Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 122-140.

Thesis (Ph.D. in Immunology) -- University of Colorado, 2006. / Typescript. Includes bibliographical references (leaves 277-285). Free to UCDHSC affiliates. Online version available via ProQuest Digital Dissertations;

No description available.

CD4 T cells and B cells are cells associated with the adaptive immune system. The adaptive immune system is designed to mount a rapid antigen-specific response to pathogens by way of clonal expansions of T and B cells bearing discrete antigen-specific receptors. During viral infection, interactions between CD4 T cells and B cells occur in a dynamic process, where B cells that bind to the virus internalize and degrade virus particles. The B cells then present viral antigens to virus-specific CD4 T cells that activate the B cells and cause them to proliferate and differentiate into virus-specific antibody-secreting cells. Yet, non-specific hypergammaglobulinemia and the production of self-reactive antibodies occur during many viral infections, and studies have suggested that viral antigen-presenting B cells may become polyclonally activated by CD4 T cells in vivo in the absence of viral engagement of the B cell receptor. This presumed polyclonal B cell activation associated with virus infection is of great medical interest because it may be involved in the initiation of autoimmunity or contribute to the long-term maintenance of B cell memory. In order to directly examine the interactions that occur between T cells and B cells, I asked what would happen to a polyclonal population of B cells that are presenting viral antigens, if they were transferred into virus-infected hosts. I performed these studies in mice using the well-characterized lymphocytic choriomeningitis virus (LCMV) model of infection. I found that the transferred population of antigen-presenting B cells had two fates. Some antigen-expressing B cells were killed in vivo by CD4 T cells in the first day after transfer into LCMV-infected hosts. However, B cells that survived the cytotoxicity underwent a dynamic polyclonal activation manifested by proliferation, changes in phenotype, and antibody production. The specific elimination of antigen-presenting B cells following adoptive transfer into LCMV-infected hosts is the first evidence that MHC class II-restricted killing can occur in vivo during viral infection. This killing was specific, because only cells expressing specific viral peptides were eliminated, and they were only eliminated in LCMV-infected mice. In addition to peptide specificity, killing was restricted to MHC class II high cells that expressed the B cell markers B220 and CD19. Mice depleted of CD4 T cells prior to adoptive transfer did not eliminate virus-specific targets, suggesting that CD4 T cells are required for this killing. I found that CD4 T cell-dependent cytotoxicity cannot be solely explained by one mechanism, but Fas-FasL interactions and perforin are mechanisms used to induce lysis. Polyclonal B cell activation, hypothesized to be the cause of virus-induced hypergammaglobulinemia, has never been formally described in vivo. Based on previous studies of virus-induced hypergammaglobulinemia, which showed that CD4 T cells were required and that hypergammaglobulinemia was more likely to occur when virus grows to high titer in vivo, it was proposed that the B cells responsible for hypergammaglobulinemia may be expressing viral antigens to virus-specific CD4 T cells in vivo. CD4 T cells would then activate the B cells. However, because the antibodies produced during hypergammaglobulinemia are predominantly not virus-specific, nonvirus-specific B cells must be presenting viral antigens in vivo. In my studies, the adoptively transferred B cells that survived the MHC class II-restricted cytotoxicity became polyclonally activated in LCMV-infected mice. Most of the surviving naïve B cells presenting class II MHC peptides underwent an extensive differentiation process involving both proliferation and secretion of antibodies. Both events required CD4 cells and CD40/CD40L interactions to occur but B cell division did not require MyD88-dependent signaling, type I interferon signaling, or interferon γ signaling within B cells. No division or activation of B cells was detected at all in virus-infected hosts in the absence of cognate CD4 T cells and class II antigen. B cells taken from immunologically tolerant donor LCMV carrier mice with high LCMV antigen load became activated following adoptive transfer into LCMV-infected hosts, suggesting that B cells can present sufficient antigen for this process during a viral infection. A transgenic population of B cells presenting viral antigens was also stimulated to undergo polyclonal activation in LCMV-infected mice. Due to the high proportion of B cells stimulated by virus infection and the fact that transgenic B cells can be activated in this manner, I conclude that virus-induced polyclonal B cell activation is independent of B cell receptor specificity. This approach, therefore, formally demonstrates and quantifies a virus-induced polyclonal proliferation and differentiation of B cells which can occur in a B cell receptor-independent manner. By examining the fate of antigen-presenting B cells following adoptive transfer into LCMV-infected mice, I have been able to observe dynamic interactions between virus-specific CD4 T cells and B cells during viral infection. Adoptive transfer of antigen-presenting B cells results in CD4 T cell-mediated killing and polyclonal activation of B cells during LCMV infection. Studies showing requirements for CD4 T cells or MHC class II to control viral infections must now take MHC class II-restricted cytotoxicity into account. Polyclonal B cell activation after viral infection has the potential to enhance the maintenance of B cell memory or lead to the onset of autoimmune disease.

Le suivi des changements dans les populations de cellules immunitaires tels que les lymphocytes, monocytes et cellules dendritiques (DC) au cours de maladies infectieuses comme le virus de l'immunodéficience humaine (VIH) chez l’homme ou son équivalent chez le singe (VIS) est crucial. Grâce aux récentes avancées technologiques en cytométrie en flux, il est maintenant possible de mesurer et d’analyser simultanément jusqu'à 14 paramètres individuels à l’échelon cellulaire. L'objectif de ce travail consiste en la mise au point de 2 panels multicouleurs de 12 anticorps permettant d'analyser simultanément les principales populations de cellules immunitaires, respectivement chez l’humain et le macaque rhésus. Au terme de ce travail, il est maintenant possible de mesurer précisément tous les principaux acteurs du système immunitaire, à savoir les lymphocytes T CD4+ et T CD8+, les lymphocytes B, les cellules NK et NKT, les sous-populations de monocytes, et toutes les sous-populations de cellules dendritiques connues à ce jour, en utilisant une approche multiparamétrique de cytométrie en flux. Ce protocole d’analyse est réalisé sur du sang total, il est rapide, il n’implique pas de technique d’isolation cellulaire, et requiert une quantité minimum de sang. De plus, l’analyse de chaque population cellulaire est plus précise grâce à une contamination minimum entre les populations séparées. L’intérêt de ce travail est d’étudier les interactions entre les différentes populations de cellules immunitaires durant l’infection par VIH chez l’homme, ou VIS chez le singe ou potentiellement d‘autres maladies, et en particulier de mieux comprendre le rôle important que les cellules dendritiques jouent dans la progression de ces maladies. / Monitoring changes in immune cell populations such as lymphocytes, monocytes and dendritic cells (DC) during infectious diseases like human immunodeficiency virus (HIV) or its counterpart in rhesus monkeys (SIV) is crucial. Thanks to recent technological advances in flow cytometry, it is now possible to measure and analyze simultaneously up to 14 individual parameters at the single cell level.The goal of this work is to develop 2 multicolor flow cytometry panels comprising of 12 antibodies, allowing measuring simultaneously the main immune cells population, respectively in humans and rhesus monkeys. After 2 years of development and optimization, we can now measure precisely all the main actors of the immune system, that is CD4+ and CD8+ T lymphocytes, B lymphocytes, NK and NKT cells, the 3 monocyte subsets, and all the dendritic cell subsets known today, by using a multicolor flow cytometry approach. This assay is done on whole blood, it is rapid to do, it does not involve a cell isolation technique, and it requires only a minimum amount of blood. Moreover, the analysis of each population is much more precise because of a minimum contamination between different cell populations. The advantage of this work is to study interactions between different cell populations of immune cells during HIV infection in humans, or SIV infection in monkeys, or potentially other diseases, and in particular to better understand the important role that dendritic cells might play in disease progression.

Le sepsis, cause majeure de décès en réanimation, entraîne des altérations immunitaires associées à un risque augmenté de décès et d'infections secondaires. En particulier, les lymphocytes T (LT) de patients présentent des altérations phénotypiques et fonctionnelles caractéristiques d'un état d'épuisement. Pour améliorer leur réponse, l'IL-7 est actuellement proposée comme immunostimulant. Son récepteur existe sous différentes formes: protéines membranaire (CD127) et soluble (sCD127) et différents transcrits. Leur expression n'a été que peu étudiée dans le sepsis. De plus, dans d'autres contextes cliniques, le phénotype CD127lowPD1high est proposé comme marqueur d'épuisement des LT mais n'a jamais été évalué dans le sepsis. L'objectif de ce projet était d'évaluer l'expression du récepteur de l'IL-7 comme biomarqueur dans le sepsis, d'étudier sa régulation chez les patients et la présence du phénotype CD127lowPD-1high en lien avec les altérations des LT. L'objectif était également de mettre au point un modèle ex vivo reproduisant les altérations intrinsèques aux LT de patients. Nous avons confirmé l'intérêt de la concentration plasmatique de sCD127 comme marqueur de mortalité chez les patients de réanimation. Nous avons mis en évidence l'association de l'expression des transcrits IL7R correspondant à des formes solubles avec la mortalité, ainsi que leur régulation intrinsèque dans les LT. Enfin, la proportion augmentée de LT CD127lowPD-1high chez les patients en choc septique en fait également un candidat potentiel comme marqueur spécifique des altérations des LT. Dans un deuxième temps, nous avons développé un modèle d'altérations induites par l'activation à partir de LT purifiés de volontaires sains reproduisant les altérations des LT de patients en choc septique. Ce modèle suggère un rôle de l'activation des LT dans le développement de leurs altérations et pourrait permettre d'étudier de nouveaux aspects de la physiopathologie des LT dans le sepsis / Sepsis is the leading cause of death in intensive care units (ICU). Septic patients develop immune dysfunctions that are associated with an increased risk of death and secondary infections. In particular, patients’ T lymphocytes present phenotypic and functional alterations characteristic of exhaustion. To restore these alterations, IL-7 is currently proposed as an immunostimulant. Its receptor exists in different forms: a membrane (CD127) and a soluble (sCD127) proteins and different transcripts. The IL-7 receptor expression has not been studied in sepsis. Moreover, the CD127lowPD-1high phenotype is proposed as a T cell exhaustion marker in other clinical contexts but has never been explored in sepsis.In this context, the aim of this project was first to evaluate the expression of the IL-7 receptor as a biomarker in sepsis, to study its regulation in patients and the CD127lowPD-1high phenotype in parallel with T cell alterations in septic shock patients. Secondly, the objective was to develop an ex vivo model reproducing phenotypic and functional T cell alterations observed in patients.We confirmed the role of sCD127 plasmatic concentration as a marker of mortality in septic shock and more generally in ICU patients. In addition, we demonstrated the association of the expression of the IL7R transcripts, corresponding to soluble forms with mortality as well as the intrinsic regulation of their expressions in T lymphocytes. Finally, we found an increased proportion of CD127lowPD-1high T cells in septic shock patients. This population could also be evaluate as a potential specific marker of T lymphocyte alterations. Secondly, we developed an ex vivo model of alterations induced by activation of purified T cell from healthy volunteers reproducing alterations observed in patients’ T cells. This model suggests a role of T cell activation in the development of their alterations and could be used to explore new aspects of T cell alterations pathophysiology in sepsis

Les maladies auto-immunes, qui touchent plus de 5% de la population, sont induites par une perte de la tolérance aux antigènes du Soi. Ces pathologies, généralement multifactorielles, résultent de l’effet combiné de plusieurs allèles de susceptibilité et de différents facteurs environnementaux. Les agents infectieux ont été tout particulièrement incriminés, mais les mécanismes en jeu restent encore mal élucidés. Les lymphocytes B, qui jouent un rôle central dans la pathogénie de nombreuses maladies auto-immunes, sont susceptibles d’être activés selon différents mécanismes au cours d’un processus infectieux et cette activation peut englober des cellules autoréactives. On ne sait cependant pas si cette activation peut entraîner la production d’auto-anticorps pathogènes de forte affinité et d’isotype IgG à partir du pool de cellules productrices d’auto-anticorps naturels de faible affinité, qui sont présentes de façon constitutive dans le répertoire B de l’individu sain. Nous avons mis au point un nouveau modèle murin knock-in pour des lymphocytes B présentant une affinité intermédiaire pour leur auto-antigène, la protéine HEL2X mutée (Hen-Egg Lysozyme). Ce modèle autoréactif d’affinité intermédiaire SWHEL X HEL2X, élaboré sur un fond génétique non autoimmun, permet de suivre le processus de maturation d’affinité des cellules B anti-HEL en présence de leur auto-antigène HEL2X au cours de l’infection chronique par la bactérie Borrelia burgdorferi. L’infection induit au niveau ganglionnaire une prolifération ainsi qu’une activation lymphocytaire B incluant des cellules anergiques. Certains clones autoréactifs sont capables de gagner les centres germinatifs ganglionnaires, de commuter vers l’isotype IgG et présentent des mutations somatiques au niveau de la région variable de la chaîne lourde de leur immunoglobuline, dans la zone d’interaction avec HEL2X, indiquant un processus de sélection par l’auto-antigène. Malgré un taux augmenté d’auto-anticorps d’isotype IgM, ces animaux ne produisent pas de plasmocytes capables de sécréter des auto-anticorps d’isotype IgG. Nos observations suggèrent l’existence de mécanismes de tolérance périphérique intrinsèques mis en place en particulier au niveau du centre germinatif. Un premier point de contrôle va éliminer les lymphocytes B autoréactifs ayant commuté de classe et présentant des mutations somatiques leur conférant une affinité augmentée pour l’auto-antigène tandis qu’un second point de contrôle va empêcher la différenciation en plasmocytes IgG+.Chez l’individu non prédisposé génétiquement, des mécanismes pourraient ainsi permettre de prévenir le développement d’une auto-immunité pathogène au cours d’un épisode infectieux. / Autoimmune diseases, affecting more than 5% of the population, reflect a loss of tolerance to selfantigens. These multifactorial diseases result from the combined effect of several susceptibility alleles and different environmental factors. Infectious agents have been particularly incriminated but there is no clear understanding of the underlying mechanisms. B lymphocytes, that appear central to the pathogenesis of several autoimmune diseases, may be activated by several mechanisms during infectious processes and this activation can encompass autoreactive cells. Whether or not the lattercan induce the production of high-affinity pathogenic IgG isotype auto-antibodies from the naturally present low-affinity self-reactive B cells is still unknown. To gain further insight into this question, we created a new intermediate affinity autoreactive mouse model called SWHEL X HEL2X. In these mice, knock-in B cells express a B cell receptor highly specific for Hen-Egg Lysozyme (HEL) that recognizes HEL2X mutated auto-antigen with intermediate affinity. This model, generated on a non-autoimmune-prone genetic background, allows the following of anti-HEL B cells affinity maturation process in presence of their auto-antigen during Borrelia burgdorferi chronic bacterial infection. The infection leads to lymph nodes lymphoproliferation and B cell activation including anergic cells. Some autoreactive clones are able to form germinal centers, toswitch their immunoglobulin heavy chain and to introduce somatic mutations in the heavy chain variable regions on amino-acids forming direct contacts with HEL2X, suggesting an auto-antigen-driven selection process. Despite increased levels of IgM autoantibodies, infected mice are unable to generate IgG autoantibody secreting plasma-cells. These observations suggest the existence of intrinsic peripheral tolerance mechanisms operating mainly at the level of germinal centers. The first checkpoint eliminates switched autoreactive B cells with increasing affinity mutations while a secondcheckpoint avoids IgG+ plasma-cell differentiation. Thus, in genetically non predisposed individuals, tolerance mechanisms may be set-up to prevent the development of pathogenic autoimmunity during the course of an infection.

INTRODUÇÃO: Após a infecção aguda pelo HIV-1, um grupo privilegiado de pessoas consegue controlar a replicação viral sem o uso de antirretrovirais para níveis de viremia abaixo dos limites de detecção pelos testes disponíveis. Alguns alelos HLA estão associados à menor replicação viral durante a infecção recente e menor progressão para doença causada pelo HIV-1, sendo o HLA-B*57 o que está mais associado a esse efeito protetor. OBJETIVO: O objetivo deste trabalho foi confirmar a associação do HLA-B*57 com o melhor controle da viremia em indivíduos com infecção recente pelo HIV-1. MÉTODOS: Foram analisadas amostras de 228 indivíduos de uma coorte prospectiva em acompanhamento na cidade de São Paulo, identificados com infecção recente pelo HIV-1, pelo algoritmo STARHS (serologic testing algorithm for recent human HIV seroconversion). Foram realizadas a contagem de linfócitos T CD4+ e CD8+, carga viral do HIV-1 e tipificação dos alelos HLA. RESULTADOS: Dos 208 indivíduos analisados para o locus B, 15 indivíduos (7,2%) expressam o alelo HLA-B*57. O alelo HLA-B*57 foi fortemente correlacionado com os indivíduos que apresentam parâmetros laboratoriais favoráveis. A presença do HLA-B*57 foi associada com maior contagem de linfócitos T CD4+ basal (p=0, 043) e menor carga viral basal (p=0, 001). Dos 15 indivíduos que expressam o HLA-B*57, oito (53,3%) apresentaram-se com a viremia menor que 400 cópias/ml na visita inicial (Grupo A) e sete (46,6%) apresentaram-se com viremia maior que 400 cópias/mL, todos eles na ausência de terapia antirretroviral. A contagem de linfócitos T CD4+, entretanto, não foi diferente entre os dois grupos. CONCLUSÃO: Concluindo, este estudo indica que indivíduos que expressam o alelo HLA-B*57, apresentam melhor resposta imunológica na infecção recente demonstrada por melhor padrão laboratorial na contagem de linfócitos T CD4+, mas que perfis diferentes de controle podem existir nesses indivíduos. A diferença entre o comportamento da viremia nestes dois grupos pode auxiliar no entendimento da fisiopatogênese da infecção pelo HIV-1. / INTRODUCTION: After HIV-1 infection, a privileged group of subjects control viral replication to low levels, without the use of antiretroviral drugs. Some HLA alleles are associated with this control and to slower progression to immunodeficiency, especially the HLA-B*57. AIM: The aim of this study was to confirm the association of HLA-B*57 with viral control in recently HIV-1-infected subjects. MATERIALS: A cohort of recently HIV-1-infected 228 subjects, prospectively followed in the City of São Paulo, were identified using STARHS (serologic testing algorithm for recent human HIV seroconversion). CD4+, CD8+ T cell counts, viral loads, and HLA typing were performed in the participants samples. RESULTS: HLA typing was performed in 208 out of 228 subjects. Of those, 15 (7.2%) were HLA-B*57. This genotype was strongly correlated with favorable laboratory outcomes. HLA-B*57 subjects presented higher CD4+ T cell counts (p=0.043) and lower viral loads at the baseline visit (p=0.001). Eight (53.3%) out of 15 HLA-B*57 subjects presented undetectable viral load at the baseline visit (Group A) and seven (46.6%)had detectable viremia (Group B). However, the CD4+ T cell counts were not different between the two groups. CONCLUSION: In conclusion, this study points to the protective association of HLA-B*57 allele with better laboratory outcomes in HIV-1 infection, demonstrated by better CD4+ T cell counts and lower viral loads. Nevertheless, different profiles may exist within this group of subjects. The diverse viral control in such subjects may help better understand the pathogenesis of HIV-1 infection.

No description available.

Les neurotrophines sont des facteurs de croissance initialement découverts dans le système nerveux et ayant pour rôle de contrôler la croissance, la prolifération et la survie des cellules neuronales et astrocytaires, mais aussi dans de nombreux autres tissus. Les neurotrophines peuvent interagir avec leurs récepteurs de haute affinité Trks. Les travaux précédemment réalisés au sein de notre équipe ont mis en évidence une boucle de régulation autocrine, en réponse à un stress cellulaire, et ce de façon dépendante des neurotrophines, notamment du BDNF, dans plusieurs lignées lymphocytaires B humaines, à différents stades de différenciation. Les cellules produisent du BDNF qui agit de manière autocrine sur son récepteur spécifique, TrkB. Le transport du BDNF est assuré par la sortiline, une protéine à domaine Vps10. Les neurotrophines sont également synthétisées sous forme de progéniteurs biologiquement actifs, les pro-neurotrophines. Le pro-BDNF interagit avec le récepteur aux neurotrophines à domaine de mort p75NTR, l’interaction du pro-BDNF avec le récepteur p75NTR et de son co-récepteur, la sortiline, induit l’apoptose des lymphocytes B. La sortiline est exprimée dans les lymphocytes B humains, les lignées de lymphocytaires B. La sortiline, également appelée NTSR3, peut lier un autre neuropeptide, la neurotensine (NTS). Identifiée, dans le système nerveux, où elle joue un rôle de neurotransmetteur, impliqué dans l’analgésie et la thermorégulation. Elle est également présente dans le tube digestif, où elle est impliquée dans la régulation de la digestion et le contrôle et de la glycémie. La fonction de la neurotensine est associée à l’activation de la sortiline mais aussi de ses deux récepteurs à protéine G, le récepteur de haute affinité, NTSR1 et le récepteur de faible affinité, NTSR2. La NTS est impliquée dans l’oncogenèse de nombreux cancers solides via sa liaison au récepteur NTSR1 principalement mais également au récepteur NTSR2, notamment dans un modèle de cancer prostatique. Nous avons démontré pour la première fois l’expression de la neurotensine et de ses récepteurs NTSR1 et NTSR2 dans les lymphocytes B humains. Le stress pro-apoptotique induit par la privation sérique favorise une relocalisation des récepteurs NTSR1 et sortiline à la membrane plasmique. Au sein de ces cellules, la neurotensine induit une augmentation de la prolifération et une diminution de l’apoptose. Ces effets de la NTS sont bloqués par l’inhibiteur de NTSR1, le SR48692/Meclinertant®. Les analyses transcriptionnelles ont détecté une surexpression du récepteur NTSR2 au sein des lymphocytes B purifiés de patients ayant une LLC et au niveau des ganglions de patients atteints de lymphomes B en revanche, l’expression de la neurotensine est réduite. La surexpression de NTSR2 induit l’activation transcriptionnelle de TrkB, autre récepteur exprimé par ces lignées comme par les cellules de LLC de patients. La co-localisation de ces 2 récepteurs a été démontrée. Ce complexe protéique induit l’activation des voies de signalisation ERK, p38MAPK et JNK, après traitement par le BDNF, le ligand de TrkB. Ces données suggèrent un phénomène de transactivation entre ces 2 récepteurs, dépendant des métalloprotéases. Le blocage de l’internalisation de ce complexe protéique, induit une augmentation de l’activation des voies de signalisation. Le trafic intra-cellulaire endosomal de ce complexe apparaît perturbé dans les cellules surexprimant NTSR2, ce qui pourrait conduire à son accumulation comme cela est détecté dans les cellules de LLC. Ces cellules leucémiques se caractérisent également par une production d’exosomes contenant le complexe TrkB/NTSR2, sécrété en extra-cellulaire et retrouvé en excès dans le plasma des patients en comparaison à des témoins volontaires sains. / Neurotrophins are growth factors, initially discovered in the nervous system and whose functions are implicated in the growth, proliferation and survival of neuronal cells and astrocytes, and also in many other tissues. Neurotrophins can interact with their high-affinity receptors Trks. Previous work in our team showed a neurotrophin-dependent survival autocrine loop in response to cellular stress, including BDNF in several human B cell lines at various stages of B lymphocytes differentiation. These cells produce BDNF which acts in an autocrine manner on its specific tyrosine kinase receptor, TrkB. BDNF transport is provided by a Vps10 domain protein named, sortilin. Neurotrophins are synthesized as biologically active precursors, pro-neurotrophins. The proBDNF may interact with a death domain neurotrophins receptor p75NTR. The interaction of proBDNF with the p75NTR receptor and its co-receptor sortilin, induces B cell apoptosis. Sortilin is expressed in human lymphocytic lines B. Sortilin can bind another neuropeptide, neurotensin (NTS) and also called NTSR3 (Neurotensin Receptor 3). Identified in the nervous system, where it acts as a neurotransmitter involved in analgesia and thermoregulation, NTS is also present in the digestive tract, and involved in the digestion and glucose regulations. Neurotensin functions are associated to the sortilin activation but also its two G-protein coupled receptors, the high and the low affinity receptors, NTSR1 and NTSR2 respectively. NTS is involved in the oncogenesis of many solid cancers, especialy by its binding to the receptor NTSR1 mainly, but also NTSR2 notably in a prostate cancer model. We have demonstrated for the first time the expression of neurotensin and its receptors NTSR1 and NTSR2 in human B lymphocytes. The pro-apoptotic stress induced by serum deprivation promotes relocation NTSR1 receptor sortilin and to the plasma membrane. Within these cells, neurotensin induces increased proliferation and decreased apoptosis. These effects are blocked by the NTSR1 antagonist, SR48692/Meclinertant®. Transcriptional analyzes have detected overexpression of the receptor NTSR2 in purified B cells from patients with CLL and in lymph nodes of B-cell lymphomas patients, in contrast, the expression neurotensin is reduced. Overexpression NTSR2 induced transcriptional activation of TrkB. This receptor is expressed by B cell lines and B cells of CLL patients. The co-localization of these 2 receptors was demonstrated. This protein complex induces the activation of signaling pathways ERK, JNK and p38MAPK, after treatment with BDNF, the TrkB ligand. These data suggest a transactivation between these two receptors, depending to the metalloproteas activation. The internalization blocking of this protein complex, induces its plasma membrane sequestration and induces an increase of the signaling pathways activation. The intracellular endosomal trafficking in cells overexpressing NTSR2 cells, as detected in CLL cells, appears disrupted, which might lead to the NTSR2/TrkB complex accumulation, and releasing to the extracellular environnement. These leukemic cells are also characterized by a production of exosomes containing the TrkB/NTSR2 complex, secreted to the extracellular environement and found in excess in the plasma of patients in comparison to healthy volunteers.