B cells are involved in the modulation of pathogenic gut immune response in food-allergic enteropathy

The signal transducer and activator of transcription 6 (STAT-6) mediates Th2 inflammation and tissue damage in a murine model of peanut-induced food allergy

INTRODUCTION

Food allergies are inflammatory conditions mediated by Th2 and probably STAT-6 dependent immune responses.

OBJECTIVE AND DESIGN

Here we investigated the role of Signal Transducer and Activator of Transcription 6 (STAT-6) in development of inflammation in peanut allergy.

METHODS

To induce food allergy, wild-type (WT) and mice deficient for STAT-6 (Stat6^-/-) were sensitized with peanut proteins and challenged with peanut seeds.

RESULTS

WT animals lost weight and refused the peanut diet, in contrast to Stat6^-/- mice, which had a better maintenance of body weight and more regular seeds' consumption. The augmented peanut-specific IgG, IgG1 and IgE in the allergic WT was abolished in Stat6^-/- animals that also presented increased IgG2a. There was an overall reduction in the gut mediators in the absence of STAT-6, including those related to inflammatory and Th2 responses, in contrast to a rising counter regulatory and Th1 reaction in Stat-6^-/- mice. These animals had IFN-γ and IL-10 similar to WT after the four-week challenge. Most interestingly, Stat-6^-/- mice had no intestinal damage, in contrast to WT animals, which had inflammatory infiltrate, tissue destruction, epithelial exulceration, edema, congestion and loss of villous architecture in the small gut segments.

CONCLUSIONS

STAT-6 plays an important role in the establishment of the Th2 inflammatory responses and intestinal damage in peanut allergy.

Effects of cyanobacteria Oscillatoria sp. lipopolysaccharide on B cell activation and Toll-like receptor 4 signaling

Cyanobacteria ("blue-green algae"), such as Oscillatoria sp., are a ubiquitous group of bacteria found in freshwater systems worldwide that are linked to illness and in some cases, death among humans and animals. Exposure to cyanobacteria occurs via ingestion of contaminated water or food-products. Exposure of the gut to these bacteria also exposes their toxins, such as lipopolysaccharide (LPS), to B cells in the gut associated lymphoid tissue. However, the effect of Oscillatoria sp. LPS on B cell activation is unknown. To test the hypothesis that Oscillatoria sp. LPS exposure to murine B cells would result in B cell activation, murine B cells were incubated in the absence or presence of Oscillatoria sp. LPS or E. coli LPS as a positive control. The data indicate that Oscillatoria sp. LPS induces B cells to proliferate, upregulate MHC II and CD86, enhance antigen uptake and induce IgM production at low levels. Additional studies demonstrate that this low level of stimulation may be due to incomplete TLR4 signaling induced by Oscillatoria sp. LPS, since IRF-3 is not induced in B cells after stimulation with Oscillatoria sp. LPS. These findings have important implications for the mechanisms of toxicity of cyanobacteria in both humans and animals.

Bortezomib treatment diminishes hazelnut-induced intestinal anaphylaxis in mice

Food allergy is a common health problem and can cause anaphylaxis. Avoidance of the offending food allergen is still the mainstay therapeutic approach. In this study, we investigated the role of plasma cell reduction by proteasome inhibition in a murine model of food allergy and examined the impact of this treatment on the systemic and local immune response. For this purpose, intestinal anaphylaxis was induced in BALB/c mice with the food allergen hazelnut, in conjunction with different adjuvants (alum and Staphylococcal enterotoxin B SEB) and different administration routes (oral and intraperitoneal). In both models, allergy symptoms were observed, but the clinical severity was more pronounced in the hazelnut-alum model than in the hazelnut-SEB model. Accordingly, allergen-specific immunoglobulin E (IgE) against hazelnut was detectable, and mast cell protease-1 in serum was increased after allergen provocation. Treatment with the proteasome inhibitor bortezomib reduced plasma cells and resulted in an abolishment of hazelnut allergen-specific IgE, which was associated with amelioration of clinical symptoms as well as a significant decrease in both CD19(+) and follicular B lymphocytes. Our data demonstrate the importance of allergen-specific IgE in food allergy and point to B cells as potential therapeutic targets for its treatment.

Role of complement in a murine model of peanut-induced anaphylaxis

Peanut allergy is severe and persisting from childhood to adulthood. However, there is no effective prophylaxis or treatment for peanut allergy. Little is known to about the molecular process in the pathogenesis of peanuts allergy, especially in innate immunity. Thus we investigated the role of complement activation in murine peanut anaphylaxis. Complement component C3 deposition on peanut extract (PE) was evaluated using sera from wild-type (WT), mannose-binding lectin associated serine protease (MASP)-1/3 deficient, MASP-2 deficient, and C4 deficient mice. Sera from interferon regulatory factor-4 (IRF-4) deficient mice, which lack serum immunoglobulin, were also used. In anaphylaxis study, mice were pretreated with propranolol and a long-acting form of IL-4, and injected with PE. Mice were then assessed for plasma C3a levels and hypothermia shock by ELISA and rectal temperature measurement, respectively. C3 deposition on PE was abolished in immunoglobulin- and C4-deficient sera. No difference in C3 deposition levels were observed among WT, MASP-1/3 deficient and MASP-2 deficient sera. IgM, IgG2b, IgG3, C1q, and ficolin-A deposits were detected on PE. In anaphylaxis study, MASP-1/3 deficient mice showed elevation of plasma C3a levels similar to WT mice. However, they were significantly reduced in C4- and MASP-2-deficient mice compared to WT mice. Consistently, PE-induced anaphylactic shock was prevented in C4 deficient mice and partially in MASP-2 deficient mice. In conclusion, PE activates complement via both the lectin and classical pathways in vivo, and the complement activation contributes to hypothermia shock in mice.

Current understanding of the immune mechanisms of food protein-induced enterocolitis syndrome

Food protein-induced enterocolitis syndrome (FPIES) is an under-recognized and frequently misdiagnosed non-IgE-mediated food hypersensitivity disorder, characterized by severe vomiting and/or diarrhea. Despite the potential severity of acute reactions, FPIES can be considered self-limiting as avoidance of the incriminating allergen(s) leads to resolution of symptoms. Symptoms typically begin in the first month of life in association with failure to thrive and may progress to acidemia and shock. Although FPIES is well established as a distinct clinical entity, its pathophysiology has not yet been clearly defined and requires further characterization. Several immunologic alterations have been reported in FPIES, suggesting the involvement of antigen-specific T cells and their production of proinflammatory cytokines that regulate the permeability of the intestinal barrier. Humoral immune responses may also be involved in the pathomechanism of FPIES. The aim of this article is to delineate the immunological characteristics of this disorder based on the existing reports and to review the possible pathophysiologic basis of this disease.