Helper CD4+ T cells for IgE response to a dietary antigen develop in the liver

Hepatoprotective Effects of Rosmarinic Acid on Ovalbumin-Induced Intestinal Food Allergy Mouse Model

Rosmarinic acid (RA) has been proven to exert antianaphylaxis in atopic dermatitis, asthma, and allergic rhinitis. The aim of this study was to determine the hepatoprotective effects of RA on ovalbumin (OVA) challenge-induced intestinal allergy. The results exhibited that RA could relieve anaphylactic symptoms, decrease diarrhea, and prevent hypothermia in allergic mice. Moreover, the elevation of OVA specific IgE (OVA-sIgE), histamine, and mouse mast cell proteinases (mMCP-1) in the serum of OVA challenged mice were remarkably inhibited by RA. OVA challenge resulted in notable increases in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) activities, liver malondialdehyde (MDA) and nitic oxide (NO) levels, and a remarkable decrease in liver superoxide dismutase (SOD) activity and glutathione (GSH) level. RA treatments succeeded in improving these biochemical parameters and promote the redox homeostasis. Cytokine expression evaluation showed that RA effectively enhanced the expression of anti-inflammatory cytokines (IL-10 and FOXP-3) in the liver of OVA-challenged mice. Meanwhile, the elevation of pro-inflammatory cytokines (TNF-α, IL-4, IL-6, mMCP-1, and iNOS) were remarkably inhibited by RA. These findings suggest that RA possesses hepatoprotective effects on OVA challenge-induced liver injury. The anti-oxidative and anti-inflammatory activities of RA potentially play vital roles in this process.

Butyrate as a bioactive human milk protective component against food allergy

BACKGROUND

Food allergy (FA) is a growing health problem worldwide. Effective strategies are advocated to limit the disease burden. Human milk (HM) could be considered as a protective factor against FA, but its mechanisms remain unclear. Butyrate is a gut microbiota-derived metabolite able to exert several immunomodulatory functions. We aimed to define the butyrate concentration in HM, and to see whether the butyrate concentration detected in HM is able to modulate the mechanisms of immune tolerance.

METHODS

HM butyrate concentration from 109 healthy women was assessed by GS-MS. The effect of HM butyrate on tolerogenic mechanisms was assessed in in vivo and in vitro models.

RESULTS

The median butyrate concentration in mature HM was 0.75 mM. This butyrate concentration was responsible for the maximum modulatory effects observed in all experimental models evaluated in this study. Data from mouse model show that in basal condition, butyrate up-regulated the expression of several biomarkers of gut barrier integrity, and of tolerogenic cytokines. Pretreatment with butyrate significantly reduced allergic response in three animal models of FA, with a stimulation of tolerogenic cytokines, inhibition of Th2 cytokines production and a modulation of oxidative stress. Data from human cell models show that butyrate stimulated human beta defensin-3, mucus components and tight junctions expression in human enterocytes, and IL-10, IFN-γ and FoxP3 expression through epigenetic mechanisms in PBMCs from FA children. Furthermore, it promoted the precursors of M2 macrophages, DCs and regulatory T cells.

CONCLUSION

The study's findings suggest the importance of butyrate as a pivotal HM compound able to protect against FA.

Post-transplant food anaphylaxis in an adult cord blood transplant recipient (Ms. No. IJHM-D-20-01037R1)

Transplant acquired food allergy (TAFA) is a well-known complication following pediatric liver transplantation, but post-cord blood transplantation (post-CBT) TAFA has rarely been reported. Here, we describe a case of new-onset food anaphylaxis after CBT in an adult patient that demonstrates that post-CBT allergen-challenge is not a risk for long-term allergic sensitization even in adult recipients. The patient was a 39-year-old Japanese man with aggressive NK cell leukemia. He had no previous history of allergies. After receiving CBT, the patient had an unbalanced diet with high preference for bread, bananas, miso-soup, cow's milk, cheese, egg, sesame and buckwheat soba noodles, and experienced repeated diarrhea. Six months later, he developed symptoms such as vomiting, epigastric pain, diarrhea, high fever and hypotension. The condition was initially diagnosed as enterocolitis, but symptoms recurred after consumption of buckwheat. Anaphylaxis induced by buckwheat was confirmed with serum radioallergosorbent tests (RAST), showing allergen-specific IgE for buckwheat (greater than 100 U/mL, Class 6) and egg ovomucoid (Class 4). Nineteen months after a buckwheat and egg-free diet, serum RAST for buckwheat and egg significantly improved. As a result, the patient acquired a tolerance and was able to consume buckwheat and egg without allergic symptoms.

Hepatic Mitochondrial Dysfunction and Immune Response in a Murine Model of Peanut Allergy

Background: Evidence suggests a relevant role for liver and mitochondrial dysfunction in allergic disease. However, the role of hepatic mitochondrial function in food allergy is largely unknown. We aimed to investigate hepatic mitochondrial dysfunction in a murine model of peanut allergy. Methods: Three-week-old C3H/HeOuJ mice were sensitized by the oral route with peanut-extract (PNT). We investigated: 1. the occurrence of effective sensitization to PNT by analysing acute allergic skin response, anaphylactic symptoms score, body temperature, serum mucosal mast cell protease-1 (mMCP-1) and anti-PNT immunoglobulin E (IgE) levels; 2. hepatic involvement by analysing interleukin (IL)-4, IL-5, IL-13, IL-10 and IFN-γ mRNA expression; 3. hepatic mitochondrial oxidation rates and efficiency by polarography, and hydrogen peroxide (H₂O₂) yield, aconitase and superoxide dysmutase activities by spectrophotometry. Results: Sensitization to PNT was demonstrated by acute allergic skin response, anaphylactic symptoms score, body temperature decrease, serum mMCP-1 and anti-peanut IgE levels. Liver involvement was demonstrated by a significant increase of hepatic Th2 cytokines (IL-4, IL-5 and IL-13) mRNA expression. Mitochondrial dysfunction was demonstrated by lower state 3 respiration rate in the presence of succinate, decreased fatty acid oxidation in the presence of palmitoyl-carnitine, increased yield of ROS proven by the inactivation of aconitase enzyme and higher H₂O₂ mitochondrial release. Conclusions: We provide evidence of hepatic mitochondrial dysfunction in a murine model of peanut allergy. These data could open the way to the identification of new mitochondrial targets for innovative preventive and therapeutic strategies against food allergy.

Transplant-acquired food allergy: current perspectives

Mechanisms that regulate the tolerance to dietary proteins or the loss of this and subsequent development of disease are poorly understood. In food allergy, there is growing awareness of the urgency in understanding these events to aid in the development of next-generation therapies and interventions. This review focuses on the accumulating evidence related to food allergy that develops after transplantation. This intriguing immunological phenomenon has been described in several different types of transplant settings and to variety of different foods. We outline these studies and the evidence from them that support transplant-acquired food allergy being a process regulated by both the donor allergic status and the recipient genetics and treatments. A number of key risk factors seem prevalent throughout transplant-acquired food allergy and include type of transplant, age and general health of the recipient, modality of immunosuppression and potentially the genetics of both donor and recipient. Importantly, these studies provide a window into better general understanding of food allergy, and facilitate clearer understanding of the critical immunological and epidemiological factors needed to allow the adoptive transfer of a food-specific allergic disease from one individual to another.

Factors Associated with Development of Food Allergy in Young Children after Liver Transplantation: A Retrospective Analysis of 10 Years' Experience

BACKGROUND

Although development of food allergy after liver transplantation is most commonly described in young children, little is known about identification of young liver-transplant recipients who are at risk of food allergy.

OBJECTIVE

This study aimed to identify the types of food allergy and the risk factors for the development of food allergy after liver transplantation.

METHODS

This was a retrospective analysis of pediatric liver transplant recipients in our organ transplantation center during 2005-2015. Relevant data of all patients who underwent liver transplantation were extracted from the center's database and the medical records. Differences in patients' characteristics were evaluated for associations between food allergy and potential risk factors. Logistic regression models were used to calculate adjusted odds ratios.

RESULTS

We obtained the data of 206 patients under 36 months of age, 42 (20.4%) of whom developed food allergy after liver transplantation. The allergy was IgE-mediated-only in 30 (71.4%) and non-IgE-mediated-only in 10 (23.8%). Multivariate analysis found eczema at liver transplantation to be a significant risk factor (adjusted odds ratio [aOR] 2.41, 95% confidence interval [CI] 1.14-4.77, P < .05). Eczema increased the risk of developing IgE-mediated food allergy after liver transplantation (aOR 3.13, 95% CI 1.41-6.93, P < .01), whereas no significant association was observed with non-IgE-mediated food allergy.

CONCLUSIONS

We identified eczema at liver transplantation as a significant risk factor for the development of IgE-mediated food allergy after liver transplantation, but not non-IgE-mediated food allergy. Our findings may contribute to a better understanding of the susceptible subgroup requiring special caution and to the establishment of effective strategies for prevention.

Immunohistopathology of the Newly Discovered Giant Papillae Tongue Disorder in Organ-Transplanted Children

BACKGROUND

Giant papillae tongue disorder (GPTD) is a newly discovered, long-lasting clinical disorder that may develop in organ-transplanted pediatric recipients. The key feature of this disorder is the unique tongue lesion, which comprises swollen fungiform papillae. The aim of this study was to characterize the immunohistopathology of this novel inflammatory condition.

METHODS

Six organ transplanted children with GPTD were included in the study. Routine histopathology and immunohistochemical stainings for CD3, CD4, CD8, CD25, FOXP3, CD20, CD138, CD68, CD1a, CD15, CD23, and mast cell tryptase were performed.

RESULTS

Immunohistochemical analyses of the oral lesions revealed a subepithelial infiltrate that was primarily composed of CD3- and CD4-positive T cells, CD20-expressing B cells, macrophages, and CD138-positive plasma cells. The CD20-positive cells did not display the typical B cell morphology, having in general a more dendritic cell-like appearance. The CD138-expressing plasma cells were distinctly localized as a dense infiltrate beneath the accumulation of T cells and B cells. Increased numbers of CD1a-expressing Langerhans cells were detected both in the epithelium and connective tissue. Because no granulomas were observed and only single lesional eosinophils were detected, GPTD does not resemble a granulomatous or eosinophilic condition.

CONCLUSIONS

We describe for the first time the immunopathological characteristics of a novel inflammatory disorder of the oral cavity, which may develop after solid organ transplantation in children.

Food allergies developing after solid organ transplant

The development of food allergy is an increasingly recognized form of morbidity after solid organ transplant. It occurs more commonly in liver transplant recipients, although it has also been reported in heart, lung, kidney, and intestinal transplants. Pediatric transplant recipients are more likely to develop symptoms compared to adults, and reports of frequency vary widely from 5% to 38% in pediatric liver transplant recipients. Multiple mechanisms have been proposed in the literature, although no single mechanism can yet account for all reported observations. As food allergy can have at worst potentially fatal consequences, and at best require lifestyle adjustment through food avoidance, it is important for recipients to be aware of the donor's food allergies and particularly in pediatrics, the possibility of completely de novo allergies. This review explores the recent reports surrounding food allergy after solid organ transplant, including epidemiology, proposed mechanisms, and implications for practice.

Cytokine profile of food-allergic post-liver transplant children is identified by high levels of IL-5 and low IL-10 secretion from patients' peripheral blood mononuclear cells

Severe allergic reaction to food following liver transplantation is a well-known phenomenon. However, the mechanisms underlying this phenomenon are not yet elucidated. This study aimed to reveal the nature of the immune response in post-transplanted allergic patients and compare them to non-allergic transplanted as well as allergic and non-allergic control subjects, with focus on cytokine milieu. Post-liver transplant patients with and without allergic reactions as well as food-allergic but otherwise healthy and healthy non-allergic control patients were recruited. We reviewed patient records and routine laboratory tests and assayed subjects' PBMCs, studying cytokine secretion profile in response to different stimuli. Post-transplant patients with food allergy showed a unique cytokine profile in response to various stimuli, with extremely elevated IL-5, low IL-10 secretion, and somewhat higher IFN-γ. T regulatory cell number was not significantly different among the groups of patients and controls. Immune response of food-allergic post-liver transplant patients is identified by a unique cytokine profile when compared to allergic but otherwise healthy individuals.

Increased 4-hydroxynonenal protein adducts in male GSTA4-4/PPAR-α double knockout mice enhance injury during early stages of alcoholic liver disease

To test the significance of lipid peroxidation in the development of alcoholic liver injury, an ethanol (EtOH) liquid diet was fed to male 129/SvJ mice (wild-type, WT) and glutathione S-transferase A4-4-null (GSTA4-/-) mice for 40 days. GSTA4-/- mice were crossed with peroxisome proliferator-activated receptor-α-null mice (PPAR-α-/-), and the effects of EtOH in the resulting double knockout (dKO) mice were compared with the other strains. EtOH increased lipid peroxidation in all except WT mice (P < 0.05). Increased steatosis and mRNA expression of the inflammatory markers CXCL2, tumor necrosis factor-α (TNF-α), and α-smooth muscle actin (α-SMA) were observed in EtOH GSTA4-/- compared with EtOH WT mice (P < 0.05). EtOH PPAR-α-/- mice had increased steatosis, serum alanine aminotransferase (ALT), and hepatic CD3+ T cell populations and elevated mRNA encoding CD14, CXCL2, TNF-α, IL-6, CD138, transforming growth factor-β, platelet-derived growth factor receptor-β (PDGFR-β), matrix metalloproteinase (MMP)-9, MMP-13, α-SMA, and collagen type 1 compared with EtOH WT mice. EtOH-fed dKO mice displayed elevation of periportal hepatic 4-hydroxynonenal adducts and serum antibodies against malondialdehyde adducts compared with EtOH feeding of GSTA4-/-, PPAR-α-/-, and WT mice (P < 0.05). ALT was higher in EtOH dKO mice compared with all other groups (P < 0.001). EtOH-fed dKO mice displayed elevated mRNAs for TNF-α and CD14, histological evidence of fibrosis, and increased PDGFR, MMP-9, and MMP-13 mRNAs compared with the EtOH GSTA4-/- or EtOH PPAR-α-/- genotype (P < 0.05). These findings demonstrate the central role lipid peroxidation plays in mediating progression of alcohol-induced necroinflammatory liver injury, stellate cell activation, matrix remodeling, and fibrosis.

New developments in transplant-acquired allergies

Transplant-acquired allergy (TAA) was firstly described as transplant-acquired food allergy (TAFA) after bone marrow transplantations and mostly observed in a transient form. The picture is complicated by numerous case reports of TAFA after the receipt of liver grafts from donors with no documented history of food allergy. The estimated prevalence of TAFA among young children in the literature has been documented in various studies ranging from 6% to 57%. Although TAA is mostly found to be associated with liver transplantation; it has been recently reported to be related with heart, intestinal, lung and even renal transplantations in adults. Previous reviews of published cases of liver TAA misleadingly emphasized the predominance of children and the absence of TAA in cardiac, pulmonary, and renal transplant recipients. In different studies, the male/female ratio is equal. Literature data suggest that children with TAFA typically present within the first year after surgery and are typically allergic to multiple foods. The pathogenesis of TAA is not still completely understood. Most of the studies support the concept that the functioning liver itself, and not only tacrolimus immunosuppression, is one of the main contributors to TAA in these patients. In the light of recent findings, other possible mechanisms can be summarized as following: (1) the recovery of delayed type hypersensitivity; (2) late manifestation of food allergy; (3) intestinal injury as well as inhibition of cellular energy production by tacrolimus; and (4) transfer of food-specific IgE or lymphocytes. Thus, interplay between hematopoietic cells from the transplanted organ and recipient specific factors (e.g., younger age and atopic background) seem to underlie the development of TAA. Most patients will have symptomatic improvement following reduced immunosuppression and an appropriately restricted diet. Nevertheless, some studies suggest that atopic diseases occur in some of pediatric liver transplant recipients, with manifestations including food allergy, eczema, allergic rhinitis, and asthma. More studies would be needed including greater number of patients to determine whether TAA is transient or not in pediatric/adult solid organ recipients.

Post-transplant food allergy in children is associated with liver and not with renal transplantation: a monocentric comparative study

Food allergy is increasingly reported after paediatric liver transplantation. The underlying physiopathological mechanism remains incompletely understood. Therefore, we aimed to determine the incidence, clinical presentation, possible risk factors, and prognosis of post-transplant food allergy in children currently followed after liver and renal transplantation. The study population consists of 49 liver and 21 renal transplant patients transplanted between the age of 22 months and 15 years. Data were collected retrospectively from medical records and via a doctor's questionnaire taken from the parents in a monocentric setting. Post-transplant food allergy has developed in 13 liver transplant patients and in none of the renal transplant recipients. Within the liver transplant group, median age at liver transplantation is significantly lower in the food-allergic (10 months) versus non-food-allergic group (3.3 years; p = 0.002). The use of tacrolimus as primary maintenance immunosuppression is associated with food allergy (p = 0.032) and mean donor age is significantly lower in the food-allergic group (p = 0.009). Compared to the renal transplant group, median age at transplantation is significantly lower in the liver patients (p < 0.001). No significant differences are found in primary immunosuppressive regimens between renal and liver transplant patients.

CONCLUSION

Post-transplant food allergy is an important clinical problem in children after liver transplantation which does not affect renal transplant patients despite similar immunosuppressive regimens. Within the group of liver transplant recipients, tacrolimus use, young age at time of transplant and younger donor age were associated with the development of food allergy.

Toll-like receptor activation in basophils contributes to the development of IgG4-related disease

BACKGROUND

IgG4-related disease (IRD) is characterized by systemic IgG4 antibody responses and by infiltration of IgG4-expressing plasma cells into the affected organs. Although T helper type 2 (Th2) cytokines are implicated in enhanced IgG4 responses, molecular mechanisms accounting for the development of IgG4 antibody responses are poorly defined. Since basophils function as antigen-presenting cells for Th2 responses, we tried to clarify the role of basophils in the development of IgG4 responses in this study.

METHODS

IgG4 and cytokine responses to various nucleotide-binding oligomerization domain-like receptor and Toll-like receptor (TLR) ligands were examined by using basophils isolated from healthy controls and from patients with IgG4-related disease.

RESULTS

Activation of TLRs in basophils from healthy controls induced IgG4 production by B cells, which effect was associated with enhanced production of B cell activating factor (BAFF) and IL-13. In addition, activation of TLRs in basophils from patients with IRD induced a large amount of IgG4 by B cells from healthy controls. This enhancement of IgG4 production was again associated with BAFF and IL-13.

CONCLUSIONS

These data suggest that innate immune responses mediated through TLRs may play a role in the development of IgG4-related disease, in part by production of BAFF from basophils.

De novo food sensitization and eosinophilic gastrointestinal disease in children post-liver transplantation

BACKGROUND

Children have increased prevalence of food allergy (FA) and eosinophilic gastrointestinal disease (EGID) following liver transplantation. The aim of this study was to identify related risk factors.

METHODS

Chart review of pediatric liver transplant (LT) recipients with de novo FA and/or EGID post-LT and non-allergic controls.

RESULTS

We identified 30 (8.5%) children with FA and/or EGID among 352 pediatric LT recipients. Median age at transplant was 0.9 inter-quartile range (IQR 0.6-2.0) years. FA developed at a median 1.0 (IQR 0.5-8.2) yr post-LT and manifested with gastrointestinal symptoms (53%) or urticaria/angioedema (40%). Commonly avoided foods included milk (60%), egg (57%), and peanut (47%). Of the 15 children with FA who underwent endoscopy, 11 had eosinophilic infiltrates in multiple segments of the esophagus alone or in combination with other bowel segments. FA and EGID were linked to transplantation at a younger age (median, 0.9 vs. 5.5 yr), higher frequency of blood eosinophilia, and prior history of rhinitis and atopic dermatitis. Tacrolimus use and tacrolimus serum levels were similar between allergic subjects and controls.

CONCLUSIONS

Findings suggest that exposure to tacrolimus alone post-LT is insufficient to initiate de novo allergic disease in LT recipients; rather, younger age and underlying predisposition to atopic disease may play larger roles.

IgE-mediated systemic anaphylaxis and impaired tolerance to food antigens in mice with enhanced IL-4 receptor signaling

BACKGROUND

In atopic subjects food ingestion drives the production of IgE antibodies that can trigger hypersensitivity reactions. The IL-4 pathway plays a critical role in this response, and genetic polymorphisms in its components have been linked to allergy.

OBJECTIVE

We sought to test whether an activating mutation in the IL-4 receptor (IL-4R) α chain enhances allergic responses to a food antigen.

METHODS

F709 mice, in which the IL-4Rα immunoreceptor tyrosine-based inhibitory motif is inactivated, were gavage fed with ovalbumin (OVA). Reactions to OVA challenge and immune responses, including antibody production and T(H)2 responses, were assessed.

RESULTS

F709 mice, but not wild-type control animals, sensitized by means of gavage with OVA and either cholera toxin or staphylococcal enterotoxin B, displayed mast cell activation and systemic anaphylaxis on enteral challenge. Anaphylaxis was elicited even in F709 mice enterally sensitized with OVA alone. Bone marrow chimera experiments established that the increased sensitivity conferred by the F709 genotype was mediated mostly by hematopoietic cells but that nonhematopoietic cells also contributed. F709 mice exhibited increased intestinal permeability to macromolecules. The F709 genotype conferred increased OVA-specific IgE but not IgG1 responses, local and systemic T(H)2 responses, and intestinal mast cell hyperplasia compared with wild-type mice. Anaphylaxis was abrogated in F709 mice lacking IgE or the high-affinity receptor for IgE (FcεRI).

CONCLUSION

Augmented IL-4Rα signaling confers increased intestinal permeability and dramatically enhanced sensitivity to food allergens. Unlike anaphylaxis to injected antigens, which in rodents can be mediated by either IgE or IgG antibodies, the food-induced response in F709 mice is solely IgE dependent.

Food allergy: transfused and transplanted

The inadvertent transfer of food allergy from an allergic donor to an unsuspecting recipient by transfusion or organ donation is a relatively rare but intriguing event with potentially catastrophic consequences. Additionally, the development of food allergy in the recipient of a transplant from a donor who was not food allergic poses questions about why this occurs, why it is observed more frequently in some situations than others, and the mechanisms that may be involved. In this review, the transfer of food allergy by transfusion, bone marrow transplantation, and the transplantation of different solid organs is explored, and potential mechanisms in addition to the importance of careful monitoring are discussed.

New-onset post-transplantation food allergy in children--is it attributable only to the immunosuppressive protocol?

New-onset post-transplantation food allergy has been described mainly after liver transplantation, and its pathogenesis was attributed to the immunomodulatory effects of tacrolimus therapy. The aim of the present study was to evaluate the association of food allergy with solid organ transplantation in our center. The medical records of children who underwent kidney transplantation and children who underwent liver or liver and kidney transplantation from 1986 to 2005 were reviewed. A total of 189 children (124 after kidney transplantation, 65 after liver or liver and kidney transplantation) received tacrolimus as part of the immunosuppressive regimen. New-onset post-transplantation food allergy was documented in four of them: two with liver transplants and two with combined kidney and liver transplants. The absence of new-onset food allergy in the children with isolated kidney transplants is compatible with other reports in the literature. This study supports the concept that the functioning liver itself, and not only tacrolimus immunosuppression, is a main contributor to food allergy in this patient population.

Two distinct T cell subsets, CD4+ and CD8+CD60+, and their cytokines are required for in vitro induction of human ragweed-specific memory IgE responses

CD8(+)CD60(+) T cells (80-98% CD45RO(+); 20% CD23(+)) are significantly increased in the blood of serum IgE(+) ragweed-sensitized (RS) compared with serum IgE-nonatopic humans (p = 0.001). CD8(+)CD60(+) T cells of the RS patients produced IL-2, IL-4, IL-10, IL-12, IFN-alpha. and IFN-gamma, but not IL-6 or IL-13. When their PBMC were cultured with ragweed Ag (RA), peak IgE responses occurred on day 10; none was induced with non-cross-reacting or without Ag; nonatopic PBMC did not respond to any stimulant. When either CD4(+) or CD8(+)CD60(+) T cells were depleted from RS PBMC before culture with RA, no IgE responses were induced. If purified CD4(+) T cells or low numbers of CD8(+)CD60(+) T cells were added back to the depleted PBMC, IgE responses were restored. However, higher numbers of CD8(+)CD60(+) T cells totally suppressed IgE responses. Total suppression also was obtained when RS PBMC were cultured with RA and either anti-IL-2, IL-4, IL-10, IL-12, IFN-gamma (all concentrations), or IFN-alpha (low concentrations), but not anti-IL-6 or IL-13. Higher concentrations of anti-IFN-alpha potentiated IgE responses.

Molecular mechanisms of portal vein tolerance

The liver has been considered as a tolerogenic organ in the sense that favors the induction of peripheral tolerance. The administration of antigens (Ags) via the portal vein causes tolerance, which is termed portal vein tolerance and can explain the occurrence of tolerogenic responses in the liver. Here we discuss the fundamental mechanisms accounting for portal vein tolerance. Antigen-presenting cells (APCs) in the liver, especially dendritic cells and sinusoidal endothelial cells, have limited the ability to produce pro-inflammatory cytokines upon stimulation with endotoxin, an effect that could be due to the continuous exposure to bacterial Ags derived from intestinal microflora. Ag presentation by liver APCs results in T cell tolerance through clonal deletion and selection of regulatory T cells. Thus, APCs with immunosuppressive functions are associated with the achievement of portal vein tolerance via the induction of clonal deletion and generation of regulatory T cells.

Seafood allergy: lessons from clinical symptoms, immunological mechanisms and molecular biology

Food allergy consists of a wide range of disorders that result from adverse immune responses to dietary antigens. Manifestations of allergic response includes acute, potentially fatal anaphylactic reactions and a variety of chronic diseases that mainly affect the gastrointestinal tract, skin, and respiratory tract. Tools for clinical diagnosis and management, which have not changed much in the past two decades, include the clinical history, tests for specific IgE antibody to suspected foods, elimination diets, oral food challenges, and provision of medications such as epinephrine for emergency treatment. On the other hand, recent immunological and molecular biological research have enhanced our understanding of the mechanisms of these disorders and revealed the identities of many food allergens. Here, we will discuss seafood allergies with respect to the clinical manifestations, diagnosis, immunological mechanisms, and molecular biology of seafood allergens. Furthermore, potential applications and future directions in the clinical management of seafood allergies are discussed.

Food allergy: what do we learn from animal models?

PURPOSE OF REVIEW

This review summarizes selected articles on animal models of food allergy published in 2003. The research areas that are covered include mechanistic studies, the search for new therapies, as well as screening models for hazard identification of potential allergens.

RECENT FINDINGS

Novel treatment options of both prevention and therapeutic strategies have been reported with promising results. The induction of de-sensitization to food proteins was achieved by exposure to a mixture of recombinant food allergens and T helper 1 (Th1)-skewing bacterial components. Furthermore, research in animal models has provided new insights into the role of protein structure, digestion, and gut permeability in sensitization and tolerance induction to food proteins. The Th2 hypothesis of food allergy was tested in mouse strains, linking genetic susceptibility to sensitization with differential Th1-Th2 responses. In this context, the role of the liver in development of food antigen-specific Th2 cells, and the importance of costimulatory molecules in Th2 skewing were demonstrated. Finally, rodent models to predict potential allergenicity of novel foods have been further developed using different routes of sensitization.

SUMMARY

Currently, several animal models of food allergy are used, including mouse, rat, swine, and dog. Continuing research in these models may elucidate the immunological mechanisms that underlie the sensitization and challenge phase of food allergy and may result in improved therapeutic options. Furthermore, the development of animal models to predict relative allergenicity of novel foods remains an important topic.