Depuis quelques décennies, le syndrome d'immunodéficience acquise a causé la mort de millions de personnes. La recherche des dernières années a permis de caractériser l'agent causal, le virus de l'immunodéficience humaine, d'identifier des cibles thérapeutiques ainsi que de développer des drogues permettant de contrôler la réplication de ce virus. Toutefois, nous constatons l'émergence de souches virales résistantes à un ou plusieurs des médicaments disponibles. De plus, bien qu'elle permette de bien contrôler la réplication du virus, la thérapie actuelle ne permet pas son éradication et il n'existe aucun vaccin efficace pour la prévention de l'infection. Le virus persiste ainsi dans certaines cellules infectées, lesquelles formeront un réservoir viral. Les monocytes représentent une population cellulaire favorable à la formation d'un tel réservoir viral. Leur dissémination et leur accumulation dans les ganglions lymphatiques constitueraient une étape critique dans la persistance du virus. Les mécanismes menant à la migration des monocytes vers les ganglions lymphatiques sont actuellement méconnus. Les travaux réalisés dans le cadre de cette thèse avaient pour objectif de mieux comprendre les évènements immunologiques et moléculaires contrôlant la migration des monocytes vers les ganglions lymphatiques. Dans un premier temps, nous avons démontré le rôle de la prostaglandine E[indice inférieur 2], une cytokine produite massivement au cours de l'infection, dans le contrôle de l'expression du récepteur de chimiokine CCR7 chez les monocytes. Ce récepteur est responsable de la migration des leucocytes vers les ganglions lymphatiques sous l'action chimiotactique des chimiokines CCL19 et CCL21. Nous avons démontré qu'une exposition des monocytes à la prostaglandine E[indice inférieur 2] entraînait une augmentation de leur migration vers ces chimiokines. Nous avons caractérisé les voies de signalisation intracellulaire activées par la prostaglandine E[indice inférieur 2] menant à l'expression de CCR7 chez les monocytes. Nous avons ainsi établi que la synthèse d'AMPc résultant de l'activation des récepteurs EP[indice inférieur 2] et EP[indice inférieur 4] entraînait l'expression de CCR7 chez les monocytes. Nous avons ensuite démontré l'implication des kinases PKA, ERK et p38 dans ce processus. Dans un second temps, nous avons vérifié l'effet de l'infection par le virus de l'immunodéficience humaine sur l'expression et la fonctionnalité du récepteur CCR7 chez les monocytes exposés à la prostaglandine E[indice inférieur 2]. Notre modèle expérimental démontre que l'exposition des monocytes au virus de l'immunodéficience humaine diminue le niveau de surface ainsi que la fonctionnalité du récepteur CCR7. Toutefois, la prostaglandine E[indice inférieur 2] augmente l'expression de CCR7 à la surface des monocytes exposés au virus, ce qui résulte en une augmentation de la sensibilité des monocytes pour la chimiokine CCL19. Nos résultats suggèrent que lors de la transmission mucosale du virus de l'immunodéficience humaine, l'exposition des monocytes au virus ainsi qu'à la prostaglandine E[indice inférieur 2] pourrait favoriser la dissémination du virus vers les ganglions lymphatiques. Une meilleure compréhension de la pathogenèse du virus ainsi que des mécanismes menant à la dissémination virale pourrait conduire à l'amélioration de l'approche thérapeutique actuelle.

Chemokines are responsible for the directed migration of leukocyte chemotactic cytokines, coordinating cell movement during inflammation and the transport of hematopoietic cells. In addition to leukocytes, chemokine receptors are also found in neoplastic cells and tumors associated with stromal cells. Among chemokines, and the CXCR4/CXCL12 CCR7/CCL21 systems have been shown the involvement of lymph node metastases or distant metastases in different cancers. Thus, aim of this study was to evaluate the expression of CXCR4, CXCL12, CCR7, CCL21 and Ki-67 in oral squamous cell carcinoma (SCC) and to correlate these markers with clinicopathological indicators, lymph node metastasis and survival. We conducted a survey of reports and paraffin blocks of excisional biopsies of patients with SCC treated at the Hospital Haroldo JuaÃaba (2001-2009). Data on anatomic location of the lesion, sex, age, patient survival, degree of histological differentiation of the tumor, tumor stage and presence or absence of lymph node metastasis, lymphovascular and perineural invasion, nuclear grade and depth of invasion were collected. For immunohistochemical analysis, followed by the technique of streptavidin-biotin-peroxidase using the anti-CXCR4, anti-CXCL12, anti-CCR7, anti-CCL21 and Ki-67 antibody. Histological sections were photomicrographed in 10 fields chosen randomly and measured for the number of labeled tumor cells and determined the percentage of each labeling antibody. The marking of CXCR4 was detected in the cytoplasm and nucleus, CXCL12, CCR7 and CCL21 were only cytoplasmic, their expression was observed in 18 (60%) 8 (22.66%) 16 (53.3%) and 3 (12%) cases, respectively. We found a significant positive association between lymphovascular invasion and immunostaining of CXCR4 (p = 0.007) and CCR7 (P = 0.01) and among these cases metastasis was present in 62.5% and 37.5%, respectively. When in combination with Ki67, we found a significant positive correlation between CXCR4 (p = 0.0086), CXCL12 (p = 0.036) and CCR7 (p = 0:04). Among patients CXCR4 + over 111 months, only 38.4% were alive (p = 0.845), whereas both patients CCR7 + (p = 0.398) as well as CXCR4 +, and CCR7 + (p = 0.441) after 62 months, everyone had already died. We conclude that these chemokines are associated with lymphovascular invasion and cell proliferation, perhaps favoring the development of metastasis and poor prognosis. / As quimiocinas sÃo citocinas quimiotÃticas responsÃveis pela migraÃÃo direcionada de leucÃcitos, coordenando o movimento celular durante a inflamaÃÃo e o transporte de cÃlulas hematopoiÃticas. AlÃm dos leucÃcitos, os receptores de quimiocinas tambÃm sÃo encontrados em cÃlulas neoplÃsicas e em tumores associados com cÃlulas estromais. Dentre as quimiocinas, os sistemas CXCR4/CXCL12 e CCR7/CCL21 tÃm sido demonstrado no envolvimento de metÃstases linfonodais ou à distÃncia em diferentes tipos de cÃncer. Dessa forma, foi objetivo desse trabalho avaliar a expressÃo de CXCR4, CXCL12, CCR7, CCL21 e Ki-67 em carcinoma de cÃlulas escamosas orais (CEC) e correlacionar estes marcadores com indicadores clÃnicopatolÃgicos, metÃstase linfonodal e sobrevida. Realizou-se um levantamento de laudos e blocos parafinados de biopsias excisionais de pacientes portadores de CEC tratados no Hospital Haroldo JuaÃaba (2001 a 2009). Foram coletados dados sobre localizaÃÃo anatÃmica da lesÃo, sexo, idade, sobrevida do paciente, grau de diferenciaÃÃo histopatolÃgica do tumor, estadiamento tumoral e presenÃa ou ausÃncia de metÃstase linfonodal, invasÃo linfovascular e perineural, grau nuclear e profundidade de invasÃo. Para reaÃÃo de imunohistoquÃmica, seguiu-se a tÃcnica da estreptavidina-biotina-peroxidase, utilizando os anticorpos anti-CXCR4, anti-CXCL12, anti-CCR7, anti-CCL21 e Ki-67. As secÃÃes histolÃgicas foram fotomicrografadas em 10 campos escolhidos aleatoriamente e quantificadas quanto ao nÃmero de cÃlulas tumorais marcadas e determinado o percentual de marcaÃÃo de cada anticorpo. A marcaÃÃo de CXCR4 foi detectada em citoplasma e nÃcleo, CXCL12, CCR7 e CCL21 tiveram marcaÃÃo apenas citoplasmÃtica, sendo observada suas expressÃes em 18 (60%), 8 (22,66%), 16 (53,3%) e 3 (12%) casos, respectivamente. Encontrou-se uma associaÃÃo significativa positiva entre a invasÃo linfovascular e a imunomarcaÃÃo do CXCR4 (p=0.007) e CCR7 (p=0.01) e dentre esses casos a metÃstase esteve presente em 62,5% e 37,5%, respectivamente. Quando em associaÃÃo com o Ki67, encontrou-se uma correlaÃÃo positiva significante entre o CXCR4 (p=0.0086), CXCL12 (p=0.036) e CCR7 (p=0.04). Dentre os pacientes CXCR4+, ao longo de 111 meses, apenas 38,4% estavam vivos (p=0.845), ao passo que tanto para pacientes CCR7+ (p = 0.398), quanto CXCR4+ e CCR7+ (p = 0.441), apÃs 62 meses, todos haviam ido a Ãbito. Conclui-se que essas quimiocinas estÃo associadas com a invasÃo linfovascular e proliferaÃÃo celular, talvez favorecendo o desenvolvimento de metÃstases e um pior prognÃstico.

<p>Chemokine receptors are members of the seven transmembrane receptor (7TMR) superfamily and are regulated by the G-protein coupled Receptor Kinase (GRK)/ b-arrestin system. CCL19 and CCL21 are endogenous agonists for the chemokine receptor CCR7. They are known to be equipotent in promoting Gi/o mediated calcium mobilization, chemotaxis and inhibition of adenylyl cyclase activity. Here we test the hypothesis that these ligands are biased agonists that differentially activate the G-protein coupled Receptor Kinase (GRK)/ b-arrestin system.</p><p>In order to test whether these ligands have distinct activity, murine T lymphocytes were used to compare the effects of CCL19 and CCL21 activation of CCR7 at endogenous expression levels. While each ligand stimulates similar chemotactic responses, we also find that CCR7 ligands lead to differential signaling. For instance, CCL19 is markedly more efficacious than CCL21 for the activation of ERK and JNK, but not AKT in these cells. Furthermore, ERK activation and chemotaxis are maintained as separate pathways, also distinguishable by their dependency upon PKC and PI3 kinase, respectively. Thus, CCL19 and CCL21 stimulate equal activation of PI3 kinase, AKT, and chemotaxis, but are in fact biased agonists leading to differential activation of MAP kinase in murine T lymphocytes. </p><p>To determine the mechanism of CCR7 ligand bias, we used HEK-293 cells expressing CCR7 to compare the proximate signaling events following CCL19 and CCL21 activation. We found striking differences in the activation of the GRK/ b-arrestin system. CCL19 leads to robust CCR7 phosphorylation and b-arrestin2 recruitment catalyzed by both GRK3 and GRK6 while CCL21 activates GRK6 alone. This differential GRK activation leads to distinct functional consequences. Only CCL19 leads to the recruitment of b-arrestin2-GFP into endocytic vesicles and classical receptor desensitization. In contrast, each agonist is fully capable of signaling to MAP kinase through b-arrestin2 in a GRK6 dependent fashion. </p><p>Therefore, CCR7 and its ligands represent a natural example of ligand bias whose mechanism involves differential GRK isoform utilization by CCL19 and CCL21 despite similar G-protein signaling. This study suggests that the GRK signatures of 7TMRs can determine the function of discrete pools of b-arrestin and thus guide its cellular effects.</p> / Dissertation

Le Récepteur de chimiokine CCR7 joue un rôle important dans la migration des cellules immunitaires, permettant ainsi l'initiation de la réponse immunitaire. Des études ont démontré qu'une déficience dans l'expression de ce récepteur ou de ces ligand CCL19 et CCL21 a un impact considérable sur la mise en place de la réaction immunitaire suite a un stimulus. D'autre part la prostaglandine de série E 2 a été identifié comme un agent régulateur important sur l'expression et la fonctionnalité du récepteur CCR7 dans l'établissement de la réponse immunitaire, principalement au niveau des cellules dendritiques. L'élévation du niveau de prostaglandine E 2 , lors de certaine infection, induit une augmentation importante de la migration des cellules immunitaires, lors de l'activation du récepteur CCR7. Ces cellules vont alors migrer vers ses ligands qui sont produit principalement au niveau des ganglions lymphatique, permettant ainsi la présentation antigénique aux cellules du système immunitaire adaptatif. Récemment, des travaux ont permis de mettre en évidence l'expression du récepteur CCR7 chez les monocyte et du rôle important de la PGE 2 dans l'expression et la fonctionnalité du récepteur chez ces cellules. Les travaux réalisés dans le cadre de cette maîtrise avaient pour but, dans un premier temps, de déterminer les mécanismes moléculaires permettant la migration cellulaire des monocytes suite à l'activation du récepteur CCR7 par la présence de son ligand CCL19. Nous avons également vérifié l'implication de la PGE 2 dans ce processus. Partant des mécanismes connus chez les cellules dendritiques et des cellules T, nous avons établi que la participation des MAPK p38, ERK et JNK sont importantes dans ce processus. La présence de PGE2 permet une phosphorylation plus rapide de ses MAPK. Nous avons ensuite vérifié la participation de la voie RhoA/ROCK, importante dans le réarrangement du cytosquelette d'actine. L'activation du récepteur CCR7 par son ligand CCL 19 permet une activation de RhoA. Cette activation survient plus rapidement lorsque les cellules sont en présence de PGE 2. Lorsque ces voies métaboliques sont bloquées par des inhibiteurs pharmacologiques, la migration des monocytes est alors inhibée, démontrant l'importance de ses voies pour la migration des monocytes vers les ligands CCL191 Dans un second temps, nous avons étudié l'impact de la maturation des monocytes en macrophage sur le récepteur CCR7. Jusqu'à maintenant, il est connu que la PGE2 permet une augmentation de l'expression de CCR7 chez les monocytes et augmente la réponse chimiotactique des cellules vers les ligands de CCR7. De plus on sait que lors de la maturation des monocytes en cellules dendritique mature, une forte augmentation de l'expression du récepteur CCR7 est observé et que la présence de PGE 2 est essentielle pour assurer la fonctionnalité du récepteur. Toutefois, l'impact de la maturation des monocytes en macrophage sur le récepteur CCR7 est encore inconnu. Nous avons alors démontré que lors de la maturation des monocytes en macrophages, il y a une importante perte de l'expression du récepteur CCR7 et que la présence inflammatoire de la PGE 2 ne permet pas une augmentation de l'expression du récepteur et de la migration des cellules chers les ligands de CCR7. La migration des macrophages vers les ganglions lymphatique ne serait alors pas attribuée à la chimiotaxie de CCR7 vers ses ligands. Ces travaux ont permis de mettre en lumière les principaux acteurs moléculaires impliqué dans la migration des monocytes suite à l'activation du récepteur CCR7 et que la PGE2 permettrait aux monocytes de migrer préférentiellement vers ses ligands au lieu de transmigrer vers les tissus où ils se différencieraient en macrophage. Suite à la différenciation des monocytes en macrophages, nous avons également pu démontrer qu'ils n'ont plus la capacité d'exprimer le récepteur CCR7 et amorcer leur migration vers les ligands CCL19 et CCL21 exerçant ainsi leur fonction en tant que cellules résidente des tissus.[ symboles non conformes]

Yes / The chemokine receptor CCR7 is expressed on lymphocytes and dendritic cells and is responsible for trafficking of these cells in and out of secondary lymphoid organs. It has recently been shown that CCR7 expression is elevated in a number of cancers, including head and neck cancers, and that its expression correlates to lymph node (LN) metastasis. However, little is known about the factors that can induce CCR7 expression in head and neck cancers. We compared the protein expression and functional responses of CCR7 under normoxia and hypoxia in head and neck cancer cell lines OSC-19, FaDu, SCC-4, A-253 and Detroit-562 cultured as monolayers, spheroids, and grown in vivo as xenografts in balb/c mice. In addition, we analysed the correlation between hypoxia marker HIF-1α and CCR7 expression in a tissue microarray comprising 80 clinical samples with various stages and grades of malignant tumour and normal tissue. Under hypoxia, the expression of CCR7 is elevated in both in vitro and in vivo models. Furthermore, in malignant tissue, a correlation is observed between hypoxia marker HIF-1α and CCR7 across all clinical stages. This correlation is also strong in early histological grade of tumours. Hypoxia plays a role in the regulation of the expression of CCR7 and it may contribute to the development of a metastatic phenotype in head and neck cancers through this axis.

Chemokines are chemotactic cytokines, which mediate cell trafficking and play a key role in mobilisation of leukocytes. More recently, chemokines and their cognate receptors have been described as key players in different aspects of cancer biology contributing to proliferation, angiogenesis and metastasis. In particular, chemokines CCL19 and CCL21 acting on their associated receptor CCR7 are postulated to be key drivers of lymph node metastasis in a number of malignancies including breast, colon, gastric, & thyroid cancers. It has been reported that the cleavage of the pre-cysteine bridge N-terminal residues of CCL21 (SDGGAQD) and of CCL19 (GTNDAED) renders both peptides incapable of fully activating CCR7. However, little is known about the nature of the interactions that occur between the N-terminal residues of CCL19 or CCL21 and the CCR7 receptor, or the role they have in activation of CCR7. The aim of this study is to investigate the role of the residues in the N-terminus of CCL19 and in particular CCL21 in the context of CCR7 activation and to use this information in the discovery of novel CCR7 antagonists or agonists. To achieve this, we synthesised a number of short (three to seven amino acids) peptides and peptidomimetics inspired by the seven N-terminal amino acid residues of CCL19 and CCL21 and pharmacologically characterised their ability to activate CCR7 or block the activation of CCR7 using a number of in vitro assays such as calcium flux, trans-well (Boyden chamber), and Western blotting. We also carried out computational studies to better understand and predict the activity of these peptides. Our results demonstrate that some of these peptides are indeed capable of acting as agonists or antagonists of CCR7. / Kuwait Health Ministry and Kuwait Civil Services Commission

According to the classical paradigm, CCR7 is a homing chemokine receptor that grants normal lymphocytes access to secondary lymphoid tissues such as lymph nodes or spleen. As such, in most lymphoproliferative disorders, CCR7 expression correlates with nodal or spleen involvement. Nonetheless, recent evidence suggests that CCR7 is more than a facilitator of lymphatic spread of tumor cells. Here, we review published data to catalogue CCR7 expression across blood cancers and appraise which classical and novel roles are attributed to this receptor in the pathogenesis of specific hematologic neoplasms. We outline why novel therapeutic strategies targeting CCR7 might provide clinical benefits to patients with CCR7-positive hematopoietic tumors.

Metastasis is a major cause of death in cancer patients but currently there are no drugs available for its treatment. Hence there is an urgent clinical need for identifying and developing anti-metastatic drugs. The activation of CC chemokine receptor 7 (CCR7) and C-X-C chemokine receptor type 4 (CXCR4) plays an important role in lymph node metastasis in a variety of cancers. Indeed, in patients with tumours which are positive for CCR7 and/or CXCR4 expression, prognosis and survival are poorer than those whose tumours are negative for these receptors. CCR7 and/or CXCR4 activation, in addition to being involved in inducing invasive phenotypes in cancer cells, promotes tumour cell growth and survival. Our group has previously identified a series of sulfonamides as CCR7 antagonists. This project aims to extend on those studies and to develop a dual CCR7 and CXCR4 antagonist to reduce metastasis in cancer. Novel potent biaryl sulfonamide CCR7 antagonists were synthesised and assessed by calcium flux assay. Several potential dual CCR7 and CXCR4 biaryl sulfonamide antagonists have been synthesised, these are hybrid compounds incorporating features from CCR7 antagonists of this project, and from known sulfonamide CXCR4 antagonists. The most potent of such compound was able to inhibit CCR7 activation in calcium flux assay (95% inhibition at 1 µM), however, the relative potency of these compounds as CXCR4 antagonists was low. Molecular docking was used to investigate the binding mode of the synthesised compounds in CCR7 and CXCR4. The generated docking poses were able to rationalise some of the calcium flux assay results.

Chemokines are chemotactic cytokines which play an important role in the migration of immune cells to distant tissues or compartments within tissues. These proteins have also been demonstrated to play a major role in cancer metastasis. The C-C chemokine receptor type 7 (CCR7) is a member of the chemokine receptor family. CCR7 along with its ligands CCL19 and CCL21 plays an important role in innate immune response by trafficking of lymphocytes. In cancer, tumour cells expressing CCR7 migrate to lymphoid organs and thus disseminate to other organs. Neutralizing the interactions between CCL21/CCR7 would therefore be expected to inhibit the progression and metastasis of many different types of cancer to regional lymph nodes or distant organs. Our objective was to identify a potent small molecule antagonist of CCR7 as a prelude to the investigation of the role of this axis in cancer metastasis. In this study, we provided a brief description of chemokines and their role in health and disease with an emphasis on the CCR7/CCL19/CCL21 axis, as well as identification of a CCR7 antagonist “hit”. The potency of the CCR7 antagonist “hit” was optimised by synthesizing different CCR7 antagonist analogues. The “hit” optimization process has led to discover the most active compound amongst a series of different analogues which have the ability to bind and block CCR7 receptor. The efficacy of the most active compound and other analogues were evaluated in vitro using a calcium flux assay which is based on detecting fluorescent light emitted upon release of calcium ions. To identify a suitable cell line, which expresses CCR7 and capably respond to it, amongst a panel of cell lines for in vitro assessment of potency of synthesised compounds, we used Western blot assay and later by flow cytometry assay. The activity and selectivity of the most effective compound against CCR7 receptor was evaluated in vitro by other functional assays such as “configured agarose spot assay” and scratch assay. We first configured the existing under agarose assay to fulfil our requirements and then used it to assess activity and selectivity of compounds. The configured agarose spot assay also describes the application of the agarose spot for evaluation of cells chemotactic response to multiple chemokines under identical experiment conditions.

Véritable immunothérapie adoptive, l’allogreffe de Cellules Souches Hématopoïétiques (CSH) est destinée à prévenir la rechute d’une hémopathie maligne grâce au combat immunologique du greffon contre la maladie (effet GVL, Graft Versus Leukemia), dans lequel les lymphocytes T apportés par le greffon sont déterminants. Ils peuvent aussi compromettre le résultat escompté, en induisant une réaction du greffon contre l'hôte (GVH, Graft Versus Host) qui reste une complication redoutée de l’allogreffe. Dans une précédente étude prospective portant sur 62 couples donneur/receveur nous avons pu étudier l'impact de la composition du greffon en cellules T de phénotypes naïfs et mémoires sur le devenir des receveurs d’allogreffes à partir d'un donneur HLA-identique apparenté ou non; et nous avons pu démontrer qu’une proportion élevée de lymphocytes T CD4+CCR7+ dans le greffon était un facteur de risque de la survenue, la précocité et la sévérité de la GVH aiguë, sans influence sur la GVH chronique ou la rechute. Dans le but de séparer l’effet GVL de la GVH, nous avons voulu à travers des travaux de cette thèse, étudier le concept d’une T déplétion partielle et sélective du greffon en lymphocytes T CD4+CCR7+. Nous travaux se sont scindés en trois parties :1) Au plan clinique, nous avons pu confirmer nos précédents résultats sur une cohorte additionnelle de 137 patients. Non seulement, nous avons confirmé qu’une proportion élevée de lymphocytes T CD4+CCR7+ dans le greffon était un facteur de risque de la survenue, de la GVH aiguë, mais également, nous avons observé un effet préférentielle de la sous-population naïve des lymphocytes T CD4+ sur l’incidence de la GVH aiguë. Bien entendu, aucun impact sur l’incidence de la rechute post-allogreffe n’a été enregistré.2) Dans un modèle expérimental utilisant des cultures lymphocytaires en présence des cellules dendritiques provenant des six couples (frère/sœur) HLA-identiques, nous avons pu démontrer que les lymphocytes T CD4+ naïfs déclenchaient la réponse allogénique la plus importante et avec un degré moindre les cellules mémoires centrales par rapport aux effecteurs mémoires T CD4+. Ces résultats non seulement, valident in vitro les constatations cliniques mais aussi mettent l’accent sur le rôle prépondérant des lymphocytes T naïfs dans l’alloréactivité, notamment en situation de compatibilité HLA.3) Nous avons dans la troisième partie pu démontrer qu’une déplétion partielle sélective des greffons en lymphocytes T CD4+CCR7+ n’altère pas la réponse immunologique secondaires vis-à-vis des virus.La suite de nos travaux se focalise sur l’effet de la déplétion partielle sélective des greffons en lymphocytes T CD4+CCR7+ sur la réaction anti-tumorale du greffon dans la situation HLA compatibilité chez l’homme.Nos résultats constituent une pierre angulaire dans le concept de déplétion partielle sélective des greffons en lymphocytes T CD4+CCR7+, ex vivo chez l’homme, en vue de réduire l’incidence de la GVHD sans altérer la réponse anti-infectieuse ou tumorale du greffon notamment chez les donneurs présentant un taux élevé de lymphocytes T CD4+ naïfs et/ou mémoire centrale . / A genuine adoptive immunotherapy, Haematopoietic Stem Cell (HSC) allotransplantation aims to prevent the recurrence of a malignant blood disease via an immunological action of the graft against disease (GVL or Graft Versus Leukaemia effect), in which the T lymphocytes supplied by the transplant play a key role. They may also compromise the targeted result, by triggering a GVH (Graft Versus Host) reaction, which remains a serious complication of allotransplantation. In a previous prospective study conducted in 62 donor/recipient pairings, we examined the impact of the transplant\\\'s naive and memory phenotype T cell composition on the fate of recipients of allotransplants from an HLA-identical donor, related to the recipient or otherwise. We demonstrated that a high proportion of CD4+CCR7+ T lymphocytes in the transplant was a risk factor for the development, early onset and severity of acute GVHD, with no influence on chronic GVHD or recurrence. With the objective of separating the GVL effect from the GVH effect, we wanted to investigate the concept of partial and selective CD4+CCR7+ T cell depletion of the graft in the studies conducted as part of this research. Our studies were split into three parts:1) Clinically, we confirmed our previous results in an additional cohort of 137 patients. In addition to confirming that a high proportion of CD4+CCR7+ T lymphocytes in the transplant was a risk factor for the development of acute GVH, we also observed a preferential effect of the naive CD4+T lymphocyte sub-population on the incidence of acute GVHD. Obviously, no impact on the incidence of post-allotransplantation recurrence was recorded.2) In an experimental model using lymphocyte cultures in the presence of dendritic cells taken from six HLA-identical pairings (brother/sister), we demonstrated that naive CD4+ T lymphocytes triggered the greatest allogenic response and, to a lesser degree, central memory cells compared to effector memory CD4+ T cells. Not only do these results validate the clinical observations made in vitro, they also highlight the dominant role of naive T lymphocytes in alloreactivity, particularly in situations of HLA incompatibility.3) In the third part, we demonstrated that selective partial CD4+CCR7+ T cell depletion of the transplants does not impair the secondary immunological response to viruses.The next phase of our research focuses on the effect of selective partial CD4+CCR7+ T cell depletion of grafts on the transplant's anti-tumoural reaction in situations of HLA compatibility in humans.Our results represent a cornerstone in the concept of partial selective T CD4+CCR7+ T cell depletion of transplants, ex vivo in humans, with a view to reducing the incidence of GVHD, without impairing the anti-infectious or anti-tumoural response of the graft, particularly in donors with high levels of naive and/or central memory CD4+ T lymphocytes.