No description available.

The three insecticides of interest were lindane (an organochlorine), malathion (an organophosphate) and piperonyl butoxide (PBO; a synergist). Based on minimum cytotoxicity (> LC25), the following concentrations were chosen for the pesticide mixture studies: 70μM lindane (Lind), 50μM malathion (Mal) and 55μM PBO. In the AlamarBlue cytotoxicity assay, individual pesticide and mixtures of malathion/PBO (MP) and malathion/lindane (ML) prompted cytotoxicity with varying intensities (Mal 18.8%, Lind 20.4%, PBO 23.5%, ML 53.6% and MP 64.9%). Cytopathological analysis revealed apoptotic features in treated cells and the DNA Ladder Assay confirmed the presence of DNA fragments. The specific mode of cell death was examined via the 7-aminoactinomycin D (7-AAD) Staining Assay. Apoptosis was detected in each treatment (Mal 6.5%, Lind 12.0%, PBO 13.2%, ML 19.3% and MP 23.4%). Furthermore, 7-AAD staining in combination with fluorescent-labeled monoclonal antibodies, PE-CD45RB/220 and FITC-CD90, was performed. B-cells were more susceptible to Mal and PBO treatments than were T-cells. The pro-oxidant activity of the pesticides was monitored via the Dichlorofluorescin Diacetate assay. Exposure to pesticides for 15 minutes increased H2O2 production above the controls, Mal 21.1%; Lind 10.8%; PBO 25.9%; ML 26.8%; MP 37.8%. The activities of antioxidant enzymes, glutathione peroxidase (GSH-Px) and glutathione reductase (GR) were altered by these treatments. GR was significantly reduced for the pesticide mixtures only (control: 51.7; Mal: 48.2; Lind: 50; PBO: 52.3; ML: 40.5; MP: 42 Units/mg). GSH-Px activity was severely reduced for all the pesticide treatments (control: 44.9; Mal: 30.2; Lind: 30.6; PBO: 32.4; ML: 21.1; MP: 21.1 Units/mg). These results indicate that exposure to these pesticide and pesticide mixtures induces apoptosis and oxidative stress. / Master of Science

Apžvelgiami klinikiniai tyrimai atlikti VU Imunologijos institute Molekulinės imunologijos laboratorijoje, bendradarbiaujant su Vilniaus universitetinės Greitosios pagalbos ligoninės Bendrosios chirurgijos centro Ginekologijos skyriumi bei „Vaisingumo klinika“. Tyrimams atlikti buvo gauti du Lietuvos Bioetikos komiteto leidimai. Darbo tikslas - nustatyti gimdos gleivinės imunines ląsteles bei įvertinti jų vaidmenį reprodukcijos procese. Medžiaga ir metodai. Tyrimuose dalyvavo vaisingos moterys (kontrolinė grupė) (n=142), nevaisingos moterys (121), moterys patyrusios savaiminį persileidimą (n=35) ir endometrioze sergančios moterys (n=181). Naudoti tyrimo metodai: ląstelių morfologiniam įvertinimui - citologinis, imuninių ląstelių fenotipo nustatymui - tėkmės citometrijos, tirpių medžiagų (citokinų, HLA-G molekulių) koncentracijos nustatymui – imunofermentinis metodas. Rezultatai ir išvados. Menstruacinio ciklo metu kito endometriumo imuninių ląstelių sudėtis, limfocitų ir makrofagų aktyvacijos molekulių ekspresija: priešmenstruaciniu periodu daugėjo makrofagų (proliferacijos fazėje – 7,3±2,8%, vėlyvos sekrecijos fazėje - 13,7±3,1%) ir NK ląstelių (proliferacijos fazėje – 18,3±5,8%, vėlyvos sekrecijos fazėje – 51,1±9,8%). Didžiausias skaičius aktyvuotų makrofagų gimdos gleivinėje, ekspresuojančių CD69 ir CD54 molekules, buvo randamas proliferacijos fazėje (14,3±5,6% ir 26,2±4,8% atitinkamai). Decidualiniame audinyje nustatėme ypatingo fenotipo intensyviai CD56... [toliau žr. visą tekstą] / Clinical tests performed in the Laboratory of Molecular Immunology of the Institute of Immunology of Vilnius University in cooperation with the Gynaecological Department of the General Surgery Center of Vilnius University Emergency Aid Hospital and Fertility Clinic, Vilnius are reviewed. Two permissions have been obtained from the Lithuanian Committee of Bioethics for carrying out the tests. The aim of the study was to determine endometrial immune cells and to evaluate their role in the reproduction process. Materials and methods. The following groups of women took part in our study: fertile women (they formed control group) (n=142), infertile women (n=121), women after miscarriage (n=35) and women with endometriosis (n=181). The following laboratory methods were used: cytological (to define the morphology of cells); flow cytometry (for detection of the phenotype of immune cells) and immunoenzyme assay – to quantify the concentration of soluble substances, such as cytokines and HLA-G molecules. Results and Conclusions. Composition of the endometrial immune cells, expression of lymphocyte and macrophage activation molecules has been changing during the menstrual cycle. In the pre-menstrual period the number of macrophages and NK cells has increased: in the stage of proliferation-7.3±2.8%; in the late stage of secretion – 13.7±3.1% and in the stage of proliferation – 18.3±5.8%, in the late stage of secretion – 51.1±9.8, respectively. The highest amount of activated macrophages... [to full text]

Les tumeurs solides sont infiltrées par des cellules immunes (TIIC) dont la nature, la fonction et la composition varient d’un patient à l'autre. Ces cellules inflammatoires influencent l'invasion tumorale en contrôlant la croissance et le potentiel métastatique d’une tumeur. Ainsi, il est proposé d’utiliser cette infiltration comme outil diagnostic et pronostic de routine. Certaines cellules sont bien connues pour jouer un rôle important dans le contrôle de la progression tumorale, comme c’est le cas des lymphocytes T cytotoxiques CD8+ alors que d’autres possèdent un rôle contradictoire. Étant donné la dépendance des tumeurs sur l’équilibre entre ces différentes cellules, il est important d’identifier les fonctions précises des cellules immunes au sein de la tumeur. De nombreuses études sont réalisées afin d’identifier des marqueurs descriptifs du phénotype et la fonction des cellules immunes dans la tumeur. Ce projet de doctorat se divise en deux parties : 1- Identifier la méthode de désagrégation des tissus tumoraux altérant le moins la biologie des TIIC pour leur caractérisation. 2- Caractériser l’expression de la molécule d’adhérence CD146 dans les TIIC et en identifier l’origine. L’identification de marqueurs pour la caractérisation phénotypique et fonctionnelle des TIIC a été réalisée, entre autres, par la détection de protéines exprimées par la cellule. Dans la première partie de ce projet, nous avons démontré que les méthodes utilisées pour désagréger les tissus tumoraux dans le but d’isoler les TIIC induisent des changements dans la biologie de ces cellules ce qui peut fausser les conclusions qui en dérivent. Nous avons donc comparé l'impact de trois méthodes de désagrégation : une dissociation mécanique utilisant la MédimachineTM et deux digestions enzymatiques utilisant une collagénase de type I seule ou combinée à de la collagénase de type IV et de la DNase I de type II. Nous nous sommes intéressés à l'effet de ces méthodes sur des paramètres tels que la viabilité cellulaire, l’altération des protéines de surface et la capacité des cellules à proliférer. Nous avons démontré que ces méthodes affectent la viabilité des cellules de manière comparable, alors que la détection de certaines protéines de surface et la capacité de proliférer est réduite/inhibée par les traitements enzymatiques. Nous concluons qu’une méthode mécanique utilisant la MédimachineTM est mieux adaptée à la caractérisation des TIIC afin de conserver leurs propriétés. Dans la deuxième partie de notre projet, nous avons adapté cette méthode à la caractérisation des TIIC. Nous avons porté une attention particulière à la molécule d’adhérence CD146 dont l’implication dans la migration des cellules immunes à travers l’endothélium vers les sites d’inflammation est de plus en plus étudiée dans les maladies autoimmunes. Nous avons mis en évidence une augmentation des proportions de cellules immunes exprimant CD146 dans les tumeurs comparativement au sang de patients de cancers. Cette expression est induite par les cellules tumorales tout en étant accrue par la nécrose de celles-ci. Nous démontrons que ces cellules sont majoritairement des lymphocytes T CD4+ présentant un profil immunosuppressif. En conclusion, nos résultats suggèrent que CD146 participe à la mise en place du contexte immunitaire dans la tumeur et augmente la capacité de migration des lymphocytes T CD4+. L’induction par les cellules tumorales de cette molécule d’adhérence dans les cellules suppressives pourrait contribuer aux mécanismes immunorégulateurs mis en place par la tumeur. CD146 pourrait être un marqueur d’intérêt pour l’identification des cellules immunosuppressives et pour le développement de nouvelles thérapies. / Solid tumors are infiltrated by immune cells (TIIC), which vary in function and proportion from patient to patient. These inflammatory cells may contribute positively or negatively to tumor invasion, by controlling the growth and the metastatic potential of tumors. It has therefore been proposed to use infiltration as a diagnostic and prognosic tool. Certain cells play an important role in the control of tumor progression, as is the case of cytotoxic CD8+ T lymphocytes, whereas others present an ill-defined role. Since the progression of tumors depends on the balance between these cell types, it is important to identify their specific functions within the tumor. Many studies have therefore focused on identifying markers, which are suggestive of phenotype and function of immune cells in the tumor. This project is divided into two parts: 1 – The identification of a tumor tissue disaggregation method which induced minimal effects on TIIC biology. 2 – The characterization of the expression of the adhesion molecule CD146 in TIIC and understand its regulation. Marker identification for phenotypic and functional characterization of TIIC is carried out by detection of cell proteins. In the first part of this project, we showed that methods used to disaggregate tumor tissue in order to isolate TIIC induce changes in cell biology, which may alter results. We thus compared the effects of three disaggregation methods: mechanical disruption using MedimachineTM and two enzymatic digestions using a type I collagenase alone or combined with type IV collagenase and type II DNase I, on parameters such as cell viability, cell surface marker detection and cell proliferation. We showed that these methods affect cell viability in a comparable manner, whereas the detection of certain surface proteins and proliferative capacity of cells was reduced by enzymatic treatments. We concluded that a mechanical method using MedimachineTM is more suitable for the characterization of TIIC. In the second part of our project, we adapted this method to the characterization of TIIC. We focused on CD146, an adhesion molecule that was shown to be involved in immune cell migration in autoimmune disease. We demonstrated an increase of CD146+ immune cells in tumors compared to the blood of the same patients. This expression was shown to be induced by tumor cells and increased by necrosis. We showed that these cells are predominantly CD4+ T lymphocytes with an immunosuppressive profile. In conclusion, our results suggest that CD146 is involved in the establishment of the tumor immune environment and may increase the migratory capacity of CD4+ T cells toward tumors. Tumor cell induction of this adhesion molecule by suppressor cells could contribute to the immunoregulatory mechanisms established by tumors. CD146 may be a useful marker for the identification of immunosuppressive cells and development of new therapies.

La sarcopénie est définie comme la diminution de la masse et de la force musculaires squelettiques au cours du vieillissement.Dans ce contexte, l’objectif principal de cette thèse était d’évaluer l’action régulatrice de la vitamine D sur le dialogue entre cellules immunitaires et musculaires et son implication dans les capacités de régénération du muscle âgé.Dans un premier temps, nous avons étudié in vitro la différenciation des cellules musculaires de la lignée L6 co-cultivée ou non avec des cellules immunitaires (PBMC : cellules mononuclées du sang périphérique), et en présence ou non de LPS. Ce modèle a permis d’établir que les PBMC stimulaient bien la différenciation musculaire. La réponse pro-inflammatoire induite par le LPS inhibait l’expression des marqueurs de différenciation. Même en présence de LPS, la stimulation de l’expression ce des marqueurs dans les L6 co-cultivées était conservée. De plus, l’environnement pro-inflammatoire induit par le LPS dans les co-cultures inhibait l’expression musculaire des marqueurs de la voie de la régénération, comme Notch. Nous avons ensuite utilisé le même système de co-cultures afin de déterminer si la vitamine D, ici la 25(OH)D, pouvait moduler les sécrétions cytokiniques des PBMC et ainsi modifier l’expression des marqueurs de différenciation musculaires. Le traitement des co-cultures à la 25(OH)D n’a modifié ni le profil de sécrétion cytokinique des PBMC, ni l’expression des marqueurs de différenciation des L6.Dans un deuxième temps, nous avons étudié à l’aide d’un modèle de rats âgés déplétés en vitamine D les mécanismes pouvant contribuer à l’atrophie musculaire observée. Nous avons mis en évidence que l’activité de la voie de signalisation Notch, voie clé du processus de régénération, ainsi que la prolifération musculaire étaient diminuées chez ces rats, et ceci même en absence de lésion. Nous avons ensuite évalué l’effet du statut en vitamine D sur un processus aigu de régénération au cours de vieillissement chez le rat. L’analyse de cette expérimentation, actuellement en cours, a déjà permis de mettre en évidence qu’au cours du vieillissement, la prolifération musculaire suite à une lésion est diminuée, d’autant plus si le rat âgé est carencé en vitamine D. Le même résultat a été retrouvé pour l’expression d’une cible de la voie Notch (Hes1). En outre, l’expression des marqueurs de différenciation semblaient être altérée chez les animaux âgés résultant probablement en un retard et/ou une inefficacité du processus de différenciation, en particulier chez les rats âgés déplétés en vitamine D. En revanche, la supplémentation en vitamine D ne semblait pas avoir d’effet sur la régénération musculaire du rat âgé.En conclusion, in vitro, la 25(OH)D ne modifiait pas l’expression des marqueurs de différenciation des cellules musculaires co-cultivées avec des cellules immunitaires. En revanche in vivo, la déplétion en vitamine D semblerait aggraver l’effet de l’âge sur la régénération musculaire.La diminution de la capacité de régénération musculaire est un facteur contribuant au développement de la sarcopénie. Ce travail a permis de montrer que le maintien d’un statut optimal en vitamine D serait nécessaire à la conservation des capacités de régénération musculaire. Il semble donc important de maintenir des statuts optimaux en vitamine D afin de limiter l’atrophie musculaire au cours du vieillissement. / One of the most striking effects of ageing is an involuntary loss of skeletal muscle mass known as sarcopenia. The development of sarcopenia appears to be multifactorial and includes anabolic resistance to dietary amino acids and sedentary lifestyle. The diminished ability of aged muscle to self-repair is also a key factor of sarcopenia. During the regeneration process, immune and muscle cells work in a cross-talk leading to an optimal muscle cell proliferation and differentiation. However, with aging, the immune response is impaired, possibly contributing to the reduction in the capacity of regeneration.Muscle and immune cells are both targets of vitamin D action. This vitamin modulates muscle cell proliferation and differentiation and stimulates the anti-inflammatory response of immune cells. With age, vitamin D insufficiencies or deficiencies develop.In this context, the main objective of this thesis was to evaluate the regulatory action of vitamin D on the cross-talk between immune and muscle cells and its implication in the ability of skeletl muscle to regenerate during aging.Initially, we studied in vitro the differentiation of L6 muscle cells co-cultured with or without immune cells (PBMC: peripheral blood mononuclear cells), and in with or without of LPS. From this model, PBMC stimulated muscle cell differentiation. The pro-inflammatory response induced by LPS inhibited the expression of muscle differentiation markers in muscle cells. Of note, these markers were stimulated even in presence of LPS. In addition, the LPS-associated pro-inflammatory environment inhibited the Notch signaling pathway, the key pathway of muscle regeneration process, in L6 cells co-cultured with PBMC. We then used the same system of co-cultures to determine whether vitamin D, in its 25 (OH)D form, could modulate PBMC cytokine secretion and thereby could alter the expression of markers of muscle differentiation. Unfortunately, the treatment of co-culture with 25 (OH) D has changed neither the profile of PBMC cytokine secretion nor the expression of differentiation markers in L6 cells.Secondly, we investigated in a model of old rats the mechanisms that contribute to muscle atrophy following vitamin D depletion. We have demonstrated that the activity of the Notch signaling pathway, as well as muscle proliferation were reduced in old vitamin D-depleted rats, even in the absence of lesions. Then we evaluated the effect of the vitamin D status on an acute muscle regeneration process, i.e. muscle infusion of notexin in old rats. This ongoing experiment has already highlighted that during aging, muscle proliferation is reduced after injury, especially if age is associated with a vitamin D deficiency. In addition, during aging, the expression of differentiation markers was altered resulting in delayed and/or incomplete differentiation process, in particular in vitamin D-depleted old rats. However, vitamin D supplementation seemed to have no beneficial or deleterious effects on muscle regeneration in aged rats.In conclusion, in vitro 25 (OH) D was unable to modulate the differentiation of muscle cells co-cultured with immune cells. However, in vivo, vitamin D depletion appeared to worse the effect of ageing on muscle regeneration.The diminished ability of aged muscle to self-repair is a factor of sarcopenia. Our work has demonstrated the importance of maintening optimal vitamin D status to preserve muscle regeneration capacity and thus to limit muscle atrophy during aging.

Today,   most traditional method used in the research of immune cells, such as flow   cytometry and microscopy, are based on average values of cell responses.   However, immune cells are heterogeneous and respond differently to a given   stimuli. There is also a risk that important, but rare, behaviors of   individual cells are missed when a larger population of immune cells is   analyzed. Also, flow cytometry and microscopy do not allow long-term survival   of cells; these methods lack the ability to do dynamic long-term analysis of   motile immune cells, i.e. studies of cell-cell interactions, morphology and proliferation.   In a   patient who is affected by cancer, the cell heterogeneity contributes to the   ability to battle various types of cancer or virus infections. In an   outbreak, immune cells recognize and kill tumor cells. However, the number of   specific immune cells is sometimes too few to kill all the tumor cells in a   successful way. One way to help these patients is to isolate, select out and   cultivate the active immune cells with capacity to kill tumor cells.   The   Cell Physic Laboratory (a part of the department of Applied Physics) at the   Royal Institute of Technology (KTH) has developed a method for single-cell   analysis where the immune cells are trapped in microwells in a silicon chip.   The immune cells are then studied by using fluorescence microscopy in an   inverted setup. The method enables high-throughput experiments due to the   parallelization. Furthermore, since the immune cells survive long periods in   the chip, the cells can be analyzed over several days up to weeks. The   research group has also developed a semi-automatic ‘cell-picker’. The   cell-picker will be used in combination with the developed method for   single-cell analysis, which enables picking of cells of interest. In this report, experiments for the characterization and evaluation of the biocompatibility of two generations of the cell-picker will be presented. The experiments include development of a protocol for the cell-picking process, studies of the survival time of transferred cells for both generation of the cell-picker and studies of surface coating in the chip in order to increase the biocompatibility. The preliminary results indicate that the cell-picker has potential to be used as a selection tool for immune cells of interest.

No description available.

Today many cell biological techniques study large cell populations where an average estimate of individual cells’ behavior is observed. On the other hand, single cell analysis is required for studying functional heterogeneities between cells within populations. This thesis presents work that combines the use of microfluidic devices, optical microscopy and automated image analysis to design various cell biological assays with single cell resolution including cell proliferation, clonal expansion, cell migration, cell-cell interaction and cell viability tracking. In fact, automated high throughput single cell techniques enable new studies in cell biology which are not possible with conventional techniques. In order to automatically track dynamic behavior of single cells, we developed a microwell based device as well as a droplet microfluidic platform. These high throughput microfluidic assays allow automated time-lapse imaging of encapsulated single cells in micro droplets or confined cells inside microwells. Algorithms for automatic quantification of cells in individual microwells and micro droplets are developed and used for the analysis of cell viability and clonal expansion. The automatic counting protocols include several image analysis steps, e.g. segmentation, feature extraction and classification. The automatic quantification results were evaluated by comparing with manual counting and revealed a high success rate. In combination these automatic cell counting protocols and our microfluidic platforms can provide statistical information to better understand behavior of cells at the individual level under various conditions or treatments in vitro exemplified by the analysis of function and regulation of immune cells. Thus, together these tools can be used for developing new cellular imaging assays with resolution at the single cell level. To automatically characterize transient migration behavior of natural killer (NK) cells compartmentalized in microwells, we developed a method for single cell tracking. Time-lapse imaging showed that the NK cells often exhibited periods of high motility, interrupted with periods of slow migration or complete arrest. These transient migration arrest periods (TMAPs) often overlapped with periods of conjugations between NK cells and target cells. Such conjugation periods sometimes led to cell-mediated killing of target cells. Analysis of cytotoxic response of NK cells revealed that a small sub-class of NK cells called serial killers was able to kill several target cells. In order to determine a starting time point for cell-cell interaction, a novel technique based on ultrasound was developed to aggregate NK and target cells into the center of the microwells. Therefore, these assays can be used to automatically and rapidly assess functional and migration behavior of cells to detect differences between health and disease or the influence of drugs. The work presented in this thesis gives good examples of how microfluidic devices combined with automated imaging and image analysis can be helpful to address cell biological questions where single cell resolution is necessary. / <p>QC 20130927</p>

The extracellular matrix (ECM) is a complex network of molecules secreted by cells, which is essential for providing structural support and facilitating cell processes including adhesion, migration and survival. Tenascin-C is an immunomodulatory ECM protein that exhibits limited expression in healthy tissues, but is transiently elevated at sites of tissue injury, and is persistently expressed in chronic inflammatory diseases and tumours. Alternative splicing of 9 of tenascin-C's fibronectin type III-like domains (FnIII- A1, A2, A3, A4, B, AD2, AD1, C and D) generates enormous diversity in form; yielding 511 possible isoforms. Post-transcriptional modification of tenascin-C has been studied in cancer and during development where disease and tissue specific isoforms exhibit distinct adhesive, migratory and proliferative effects. However, little is known of how tenascin-C is expressed or alternatively spliced during inflammation. This study characterises inflammation and disease specific tenascin-C isoforms made by immune cells and fibroblasts, and investigates their functional relevance. Biosynthesis and alternative splicing of tenascin-C was examined using standard curve qPCR, ELISA, Western blot and confocal immunocytochemistry in resting and activated primary human immune cells, dermal fibroblasts, and in synovial fibroblasts isolated from healthy controls and from osteoarthritis (OA) and rheumatoid arthritis (RA) patients. Based on these data, three recombinant proteins comprising FnIII domains AD2-AD1, B-C-D and B-AD2-AD1-C-D were cloned, expressed and purified, and their impact on cell behaviour including adhesion, morphology and migration was assessed. Basal tenascin-C expression was lower in myeloid and lymphoid cells than fibroblasts, and was induced in all following inflammatory stimulation. Tenascin-C expression was elevated in disease with RA and OA synovial fibroblasts containing higher levels than healthy controls. Alternative splicing following cell activation was cell-type specific: all FnIII except AD2 and AD1 were upregulated in dendritic cells and macrophages, in T-cells all FnIII remained unchanged with FnIII A1 absent; and no change in splicing was observed in activated dermal fibroblasts. Normal and OA synovial fibroblasts exhibited similar tenascin-C splicing patterns, but FnIII B and D were specifically elevated in RA. Functional analysis revealed differences in the adhesion, morphology and migration of myeloid cells and dermal fibroblasts cultured on FnIII AD2-AD1, B-C-D, B-AD2-AD1-C-D and full length tenascin-C substrates; FnIII B-C-D promoted MDDC migration while B-AD2-AD1-C-D promoted fibroblast adhesion, compared to full length tenascin-C. For the first time, this study reveals differences in tenascin-C biosynthesis and alternative splicing by immune cells and fibroblasts following activation with inflammatory stimuli; and starts to reveal how alternative splicing of tenascin-C may influence the behaviours of both stromal and immune cells types during inflammation and in inflammatory diseases.

Les Formes réactives de l’oxygène (FRO) ont un rôle bien établi dans l’oncogénèse en augmentant les capacités de prolifération et d’invasion des cellules tumorales. Mais les FRO exercent aussi un effet important sur le microenvironnement tumoral, en particulier en participant à l’échappement des tumeurs au système immunitaire. Une modulation pharmacologique de l’équilibre oxydo-réductif tumoral est donc susceptible d’influencer la progression tumorale. Il a été montré que l’induction pharmacologique d’un stress oxydant dans les cellules tumorales peut induire un effet cytotoxique mais ses effets sur le microenvironnement sont moins bien connus. L’objectif de nos travaux était d’étudier l’effet d’une modulation du stress oxydant sur les cellules immunitaires du microenvironnement tumoral et in fine de préciser les conséquences potentielles sur la progression tumorale. L’arsenic trioxyde (As2O3), inducteur de FRO, présentait à faible dose, dénuée d’effet cytotoxique direct sur les cellules malignes, un effet antitumoral dans un modèle de cancer colique murin. Cet effet était lié à une déplétion sélective en lymphocytes T régulateurs (Tregs) et était médié par la génération d’anions superoxyde (O2°-) et de monoxyde d’azote (NO), eux même responsables de la formation de peroxynitrite. Les Tregs présentaient un niveau basal de FRO plus élevé que les autres populations lymphocytaires, qui pourrait expliquer leur plus grande sensibilité à un surcroît de stress oxydant induit par l’As2O3. Un cytotoxique antitumoral, la vinorelbine, s’est également montré capable d’exercer un effet sur le microenvironnement tumoral. Par co-cultures, nous avons montré que la vinorelbine induisait un effet bystander toxique sur les cellules immunitaires effectrices voisines des cellules tumorales. In vivo, le prétraitement par vinorelbine de cellules malignes implantées à la souris était responsable d’une perte de la réactivité anti-tumorale des cellules mono-nuclées. Cet effet était dépendant de la production d’O2°- et de NO par les cellules malignes. Un modulateur du stress oxydant, le mangafodipir, inhibait cet effet, permettant ainsi de restaurer la réponse immunitaire antitumorale locale. Notre travail a donc permis de mettre en évidence que des modulateurs du stress oxydant peuvent agir sur le microenvironnement, et spécialement sur les cellules immunitaires. Ils pourraient être utilisés en clinique pour restaurer la réponse immunitaire antitumorale. Une meilleure compréhension du rôle du stress oxydant dans la défaillance de l’immunité antitumorale est nécessaire. / Several reports have demonstrated the involvement of reactive oxygen species (ROS) in carcinogenesis, through promotion of cancer cell proliferation and invasion. But ROS could also have consequences on non cancerous cells which are part of the tumor microenvironment, such as immune cells. Therefore, a pharmacological modulation of oxidative stress can induce a cytotoxic effect on tumor cells but its consequences on microenvironment are unknown. The aim of our studies was to evaluate the effects of a pharmacological modulation of oxidative stress on immune cells from the tumor microenvironment. At low dose, Arsenic trioxide (As203), an oxidative stress modulator, was shown to exert antitumor effects in colon tumor-bearing mice. We observed that this effect was related to As203-induced regulatory T cells (Tregs) -selective depletion in vitro and in vivo and was mediated by oxidative and nitrosative bursts. The differential effect of As203 on Tregs versus other CD4 cells was related to difference in the cells’redox status. We also observed that vinorelbine, an anticancer agent, could interfere with the antitumor immune response. We showed that vinorelbine could alter the function of immune cells surrounding tumor cells by a bystander toxic effect against tumor effector cells. In vivo experiment in A549 tumor bearing nude mice showed that adoptive transfer of A549 immune splenocytes was not able to delay tumor growth when vinorelbine-pretreated A549 cells were used for immunization. This effect was mediated by ROS and was inhibited by an oxidative stress modulator, mangafodipir, which restored antitumor immune function. Therefore, our work showed that oxidative stress modulators can influence tumor microenvironment and more specifically, immune cells. They could be used to restore antitumor immune response.