Dendritic cell is one of the professional antigen presenting cells, and it bridges innate immunity and adaptive immunity. To fully activate naïve T cells, it requires DC to provide at least two signals, the interaction between T cell receptor and the MHC class II molecule loaded with antigen processed by DC, and the co-stimulatory signals provided by the co-stimulatory molecules expressed on DC. The identification of more and more co-stimulatory molecules expressed on DC and the studies on their functions highlight the importance of co-stimulatory molecules on the regulation of DC functions. We here hypothesized that different expression levels of co-stimulatory molecules expressed on DC is pivotal of directing DC function towards immunity, tolerance and polarization of Th1/Th2 immune response. Using CD40 as the model molecule to study the effect of its expression levels on DC functions, we found that no/low expression level of CD40 on DC induced antigen-specific immunological tolerance was due to the induction of CD4+CD25+Foxp3+ regulatory T cells, while the polarization of Th2 immune response induced by DC with medium expression level of CD40 was partially due to the impaired IL-12 production by DC during CD40 crosslinking. Our findings that different levels of co-stimulatory molecules have different regulations on DC functions has the significance in DC based immunotherapy for GVHD as well as the Th1 diseases.

Dendritic cell is one of the professional antigen presenting cells, and it bridges innate immunity and adaptive immunity. To fully activate naïve T cells, it requires DC to provide at least two signals, the interaction between T cell receptor and the MHC class II molecule loaded with antigen processed by DC, and the co-stimulatory signals provided by the co-stimulatory molecules expressed on DC. The identification of more and more co-stimulatory molecules expressed on DC and the studies on their functions highlight the importance of co-stimulatory molecules on the regulation of DC functions. We here hypothesized that different expression levels of co-stimulatory molecules expressed on DC is pivotal of directing DC function towards immunity, tolerance and polarization of Th1/Th2 immune response. Using CD40 as the model molecule to study the effect of its expression levels on DC functions, we found that no/low expression level of CD40 on DC induced antigen-specific immunological tolerance was due to the induction of CD4+CD25+Foxp3+ regulatory T cells, while the polarization of Th2 immune response induced by DC with medium expression level of CD40 was partially due to the impaired IL-12 production by DC during CD40 crosslinking. Our findings that different levels of co-stimulatory molecules have different regulations on DC functions has the significance in DC based immunotherapy for GVHD as well as the Th1 diseases.

Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. 101-110. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Lorsque le lymphocyte B entre en contact avec son antigène, plusieurs interactions sont essentielles. Parmi celles-ci, l'engagement de son récepteur CD40 avec le ligand CD154 d'un lymphocyte T activé est primordial. Des études réalisées in vitro ont démontré que l'intensité et la durée de l'interaction CD40-CD154 entraînent différentiellement l'évolution des lymphocytes B matures naïfs et à mémoire. En conséquence, une source de CD 154 soluble pour stimuler les lymphocytes B a été utilisée dans le but de vérifier comment la modulation de l'interaction modifiait les caractéristiques des populations de lymphocytes B par la transmission intracellulaire du signal, de CD40 au noyau. Les résultats obtenus lors de cette étude suggèrent que certaines voies de signalisation, principalement de la famille des MAPK soit, ERK.1/2 et p38, pourraient être empruntées différemment lors de la liaison de CD40 avec CD154. L'activation modulée des voies de signalisation pourrait participer à la régulation de la réponse immunitaire.

Les populations CD19+CD27+ et CD19+CD27+ de lymphocytes B cultivées dans le système CD40-CD154 évoluent différemment selon l'intensité de cette interaction. Les cellules CD27+ prolifèrent bien en présence d'une forte interaction CD40-CD154 lorsqu'elles sont cultivées seules, mais disparaissent lorsque les cellules CD27" sont présentes. Des facteurs solubles ou des interactions membranaires pourraient être la cause de l'évolution différente des populations. L'étude des facteurs solubles a démontré qu'ils n'étaient pas la cause du changement d'équilibre des populations. Ils avaient une certaine influence, mais ne pouvaient pas à eux seuls changer cette évolution. Ce qui suggérait que les interactions membranaires entre les cellules étaient impliquées. En effet, certains marqueurs de surface, comme CD54, CD38 et CD70, étaient différemment exprimés au sein des populations CD27" et CD27+ . Par conséquent, CD70, le ligand de CD27, devenait un acteur intéressant. Effectivement, lorsque l'interaction CD70-CD27 était bloquée, la prolifération était ralentie et les cellules CD27+ étaient maintenues en plus grande proportion. L'interaction CD27- CD70 pourrait donc avoir un rôle dans l'évolution des populations de lymphocytes B suite à leur activation via CD40.

Most studies of the induction of cytokine synthesis in monocytes have employed an exogenous triggering agent such as lipopolysaccharide. However, in nonseptic inflammatory responses (e.g. rheumatoid arthritis) monocyte activation occurs as a result of T cell‐generated signals. In previous reports, we and others have demonstrated that contact‐dependent T cell‐generated signals are capable of contributing to macrophage activation. We have shown that plasma membranes from anti‐CD3 activated purified peripheral CD4+ T cells (TmA) but not from resting CD4+ cells (TmR) induce monocytes to synthesize interleukin (IL)‐1 in the absence of co‐stimulatory cytokines. Studies to determine the expression kinetics of the molecule(s) unique to activated CD4+ T cells which interact with monocytes to induce IL‐1 revealed that optimal expression occurred at 6 h post activation. This matched the previously reported kinetics of expression of CD40 ligand (CD40L) on activated peripheral T cells, implicating the CD40‐CD40L interaction as a candidate for the initiator of the IL‐1 signaling event. The ability of TmA to induce IL‐1 synthesis in resting monocytes could be markedly reduced by addition of a monoclonal anti‐CD40L antibody, 5c8. In addition, a monoclonal anti‐CD40 IgM (BL‐C4) proved dramatic in its ability to induce resting monocytes to synthesize IL‐1. In summary, these results demonstrate that the CD40‐CD40L interaction provides a critical component of CD4+ T cell contact‐dependent activation of monocyte IL‐1 synthesis.

No description available.

No description available.

O receptor CD40 e seu ligante CD40L possuem um papel importante na interface entre a resposta imune inata e a adaptativa. Disfunções desta via de sinalização são descritas em doenças de origem inflamatória e autoimunes. Em Lúpus eritematoso sistêmico (LES) foi descrito um aumento nos níveis séricos de CD40L solúvel, que participa na produção de autoanticorpos. Receptores ativados por proliferadores de peroxisomos (PPARs) são fatores de transcrição que inicialmente foram descritos como envolvidos apenas no metabolismo lipídico, mas que atualmente são também descritos como atuantes no controle da resposta imune. Com isso, nosso objetivo é determinar se a ativação dos PPARs modula o processo inflamatório através da interação com CD40/CD40L in vitro ou in vivo. Células de linhagem monocítica humana THP-1 foram tratadas por 24 horas com forbol-éster (PMA, 40 nM) e posteriormente estimuladas com CD40L recombinante (rhCD40L, 1 g/ml) por diferentes períodos. Transcritos de mRNA foram analisados por real time PCR e os resultados expressos como razão da expressão do gene housekeeping GAPDH. As células THP-1 apresentam um aumento na expressão de PPAR e após 16 e 2 horas de estímulo com rhCD40L, respectivamente. Estas células também foram estimuladas com LPS (10 g/ml) e LPS+rhCD40L para sabermos se a resposta obtida anteriormente era específica ao estímulo com rhCD40L. O resultado mostra que há uma diminuição na expressão de PPAR e após o estimulo com LPS ou LPS+rhCD40L, indicando que nessas condições a modulação da expressão de PPARs é especifica para a via de sinalização CD40/CD40L. Foi medida também a expressão de CD36, que é descrito na literatura como um indicador da atividade de PPARs. O resultado mostra que o estímulo com CD40L promove um aumento de CD36, o que indica indiretamente que o PPAR estava ativo neste modelo experimental. Para mostrar a interação direta destas duas vias de sinalização, silenciamos o gene de PPAR por siRNA e posteriormente anlisamos a expressão de CD80, cuja expressão encontra-se aumentada logo após a ativação do CD40 de acordo com a literatura. O resultado mostra que, com o silenciamento de PPAR , há um aumento de CD80 logo após a ativação do CD40, evidenciando assim a interação entre essas duas vias de sinalização. A fim de verificar se os achados encontrados in vitro poderiam ser observados in vivo, foi isolada a fração mononuclear de sangue periférico de pacientes com LES com a doença em atividade (n=17), a doença inativa (n=21) ou doadores saudáveis (n=12) e foi medida a expressão de PPAR e por real time PCR. PPAR apresenta um aumento em pacientes com a doença ativa ou inativa em comparação aos doadores saudáveis. Já a expressão de PPAR apresenta aumento apenas em lúpicos em atividade quando comparados com lúpicos inativos ou doadores saudáveis. Quando considerado nesta análise o efeito do tratamento dos pacientes com corticosteróides nos níveis de PPAR, obsevou-se que a expressão de PPAR apresenta o mesmo padrão anterior. Estes resultados sugerem a hipótese de que PPAR seja um possível marcador de atividade de LES. Para confirmar esta especificidade, foram adicionadas à analise células mononucleares retiradas de pacientes com tuberculose e com infecções agudas. Os dados mostram que os níveis elevados de PPAR se mantém apenas em pacientes com lúpus ativo, o que confirma nossa hipótese. Nossos achados sugerem que PPAR e são regulados especificamente em reposta a ativação da via do CD40/CD40L, em monócitos em cultura e em células obtidas de pacientes com LES. Podemos também sugerir que PPAR possa ser um marcador para a atividade de LES. Estes resultados podem representar um novo mecanismo de controle da via de sinalização do CD40/CD40L, participando no controle da resposta inflamatória em cultura e em células de pacientes lúpicos / The membrane receptor CD40 and its ligand CD40L play an important role in the interface between innate and acquired immunity. Dysfunction of this signaling pathway was described in inflammatory and autoimmune diseases. In systemic lupus erythematosus (SLE), increased serum levels of soluble CD40L have been detected, where it plays a significant role in the generation of auto-antibodies. Peroxisome proliferator activator receptors (PPARs) are transcription factors originally described in lipid metabolism. More recently, they were also characterized as inflammatory modulators. Therefore, our objective was to determine whether the activation of PPARs may modulate the inflammatory process through interaction with the CD40/CD40L signaling pathway in vitro and in vivo. Macrophages derived from the human monocytic cell line THP-1 by 24h-treatment with PMA (40 nM) were stimulated with human recombinant CD40L (rhCD40L, 1 g/ml) for different periods. Messenger RNA (mRNA) transcripts for PPAR , and were determined by real time PCR and expressed as a ratio of the housekeeping gene GAPDH transcripts. THP-1 cells express a basal level of PPAR and gene transcription, which is increased 16 and 2 hours after exposure to rhCD40L, respectively. We also stimulated the THP-1 cells with LPS (10 g/ml) and LPS+rhCD40L to see if the increase of PPAR was a response specific to the rhCD40L stimuli. The data show that there is a decrease in PPAR and genes expression upon LPS or LPS+rhCD40L stimulation, indicating that in these times (2 and 16 hours) the response is specific for the CD40/CD40L signaling pathway. Increased expression of CD36 is known as an indicator of PPARs activity. We measured CD36 and saw an increase of this receptor after rhCD40L stimulus, indicating indirectly that PPARs were active in this experimental model. To prove the direct interaction between CD40/CD40L and PPAR , we silenced the PPAR gene by siRNA and analyzed the expression of CD80, which is known to increase after CD40 activation. The results show an increase in CD40L-stimulated CD80 expression upon silencing of PPAR , showing that there is an interaction between these signaling pathways. To confirm whether these findings also occur in vivo, mononuclear cells were isolated from whole blood samples from SLE patients with active (n=17) and inactive disease (n=21), and healthy donors (n=12). The mRNA transcripts for PPARs were detected by real time PCR. In both active and inactive SLE patients, monocytes show an increase in PPAR mRNA expression, as compared to healthy donors. PPAR mRNA is increased only in active patients when compared to healthy donors and inactive lupus patients. Further in this analysis, when we separated the patients with and without the administration of corticosteroids, PPAR displayed the same pattern as above. These results suggested that PPAR may be a marker for lupus activity. To validate this hypothesis, we compared the results obtained from patients with tuberculosis and acute infections. Results showed that only active-lupus patients have an increase in PPAR , confirming the specificity of this phenomenon and hence our hypothesis Our findings suggest that PPAR and are up-regulated specifically in response to CD40/CD40L activation, in both cultured macrophages and in monocytes obtained from SLE patients. We could also suggest that PPAR may be marker for lupus activity. Our results may represent a new control mechanism of the CD40/CD40L signaling pathway and seem to be implicated in the control of the inflammatory response in both human macrophages in vitro and SLE patients

TRAIL is a member of TNF superfamily and mediates apoptosis by binding to two DRs, TRAILR1 and TRAILR2. Despite the fact that there are other TRAILRs, TRAILR1 and TRAILR2 receive the major research interest due to their ability to trigger apoptosis and their possible use as targets in tumor therapy. Due to the potential advantages of TRAILR1- or TRAILR2-specific targeting, we investigated recently published TRAIL DR-specific mutants, one conferring specificity for TRAILR1 (TRAILmutR1) and one for TRAILR2 (TRAILmutR2). It was well proved in this work that TRAILmutR1 shows specific binding to TRAILR1 and no specific binding to TRAILR2. TRAILmutR2 vice versa shows specific binding to TRAILR2 and no significant binding to TRAILR1. Moreover, these mutants were able to induce caspase activation and cell death in a TRAILR1/2-specific manner. Moreover, the enhancement of TRAILR2-induced apoptosis by secondary oligomerization of soluble wild-type TRAIL was confirmed for the TRAILR2-specifc TRAIL mutant and similar findings were made with the TRAILR1-specific TRAIL mutant. The soluble form of TRAIL exhibits weak apoptotic activity as compared to transmembrane TRAIL. Therefore, there is the challenge in clinical research to improve the activity of soluble TRAIL. A second strategy besides the above mentioned oligomerization to improve soluble TRAIL activity is anchoring of the molecule to the cell surface, e.g. through the genetic fusion with a scFv domain recognizing a cell surface antigen. In this work, we generated fusion proteins of TRAIL, TRAILmutR1 and TRAILmutR2 with a scFv recognizing CD40 (scFv:G28). Initially, we analyzed the functionality of both the TRAIL domain and the scFv:G28 domain of the corresponding fusion proteins. TRAIL functionality was well proved through its ability to induce cell death in TRAIL sensitive cells such as Jurkat cells, provided that scFv:G28-TRAIL fusion proteins were oligomerized by anti-Flag mAb M2. Concerning the scFv:G28 domain, the fusion proteins showed enhanced binding affinity to cell lines expressing CD40 as compared to their parental CD40-negative cells. Consistent with previous studies investigating TRAIL fusion proteins with other cell surface antigen-targeting scFvs, the scFv:G28 fusion proteins with TRAIL, TRAILmutR1 and TRAILmutR2 showed enhanced induction of cell death in a CD40-dependent manner. Moreover, our results revealed that these fusion proteins have a significant paracrine apoptotic effect on CD40-negative bystander cells upon anchoring to CD40-positive cells which are TRAIL resistant. Thus, the current work provides for the first time scFv fusion proteins of TRAIL and TRAILR1- and TRAILR2-specific TRAIL mutants with CD40-restricted activity. These fusion proteins provide the advantage of attenuating the off-target effects and the potential side effects of per se highly active TRAIL variants on one hand due to the CD40-binding dependent enhancement of activity and on the other hand due to the differential use of TRAILR1 and TRAILR2. CD40 represents a tumor associated marker which is expressed on many tumor cells but also on immune cells. Therefore, the last part of this work focused on the analysis of the ability of scFv:G28-TRAIL fusion proteins to induce CD40 signaling both in tumor cells and also in immune cells. It turned out that the scFv:G28-TRAIL fusion proteins are able to induce CD40 signaling in CD40-positive tumor cells but especially also in immune cells such as iDCs leading to their maturation and further activation of immune responses. Taken together, this work provides novel bifunctional scFv-TRAIL fusion proteins which combine the induction of apoptosis via TRAIL DR with stimulation of CD40 signaling which possibly enhances antitumor immunity. / TRAIL ist ein Mitglied der TNF-Superfamilie und vermittelt Apoptose durch die Aktivierung der Todesrezeptoren, TRAILR1 und TRAILR2. Obwohl es weitere TRAIL-Rezeptoren gibt, liegt das Hauptaugenmerk auf den beiden Apoptose induzierenden Rezeptoren TRAILR1 und TRAILR2 auf Grund ihrer möglichen Anwendung in der Tumortherapie. Wegen der möglichen Vorteile eines spezifischen TRAILR1- und TRAILR2-Targetings, haben wir kürzlich publizierte TRAIL-Todesrezeptor spezifische TRAIL Mutanten untersucht, von denen eine spezifisch für TRAILR1 (TRAILmutR1) und die andere spezifisch für TRAILR2 (TRAILmutR2) ist. Es konnte in dieser Arbeit sehr gut belegt werden, dass TRAILmutR1 spezifisch an TRAILR1 bindet und keine Bindung an TRAILR2 zeigte. Dem entsprechend zeigte die Variante TRAILmutR2 nur eine spezifische Bindung an TRAILR2 und keine signifikante Bindung an TRAILR1. Des Weiteren waren die Mutanten in der Lage, die Caspase-Aktivierung und den Zelltod TRAILR1/2-abhängig zu induzieren. Außerdem konnte eine Erhöhung der TRAILR2-induzierten Apoptose durch eine sekundäre Oligomerisierung der TRAILR2-spezifische TRAIL-Mutante erzielt werden. Ähnliche Ergebnisse zeigte die TRAILR1-spezifische TRAIL-Mutante. Um die Aktivität des löslichen TRAIL Oligomerisierung unabhängig zu erhöhen, wurden in dieser Arbeit TRAIL-Fusionsproteine mit einem scFv (scFv:G28), der CD40 erkennt generiert. In Übereinstimmung mit früheren Studien, die mit TRAIL-Fusionsproteinen von anderen Zelloberflächenantigen-spezifischen scFvs wurden, zeigten die CD40-spezifischen scFv:G28 Fusionsproteine mit TRAIL, TRAILmutR1 und TRAILmutR2 eine verstärkte CD40-abhängige Induktion des Zelltods. Darüber hinaus zeigten unsere Ergebnisse, dass diese Fusionsproteine nach Bindung an CD40-positive Zellen einen parakrinen apoptotischen Effekt, auf umliegende CD40-negative Zellen haben. Diese Arbeit beschreibt somit zum ersten Mal scFv-TRAIL Fusionsproteine mit einer CD40-abhängigen TRAILR1- und TRAILR2-spezifischen Aktivität. CD40 repräsentiert einen tumorassoziierten Marker, der in vielen Tumorzellen aber auch in Zellen des Immunsystems exprimiert wird. Aus diesem Grund fokussierte sich der zweite Teil dieser Arbeit auf die Analyse der Fähigkeit der scFv:G28-TRAIL Fusionsproteine, CD40-Signaling sowohl in Tumor- als auch in Immunzellen zu stimulieren. Es konnte festgestellt werden, dass die scFv:G28-TRAIL Fusionsproteine in der Lage sind, CD40-Signaling in CD40-positiven Tumorzellen, aber auch in Immunzellen, z.B. in iDCs, in denen die ScFv-TRAIL Fusionsproteine die Reifung und Aktivierung induzieren ohne Zelltod auszulösen. Zusammengefasst beschreibt diese Arbeit neue bifunktionelle scFv-TRAIL Fusionsproteine, die die Induktion der Apoptose via TRAIL-Todesrezeptoren und die Stimulation des kostimulatorischen CD40-Moleküls kombinieren, was zu einer synergistischen dualen Antitumor-Aktivität führen kann.