RESUMEN
Infection of mice with the intestinal bacterial pathogen Citrobacter rodentium results in colonic mucosal hyperplasia and a local Th1 inflammatory response similar to that seen in mouse models of inflammatory bowel disease. Matrix metalloproteinases (MMPs) have been shown to mediate matrix remodeling and cell migration during tissue injury and repair in the intestine. We have previously shown enhanced pathology in infected TNFRp55-/-, IL-12p40-/-, and IFN-gamma-/- mice, and here we show that this is associated with an increase in stromelysin-1 (MMP3) transcripts in colonic tissues. We have therefore investigated the role of MMP3 in colonic mucosal hyperplasia and the local Th1 responses using MMP3-/- mice. In MMP3-/- mice, similar mucosal thickening was observed after infection as in wild-type (WT) mice. Colonic tissues from MMP3-/- mice showed a compensatory increase in the expression of other MMP transcripts, such as MMP7 and MMP12. However, MMP3-/- mice showed delayed clearance of bacteria and delayed appearance of CD4+ T lymphocytes into intestinal lamina propria. CSFE-labeled mesenteric lymph node CD4+ T lymphocytes from infected WT mice migrated in fewer numbers into the mesenteric lymph nodes and colon of MMP3-/- mice than into those of WT mice. These studies show that mucosal remodeling can occur in the absence of MMP3, but that MMP3 plays a role in the migration of CD4+ T lymphocytes to the intestinal mucosa.
Asunto(s)
Citrobacter rodentium , Infecciones por Enterobacteriaceae/inmunología , Enfermedades Intestinales/inmunología , Metaloproteinasa 3 de la Matriz/fisiología , Animales , Antígenos CD/fisiología , Linfocitos T CD4-Positivos/fisiología , Movimiento Celular , Colon/enzimología , Colon/patología , Células Dendríticas/fisiología , Infecciones por Enterobacteriaceae/patología , Femenino , Interferón gamma/fisiología , Interleucina-12/fisiología , Subunidad p40 de la Interleucina-12 , Enfermedades Intestinales/patología , Metaloproteinasa 3 de la Matriz/deficiencia , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Subunidades de Proteína/fisiología , Receptores del Factor de Necrosis Tumoral/fisiología , Receptores Tipo I de Factores de Necrosis TumoralRESUMEN
Citrobacter rodentium is a natural non-invasive bacterial pathogen which infects the distal colon of mice. It uses the same molecular mechanisms of type III secretion as human enteropathogenic and enterohemorrhagic Escherichia coli to colonise the epithelial cells of the gut and is therefore an ideal model to study host-bacterial pathogen interactions in vivo. Infection elicits mucosal inflammation with similarities to inflammatory bowel disease, and so it is a readily accessible model to investigate the relationship between inflammation and anti-bacterial immunity in the gut.
Asunto(s)
Citrobacter freundii/patogenicidad , Infecciones por Enterobacteriaceae/inmunología , Proteínas de Escherichia coli , Adhesinas Bacterianas/metabolismo , Animales , Proteínas Portadoras/metabolismo , Citrobacter freundii/inmunología , Colon/patología , Modelos Animales de Enfermedad , Humanos , Hiperplasia/etiología , Inmunidad Mucosa , Inflamación , Ratones , Ratones Endogámicos C57BLRESUMEN
Intimin-conjugated fluorescent beads bind to spleen CD4 T cells and Peyer's patch, mesenteric lymph node, and cecal follicle lymphocytes, with less binding to lamina propria T cells and intraepithelial lymphocytes. Intimin costimulates proliferation of spleen CD4 T cells and cells from organized lymphoid tissues but does not costimulate cells from the lamina propria of normal or inflamed colon.
Asunto(s)
Adhesinas Bacterianas/metabolismo , Linfocitos T CD4-Positivos/metabolismo , Proteínas Portadoras/metabolismo , Proteínas de Escherichia coli/metabolismo , Adhesinas Bacterianas/farmacología , Animales , Complejo CD3/inmunología , Proteínas Portadoras/farmacología , Femenino , Activación de Linfocitos/efectos de los fármacos , Ratones , Ratones Endogámicos BALB CRESUMEN
Mice infected with Citrobacter rodentium represent an excellent model in which to examine immune defenses against an attaching-effacing enteric bacterial pathogen. Colonic tissue from mice infected with C. rodentium harbors increased transcripts for IL-12 and IFN-gamma and displays mucosal pathology compared with uninfected controls. In this study, the role of IL-12 and IFN-gamma in host defense and mucosal injury during C. rodentium infection was examined using gene knockout mice. IL-12p40(-/-) and IFN-gamma(-/-) mice were significantly more susceptible to mucosal and gut-derived systemic C. rodentium infection. In particular, a proportion of IL-12p40(-/-) mice died during infection. Analysis of the gut mucosa of IL-12p40(-/-) mice revealed an influx of CD4(+) T cells and a local IFN-gamma response. Infected IL-12p40(-/-) and IFN-gamma(-/-) mice also mounted anti-Citrobacter serum and gut-associated IgA responses and strongly expressed inducible NO synthase (iNOS) in mucosal tissue, despite diminished serum nitrite/nitrate levels. However, iNOS does not detectably contribute to host defense against C. rodentium, as iNOS(-/-) mice were not more susceptible to infection. However, C57BL/6 mice infected with C. rodentium up-regulated expression of the mouse beta-defensin (mBD)-1 and mBD-3 in colonic tissue. In contrast, expression of mBD-3, but not mBD-1, was significantly attenuated during infection of IL-12- and IFN-gamma-deficient mice, suggesting mBD-3 may contribute to host defense. These studies are among the first to examine mechanisms of host resistance to an attaching-effacing pathogen and show an important role for IL-12 and IFN-gamma in limiting bacterial infection of the colonic epithelium.