Divalent hapten-induced intestinal anaphylaxis in the mouse enhances macromolecular uptake from the stomach

IL-9 and Mast Cells Are Key Players of Candida albicans Commensalism and Pathogenesis in the Gut

Candida albicans is implicated in intestinal diseases. Identifying host signatures that discriminate between the pathogenic versus commensal nature of this human commensal is clinically relevant. In the present study, we identify IL-9 and mast cells (MCs) as key players of Candida commensalism and pathogenicity. By inducing TGF-β in stromal MCs, IL-9 pivotally contributes to mucosal immune tolerance via the indoleamine 2,3-dioxygenase enzyme. However, Candida-driven IL-9 and mucosal MCs also contribute to barrier function loss, dissemination, and inflammation in experimental leaky gut models and are upregulated in patients with celiac disease. Inflammatory dysbiosis occurs with IL-9 and MC deficiency, indicating that the activity of IL-9 and MCs may go beyond host immunity to include regulation of the microbiota. Thus, the output of the IL-9/MC axis is highly contextual during Candida colonization and reveals how host immunity and the microbiota finely tune Candida behavior in the gut.

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IL-9/IL-9R signaling affects MC function in mucosal candidiasis

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IL-9 and mucosal MCs contribute to barrier function loss in leaky gut models

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IL-9 and stromal MCs induce local protective tolerance in infection via IDO1

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IL-9 and mucosal MCs expand and IDO1 decreases in human celiac disease

A murine model of IgE-mediated cow's milk hypersensitivity

BACKGROUND

Cow's milk allergy (CMA) is one of the leading causes of food allergy in children. Understanding the mechanisms involved in the development of CMA has been hampered by the lack of suitable animal models.

OBJECTIVE

We sought to develop a mouse model of IgE-mediated cow's milk hypersensitivity (CMH) that mimics the clinical features of immediate CMA in humans.

METHODS

Three-week-old C3H/HeJ mice were sensitized by intragastric administration of cow's milk (CM) plus cholera toxin and boosted 5 times at weekly intervals.

RESULTS

CM-specific IgE antibody levels were significantly increased at 3 weeks and peaked at 6 weeks after the initial feeding. Intragastric challenge with CM at week 6 elicited systemic anaphylaxis accompanied by vascular leakage, significantly increased plasma histamine, and increased intestinal permeability to casein. Histologic examination of intestinal tissue revealed marked vascular congestion, edema, and sloughing of enterocytes. The role of IgE in mediating CMH was confirmed by abrogation of passive cutaneous anaphylaxis reactions by heat inactivation of immune sera. Development of IgE-mediated CMH in this model is likely to be TH2 cell mediated because in vitro stimulation of spleen cells from mice allergic to CM induced significant increases in the levels of IL-4 and IL-5, but not IFN-gamma.

CONCLUSION

This model should provide a useful tool for evaluating the immunopathogenic mechanisms involved in CMA and for exploring new therapeutic approaches.

Positive association between Helicobacter pylori infection and food allergy in children

BACKGROUND

In children Helicobacter pylori has been involved as a pathogenetic factor in gastritis and duodenal ulcer and as a cofactor in protein-losing enteropathy, chronic diarrhoea, short stature, and gastritis lymphoproliferative disease. A subset of an H. pylori strain possesses an antigen, CagA, as a virulence factor. In the present study we determined anti-H. pylori IgG and anti-CagA IgG titres in children with food allergy.

METHODS

Ninety paediatric patients were studied: 30 with food allergy, 30 with atopic asthma, and 30 with inflammatory bowel disease. Anti-H. pylori IgG and anti-CagA IgG were determined in all children by means of a commercial enzyme immunoassay (ELISA).

RESULTS

The anti-H. pylori IgG titre was significantly higher in allergic patients than in the other two groups. The anti-CagA IgG titre did not differ significantly between the patients.

CONCLUSIONS

These findings show a positive association between H. pylori infection and food allergy in children. We hypothesize that virulence factors other than CagA may be involved in the pathogenesis of H. pylori infection in paediatric patients with food allergy.

Induction of B cell responses in the stomach of Helicobacter pylori- infected subjects after oral cholera vaccination

We have evaluated the possibility of inducing antibody responses locally in the human stomach as a prerequisite for the development of a vaccine against Helicobacter pylori. Both H. pylori-infected and noninfected subjects were immunized with an oral B subunit whole cell (BS-WC) cholera vaccine, and total and vaccine-specific antibody-secreting cells (ASC) were determined by the enzyme-linked immunospot (ELISPOT) technique in cells isolated from the antrum and duodenum, respectively, before and after vaccination. Most of the subjects responded to the vaccination with high frequencies of vaccine-specific ASCs in the duodenum as well as high-serum antibody titers, and no significant differences were seen in the responses between H. pylori- infected and noninfected subjects. When studying the gastric mucosa, on the other hand, there were dramatic differences between the H. pylori-infected and the noninfected subjects. Thus, whereas none of the noninfected subjects responded to the immunization in antrum, most of the H. pylori-infected subjects had high frequencies of vaccine-specific ASCs in this location after vaccination. Furthermore, the H. pylori-infected subjects had strikingly higher (as a mean 80-fold) frequencies of total IgA-secreting cells in antrum than the noninfected subjects, whereas the frequencies of total IgA-secreting cells in the duodenum were comparable between the groups. In conclusion, these results demonstrate the possibility of inducing antibody responses locally in the gastric mucosa of H. pylori-infected individuals, a finding with obvious implications for the future development of a therapeutic vaccine against H. pylori.

In situ expression of cell adhesion molecules in chronic gastritis with Helicobacter pylori infection

Helicobacter pylori infection of the stomach results in acute inflammation followed by chronic inflammation, but the mechanism is unknown. Adhesion molecules such as ICAM-1, Mac-1, and LFA-1 may help regulate interactions of immune cells and inflammatory cells. We used immunohistochemistry to locate these molecules in the gastric mucosa of patients with chronic gastritis arising from H. pylori infection. Biopsy specimens were taken from five H. pylori-negative healthy volunteers and 20 H. pylori-positive patients with chronic gastritis for immunohistochemical studies of adhesion molecules. In the gastric mucosa of patients with H. pylori-associated chronic gastritis, ICAM-1 expression was prominent in most of the vessels and inflammatory cells, such as lymphocytes and granulocytes, in the lamina propria. However, no intraepithelial lymphocytes and surface epithelial cells expressed ICAM-1. Antigen-presenting cells (APCs), such as macrophages, expressed ICAM-1 as well as HLA-DR antigen. LFA-1 and Mac-1 were strongly expressed in these immune and inflammatory cells. The number of vascular endothelial cells positive for P-selectin was also greater in H. pylori-positive mucosa. The expression of these molecules decreased remarkably after successful eradication of H. pylori. In conclusion, ICAM-1 is the predominant form among the cell adhesion molecules that are expressed in response to chronic H. pylori infection. The increased expression of ICAM-1 is linked with massive infiltration of inflammatory cells that express LFA-1 and Mac-1, and also with APCs that express HLA-DR, suggesting that ICAM-1 exerts a key role in immuno-inflammatory responses in gastric mucosa of patients with H. pylori-associated gastritis.

Sucrose permeability in children with gastric damage and Helicobacter pylori infection

BACKGROUND

Increased permeability to sucrose has been recently shown to be a good marker of gastric mucosal damage in adults.

METHODS

This test was evaluated in 40 children consulting for recurrent abdominal pain and the results were correlated with endoscopic and histologic findings and with the presence of H. pylori.

RESULTS

The gastric mucosa was considered endoscopically normal in 31 children; 3 had duodenitis and 6 had mild gastritis. Abnormal endoscopic findings were associated with increased urinary sucrose excretion (MANOVA F = 7.30; p = 0.002). In the 6 children with mild gastritis, mean sucrose excretion was twice that of controls (0.060 +/- 0.024 vs. 0.029 +/- 0.018, respectively; p = 0.019) and significantly higher than the group with duodenitis (0.037 +/- 0.013; p = 0.038). The specificity and sensitivity of sucrose permeability test for detection of gastric damage were 90.3% and 83.3%, respectively. H. pylori was detected in 62.5% of children including all patients with mild gastritis, in 2 out of 3 with duodenitis and 17 out of 31 endoscopically normal controls. No differences in sucrose excretion were observed in relation with the presence of H. pylori or histological findings in the control group.

CONCLUSIONS

Urinary sucrose excretion is a good marker of mucosal gastric damage in children and may be used as a screening test in large groups of populations.

Mediators of antigen-induced gastrin release: role of antigen-antibody complexes and the complement system

That orally administered antigen was shown to induce gastrin release in immunized animals was a new aspect of gastrointestinal physiology. The mediators responsible for this immunological effect are still unclear. In an attempt to discover more about the mechanisms regarding antigen-induced gastrin release, we developed an in vitro system where fragments of rat antral mucosa were challenged. This makes it possible to determine the role of antigen-antibody complexes and the complement system in the mechanism of antigen-induced gastrin release. Wistar rats were immunized in vivo with NIP-OVA and mucosal fragments were challenge, in vitro with NIP-HGG. Gastrin was determined after a preincubation and a challenged incubation period without supernatants. After antigenic challenge, supernatants were used for in vitro challenge in order to rule out the presence of a soluble mediator and activation of complement. In a second group of experiments Wistar rats were used to study in vitro the release of specific antibodies after antigenic challenge. With this experimental design we were able to show increased gastrin secretion after antigenic challenge in vitro in the presence of intact tissue. It is shown that the increased gastrin release is most probably mediated by activation of the complement system in the presence of antigen-antibody complexes. These are built up by specific anti-NIP antibodies and NIP-HGG used for the challenge. The complement system might be the final pathway of the observed increased gastrin release.

Characterization of lymphocytic infiltrates in Helicobacter pylori-associated gastritis

BACKGROUND

This study evaluated the specific subset composition of lymphocytes present in Helicobacter pylori-associated gastritis (HAG), since reports so far have led to inconclusive and conflicting results.

METHODS

Endoscopic biopsy specimens from 56 patients were studied by quantitative immunohistochemistry using monoclonal antibodies against the lymphocyte markers CD3, CD22, CD4, CD8, CD45RO, CD1O3, TCR alpha/beta, and TCR gamma/delta. Lamina propria and intraepithelial compartments were evaluated separately. Grade, activity, and density of bacterial colonisation were assessed histologically and with Warthin-Starry stain.

RESULTS

Evaluation showed a significant increase in CD4+, CD45RO+, TCR alpha/beta+ activated lamina propria lymphocytes in HAG which correlated with grade and activity of gastritis and degree of bacterial colonisation, whereas subsets of intraepithelial lymphocytes did not change significantly. TCR gamma/delta+ T cells were not found to be increased in HAG.

CONCLUSIONS

Selective expansion of CD4+, CD45RO+ memory-type T cells could reflect an antigen-specific and/or chemokine-mediated effect in HAG. Locally produced CC chemokines such as RANTES have been detected in HAG.

Mucosal exudation of plasma is a noninjurious intestinal defense mechanism

We have demonstrated in sensitized rats that the immediate response to endointestinal challenge with allergen (10(-6) M ovalbumin) is characterized by mucosal exudation of plasma with little or no concomitant change in the mucosal absorption capacity. The luminal entry of plasma macromolecules also leaves the light microscopic structure and the ultrastructure of the mucosa unaffected. It is possible that the plasticity of epithelial zonulae occludens allows a noninjurious and unidirectional paracellular flux of extravasated plasma into the gut lumen. We propose that inflammatory-stimulus-induced mucosal exudation of plasma belongs to the first-line defense mechanisms of the intact lining of the intestine.

Allergen-induced mucosal exudation of plasma into rat ileum and its inhibition by budesonide

Exudation of plasma across the airway mucosa is a specific defence/inflammatory response finely regulated by mediators and (in rodents) a capsaicin-sensitive innervation. This study examines plasma exudation responses to endointestinal challenges and effects of a glucocorticoid. The ileum of anesthetized rats was catheterized and ligated at two points 10 cm apart for mucosal challenge (0.5 ml) and repeated lavages (5 ml). Lavage fluid levels of the plasma tracer 125I-albumin, previously injected intravenously, showed a stable, low base line greater than 2 h. Challenge with mediators (10(-5) M bradykinin, 10(-5)-10(-3) M serotonin, 10(-6)-10(-4) M histamine, 2.10(-9)-2.10(-7) M leukotriene D4 (LTD4), or 10(-5)-10(-3) M capsaicin did not increase luminal radioactivity. However, allergen (10(-6) M ovalbumin, in previously sensitized animals) produced prompt mucosal exudation of 125I-albumin, peaking within 30 min (p less than 0.001) and returning to base line within 90 min. Separate experiments suggested that absorption was not increased during the mucosal exudation. The glucocorticoid budesonide (10-1000 micrograms/kg given by gavage 24 h before challenge) dose-dependently inhibited the allergen-induced exudation (p less than 0.01). The route of administration and the antiexudative versus the systemic potency (reduced thymus weight) suggest the possibility of a topical action of budesonide. We conclude that endointestinal allergen challenge produces reversible and glucocorticoid-inhibitable exudation of plasma across the mucosa. It appears less likely that bradykinin, serotonin, histamine, LTD4, or a capsaicin-sensitive innervation is involved in producing this exudative effect.

Milk protein enteropathy after acute infectious gastroenteritis: experimental and clinical observations

Animal models of allergic gastroenteropathy have defined both morphologic and physiologic changes that accompany the immune-mediated reaction to a dietary protein. In such models a broadening of the allergic response to other dietary proteins present in the gastrointestinal tract may occur during the localized anaphylactic reaction. The characteristic histologic intestinal findings of food protein-induced enteropathy may develop in selected infants with protracted diarrhea after infectious enteritis. Mechanisms underlying the induction of this response remain to be explained, but they may in part be similar to the broadening of the hypersensitivity response seen in experimental models of allergic enteropathy.