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Abstract Background Hematopoietic stem cell transplantation is increasingly performed for hematologic diseases. As a major side effect, acute graft versus host disease (GvHD) with serious gastrointestinal symptoms including diarrhea, gastrointestinal bleeding and high mortality can be observed. Because surveillance and biopsies of human gastrointestinal GvHD are difficult to perform, rare information of the alterations of the gastrointestinal barrier exists resulting in a need for systematic animal models. Methods To investigate the effects of GvHD on the intestinal barrier of the small intestine we utilized an established acute semi allogenic GvHD in C57BL/6 and B6D2F1 mice. Results By assessing the differential uptake of lactulose and mannitol in the jejunum, we observed an increased paracellular permeability as a likely mechanism for disturbed intestinal barrier function. Electron microscopy, immunohistochemistry and PCR analysis indicated profound changes of the tight-junction complex, characterized by downregulation of the tight junction protein occludin without any changes in ZO-1. Furthermore TNF-α expression was significantly upregulated. Conclusions This analysis in a murine model of GvHD of the small intestine demonstrates serious impairment of intestinal barrier function in the jejunum, with an increased permeability and morphological changes through downregulation and localization shift of the tight junction protein occludin.

Although a profound barrier dysfunction has been reported, little is known about the pathophysiological mechanism evoking gastrointestinal graft-vs.-host disease (GI-GvHD) and apparent therapeutic options. The aim of this study was to evaluate the influence of oral glutamine on the course of GI-GvHD in an acute semiallogenic graft-vs.-host disease (GvHD) in irradiated B6D2F1 mice. An acute semiallogenic GvHD was induced by intraperitoneal injection of lymphocytes from C57BL/6 mice to irradiated B6D2F1 mice. Half of the GvHD animals received oral glutamine supplementation for 6 days started at the time of lymphocyte transfer. Six days after induction of the semiallogenic GvHD, jejunum specimens were prepared. The expression of the proinflammatory cytokine TNF-α and the tight junction protein occludin was investigated by PCR. Histological changes along with the apoptotic response were evaluated and intestinal permeability was assessed. Animals with GvHD showed a strong increase in paracellular permeability as a sign of the disturbed barrier function. TNF-α expression was significantly increased and the expression of the tight junction protein occludin decreased. GvHD led to mucosal atrophy, crypt hyperplasia, crypt apoptosis, and a disintegration of the tight junctions. Glutamine-treated mice showed reduced expression of TNF-α, increased occludin expression, fewer histological changes in the jejunum, smaller number of apoptotic cells in the crypt, and reduced gastrointestinal permeability. In conclusion, oral glutamine seems to have beneficial effects on the severity of inflammatory changes in the course of GvHD and might be a therapeutic option.

Background: Hematopoietic stem cell transplantation is increasingly performed for hematologic diseases. As a major side effect, acute graft versus host disease (GvHD) with serious gastrointestinal symptoms including diarrhea, gastrointestinal bleeding and high mortality can be observed. Because surveillance and biopsies of human gastrointestinal GvHD are difficult to perform, rare information of the alterations of the gastrointestinal barrier exists resulting in a need for systematic animal models., Methods: To investigate the effects of GvHD on the intestinal barrier of the small intestine we utilized an established acute semi allogenic GvHD in C57BL/6 and B6D2F1 mice., Results: By assessing the differential uptake of lactulose and mannitol in the jejunum, we observed an increased paracellular permeability as a likely mechanism for disturbed intestinal barrier function. Electron microscopy, immunohistochemistry and PCR analysis indicated profound changes of the tight-junction complex, characterized by downregulation of the tight junction protein occludin without any changes in ZO-1. Furthermore TNF-α expression was significantly upregulated., Conclusions: This analysis in a murine model of GvHD of the small intestine demonstrates serious impairment of intestinal barrier function in the jejunum, with an increased permeability and morphological changes through downregulation and localization shift of the tight junction protein occludin.

Chronic diarrheal illness and malabsorption are challenging diagnostic and clinical problems. The identification of the causative pathogens that are involved in gastrointestinal infections is often difficult. It took 85 years after the first description of a case of intestinal lipodystrophy by Georg Whipple in 1907 until the causative bacterium was characterized by using molecular genetics techniques. We here report the complicated clinical course of a young patient with chronic diarrhea accompanied by severe, life-threatening malabsorption with extensive weight loss. Histology and glucose hydrogen breath test were suggestive of a bacterial overgrowth syndrome in the small bowel, but standard culture-based techniques and serology failed to identify the causative bacteria. Thus, bacterial ribosomal DNA (16S ribosomal DNA) was extracted from duodenal biopsy samples and analyzed by community fingerprinting and species-specific polymerase chain reaction. Stenotrophomonas maltophilia was identified as the cause of chronic infectious enteritis. Only specific long-term antibiotic treatment with co-trimoxazole had a durable clinical effect and led to normalization of 16S ribosomal DNA profiles. This case shows the role of rare and uncommon bacteria in refractory and chronic human gastrointestinal infections. Genomic techniques, including 16S-based single-strand conformation polymorphism analysis, will play an increasing role in the diagnosis of chronic infections with facultatively pathogenic bacteria or in the clinical analysis of complex bacterial communities such as the intestinal bacterial microflora. Future enhancements in detection techniques will show that chronic bacterial infections are more frequent as a cause of gastrointestinal malfunction than commonly thought.

Background & Aims: The intestinal histology of murine semiallogeneic graft-versus-host (GVH) disease is characterized by lymphocytic infiltrates, crypt hyperplasia, and villous atrophy. Mechanisms of T cell-mediated changes of the mucosal architecture were investigated., Methods: The rate of cellular apoptosis and proliferation, changes in the composition of extracellular matrix (ECM), and the role of OX40-OX40L interactions in the pathogenesis of villous atrophy and crypt hyperplasia were examined., Results: The rate of apoptosis and the number of proliferating cells were significantly increased in GVH animals compared with control animals. In addition, expression of tenascin, an ECM component, was down-regulated in GVH animals. Inhibition of OX40-OX40L interactions in GVH animals by administration of an OX40-Ig fusion protein completely prevented the development of crypt hyperplasia and villous atrophy in GVH animals. Tenascin expression was up-regulated in OX40-Ig-treated mice compared with GVH animals, suggesting an important function of this ECM component in mucosal repair., Conclusions: The OX40-OX40L interaction is crucial in the pathogenesis of GVH, a T cell-mediated intestinal disease. The data suggest that the ECM component tenascin is probably relevant for the regeneration and maintenance of intestinal tissue architecture.

OX40 is a member of the TNF/NGF-receptor family expressed on activated T cells, whose ligand is found on activated T and B cells. In the present study, we show that cross-linking of OX40L on CD40L-stimulated B cells, alpha IgD dextran-stimulated B cells, or both results in a significantly enhanced proliferative response with no change in the cell survival rate. Furthermore, OX40 stimulation increases immunoglobulin heavy chain mRNA levels and immunoglobulin secretion, which could not be blocked by anti-cytokine antibodies. In additional molecular studies, we show that OX40L cross-linking results in the down-regulation of the transcription factor BSAP. This, in turn, leads to a change in the in vivo binding pattern of the immunoglobulin heavy chain gene 3' alpha enhancer, suggesting its activation. This effect may thus be one mechanism for OX40-induced increase in immunoglobulin secretion. In conclusion, our data suggest that the OX40-OX40L interaction is a novel pathway in T cell-dependent B cell proliferation and differentiation.