this regulation is poorly understood but involvement of a receptor for IgG, FcγRII, has been suggested. It is shown in this thesis that IgG and also IgE induce immunosuppression against sheep erythrocytes to a similar extent both in mice lacking all the known Fc receptors as in wild-type animals. These findings imply that antibody-mediated suppression of humoral responses against particulate antigens is Fc-independent and that the major operating mechanism is masking of epitopes. Immunization with soluble antigens in complex with specific IgG leads to an augmentation of antibody production. The cellular mechanism behind this control is examined here and it is found that the capture of IgG2a immune complexes by a bone marrow-derived cell expressing FcγRI (and FcγRIII) is essential. An analysis of the ability of IgG3 to mediate this regulation indicated that, in contrast, this subclass of IgG augments antibody responses independently of FcγRI (and FcγRIII). These findings suggest that distinct mechanisms mediate the enhancing effect of different subclasses of antibodies. Finally, the contribution of FcγRIII was studied in the development of collagen-induced arthritis (CIA), an animal model for rheumatoid arthritis in humans. It was discovered that while DBA/1 wild-type control mice frequently developed severe CIA, with high incidence, FcγRIII-deficient mice were almost completely protected, indicating a crucial role for FcγRIII in CIA. The results presented here help to understand how immune complexes regulate immune responses in vivo and show that Fc receptors for IgG, if involved, could be new targets for the treatment of immune complex-related disorders.