RESUMEN
Isolated lymphoid follicles (ILFs) develop after birth in the small and large intestines (SI and LI) and represent a dynamic response of the gut immune system to the microbiota. Despite their similarities, ILF development in the SI and LI differs on a number of levels. We show that unlike ILF in the SI, the microbiota inhibits ILF development in the colon as conventionalization of germ-free mice reduced colonic ILFs. From this, we identified a novel mechanism regulating colonic ILF development through the action of interleukin (IL)-25 on IL-23 and its ability to modulate T regulatory cell (Treg) differentiation. Colonic ILF develop in the absence of a number of factors required for the development of their SI counterparts and can be specifically suppressed by factors other than IL-25. However, IL-23 is the only factor identified that specifically promotes colonic ILFs without affecting SI-ILF development. Both IL-23 and ILFs are associated with inflammatory bowel disease, suggesting that disruption to this pathway may have an important role in the breakdown of microbiota-immune homeostasis.
Asunto(s)
Linfocitos B/inmunología , Enfermedades Inflamatorias del Intestino/inmunología , Interleucina-23/inmunología , Interleucinas/inmunología , Intestino Grueso/inmunología , Ganglios Linfáticos Agregados/inmunología , Animales , Linfocitos B/patología , Modelos Animales de Enfermedad , Regulación de la Expresión Génica , Enfermedades Inflamatorias del Intestino/genética , Enfermedades Inflamatorias del Intestino/patología , Interleucina-23/genética , Interleucinas/deficiencia , Interleucinas/genética , Intestino Grueso/patología , Intestino Delgado/inmunología , Intestino Delgado/patología , Activación de Linfocitos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ganglios Linfáticos Agregados/patología , Transducción de SeñalRESUMEN
The transcytosis of antigens across the gut epithelium by microfold cells (M cells) is important for the induction of efficient immune responses to some mucosal antigens in Peyer's patches. Recently, substantial progress has been made in our understanding of the factors that influence the development and function of M cells. This review highlights these important advances, with particular emphasis on: the host genes which control the functional maturation of M cells; how this knowledge has led to the rapid advance in our understanding of M-cell biology in the steady state and during aging; molecules expressed on M cells which appear to be used as "immunosurveillance" receptors to sample pathogenic microorganisms in the gut; how certain pathogens appear to exploit M cells to infect the host; and finally how this knowledge has been used to specifically target antigens to M cells to attempt to improve the efficacy of mucosal vaccines.
Asunto(s)
Mucosa Intestinal/citología , Mucosa Intestinal/inmunología , Ganglios Linfáticos Agregados/citología , Ganglios Linfáticos Agregados/inmunología , Factores de Edad , Animales , Antígenos/inmunología , Antígenos/metabolismo , Antígenos de Superficie/inmunología , Antígenos de Superficie/metabolismo , Comunicación Celular/inmunología , Diferenciación Celular , Interacciones Huésped-Patógeno/inmunología , Humanos , Mucosa Intestinal/metabolismo , Monitorización Inmunológica , Ganglios Linfáticos Agregados/metabolismo , Ligando RANK/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Células Madre/citología , Células Madre/metabolismo , Factores de Transcripción/metabolismoRESUMEN
The transcytosis of antigens across the follicle-associated epithelium (FAE) of Peyer's patches by microfold cells (M cells) is important for the induction of efficient immune responses to mucosal antigens. The mucosal immune response is compromised by ageing, but effects on M cells were unknown. We show that M-cell density in the FAE of aged mice was dramatically reduced. As a consequence, aged Peyer's patches were significantly deficient in their ability to transcytose particulate lumenal antigen across the FAE. Ageing specifically impaired the expression of Spi-B and the downstream functional maturation of M cells. Ageing also dramatically impaired C-C motif chemokine ligand 20 expression by the FAE. As a consequence, fewer B cells were attracted towards the FAE, potentially reducing their ability to promote M-cell maturation. Our study demonstrates that ageing dramatically impedes the functional maturation of M cells, revealing an important ageing-related defect in the mucosal immune system's ability to sample lumenal antigens.
Asunto(s)
Envejecimiento/inmunología , Células Epiteliales/inmunología , Ganglios Linfáticos Agregados/metabolismo , Animales , Antígenos/metabolismo , Diferenciación Celular , Células Cultivadas , Quimiocina CCL20/genética , Quimiocina CCL20/metabolismo , Regulación hacia Abajo , Inmunidad Mucosa , Ratones , Ratones Endogámicos C57BL , Membrana Mucosa/metabolismo , Ganglios Linfáticos Agregados/citología , Proteínas Proto-Oncogénicas c-ets/genética , Proteínas Proto-Oncogénicas c-ets/metabolismo , Transcitosis/fisiologíaRESUMEN
Many prion diseases are orally acquired. Our data show that after oral exposure, early prion replication upon follicular dendritic cells (FDC) in Peyer's patches is obligatory for the efficient spread of disease to the brain (termed neuroinvasion). For prions to replicate on FDC within Peyer's patches after ingestion of a contaminated meal, they must first cross the gut epithelium. However, the mechanism through which prions are conveyed into Peyer's patches is uncertain. Within the follicle-associated epithelium overlying Peyer's patches are microfold cells (M cells), unique epithelial cells specialized for the transcytosis of particles. We show that following M cell-depletion, early prion accumulation upon FDC in Peyer's patches is blocked. Furthermore, in the absence of M cells at the time of oral exposure, neuroinvasion and disease development are likewise blocked. These data suggest M cells are important sites of prion uptake from the gut lumen into Peyer's patches.
Asunto(s)
Encéfalo/metabolismo , Células Dendríticas Foliculares/inmunología , Enterocitos/patología , Ganglios Linfáticos Agregados/inmunología , Enfermedades por Prión/inmunología , Priones/inmunología , Ligando RANK/inmunología , Administración Oral , Animales , Encéfalo/inmunología , Encéfalo/patología , Diferenciación Celular/genética , Células Cultivadas , Células Dendríticas Foliculares/patología , Progresión de la Enfermedad , Ingestión de Alimentos , Enterocitos/inmunología , Enterocitos/metabolismo , Exposición a Riesgos Ambientales/efectos adversos , Carne , Ratones , Ratones Noqueados , Ganglios Linfáticos Agregados/patología , Enfermedades por Prión/patología , Enfermedades por Prión/prevención & control , Enfermedades por Prión/transmisión , Transcitosis/genética , Transcitosis/inmunologíaRESUMEN
Following peripheral exposure to transmissible spongiform encephalopathies (TSEs), infectivity usually accumulates in lymphoid tissues before neuroinvasion. The host prion protein (PrPc) is critical for TSE agent replication and accumulates as an abnormal, detergent insoluble, relatively proteinase-resistant isoform (PrPSc) in diseased tissues. Early PrPSc accumulation takes place on follicular dendritic cells (FDCs) within germinal centers in lymphoid tissues of patients with variant Creutzfeldt-Jakob disease (vCJD), sheep with natural scrapie or rodents following experimental peripheral infection with scrapie. In mouse scrapie models, the absence of FDCs blocks scrapie replication and PrPSc accumulation in the spleen, and neuroinvasion is significantly impaired. The mechanisms by which the TSE agent initially localizes to lymphoid follicles and interacts with FDCs are unknown. Antigens are trapped and retained on the surface of FDCs through interactions between complement and cellular complement receptors. Here we show that in mice, both temporary depletion of complement component C3 or genetic deficiency of C1q significantly delays the onset of disease following peripheral infection, and reduces the early accumulation of PrPSc in the spleen. Thus, in the early stages of infection, C3 and perhaps C1q contribute to the localization of TSE infectivity in lymphoid tissue and may be therapeutic targets.
Asunto(s)
Complemento C1q/deficiencia , Complemento C3/deficiencia , Scrapie/etiología , Scrapie/inmunología , Animales , Complemento C1q/genética , Células Dendríticas Foliculares/inmunología , Células Dendríticas Foliculares/metabolismo , Modelos Animales de Enfermedad , Femenino , Humanos , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas PrPSc/metabolismo , Scrapie/metabolismo , Ovinos , Factores de TiempoRESUMEN
The pathogenesis of transmissible spongiform encephalopathies (TSEs) often includes a replication phase in lymphoid tissues before infection spreads to the central nervous system. Recent studies show that the follicular dendritic cells of the germinal centres are critical for this replication. These cells are therefore potential targets for therapy or prophylaxis in natural TSEs, such as variant Creutzfeldt-Jakob disease.
Asunto(s)
Síndrome de Creutzfeldt-Jakob/etiología , Células Dendríticas Foliculares/fisiología , Encefalopatía Espongiforme Bovina/etiología , Scrapie/etiología , Animales , Humanos , Ratones , Ratones SCID , Priones/fisiologíaAsunto(s)
Células Dendríticas Foliculares , Enfermedades por Prión/prevención & control , Receptores del Factor de Necrosis Tumoral/uso terapéutico , Animales , Modelos Animales de Enfermedad , Inmunoglobulinas/genética , Receptor beta de Linfotoxina , Ratones , Receptores del Factor de Necrosis Tumoral/genética , Proteínas Recombinantes de Fusión/uso terapéutico , Scrapie/prevención & controlRESUMEN
In most peripheral infections of rodents and sheep with scrapie, infectivity is found first in lymphoid tissues and later in the central nervous system (CNS). Cells within the germinal centers (GCs) of the spleen and lymph nodes are important sites of extraneural replication, from which infection is likely to spread to the CNS along peripheral nerves. Here, using immunodeficient mice, we investigate the identity of the cells in the spleen that are important for disease propagation. Despite possessing functional T and B lymphocytes, tumor necrosis factor alpha-deficient (TNF-alpha(-/-)) mice lack GCs and follicular dendritic cell (FDC) networks in lymphoid tissues. In contrast, lymphoid tissues of interleukin-6-deficient (IL-6(-/-)) mice possess FDC networks but have impaired GCs. When the CNSs of TNF-alpha(-/-), IL-6(-/-), and wild-type mice were directly challenged with the ME7 scrapie strain, 100% of the mice were susceptible, developing disease after closely similar incubation periods. However, when challenged peripherally (intraperitoneally), most TNF-alpha(-/-) mice failed to develop scrapie up to 503 days postinjection. All wild-type and IL-6(-/-) mice succumbed to disease approximately 300 days after the peripheral challenge. High levels of scrapie infection and the disease-specific isomer of the prion protein, PrP(Sc), were detectable in spleens from challenged wild-type and IL-6(-/-) mice but not from TNF-alpha(-/-) mice. Histopathological analysis of spleen tissue demonstrated heavy PrP accumulations in direct association with FDCs in challenged wild-type and IL-6(-/-) mice. No PrP(Sc) accumulation was detected in spleens from TNF-alpha(-/-) mice. We conclude that, for the ME7 scrapie strain, mature FDCs are critical for replication in lymphoid tissues and that in their absence, neuroinvasion following peripheral challenge is impaired.
Asunto(s)
Interleucina-6/genética , Scrapie/genética , Factor de Necrosis Tumoral alfa/genética , Animales , Predisposición Genética a la Enfermedad , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas PrPSc/metabolismo , Proteínas PrPSc/patogenicidadRESUMEN
The immune system is central in the pathogenesis of scrapie and other transmissible spongiform encephalopathies (TSEs) or 'prion' diseases. After infecting by peripheral (intraperitoneal or oral) routes, most TSE agents replicate in spleen and lymph nodes before neuroinvasion. Characterization of the cells supporting replication in these tissues is essential to understanding early pathogenesis and may indicate potential targets for therapy, for example, in 'new variant' Creutzfeldt-Jakob disease. The host 'prion' protein (PrP) is required for TSE agent replication and accumulates in modified forms in infected tissues. Abnormal PrP is detected readily on follicular dendritic cells (FDCs) in lymphoid tissues of patients with 'new variant' Creutzfeldt-Jakob disease, sheep with natural scrapie and mice experimentally infected with scrapie. The normal protein is present on FDCs in uninfected mice and, at lower levels, on lymphocytes. Studies using severe combined immunodeficiency (SCID) mice, with and without bone marrow (BM) grafts, have indicated involvement of FDCs and/or lymphocytes in scrapie pathogenesis. To clarify the separate roles of FDCs and lymphocytes, we produced chimeric mice with a mismatch in PrP status between FDCs and other cells of the immune system, by grafting bone marrow from PrP-deficient knockout mice into PrP-expressing mice and vice versa. Using these chimeric models, we obtained strong evidence that FDCs themselves produce PrP and that replication of a mouse-passaged scrapie strain in spleen depends on PrP-expressing FDCs rather than on lymphocytes or other bone marrow-derived cells.
Asunto(s)
Células Dendríticas Foliculares/metabolismo , Tejido Linfoide/metabolismo , Proteínas PrPSc/biosíntesis , Scrapie/inmunología , Animales , Células Dendríticas Foliculares/inmunología , Inmunohistoquímica , Tejido Linfoide/inmunología , Ratones , Ratones Noqueados , Ratones SCID , Scrapie/metabolismo , Factor de Necrosis Tumoral alfa/genéticaRESUMEN
Infection of mice with African trypanosomes leads to a severe immunosuppression, mediated by suppressor macrophages. Using ex vivo macrophage culture and in vivo cell transfer, it has been shown that nitric oxide (NO) is a potent effector product of these cells and causes both lymphocyte unresponsiveness and dyserythropoiesis. We explored the role of NO in vivo during trypanosome infection using mice with a disrupted interferon-gamma-receptor gene, which were unable to respond with macrophage activation and NO synthesis. These mice were less effective at controlling parasitaemia than the wild types, but showed an improved splenic T-cell responsiveness and reduced anaemia during the early stages of infection. The data indicate that, in the mouse, NO is a significant mediator of immunosuppression only in early infection. Beyond day 10 of infection, NO-independent mechanisms are of primary significance and the control of parasitaemia and T-cell responsiveness are not directly related.
Asunto(s)
Interferón gamma , Óxido Nítrico/metabolismo , Receptores de Interferón/metabolismo , Linfocitos T/inmunología , Tripanosomiasis Africana/inmunología , Anemia/inmunología , Anemia/metabolismo , Anemia/parasitología , Animales , Células Cultivadas , Concanavalina A/farmacología , Femenino , Activación de Linfocitos/efectos de los fármacos , Macrófagos/metabolismo , Ratones , Ratones Noqueados , Óxido Nítrico Sintasa/análisis , Óxido Nítrico Sintasa/metabolismo , Linfocitos T/metabolismo , Tripanosomiasis Africana/metabolismo , omega-N-Metilarginina/farmacologíaAsunto(s)
Enfermedades por Prión/inmunología , Animales , Humanos , Sistema Inmunológico/fisiología , RatonesRESUMEN
Mice vaccinated with radiation-attenuated cercariae of Schistosoma mansoni exhibit high levels of protection against a challenge with normal larvae. The immune effector mechanism, which operates against schistosomula in the lungs, requires CD4+ T cells capable of producing interferon-gamma (IFN-gamma). This cytokine can stimulate production of nitric oxide (NO), via its ability to up-regulate inducible nitric oxide synthase (iNOS). We have therefore evaluated the potential role of NO in the effector mechanism operating in vaccinated mice. Evidence for the production of NO in the lungs of such animals was obtained from assays on antigen-stimulated airway cell cultures. Enhanced levels of NO, compared with those in cultures from control mice, were detected both after vaccination and after challenge; elevated levels of iNOS mRNA were also present in whole lung after challenge. However, administration of an iNOS inhibitor to vaccinated mice after percutaneous challenge did not significantly increase the worm burden. Furthermore, when mice with a disrupted iNOS gene were vaccinated they showed a highly significant level of protection. Although NO from activated macrophages can mediate cytotoxic killing of newly transformed schistosomula in vitro, we have demonstrated that the addition of erythrocytes to these larvicidal assays abolishes its effects. We interpret this to mean that once migrating schistosomula enter the bloodstream they will be protected against the cytotoxic actions of NO. Our data thus provide little evidence to implicate NO as a major component of the pulmonary effector response to S. mansoni in vaccinated mice.
Asunto(s)
Pulmón/inmunología , Óxido Nítrico/inmunología , Schistosoma mansoni/inmunología , Esquistosomiasis mansoni/inmunología , Vacunas Atenuadas/inmunología , Animales , Técnicas de Cultivo de Célula , Expresión Génica , Activación de Macrófagos/inmunología , Ratones , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Óxido Nítrico/biosíntesis , Óxido Nítrico Sintasa/antagonistas & inhibidores , Óxido Nítrico Sintasa/biosíntesis , Óxido Nítrico Sintasa/genética , Óxido Nítrico Sintasa de Tipo II , ARN Mensajero/genética , Esquistosomiasis mansoni/prevención & control , Vacunación , omega-N-Metilarginina/farmacologíaRESUMEN
The transmissible spongiform encephalopathies are neurodegenerative disorders which include Creutzfeldt-Jakob disease in humans, and scrapie and bovine spongiform encephalopathy in animals. A major component of the infectious agent responsible for these diseases is considered to be a post-translationally modified form of a host-encoded glycoprotein PrPc, termed PrPSc. While PrPc is abundantly expressed in tissues of the central nervous system (CNS), little is known about its normal function. The expression of PrPc is not restricted to the CNS, as this protein can also be detected in the lymphoid tissues of mice and sheep. In this report we demonstrate that resting murine splenic lymphocytes express PrPc protein on their cell membranes. Furthermore, expression of PrPc was significantly enhanced following in vitro stimulation with the non-specific T-cell mitogen concanavalin A (Con A). Genetically engineered mice with an inactive PrPc gene (PrP-/- mice), were utilized to investigate the involvement of PrPc in lymphocyte activation. Experiments revealed that the Con A-induced proliferation of lymphocytes from PrP-/- mice was significantly reduced to approximately 50-80% that of wild-type (PrP+/+) mice 48 hr post-stimulation. These findings demonstrate an important role for PrPc in extra-neuronal tissues and suggest that PrPc is a lymphocyte surface molecule that participates in T-cell activation.
Asunto(s)
Activación de Linfocitos , Priones/metabolismo , Linfocitos T/inmunología , Animales , Técnicas de Cultivo de Célula , División Celular/inmunología , Concanavalina A/inmunología , Masculino , Ratones , Ratones Mutantes , Priones/inmunología , Bazo/inmunologíaRESUMEN
African trypanosome infections result in lymphocyte unresponsiveness and anemia in the mammalian host. In murine infections, these effects are mediated by suppressor macrophages releasing nitric oxide (NO). We investigated the mechanism of activation of macrophages to produce NO during trypanosomiasis in vitro. A soluble component of trypanosome lysates induced NO synthesis in peritoneal macrophage cultures only when the macrophages were co-stimulated with interferon-gamma (IFN-gamma). The macrophage-activating factor was also released in a soluble form by live bloodstream-form trypanosomes, but not procyclic trypanosomes. When splenocyte cultures were exposed to IFN-gamma and trypanosomes, an NO-dependent suppression of T cell proliferation occurred. This is similar to the suppression observed in the spleens of trypanosome-infected mice, suggesting that a combination of trypanosome-released macrophage-activating factors and IFN-gamma are a trigger of immune dysfunction in trypanosomiasis.
Asunto(s)
Interferón gamma/farmacología , Óxido Nítrico Sintasa/biosíntesis , Óxido Nítrico/farmacología , Proteínas Protozoarias/farmacología , Linfocitos T/enzimología , Trypanosoma brucei brucei/inmunología , Tripanosomiasis Africana/inmunología , Animales , Células Cultivadas , Sinergismo Farmacológico , Inducción Enzimática/efectos de los fármacos , Inducción Enzimática/inmunología , Femenino , Tolerancia Inmunológica/efectos de los fármacos , Interferón gamma/fisiología , Activación de Linfocitos/efectos de los fármacos , Ratones , Ratones Endogámicos C3H , Solubilidad , Bazo/citología , Linfocitos T/efectos de los fármacos , Trypanosoma brucei brucei/fisiología , Tripanosomiasis Africana/enzimologíaRESUMEN
African trypanosome infections cause immunosuppression in both experimental rodent and natural hosts. One characteristic of this is an eliciting of suppressor macrophages which results in an unresponsiveness in lymphocytes. Macrophages from Trypanosoma brucei-infected mice have previously been shown to produce high levels of nitric oxide (NO). Using model systems based on in vivo macrophage transfer and drug cure, we have sought to determine the relationship between NO and suppressed lymphocyte responses. Peritoneal macrophages from T. brucei-infected mice inhibited the Concanavalin A (Con-A) response of spleen cells from syngeneic recipients 3-4 days after transfer in vivo due to the activity of suppressor macrophages. When macrophage NO synthesis was inhibited either in vitro or in vivo the suppressive effects were partially abrogated. These data provide evidence of a role for NO in mediating immunosuppression during murine T. brucei infection. Suppression in spleens of mice receiving suppressor macrophages was transient, with total recovery of spleen cell mitogen responses six days after transfer. Suppression and recovery was found to coincide with the presence or absence (respectively) of donor macrophages in recipient spleens. When T. brucei-infected mice were treated with a curative dose of a trypanocide there followed a recovery of lymphocyte responsiveness after a period of 4-5 days, and this directly correlated with a reduction of macrophage NO synthesis to control levels both in vivo and in vitro. The apparent loss of suppressor macrophage activity after 4-6 days in both drug cured animals and recipients of macrophage transfer was shown to be due to NO-mediated apoptosis of these cells.
Asunto(s)
Macrófagos Peritoneales/inmunología , Óxido Nítrico/fisiología , Trypanosoma brucei brucei/inmunología , Tripanosomiasis Africana/inmunología , Animales , Antiprotozoarios/uso terapéutico , Apoptosis/fisiología , Daño del ADN/fisiología , Diminazeno/análogos & derivados , Diminazeno/uso terapéutico , Femenino , Tolerancia Inmunológica , Inmunoterapia Adoptiva , Activación de Linfocitos/inmunología , Macrófagos Peritoneales/metabolismo , Ratones , Ratones Endogámicos C3H , Óxido Nítrico/biosíntesis , Bazo/inmunología , Linfocitos T/inmunología , Tripanosomiasis Africana/tratamiento farmacológicoRESUMEN
In mice infected with Trypanosoma brucei, splenic and peritoneal macrophages release substantial amounts of nitric oxide (NO). The production of NO by activated macrophages has been reported to be a nonspecific immune-effector mechanism against several parasites, and in this work we investigate the role of NO in killing T. brucei. Addition of bloodstream trypanosomes to peritoneal macrophages activated in vitro resulted in an NO-dependent inhibition of parasite growth. This effect was totally abrogated when dilutions of whole blood were included in the cultures, suggesting that bloodstream parasites such as T. brucei are not susceptible to NO-mediated killing in vivo.