Literatura académica sobre el tema "Lymphocytes B intestinaux"

Lack of clear clinical and laboratory picture of subjective evaluation of bowel viability, the progression of bowel necrosis in the postoperative period with acute mesenteric ischemia (АМI) contributes to the high mortality rate. Earlier experiments we proved that gut necrosis leads to changes in the subpopulation structure of blood lymphocytes. This prompted us to determine the clinical significance of the subpopulation structure of venous blood lymphocytes in patients with acute mesenteric ischemia. The paper is based on a retrospective analysis of the results of a controlled clinical and immunological examination of 18 patients aged 62 to 78 years (control group and a group of АМI). Evaluation lymphocyte subpopulation structure was performed by the standard method of direct immunofluorescence staining of whole blood. The obtained data were processed with nonparametric statistical methods. Study of lymphocyte subpopulation structure in patients with АМI patients showed a decrease in the absolute and relative number of CD8, CD4, B, NK cells on the indicators in the control group. Ischemia and necrosis of the intestinal mucosa accompanied by a massive translocation of intestinal microflora through the impaired intestinal barrier along with the migration of lymphocytes into the lesion and death, which is manifested in a decrease in the number of lymphocytes of the peripheral blood. Comprehensive assessment of venous blood lymphocyte subpopulation structure can be used as an additional diagnostic criterion necrotic step АМI, serve as criteria for selection of patients for immunotherapy.

Isolated lymphoid follicles (ILFs) are organized intestinal lymphoid structures whose formation can be induced by luminal stimuli. ILFs have been demonstrated to act as inductive sites for the generation of immune responses directed toward luminal stimuli; however, the phenotype of the immune response initiated within ILFs has largely been uninvestigated. To gain a better understanding of the immune responses initiated within ILFs, we examined phenotypic and functional aspects of the largest cellular component of the murine ILF lymphocyte population, B lymphocytes. We observed that murine ILF B lymphocytes are composed of a relatively homogenous population of follicular B-2 B lymphocytes. Consistent with their proximity to multiple stimuli, ILF B lymphocytes displayed a more activated phenotype compared with their counterparts in the spleen and Peyer's patch (PP). ILF B lymphocytes also expressed higher levels of immunomodulatory B7 and CD28 family members B7X and programmed death-1 compared with their counterparts in the spleen and PP. ILF B lymphocytes preferentially differentiate into IgA-producing plasma cells and produce more IL-4 and IL-10 and less interferon-γ compared with their counterparts in the spleen. Immunoglobulin repertoire analysis from individual ILFs demonstrated that ILFs contain a polyclonal population of B lymphocytes. These findings indicate that murine ILFs contain a polyclonal population of follicular B-2 B lymphocytes with a phenotype similar to PP B lymphocytes and that, in unchallenged animals, ILFs promote immune responses with a homeostatic phenotype.

ABSTRACTObjectiveNucleotides, the building blocks of nucleic acids, are normal components of the mammalian diet. These molecules have been implicated in biologic processes, such as the stimulation of the immunologic response. Nucleotides have also been considered as conditionally essential nutrients for infant formulas. The authors evaluated the influence of dietary nucleotides on the expression of several surface antigens by different intestinal lymphocyte populations in weanling mice.MethodsMice at weaning were fed a semipurified diet with or without 3 g/kg of each of the following nucleotides: adenosine monophosphate, cytosine monophosphate, guanosine monophosphate, and uridine monophosphate. Animals were killed at different times (0, 4, 7, 12, and 18 days) after weaning, and lymphocytes from intestinal Peyer's patches, epithelium, and lamina propria were isolated. The expression of different antigens (CD3, CD4, CD8α, CD8β, TCRαβ, TCRγδ, CD5, CD22 and CD45R) was analyzed by flow cytometry.ResultsThe expression of these antigens changed parallel to the maturation of the lymphocytes from Peyer's patches, epithelium, and lamina propria. However, developmental changes of expression for most of the antigens occurred sooner in the animals fed the diet supplemented with nucleotides. The expression of T and B antigens was different in the lymphocyte populations analyzed and also changed according to the diet within each population. In general, nucleotides promoted the expression of B‐ and T‐helper cell antigens.ConclusionsThe authors conclude that dietary nucleotides may affect the process of maturation and differentiation of intestinal lymphocytes, which usually takes place at weaning.

Although previous studies have implicated lymphocytes in the gut microvascular and inflammatory responses to ischemia-reperfusion (I/R), the lymphocyte population and lymphocyte-derived products that mediate these responses have not been defined. Platelet and leukocyte adhesion was measured in intestinal postcapillary venules of wild-type (WT) mice and mice genetically deficient in either CD4+ T cells (CD4−/−), CD8+ T cells (CD8−/−), B cells (B cell−/−), or interferon-γ (IFN-γ−/−) subjected to 45 min of ischemia and 4 h of reperfusion. The I/R-induced platelet and leukocyte recruitment responses were also evaluated following adoptive transfer of WT splenocytes into CD4−/−, CD8−/−, B cell−/−, and IFN-γ−/− mice. WT mice exposed to gut I/R exhibited significant increases in the adhesion of both platelets and leukocytes, compared with sham-WT mice. These blood cell adhesion responses to I/R were greatly attenuated in CD4−/−, CD8−/−, B cell−/−, and IFN-γ−/− mice. Adoptive transfer of WT splenocytes restored the WT responses to I/R in all mutants except the B cell−/− mice. These findings implicate both T and B cells and lymphocyte-derived IFN-γ as mediators of the proinflammatory and prothrombogenic phenotype assumed by intestinal microvessels after I/R.

Abstract Gastrointestinal microflora has been shown to have a bi-directional relationship with the host immune system. A variety of fermentable carbohydrate polymers largely pass through the small intestine, providing fermentable substrates for gut microflora. Dietary fibre supplementation may provide a strategy for manipulating the intestinal bacterial profile, changing the interaction with the mucosal immune system, thereby modulating the host immune system. Over a six week trial, 30 weanling BioBreeding rats were fed either control diet alone or supplemented with oat bran or wheat bran fibre. We have shown that wheat bran fibre increases mesenteric lymph node (MLN) B lymphocyte numbers, and decreases systemic IL4 production, MLN T lymphocytes, and intestinal IgA, concurrent with increased colonic bacterial population diversity. We also observed no evidence of pro-inflammatory responses resulting from dietary fibre supplementation. This lends support to the hypothesis that dietary fibre may modulate the host immune system through modification of the gut microflora profile. The research is funded by the Advanced Foods and Materials Network

The effect of feeding lactic-acid bacteria on indices of functions of lymphocytes obtained from Peyer's patches, peripheral blood and spleen from inbred Wistar-Furth rats were studied. Rats were fed on purified diets supplemented with 350 g milk or yoghurt/kg diet for 4 weeks. At the end of the feeding period, immune cells from the three sites were isolated and proliferation, interferon-γ production and lymphocyte subset composition were studied. Rats consuming yoghurt had a greater in vitro proliferative response to yoghurt bacteria in the three lymphoid compartments, a greater interferon-γ production in response to bacteria and concanavalin A in Peyer's patches and spleen, and a greater number of Peyer's patches B lymphocytes than milk-fed rats. Macrophage and T lymphocyte proportions and lymphocyte subset composition in the three sites were unaffected by yoghurt. These results indicate that feeding live bacteria contained in yoghurt may interact with the intestinal immune system, and influence the systemic immune system.

Abstract Upon encountering the relevant vascular bed, lymphocytes attach to endothelial adhesion molecules, transmigrate out of circulation, and localize within tissues. Lymphocytes may then be retained at microanatomic sites, as in tissues, or they may continue to migrate to the lymphatics and recirculate in the blood. Lymphocytes also interact transiently, but with high avidity, with target cells or APC that are infected with microbes or have taken up exogenous foreign Ags. This array of adhesive capabilities is mediated by the selective expression of lymphocyte adhesion molecules. Here, we developed the 6F10 mAb, which recognizes a cell surface glycoprotein designated lymphocyte endothelial-epithelial cell adhesion molecule (LEEP-CAM), that is distinct in biochemical characteristics and distribution of expression from other molecules known to play a role in lymphocyte adhesion. LEEP-CAM is expressed on particular epithelia, including the suprabasal region of the epidermis, the basal layer of bronchial and breast epithelia, and throughout the tonsillar and vaginal epithelia. Yet, it is absent from intestinal and renal epithelia. Interestingly, it is expressed also on vascular endothelium, especially high endothelial venules (HEV) in lymphoid organs, such as tonsil and appendix. The anti-LEEP-CAM mAb specifically blocked T and B lymphocyte adhesion to monolayers of epithelial cells and to vascular endothelial cells in static cell-to-cell binding assays by ∼40–60% when compared with control mAbs. These data suggest a role for this newly identified molecule in lymphocyte binding to endothelium, as well as adhesive interactions within selected epithelia.

ABSTRACT Little is known regarding the timing of immune ontogeny and effector function in fetal humans and nonhuman primates. We studied the organization of lymphocyte and antigen-presenting cell populations in developing lymphoid tissues of rhesus monkey fetuses during the second and third trimesters (65 to 145 days of gestation; term = 165 days). Immunoglobulin-secreting and cytokine-secreting cells were detected at day 80. The thymus, spleen, lymph nodes, and intestinal mucosa were examined for cells expressing CD3, CD5, CD20, CD68, p55, and HLA-DR. In the spleens of 65-day-old fetuses (early second trimester), the overwhelming majority of total lymphocytes were CD5+ CD20+ B-1 cells. The remaining lymphocytes were CD3+ T cells. By day 80, splenic B and T cells were equal in number. Intraepithelial CD3+ CD5− T cells and lamina propria CD20+ CD5+ B cells were present in the intestines of 65-day-old fetuses. By day 80, numerous CD20+ CD5+ B cells were present in the jejunums and colons and early lymphocyte aggregate formation was evident. The spleens of 80- to 145-day-old fetuses contained immunoglobulin M (IgM)-secreting cells, while IgA-, IgG-, interleukin-6-, and gamma interferon-secreting cells were numerous in the spleens and colons. Thus, by the second trimester, the lymphoid tissues of the rhesus monkey fetus have a complete repertoire of properly organized antigen-presenting cells, T cells, and B cells.

Abstract The metaphase arrest technique was used to determine the rate at which cells divide in the Peyer's patches (PP) and the thymus of 5 to 8 wk old lambs. The metaphase indices of these tissues were determined by analyzing cell suspensions of tissues taken before and 1, 2, 3, and 4 hr after metaphase arrest was initiated with i.v. vincristine. The metaphase indices increased in both tissues at a linear rate, which provided an estimate of the rate at which cells entered mitosis and of the lymphocyte birth rate. The ileal PP had the highest lymphocyte birth rate, 2.8% of the lymphocytes entered mitosis each hour; the rate was lower in jejunal PP (1.0%/hr) and thymus (0.5%/hr). With these values and estimates of the lymphocyte content in all PP (1.45 X 10(11)) and in the thymus (1.71 X 10(11)), it was calculated that the hourly lymphocyte production by PP in a lamb was 3.61 X 10(9) cells, which is four to five times greater than for the thymus (0.82 X 10(9)). Lymphocyte production in PP could then be compared with the number of lymphocytes that emigrated from the small intestine. Newly produced cells leave PP via the intestinal lymph, which could be collected from the entire small intestine after removal of the mesenteric lymph nodes. Cells entered the lymph at a rate of 0.8 X 10(9)/hr, but the output fell rapidly during chronic lymphatic drainage, a procedure known to deplete long-lived recirculating cells. It was concluded that most of the cells in intestinal lymph were recirculating cells, and newly formed lymphocytes produced in PP probably account for less than 25% of the total or 0.2 X 10(9)/hr. It seems unlikely that emigration could occur at a rate comparable with the rate of production in the PP. At most, only 5% of the PP cells seemed destined to leave their site of production, and it is proposed that most die within the PP follicles. The high mortality rate associated with the production of large numbers of B lymphocytes in lamb PP seems likely to have a significant impact on the nature of the contribution that these tissues make to the immune system.

ABSTRACT We have previously studied B cells, from people and mice, that express rotavirus-specific surface immunoglobulin (RV-sIg) by flow cytometry with recombinant virus-like particles that contain green fluorescent protein. In the present study we characterized circulating B cells with RV-sIg in children with acute and convalescent infection. During acute infection, circulating RV-sIgD− B cells are predominantly large, CD38high, CD27high, CD138+/−, CCR6−, α4β7+, CCR9+, CCR10+, cutaneous lymphocyte antigen-negative (CLA−), L-selectinint/−, and sIgM+, sIgG−, sIgA+/− lymphocytes. This phenotype likely corresponds to gut-targeted plasma cells and plasmablasts. During convalescence the phenotype switches to small and large lymphocytes, CD38int/−, CD27int/−, CCR6+, α4β7+/−, CCR9+/− and CCR10−, most likely representing RV-specific memory B cells with both gut and systemic trafficking profiles. Of note, during acute RV infection both total and RV-specific murine IgM and IgA antibody-secreting cells migrate efficiently to CCL28 (the CCR10 ligand) and to a lesser extent to CCL25 (the CCR9 ligand). Our results show that CCR10 and CCR9 can be expressed on IgM as well as IgA antibody-secreting cells in response to acute intestinal infection, likely helping target these cells to the gut. However, these intestinal infection-induced plasmablasts lack the CLA homing receptor for skin, consistent with mechanisms of differential CCR10 participation in skin T versus intestinal plasma cell homing. Interestingly, RV memory cells generally lack CCR9 and CCR10 and instead express CCR6, which may enable recruitment to diverse epithelial sites of inflammation.

La sclérose en plaques (SEP) est une maladie auto-immune, inflammatoire chronique du système nerveux central. L’étiologie de la SEP est mal connue mais plusieurs facteurs, notamment génétiques et environnementaux sont associés à une susceptibilité à la SEP. L’intestin, exposé au microbiote intestinal, représente une interface majeure des cellules immunitaires avec l’environnement. Des études chez l’Homme ont montré que la composition du microbiote intestinal était différente entre sujets sains et patients SEP. Chez le modèle murin de la SEP, il a été observé que la composition du microbiote intestinal influence le développement de la maladie. De plus, les plasmocytes sécréteurs d’immunoglobulines de type A (IgA) présents dans le liquide céphalo rachidien des patients présentant une SEP active ont été montrés comme provenant majoritairement de l'intestin. Historiquement, un rôle des LB a été proposé dans la SEP suite à la découverte d’anticorps dans le liquide céphalo rachidien des patients SEP témoignant d’une expansion des LB. Or, le succès récent des thérapies de déplétion des LB a mis en évidence un rôle des LB indépendant de la production d’anticorps dans la pathologie de la SEP. Dans ce contexte, nous nous intéressons aux lymphocytes B (LB) dérivant de l’intestin dans la pathogénicité de la SEP. Pour identifier les LB dérivant de l’intestin nous utilisons l’expression de l’intégrine7. En effet, l’expression de l’intégrine b7 est induite chez les lymphocytes naïfs au niveau de site inducteur de l’intestin. Une fois exprimée, les lymphocytes rejoignent alors la circulation sanguine pour finalement revenir dans l’intestin grâce au ligand de l’intégrine b7, MADCAM, exprimé par les cellules endothéliales mucosales. L’expression de l’intégrine b7 par les lymphocytes dans le sang nous permet alors d’identifier les cellules dites « primées » dans l’intestin.Nous avons tout d'abord étudié le phénotype de ces LB dérivant de l’intestin chez les sujets sains puisque leurs propriétés sont peu connues. Nous avons pu observer que les LB IgD+ CD27+ dit marginaux b7+ ont un profil plus inflammatoire comparé aux LB mémoires (IgD- CD27+) dérivés ou non de l'intestin et aux LB marginaux n'exprimant pas l'intégrine b7. En effet, les LB marginaux b7+ sécrètent des niveaux de cytokines inflammatoires plus important notamment l'IL-6, le TNFa et la LT-a. De façon intéressante, cette population sécrète également plus d’IL-10, une cytokine régulatrice.Dans un second temps, nous avons étudié les caractéristiques des LB chez les patients atteints de SEP. Nous avons deux séries d’expériences. Dans la première série d’expérience, nous avons pu observer que les LB CD27+ de certains patients SEP exprimaient plus d’IL-6 que les LB de donneurs sains comme précédemment décrit dans la littérature. Nous avons pu déterminer que cette augmentation était due à une proportion plus élevée de LB mémoires exprimant l'intégrine b7+ capable de sécréter l'IL-6. Lors de la seconde série d'expérience, nous n’avons pas observé de différence entre les patients et les donneurs sains pour l’expression de l’IL-6 sans doute car les patients étudiés étaient sous immuno-modulateurs / immuno-suppresseurs et/ou ne présentaient pas une maladie active au moment des prélèvements.En résumé, chez les sujets sains, les LB de l’intestin présentent un profil cytokinique à la fois plus inflammatoire et régulateur potentiellement dû à leur exposition au microbiote intestinal. Dans la SEP, nous avons pu observer que la plus forte expression d’IL-6 par les LB décrite dans la littérature provenait des LB b7+, suggérant que les LB dérivés de l'intestin pourraient devenir pathogénique dans la SEP notamment en favorisant l’inflammation au niveau du système nerveux central
Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system. The aetiology of MS is poorly understood but several factors, including genetic and environmental factors, are associated with susceptibility to MS. The gut, exposed to the intestinal microbiota, represents a major interface of immune cells with the environment. Studies in humans have shown that the composition of the gut microbiota is different between healthy subjects and MS patients. In the mouse model of MS, it has been observed that the composition of the gut microbiota influences the development of the disease. In addition, IgA-secreting B cells present in the cerebrospinal fluid of patients with active MS were found to mainly originated from the intestinal. In this context, we are interested in gut-derived B cells in the pathogenicity of MS. Historically, a role for B cells was proposed in MS following the discovery of antibodies in the cerebrospinal fluid of MS patients as it indicates an abnormal expansion of B cells. However, the recent success of B cell depletion therapies has highlighted a role for B cells independent of antibody production in MS pathology. We therefore aimed at determining the role of gut-derived B cells in MS pathology. To identify gut-derived B cells we used integrin b7 expression. Indeed, the expression of integrin b7 is initiated in naive lymphocytes at the inducer site of the intestine. Once expressed, the lymphocytes then enter the bloodstream and finally return to the intestine via the integrin b7 ligand, MADCAM, expressed by mucosal endothelial cells. The expression of integrin b7 by lymphocytes in the blood then allows us to identify the cells primed in the gut.We first studied the phenotype of these gut-derived B cells in healthy subjects in order to characterise them physiologically as they are poorly described in the literature. We were able to observe that IgD+ CD27+ B cells, also known as b7+ marginal B cells, have a more inflammatory profile compared to the memory B cells (IgD- CD27+) derived or not from the intestine and the marginal B cells not expressing the b7 integrin. Indeed, b7+ marginal B cells secrete higher levels of inflammatory cytokines, notably IL-6, TNFa and LT-a. Interestingly, this population also secretes higher levels of the immuno-regulatory cytokine IL-10.In a second step, we studied the characteristics of B cells in MS patients. We performed two sets of experiments. In the first set of experiments, we could observe that CD27+ B cells from some MS patients expressed more IL-6 than B cells from healthy donors as previously described. We determined that this higher secretion originates from b7+ memory B cells. In the second series of experiments, we did not observe any difference between patients and healthy donors for IL-6 expression, presumably because the patients studied were on immunomodulators/immunosuppressants and/or did not have active disease at the time of the sampling.In summary, in healthy subjects, B cells from the gut show both a more inflammatory and regulatory cytokine expression profile probably due to their exposure to the highly inflammatory environment of the intestine. In MS, we observed that the increased expression of IL-6 by B cells described in the literature is originated from b7+ B cells, suggesting that gut-derived B cells could be highly pathogenic in MS, notably by promoting inflammation in the central nervous system

Au cours de l'infection par schistosoma mansoni, la muqueuse intestinale est particulierement sollicitee puisque les oeufs pondus par les vers franchissent par effraction la paroi intestinale pour gagner la lumiere. Les muqueuses de l'organisme secretent un type particulier d'anticorps : les iga dont les caracteristiques anti-inflammatoires et de resistance a la proteolyse en font un isotype adapte a la defense des tractus. La relation etablie dans les schistosomiases humaines entre les iga specifiques de l'antigene sm28gst, l'inhibition de son activite enzymatique et la reduction de la fecondite parasitaire nous a conduits a approcher les mecanismes cellulaires et moleculaires impliques dans l'expression de cet isotype, au cours de l'infection murine. Ces travaux revelent le role majeur des oeufs dans l'induction de la reponse iga anti-parasitaire. Cette induction depend de deux parametres : 1) la qualite intrinseque des antigenes d'oeufs qui oriente la reponse t vers un profil th2 apres la s6, ces proprietes polarisatrices s'exercant egalement lors d'immunisations par l'antigene sm28gst et 2) la presence des oeufs dans les sites inducteurs de la muqueuse intestinale. D'autre part, nos travaux devoilent l'implication des lymphocytes b1 dans l'expression de la reponse iga muqueuse. L'infection entraine une expansion de ces lymphocytes, qui secretent, in vitro, des iga specifiques dont la production est potentialisee par l'il-4 et l'il-5. La deficience genetique en cellules b1 entraine une reduction considerable des reponses iga intestinales et seriques, restaurables par le transfert de cellules peritoneales de souris competentes. Les souris deficientes presentent une mortalite importante, une charge en oeufs tissulaires superieure aux controles, associees a des taux d'ige et d'igg1 accrus ainsi qu'a une secretion d'il-4 et d'ifn- plus importante et une diminution des taux d'il-10.

Lors de l’infection orale par le parasite T. gondii, la réponse immunitaire intestinale fait intervenir des acteurs cellulaires et moléculaires initiateurs de l’inflammation servant à combattre l’infection. Cette réponse inflammatoire requiert l’intervention de mécanismes immuno-régulateurs pour permettre le maintien de l’homéostasie intestinale. Nous avons étudié le rôle du TLR9 dans l’initiation de la réponse immunitaire à T. gondii. Ce récepteur de l’immunité innée est largement distribué dans le système lymphoïde associé à la muqueuse intestinale, à la fois par les cellules constituant la barrière épithéliale et dans la lamina propria. L’expression du TLR9 est requise dans ces différents compartiments pour initier une réponse immunitaire protectrice contre l’infection par T. gondii. L’activation des voies de signalisation du TLR9, par la reconnaissance directe de motifs moléculaires exprimés par T. gondii, induit la production d’interférons (IFNs) de type I a et ß dans l’intestin grêle des souris infectées. Ces cytokines stimulent la production de Cryptdines (Crp-3 et -5) par les cellules de Paneth et leur libération dans la lumière intestinale. Au-delà de leur activité antimicrobienne, les Crps participent au recrutement de lymphocytes T CD4+ producteurs d’IFN-? en renforçant la production de chimiokines inflammatoires comme CCL2, CCL3 et CCL5. Dans la lamina propria, les cellules dendritiques initient la réponse inflammatoire au parasite par des mécanismes TLR9-depéndants. L’engagement de ce récepteur par T. gondii polarise la réponse immunitaire au parasite, induite par les cellules dendritiques, vers un profil Th1. Les lymphocytes B, bien qu’exprimant le TLR9, ne participent pas à l’initiation de la réponse inflammatoire à T. gondii. En revanche consécutivement à l’infection orale par le parasite, les cellules B activées amplifient d’une part le recrutement de cellules T CD4+ dans la lamina propria par la production de la chimiokine CCL3. D’autre part renforcent la production de la cytokine inflammatoire IFN-?, par les cellules T effectrices, par des interactions de contact faisant intervenir leur TNF-a membranaire. La réponse immunitaire à T. gondii dégénère chez les souris C57BL/6 en iléite létale. Les lymphocytes T régulateurs sont naturellement générés au cours de l’infection. La sensibilisation des cellules T regs par des antigènes de T. gondii, préalablement à l’infection par le parasite, protège dans notre modèle de la génération de l’iléite. Les T regs sensibilisés ont une expression renforcée des marqueurs de domiciliation intestinale CCR5 et a4ß7. Ils rééquilibrent la balance cytokinique dans le système lymphoïde associé à la muqueuse intestinale des souris infectées en limitant la production de cytokines Th1 par les lymphocytes purifiés de la lamina propria et renforçant leur production de cytokines Th2 et Th3
We have investigated the role of TLR9 in the initiation of the immune response in the gut against Toxoplasma gondii. This innate immune receptor is widely expressed in the gut associated lymphoid tissue (GALT) : at the epithelial barrier and in the lamina propria. Expression of TLR9 is requiered in both these compartments to initiate a protective immune response against T. Gondii. Activation of TLR9 signaling pathways, by direct recognition of molecular motives expressed by T. gondii, induces the production of type I interferons (IFNs) in the small intestine. These interferons tregger the production of cryptdines (Crp-3 and -5) by paneth cells and their released into the lumen. Crps indirectly promote T cells (CD4 + IFN-y+) recruitmnent by enhancing the production of inflammatory chemokines. B-lymphocites express the TLR9 but do not contribute to the initiation of inflammatory response against T. gondii. However consecutively to the oral infection by the parasite, activated B cells amplify the inflammatory cytokine production (IFN-y), by effector T cells, via cell-cell interactions involving their mambrane bound TNF-a. In C57BL/6 mice, immune response against T. Gondii degenerates into a lethal ileitis. Regulatory T cells are naturally generated during infection. The sensibilisation of T regs by T. Gondii antigens, prior infection by the parasite, protects against the ileitis in our model. Sensibilized T regs overexpress gut homing receptors such as CCR5 AND a4ß7. By increasing their Th2 and Th3 cytokines production, sensibilized T regs readjust the cytokine balance in GALT of infected mice

Il y a 10 à 100 fois plus de microorganismes dans l’intestin que de cellules dans l’ensemble du corps humain. Ces microorganismes forment le microbiote essentiel à de nombreuses fonctions comme la digestion. Il est cependant crucial que le microbiote reste compartimenté dans la lumière intestinale. Le système immunitaire intestinal (SII) a un rôle majeur dans le contrôle du microbiote. La cytokine immunosuppressive TGF-b empêche de l’activation du SII contre le microbiote, et protège donc de l’apparition de maladie inflammatoire chronique intestinale (MICI) comme la maladie de Crohn ou la colite ulcérative. Le TGF-b est également très impliqué dans la génération des lymphocytes Th17, qui participent activement au maintien de l’homéostasie intestinale et au cloisonnement du microbiote. Cependant, le rôle du TGF-b dans la biologie des Th17 déjà différentiés n’est pas clair. Mes travaux ont montré qu’en absence de TGF-b, les Th17 acquièrent un phénotype de type Th1 fortement inflammatoire, et sont responsables de la mise en place d’une forte inflammation intestinale pouvant évoluer en cancer
There is 10 to 100 more microorganism in the gut than human cells in the hole organism. Those microorganisms form the microbiota, and they are crucial to some vital functions like digestion. However, it is required to prevent from the microbiota dissemination in the organism. The immune system is highly involved in the control and the compartmentation of the microbiota. The immunosuppressive TGF-b prevents from over-activation of the immune cells versus the microbiota, and so protects from chronic inflammatory disease of the gut like Crohn’s disease or ulcerative colitis. TGF-b is also very involved in Th17 generation, a subset of cells with major role in microbiota control and maintenance of gut homeostasis. However, how TGFb acts on already differentiated Th17 is still under investigation. My results demonstrate that TGFb signaling in Th17 is required to maintain their lineage. In absence of TGF-b, Th17 switch to Th1 phenotype and produces important amount of inflammatory cytokines, leading to a strong inflammation of the gut, that may promotes cancer development

Thesis (MScMedSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Introduction: Chronic HIV-1 infection is characterized by immune activation and dysregulation of immune homeostasis, which impacts on multiple immune cell types. The B-cell compartment, which plays an important role in the producing neutralizing antibodies, is also dysregulated in HIV- 1 infection. In this study we investigated peripheral blood B-cell subset distribution, and changes in expression of cellular activation, inhibition, and apoptosis signaling markers in both untreated chronic HIV-1 infected individuals and healthy uninfected controls. The neuropeptide immune modulator, vasoactive intestinal peptide (VIP) is known to selectively down-regulate activation of CD4+ T-cells in various disease settings including HIV-1, however to our knowledge, no studies have investigated the effect of VIP inhibition on B-cell activation. Materials & Methods: A total of 21 HIV+ve (CD4 count >250 cells/µl), and 19 HIV-ve individuals were recruited from the Emavundleni voluntary testing and counseling clinic in Crossroads, Western Province, South Africa. Whole blood was stained to distinguish B-cell subsets (activated memory (AM: CD21-CD27+), resting memory (RM: CD21+CD27+), mature naïve (MN: CD21+CD27-), or tissue-like memory (TLM: CD21loCD27lo). In addition expression of markers of B-cell activation (CD126, CD86, CD38, CD284, CD287), inhibition (CD72, CD85j, CD300a, CD305, CD307d), and apoptosis signaling (CD95), was assessed ex vivo by flow cytometry (BD FACSCanto II). For determination of functional responsiveness isolated B-cells (RosetteSep, Stemcell Technologies) were cultured for 18h (37°C, 5%CO2) without stimulation or stimulated with TLR ligands (LPS or R848). Stimulation experiments were also performed in the presence or absence of VIP. Results: Chronic HIV-1 infection affected B-cell subset distribution. The percentage (%) of TLM was increased by 59.24%, and %RM was decreased by 22.73% (both p<0.01). Total expression of the VIP receptor VPAC2 was decreased by 47.35% (p=0.0296). Subsets had a mixed phenotype ex vivo; HIV infection upregulated CD38 (by 59.56%, p=0.0004), CD72 (by 60.70%, p=0.0396), CD307d (by 68.63%, p=0.0015) on AM, while RM B-cells had increased expression of TLR4 (by 107.04%, p=0.0057) and TLR7 (by 208.14%, p=0.0199). TLM B cells (i.e. exhausted phenotype) displayed upregulated TLR7 (by 550%, p=0.0128) and CD307d (by 72.40% p=0.045) expression. MN B-cells had increased CD72 expression (by 70.98%, p=0.0026). R848 upregulated CD86 expression by 42.20% on AM (p<0.01), and by 56.06% on RM B-cells (p<0.01), which was significantly downregulated with VIP inhibition (both p<0.05). Similarly, CD95 expression on RM, TLM, and MN B-cells increased by 31.10% (p<0.001), 21.46% (p<0.01), and 39.92% (p<0.01) with R848 stimulation respectively, which was also significantly downregulated with VIP inhibition. Conclusion: These data indicate that B-cells in untreated HIV infection display increased levels of activation, and also the potential for increased susceptibility to apoptosis as evidenced by increased FAS (CD95) expression. VIP significantly down-regulated markers of activation, inhibition, and apoptosis signaling. Dysregulation of B-cells is thus apparent in asymptomatic stable chronic HIV-1 infection, which may impact on both inefficient neutralizing antibody production and hypergammaglobulinemia. The ability of VIP to prevent stimulationassociated marker upregulation may indicate that VIP is a potential therapeutic agent. Its immuno-modulatory properties were demonstrated to limit B-cell hyperactivation, and selectively down-regulate apoptosis and mark it out for further investigation.
AFRIKAANSE OPSOMMING: Inleiding: Immunaktivering en ongekoppelde immuun-homeostase is kenmerke van chroniese MIVinfeksie. Ons het perifere bloed B-sel subgroep-verspreiding, en veranderinge in die uitdrukking van merkers van aktivering, inhibisie, en apoptose in 'n onbehandelde MIV-1 besmettende groep ondersoek (in vergelyk met 'n gesonde onbesmettende kontrole). Die immuun-moduleerder, vasoaktiewe intestinale peptied (VIP) is bekend om aktivasie van geaktiveerde CD4+ T-selle te verminder, maar tot ons kennis, is daar geen studies wat die effek van VIP-inhibisie op B-sel aktivering ondersoek het, in die konteks van MIV-1 infeksie. Materiaal & Metodes: MIV+we individue (CD4-telling >250 selle/µl) , en MIVwe kontroles is gewerf uit die vrywillige toetsing en berading Emavundleni kliniek, Crossroads, Westelike Provinsie, Suid-Afrika. Bsel subgroepe is gedefinieer as geaktiveerde geheue (AM: CD21- CD27+ ), rusende geheue (RM: CD21+ CD27+ ), volwasse naïef (MN: CD21+ CD27- ), of weefsel-agtige geheue (TLM: CD21loCD27lo). Merkers van aktivering (CD126, CD86, CD38, CD284, CD287), inhibisie (CD72, CD85j, CD300a, CD305, CD307d), en apoptose signalering (CD95) is via vloeisitometrie (BD FACSCanto II) op B-selle ex vivo en ook op geïsoleerde B-selle (RosetteSep, Cell Technologies) ondersoek. Vir die bepaling van funksionele responsiwiteit, geïsoleerde B-selle (RosetteSep, StemCell Technologies) was vir 18h (37°C, 5%CO2) gekweek, sonder stimulasie of gestimuleer met TLR ligande (LPS of R848). Stimulasie eksperimente het ook in die teenwoordigheid of afwesigheid van VIP plaasgevind. Resultate: Chroniese MIV-1 infeksie het B-sel subset verspreiding geraak. Die persentasie (%) van TLM is verhoog deur 59,24%, en% RM het met 22.73% afgeneem (beide p <0,01). Totale uitdrukking van die VIP reseptor VPAC2 het met 47,35% afgeneem (p = 0,0296). Subgroepe het 'n gemengde ex vivo fenotipe; MIV-infeksie het CD38 (deur 59,56%, p=0,0004), CD72 (deur 60,70%, p=0,0396), CD307d (deur 68,63%, p=0,0015) op AM verhoog, terwyl RM Bselle het verhoogde uitdrukking van TLR4 (deur 107,04%, p=0,0057) en TLR7 (deur 208,14%, p=0,0199). TLM B-selle (die uitgeputtende fenotiep) het verhoogde TLR7 (deur 550%, p=0,0128) en CD307d (deur 72,40% p=0.045) uitdrukking gewys. MN B-selle het verhoogde uitdrukking van CD72 (deur 70,98%, p = 0,0026). R848 het CD86 uitdrukking op AM deur 42,20%, en op RM deur 56,06% toegeneem (beide p <0,01). Dit het met VIP inhibisie beduidend afgeneem (beide p <0.05). CD95 uitdrukking was soortgelyk verhoog op RM, TLM, en MN B-selle met 31.10% (p <0.001), 21,46% (p <0,01), en 39,92% (p <0,01) met R848 stimulasie. Al drie het beduidend afgeneem met VIP inhibisie. Gevolgtrekking: Hierdie data dui daarop dat B-selle in onbehandelde MIV-infeksie vertoon verhoogde aktiveringsvlakke, en ook die potensiaal vir verhoogde vatbaarheid vir apoptose soos bewys deur verhoogde uitdrukking van FAS (CD95). VIP het beduidend merkers van aktivering, inhibisie, en apoptose af-gereguleer. Wanfunksie van B-selle is dus in asimptomatiese stabiele chroniese MIV-1 infeksie duidelik, wat impak kan hê op beide oneffektiewe neutraliserende teenliggaampie produksie, en hiepergammaglobulinimie. Die vermoë van VIP stimulasie-verwante merker opregulasie te voorkom kan aandui dat VIP 'n potensiële terapeutiese agent is. VIP se immuno-moduleerende eiendomme is gedemonstreer om Bsel hieperaktiveering te beperk, en selektief apoptose afreguleer, en merk dit vir verdere ondersoek.

La rectocolite hémorragique (RCH) est une maladie inflammatoire chronique intestinale (MICI) qui est caractérisée par l’inflammation chronique du rectum et/ou du côlon. Bien que l’idée qu’il existe une réponse immunitaire exagérée contre le microbiote intestinal soit communément acceptée, la physiopathologie est encore insuffisamment connue. Parmi les dysfonctions immunitaires, il existe des arguments en faveur d’un dérèglement de la biologie des lymphocytes B. A l’aide de plusieurs techniques (dont la cytométrie en flux, le single-cell RNA sequencing et le single-cell BCR sequencing), nous avons mis en évidence des modifications marquées des populations plasmocytaires coliques chez des patients avec RCH, dont une augmentation de l’expression des IgG et IgA1 et une diminution en IgA2 associées à l’accroissement de la proportion des plasmocytes à durée de vie courte. Ce turnover accru se reflétait dans la circulation sanguine par l’élévation des plasmablastes ?7+ à tropisme intestinal, associé à l’activité de la maladie et à la survenue de complications. Notre second travail s’intéressait au mécanisme d’action du vedolizumab (anti-?4?7), traitement couramment utilisé dans les MICI et prometteur pour le VIH. Dans une cohorte de patients atteints à la fois de MICI et du VIH, mous avons mis en évidence un impact majeur sur les follicules lymphoïdes intestinaux avec une absence d’effet significatif sur la fréquence des lymphocytes T effecteurs de la lamina propria. Cette découverte, décrite pour la première fois chez l’homme, ouvre de nouvelles perspectives quant au mécanisme d’action du vedolizumab dans les MICI et le VIH
Ulcerative Colitis (UC) is an inflammatory bowel disease (IBD) that leads to chronic inflammation of the rectum and the colon. Even though it is commonly accepted that it results from an exaggerated immune response toward the gut microbiota, the pathophysiology is still not fully understood. Among immune defects, many evidences exist supporting a disturbed B cell system, including the presence of (auto-)antibodies and the infiltration of the lamina propria by plasma cells. Using multiple advanced techniques including single-cell RNA sequencing and single-cell BCR sequencing we extensively characterized the B cell compartment in the blood and the intestinal mucosa of UC patients. We found that the colonic plasma cells phenotype was skewed toward an increased expression of IgG and IgA1 and an increased proportion of short-lived plasma cells. This increased turnover was reflected in the blood by the expansion of ?7+ plasmablasts, which correlated with disease activity and predicted disease course. Our second work focused on the mechanism of action of vedolizumab, a monoclonal antibody targeting the ?4?7 integrin, for both IBD and HIV. In a unique cohort of patients with concomitant IBD and HIV, we unexpectedly found that memory T cells within the lamina propria were not significantly affected. Conversely, lymphoid aggregates, mostly in the terminal ileum were massively impacted. These findings are being further explored and may change the paradigm regarding the mechanism of action of vedolizumab

La vaccination muqueuse est un moyen efficace de lutter contre les pathogènes qui utilisent les muqueuses comme porte d'entrée. Cependant, la vaccination muqueuse avec des antigènes non réplicatifs nécessite l'utilisation d'adjuvants. Les molécules de la famille de la toxine du choléra, l'entérotoxine thermolabile d'E.coli (LT), la toxine du choléra (CT) ainsi que le mutant LT-R192G et les sous-unités B non toxiques de ces toxines (LTB et CTB) ont été montrées augmenter les réponses immunitaires contre des antigènes coadministrés par voie muqueuse. Cependant leur mécanisme d'action est complexe et reste encore mal connu et des différences entre molécules entières et sous-unités B ont été rapportées ainsi que, pour une même molécule, des différences selon le modèle utilisé. Dans ce travail, nous avons étudié les effets de ces cinq molécules sur les réponses anticorps ainsi que sur les lymphocytes T CD4 dans un modèle murin d'immunisation intrarectale avec des pseudoparticules virales de rotavirus (VLP-2/6). Chez les souris non immunisées, nous avons montré que ces molécules, à l'exception de la CTB, diminuent in vitro les lymphocytes T régulateurs naturels CD4+CD25+Foxp3+, probablement par un mécanisme d'apoptose. Chez les souris immunisées, toutes les molécules étudiées induisent une même réponse anticorps sérique et fécale spécifique des VLP-2/6, qu'il s'agisse des molécules entières connues pour leur fort pouvoir adjuvant ou des sous-unités B qui, elles, ont été rapportées avoir un plus faible effet adjuvant voire un effet tolérogène dans certaines études. Concernant la réponse T CD4, les réponses spécifiques de l'antigène et de l'adjuvant ont été analysées. Des différences importantes ont été mises en évidence entre ces molécules. Notamment, seules les molécules entières (LT, LT-R192G et CT) induisent la production d'IL-2 et l'activation de lymphocytes T CD4+CD25+Foxp3- mémoires spécifiques de l'antigène tout en permettant la mise en place d'une régulation médiée par des lymphocytes T régulateurs CD4+CD25+Foxp3+ (boucle d'autorégulation), qui pourraient jouer un rôle majeur lors d'une réponse secondaire, afin d'éviter les réactions inflammatoires délétères. Malgré ces différences, toutes les molécules étudiées induisent la production d'IL-17, suggérant le rôle majeur de cette cytokine dans l'effet adjuvant.L'influence de la voie d'administration sur ces effets est en cours d'étude grâce à la comparaison avec la voie intranasale

Primary gastrointestinal lymphoma is the most common extranodal lymphoma and is almost exclusively of non-Hodgkin type. It is defined as lymphoma that has presented with the main bulk of disease in the gastrointestinal tract, with or without involvement of contiguous lymph nodes. MALT lymphoma is an indolent B-cell lymphoma whose histology recapitulates the features of mucosa-associated lymphoid tissue (MALT). It most commonly affects the stomach, presenting with nonspecific dyspepsia. Most cases appear to be driven by Helicobacter pylori, with 75% regressing following eradication of the organism with appropriate antibiotics. Deeply invasive lymphomas and those with adverse histological or cytogenetic features are unlikely to respond. Mantle cell lymphoma and follicular lymphoma are adult B-cell lymphomas that can present as gastrointestinal lymphomas. Diffuse large B-cell lymphoma is an aggressive lymphoma that is relatively frequently encountered in gastrointestinal locations. Burkitt’s lymphoma is also an aggressive B-cell lymphoma, and is the most frequent childhood gastrointestinal lymphoma. Enteropathy-associated T-cell lymphoma is an intestinal lymphoma of intraepithelial T lymphocytes that occurs most commonly in the jejunum or ileum and is associated with coeliac disease. It presents with abdominal pain, often due to intestinal perforation. The prognosis is usually poor, with death frequently resulting from abdominal complications in patients already weakened by uncontrolled malabsorption.