IgE receptor and signal transduction in mast cells and basophils

The B Cell Response and Formation of Allergenic and Anti-Allergenic Antibodies in Food Allergy

Food allergies are a growing public health concern worldwide, especially in children and young adults. Allergen-specific IgE plays a central role in the pathogenesis of food allergies, but their titers poorly correlate with allergy development. Host immune systems yield allergen-specific immunoglobulin (Ig)A, IgE and IgG subclasses with low or high affinities and differential Fc N-glycosylation patterns that can affect the allergic reaction to food in multiple ways. High-affinity IgE is required to induce strong mast cell activation eventually leading to allergic anaphylaxis, while low-affinity IgE can even inhibit the development of clinically relevant allergic symptoms. IgA and IgG antibodies can inhibit IgE-mediated mast cell activation through various mechanisms, thereby protecting IgE-positive individuals from allergy development. The production of IgE and IgG with differential allergenic potential seems to be affected by the signaling strength of individual B cell receptors, and by cytokines from T cells. This review provides an overview of the diversity of the B cell response and the diverse roles of antibodies in food allergy.

Further explorations into the role of mast cells in deaths associated with fatal asphyxia: an immunohistochemical study utilizing CD 117 marker

Asphyxia-related deaths have always been a challenging task in the speciality of forensic pathology. Apart from helpful macroscopical signs (e.g., strangulation mark, cyanosis, petechial haemorrhage, and lung oedema), recent literature indicates that prolonged asphyxia is sufficient to induce an increase in mast cells (MC). Inflammatory cells migrate from the bone marrow to the lungs, aiding in the diagnosis of fatal asphyxial deaths. HIF1-α, a key regulator protein, is released from lung tissue capillaries during catastrophic hypoxia circumstances, as previously demonstrated in immunohistochemistry (IHC) research. The present study analyzed lung samples from 164 medico-legal autopsy cases, including 57 asphyxia/hypoxia deaths and 107 controls (non-asphyxial deaths). Peribronchial, perivascular and perialveolar MCs were detected using CD117 antibody, and the average of MCs in each of these locations was noted in each case. The results indicated a statistically significant increase in peribronchial and perialveolar mast cells (MC) in fatal asphyxial deaths, including those caused by hanging, drowning, or postural asphyxia. Peri-bronchial MC in lung sections of asphyxial deaths were in the range of 0.2-5.4 and in non-asphyxial samples were in the range of 0.0-2.2. Peri-alveolar MCs in lung sections of asphyxial deaths were in the range of 0.0-0.6 and in non-asphyxial samples were in the range of 0.0-0.2. Our data suggest that mast cells (MC) play an important role in fatal hypoxia-related mortality and CD 117 may be a reliable marker for detection of mast cells in asphyxial deaths. It could be very beneficial to forensic pathologists tasked with differentiating fatal asphyxia fatalities from other causes of death.

Quantitative estimation of TNF-α and IL-3 by using ELISA from human lung tissue in fatal asphyxial deaths

Asphyxia-related deaths have always been a challenging task in the specialty of forensic pathology. Apart from helpful macroscopical signs (e.g., strangulation marks, cyanosis, petechial haemorrhage, and lung edema), recent literature indicates that prolonged asphyxia is sufficient to induce an increase in mast cells (MC). Inflammatory cells migrate from the bone marrow to the lungs, aiding in the diagnosis of fatal asphyxial death. The present study analyzed human lung tissue samples from 90 medico-legal autopsy cases, including 45 asphyxial deaths and 45 controls (non-asphyxial deaths). The cases ranged from 2 to 68 years, with a mean age of 33.23 years. In 90 cases, 74 cases were of males, and 16 were of females. Human lung tissue samples were analyzed by using the sandwich ELISA method. The results indicated a statistically significant increase in TNF-α and IL-3 concentration in fatal asphyxial deaths, including those caused by hanging, drowning, and smothering. Mean ± SD in asphyxial and non-asphyxial cases for the TNF-α and IL-3 concentration statistically analysed. In asphyxial cases, the average IL-3 concentration (Conc.) was 1558.50 ± 350.53 pg/ml, and the average TNF-α concentration (Conc.) was 499.75 ± 479.41 pg/ml. In contrast, in non-asphyxial cases, the average IL-3 concentration (Conc.) was found to be 849.73 ± 484.99 pg/ml, and the average TNF-α concentration (Conc.) was 208.08 ± 81.23 pg/ml. The mean change in IL-3 and TNF-α (Conc.) values are found to significant (<0.01) in asphyxial cases as compared to non-asphyxial cases. The ROC (Receiver operating characteristic curve) analysis revealed that TNF-α (AUC = 0.89) and IL-3 (AUC = 0.87) concentration (conc.) were stronger predictors of asphyxial deaths with an optimal cut-off value of 455.20 pg/ml for TNF-alpha and 1700.62 pg/ml for IL-3 respectively. Our findings imply that mast cells (MC) are critical in fatal hypoxia-related mortality and that TNF-α and IL-3 can be reliable markers for detecting mast cells in asphyxial deaths. It could be very beneficial to forensic pathologists tasked with differentiating fatal asphyxial fatalities from other causes of death.

Anti-atopic dermatitis effects of Parasenecio auriculatus via simultaneous inhibition of multiple inflammatory pathways

The treatment of atopic dermatitis (AD) is challenging due to its complex etiology. From epidermal disruption to chronic inflammation, various cells and inflammatory pathways contribute to the progression of AD. As with immunosuppressants, general inhibition of inflammatory pathways can be effective, but this approach is not suitable for long-term treatment due to its side effects. This study aimed to identify a plant extract (PE) with anti-inflammatory effects on multiple cell types involved in AD development and provide relevant mechanistic evidence. Degranulation was measured in RBL-2H3 cells to screen 30 PEs native to South Korea. To investigate the anti-inflammatory effects of Parasenecio auriculatus var. matsumurana Nakai extract (PAE) in AD, production of cytokines and nitric oxide, activation status of FcεRI and TLR4 signaling, cell-cell junction, and cell viability were evaluated using qRT-PCR, western blotting, confocal microscopy, Griess system, and an MTT assay in RBL-2H3, HEK293, RAW264.7, and HaCaT cells. For in vivo experiments, a DNCB-induced AD mouse model was constructed, and hematoxylin and eosin, periodic acid-Schiff, toluidine blue, and F4/80-staining were performed. The chemical constituents of PAE were analyzed by HPLC-MS. By measuring the anti-degranulation effects of 30 PEs in RBL-2H3 cells, we found that Paeonia lactiflora Pall., PA, and Rehmannia glutinosa (Gaertn.) Libosch. ex Steud. show an inhibitory activity of more than 50%. Of these, PAE most dramatically and consistently suppressed cytokine expression, including IL-4, IL-9, IL-13, and TNF-α. PAE potently inhibited FcεRI signaling, which mechanistically supports its basophil-stabilizing effects, and PAE downregulated cytokines and NO production in macrophages via perturbation of toll-like receptor signaling. Moreover, PAE suppressed cytokine production in keratinocytes and upregulated the expression of tight junction molecules ZO-1 and occludin. In a DNCB-induced AD mouse model, the topical application of PAE significantly improved atopic index scores, immune cell infiltration, cytokine expression, abnormal activation of signaling molecules in FcεRI and TLR signaling, and damaged skin structure compared with dexamethasone. The anti-inflammatory effect of PAE was mainly due to integerrimine. Our findings suggest that PAE could potently inhibit multi-inflammatory cells involved in AD development, synergistically block the propagation of inflammatory responses, and thus alleviate AD symptoms.

Overexpression of FcεRI on Bone Marrow Mast Cells, but Not MRGPRX2, in Clonal Mast Cell Disorders With Wasp Venom Anaphylaxis

Background

Uncertainties remain about the molecular mechanisms governing clonal mast cell disorders (CMCD) and anaphylaxis.

Objective

This study aims at comparing the burden, phenotype and behavior of mast cells (MCs) and basophils in patients with CMCD with wasp venom anaphylaxis (CMCD/WVA⁺), CMCD patients without anaphylaxis (CMCD/ANA^-), patients with an elevated baseline serum tryptase (EBST), patients with wasp venom anaphylaxis without CMCD (WVA⁺) and patients with a non-mast cell haematological pathology (NMHP).

Methods

This study included 20 patients with CMCD/WVA⁺, 24 with CMCD/ANA^-, 19 with WVA⁺, 6 with EBST and 5 with NMHP. We immunophenotyped MCs and basophils and compared baseline serum tryptase (bST) and both total and venom specific IgE in the different groups. For basophil studies, 13 healthy controls were also included.

Results

Higher levels of bST were found in CMCD patients with wasp venom anaphylaxis, CMCD patients without anaphylaxis and EBST patients. Total IgE levels were highest in patients with wasp venom anaphylaxis with and without CMCD. Bone marrow MCs of patients with CMCD showed lower CD117 expression and higher expression of CD45, CD203c, CD63, CD300a and FcεRI. Within the CMCD population, patients with wasp venom anaphylaxis showed a higher expression of FcεRI as compared to patients without anaphylaxis. Expression of MRGPRX2 on MCs did not differ between the study populations. Basophils are phenotypically and functionally comparable between the different patient populations.

Conclusion

Patients with CMCD show an elevated burden of aberrant activated MCs with a significant overexpression of FcεRI in patients with a wasp venom anaphylaxis.

Neuronal FcεRIα directly mediates ocular itch via IgE-immune complex in a mouse model of allergic conjunctivitis

Background

Classical understanding of allergic conjunctivitis (ACJ) suggests that ocular itch results from a mast cell-dependent inflammatory process. However, treatments that target inflammatory mediators or immune cells are often unsatisfying in relieving the stubborn itch symptom. This suggests that additional mechanisms are responsible for ocular itch in ACJ. In this study, we aim to determine the role of neuronal FcεRIa in allergic ocular itch.

Methods

Calcium imaging was applied to observe the effect of IgE-immune complex in trigeminal neurons. Genomic FcεRIa knockout mice and adeno-associated virus (AAV) mediated sensory neuron FcεRIa knockdown mice were used in conjunction with behavioral tests to determine ocular itch. In addition, immunohistochemistry, Western blot and quantitative RT-PCR were used for in vitro experiments.

Results

We found that FcεRIα was expressed in a subpopulation of conjunctiva sensory neurons. IgE-IC directly activated trigeminal neurons and evoked acute ocular itch without detectible conjunctival inflammation. These effects were attenuated in both a global FcεRIa-knockout mice and after sensory neuronal-specific FcεRIa-knockdown in the mouse trigeminal ganglion. In an ovalbumin (OVA) induced murine ACJ model, FcεRIα was found upregulated in conjunctiva-innervating CGRP+ sensory neurons. Sensory neuronal-specific knockdown of FcεRIa significantly alleviated ocular itch in the ACJ mice without affecting the immune cell infiltration and mast cell activation in conjunctiva. Although FcεRIα mRNA expression was not increased by IgE in dissociated trigeminal ganglion neurons, FcεRIα protein level was enhanced by IgE in a cycloheximide-resistance manner, with concordant enhancement of neuronal responses to IgE-IC. In addition, incremental sensitization gradually enhanced the expression of FcεRIα in small-sized trigeminal neurons and aggravated OVA induced ocular itch.

Conclusions

Our study demonstrates that FcεRIα in pruriceptive neurons directly mediates IgE-IC evoked itch and plays an important role in ocular itch in a mouse model of ACJ. These findings reveal another axis of neuroimmune interaction in allergic itch condition independent to the classical IgE-mast cell pathway, and might suggest novel therapeutic strategies for the treatment of pruritus in ACJ and other immune-related disorders.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02417-x.

Anti-Inflammatory and Anti-Allergic Effects of Saponarin and Its Impact on Signaling Pathways of RAW 264.7, RBL-2H3, and HaCaT Cells

Saponarin{5-hydroxy-2-(4-hydroxyphenyl)-6-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]-7-[3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxychromen-4-one}, a flavone found in young green barley leaves, is known to possess antioxidant, antidiabetic, and hepatoprotective effects. In the present study, the anti-inflammatory, anti-allergic, and skin-protective effects of saponarin were investigated to evaluate its usefulness as a functional ingredient in cosmetics. In lipopolysaccharide-induced RAW264.7 (murine macrophage) cells, saponarin (80 μM) significantly inhibited cytokine expression, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, inducible nitric oxide synthase, and cyclooxygenase (COX)-2. Saponarin (80 μM) also inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 involved in the mitogen-activated protein kinase signaling pathway in RAW264.7 cells. Saponarin (40 μM) significantly inhibited β-hexosaminidase degranulation as well as the phosphorylation of signaling effectors (Syk, phospholipase Cγ1, ERK, JNK, and p38) and the expression of inflammatory mediators (tumor necrosis factor [TNF]-α, IL-4, IL-5, IL-6, IL-13, COX-2, and FcεRIα/γ) in DNP-IgE- and DNP-BSA-stimulated RBL-2H3 (rat basophilic leukemia) cells. In addition, saponarin (100 μM) significantly inhibited the expression of macrophage-derived chemokine, thymus and activation-regulated chemokine, IL-33, thymic stromal lymphopoietin, and the phosphorylation of signaling molecules (ERK, p38 and signal transducer and activator of transcription 1 [STAT1]) in TNF-α- and interferon (IFN)-γ-stimulated HaCaT (human immortalized keratinocyte) cells. Saponarin (100 μM) also significantly induced the expression of hyaluronan synthase-3, aquaporin 3, and cathelicidin antimicrobial peptide (LL-37) in HaCaT cells, which play an important role as skin barriers. Saponarin remarkably inhibited the essential factors involved in the inflammatory and allergic responses of RAW264.7, RBL-2H3, and HaCaT cells, and induced the expression of factors that function as physical and chemical skin barriers in HaCaT cells. Therefore, saponarin could potentially be used to prevent and relieve immune-related skin diseases, including atopic dermatitis.

Hymenoptera Venom Immunotherapy: Immune Mechanisms of Induced Protection and Tolerance

Hymenoptera venom allergy is one of the most severe allergic diseases, with a considerable prevalence of anaphylactic reaction, making it potentially lethal. In this review, we provide an overview of the current knowledge and recent findings in understanding induced immune mechanisms during different phases of venom immunotherapy. We focus on protection mechanisms that occur early, during the build-up phase, and on the immune tolerance, which occurs later, during and after Hymenoptera venom immunotherapy. The short-term protection seems to be established by the early desensitization of mast cells and basophils, which plays a crucial role in preventing anaphylaxis during the build-up phase of treatment. The early generation of blocking IgG antibodies seems to be one of the main reasons for the lower activation of effector cells. Long-term tolerance is reached after at least three years of venom immunotherapy. A decrease in basophil responsiveness correlates with tolerated sting challenge. Furthermore, the persistent decline in IgE levels and, by monitoring the cytokine profiles, a shift from a Th2 to Th1 immune response, can be observed. In addition, the generation of regulatory T and B cells has proven to be essential for inducing allergen tolerance. Most studies on the mechanisms and effectiveness data have been obtained during venom immunotherapy (VIT). Despite the high success rate of VIT, allergen tolerance may not persist for a prolonged time. There is not much known about immune mechanisms that assure long-term tolerance post-therapy.

Significance of detecting postmortem serum IgE in frozen corpses for the diagnosis of anaphylaxis in forensic

The aim of this study was to detect the postmortem serum total IgE levels in frozen corpses and identify whether the death incident caused by an anaphylaxis in forensic medicine. Autopsy cases with pathological death (total, n = 106; 4-214 h postmortem) include cardiac disease (n = 15), pulmonary infection (n = 12), central nervous system disorder (n = 6), pulmonary emboliszn (n = 7), hapetic disease (n = 5), kidney disease (n = 6), enteric disease (n = 10), necrotizing pancreatitis (n = 7), diffuse peritonitis (n = 6), MODS (n = 6), toxicosis (n = 5:), anaphylactic shock (n = 7), bronchial asthma (n = 8) and other disease (n = 6) were examined. Results showed that there was no significant difference between serum IgE levels and ages, postmortem intervals (PMIs), gender as well as survival time. Serum IgE levels of deaths due to anaphylactic shock and bronchial asthma were higher than that of other groups. Forensic pathology examination results showed the main pathology changes of bronchial asthma were mucous congestion in bronchial lumen and eosinophils infiltration in bronchial mucosa. The main pathological features of anaphylactic shock were laryngeal edema and eosinophils infiltration in multiple organs (lung and spleen). This research proved that there was a great significance for IgE to infer whether the individual died due to an anaphylaxis even for a long PMI in frozen corpses. Furthermore, we can also preliminarily determine the type of allergic death combined with the examination of forensic pathology. These findings further verify the feasibility of postmortem serum IgE in the diagnosis of forensic causes of death and broaden the application scope of this marker.

Mast Cell Regulation and Irritable Bowel Syndrome: Effects of Food Components with Potential Nutraceutical Use

Mast cells are key actors in inflammatory reactions. Upon activation, they release histamine, heparin and nerve growth factor, among many other mediators that modulate immune response and neuron sensitization. One important feature of mast cells is that their population is usually increased in animal models and biopsies from patients with irritable bowel syndrome (IBS). Therefore, mast cells and mast cell mediators are regarded as key components in IBS pathophysiology. IBS is a common functional gastrointestinal disorder affecting the quality of life of up to 20% of the population worldwide. It is characterized by abdominal pain and altered bowel habits, with heterogeneous phenotypes ranging from constipation to diarrhea, with a mixed subtype and even an unclassified form. Nutrient intake is one of the triggering factors of IBS. In this respect, certain components of the daily food, such as fatty acids, amino acids or plant-derived substances like flavonoids, have been described to modulate mast cells' activity. In this review, we will focus on the effect of these molecules, either stimulatory or inhibitory, on mast cell degranulation, looking for a nutraceutical capable of decreasing IBS symptoms.

Is There a Role for Basophils in Cancer?

Basophils were identified in human peripheral blood by Paul Ehrlich over 140 years ago. Human basophils represent <1% of peripheral blood leukocytes. During the last decades, basophils have been described also in mice, guinea pigs, rabbits, and monkeys. There are many similarities, but also several immunological differences between human and mouse basophils. There are currently several strains of mice with profound constitutive or inducible basophil deficiency useful to prove that these cells have specific roles in vivo. However, none of these mice are solely and completely devoid of all basophils. Therefore, the relevance of these findings to humans remains to be established. It has been known for some time that basophils have the propensity to migrate into the site of inflammation. Recent observations indicate that tissue resident basophils contribute to lung development and locally promote M2 polarization of macrophages. Moreover, there is increasing evidence that lung-resident basophils exhibit a specific phenotype, different from circulating basophils. Activated human and mouse basophils synthesize restricted and distinct profiles of cytokines. Human basophils produce several canonical (e.g., VEGFs, angiopoietin 1) and non-canonical (i.e., cysteinyl leukotriene C₄) angiogenic factors. Activated human and mouse basophils release extracellular DNA traps that may have multiple effects in cancer. Hyperresponsiveness of basophils has been demonstrated in patients with JAK2^V617F-positive polycythemia vera. Basophils are present in the immune landscape of human lung adenocarcinoma and pancreatic cancer and can promote inflammation-driven skin tumor growth. The few studies conducted thus far using different models of basophil-deficient mice have provided informative results on the roles of these cells in tumorigenesis. Much more remains to be discovered before we unravel the hitherto mysterious roles of basophils in human and experimental cancers.

Effects of Apigenin on RBL-2H3, RAW264.7, and HaCaT Cells: Anti-Allergic, Anti-Inflammatory, and Skin-Protective Activities

Apigenin (4',5,7-trihydroxyflavone, flavonoid) is a phenolic compound that is known to reduce the risk of chronic disease owing to its low toxicity. The first study on apigenin analyzed its effect on histamine release in the 1950s. Since then, anti-mutation and antitumor properties of apigenin have been widely reported. In the present study, we evaluated the apigenin-mediated amelioration of skin disease and investigated its applicability as a functional ingredient, especially in cosmetics. The effect of apigenin on RAW264.7 (murine macrophage), RBL-2H3 (rat basophilic leukemia), and HaCaT (human immortalized keratinocyte) cells were analyzed. Apigenin (100 μM) significantly inhibited nitric oxide (NO) production, cytokine expression (interleukin (IL)-1β, IL6, cyclooxygenase (COX)-2, and inducible nitric oxide synthase [iNOS]), and phosphorylation of mitogen-activated protein kinase (MAPK) signal molecules, including extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK) in RAW264.7 cells. Apigenin (30 M) also inhibited the phosphorylation of signaling molecules (Lyn, Syk, phospholipase Cγ1, ERK, and JNK) and the expression of high-affinity IgE receptor FcεRIα and cytokines (tumor necrosis factor (TNF)-α, IL-4, IL-5, IL-6, IL-13, and COX-2) that are known to induce inflammation and allergic responses in RBL-2H3 cells. Further, apigenin (20 μM) significantly induced the expression of filaggrin, loricrin, aquaporin-3, hyaluronic acid, hyaluronic acid synthase (HAS)-1, HAS-2, and HAS-3 in HaCaT cells that are the main components of the physical barrier of the skin. Moreover, it promoted the expression of human β-defensin (HBD)-1, HBD-2, HBD-3, and cathelicidin (LL-37) in HaCaT cells. These antimicrobial peptides are known to play an important role in the skin as chemical barriers. Apigenin significantly suppressed the inflammatory and allergic responses of RAW264.7 and RBL cells, respectively, and would, therefore, serve as a potential prophylactic and therapeutic agent for immune-related diseases. Apigenin could also be used to improve the functions of the physical and chemical skin barriers and to alleviate psoriasis, acne, and atopic dermatitis.

An FcεRI-IgE-based genetically encoded microfluidic cell sensor for fast Gram-negative bacterial screening in food samples

An FcεRI-IgE-based genetically encoded microfluidic cell sensor was constructed for fast Gram-negative bacterial screening in food samples. CD14-Fcε IgE, produced by the gene engineered antibodies (GEAs) technology, was used for the recognition of the target bacteria or lipopolysaccharide (LPS). Stable cell lines expressing GCaMP6s, a genetically encoded indicator of calcium flux, were first established for monitoring mast cell activation and improving detection sensitivity. The microfluidic system was designed to improve automation and control the reaction time. Once Gram-negative bacteria bound to the CD14-Fcε IgE on the RBL-2H3 cell surface, RBL-2H3 cell receptor (FcεRI)-induced Ca2+ signaling pathway was immediately activated to release Ca2+. The elevated intracellular Ca2+ triggers GCaMP6s for reporting the presence of Gram-negative bacteria. The developed biosensor was able to detect 80 CFU mL-1 Gram-negative bacteria within 2.5 min in pure culture samples. The biosensor was used to detect Gram-negative bacteria in pork samples. With its short screening time and easy operation, the proposed biosensor shows promise in future applications of foodborne pathogen testing in 1 h to 1 day.

Inflammation-induced IgE promotes epithelial hyperplasia and tumour growth

IgE is the least abundant circulating antibody class but is constitutively present in healthy tissues bound to resident cells via its high-affinity receptor, FcεRI. The physiological role of endogenous IgE antibodies is unclear but it has been suggested that they provide host protection against a variety of noxious environmental substances and parasitic infections at epithelial barrier surfaces. Here we show, in mice, that skin inflammation enhances levels of IgE antibodies that have natural specificities and a repertoire, VDJ rearrangements and CDRH3 characteristics similar to those of IgE antibodies in healthy tissue. IgE-bearing basophils are recruited to inflamed skin via CXCL12 and thymic stromal lymphopoietin (TSLP)/IL-3-dependent upregulation of CXCR4. In the inflamed skin, IgE/FcεRI-signalling in basophils promotes epithelial cell growth and differentiation, partly through histamine engagement of H1R and H4R. Furthermore, this IgE response strongly drives tumour outgrowth of epithelial cells harbouring oncogenic mutation. These findings indicate that natural IgE antibodies support skin barrier defences, but that during chronic tissue inflammation this role may be subverted to promote tumour growth.

An overview on marine anti-allergic active substances for alleviating food-induced allergy

Food provides energy and various nutrients and is the most important substance for the survival of living beings. However, for allergic people, certain foods cause strong reactions, and sometimes even cause shock or death. Food allergy has been recognized by the World Health Organization (WHO) as a major global food safety issue which affect the quality of life of nearly 5% of adults and 8% of children, and the incidence continues to rise but there is no effective cure. Drug alleviation methods for food allergies often have shortcomings such as side effects, poor safety, and high cost. At present, domestic and foreign scientists have turned to research and develop various new, safe and efficient natural sources of hypoallergenic or anti-allergic drugs or foods. There are many kinds of anti-allergic substances obtained from the plants and animals have been reported. Besides, probiotics and bifidobacteria also have certain anti-allergic effects. Of all the sources of anti-allergic substances, the ocean is rich in effective active substances due to its remarkable biodiversity and extremely complex living environment, and plays a huge role in the field of anti-food allergy. In this paper, the anti-food allergic bioactive substances isolated from marine organisms encompassing marine microbial, plant, animal sources and their mechanism were reviewed and the possible targets of anti-allergic substances exerting effects are illustrated by drawing. In addition, the development prospects of marine anti-allergic market are discussed and forecasted, which can provide reference for future research on anti-allergic substances.

Deletion of ΔdblGata motif leads to increased predisposition and severity of IgE-mediated food-induced anaphylaxis response

BACKGROUND

Previous studies have revealed an important role for the transcription factor GATA-1 in mast cell maturation and degranulation. However, there have been conflicting reports with respect to the requirement of GATA-1 function in mast cell dependent inflammatory processes. Herein, we examine the requirement of GATA-1 signaling in mast cell effector function and IgE-mast cell-dependent anaphylaxis.

OBJECTIVE

To study the requirement of GATA-1 dependent signaling in the development and severity of IgE-mast cell-dependent anaphylaxis in mice.

METHODS

Wild type (Balb/c) and mutant ΔdblGata (Balb/c) mice were employed to study the role of GATA-1 signaling in in vitro IgE-mediated activation of bone marrow derived mast cells (BMMCs). Murine models of passive IgE-mediated and oral antigen-induced IgE-mediated anaphylaxis were employed in mice. Frequency of steady state mast cells in various tissues (duodenum, ear, and tongue), peritoneal cavity, and clinical symptoms (diarrhea, shock, and mast cell activation) and intestinal Type 2 immune cell analysis including CD4+ Th2 cells, type 2 innate lymphoid cells (ILC2), and IL-9 secreting mucosal mast cells (MMC9) were assessed.

RESULTS

In vitro analysis revealed that ΔdblGata BMMCs exhibit a reduced maturation rate, decreased expression of FcεRIα, and degranulation capacity when compared to their wildtype (WT) counterparts. These in vitro differences did not impact tissue resident mast cell numbers, total IgE, and susceptibility to or severity of IgE-mediated passive anaphylaxis. Surprisingly, ΔdblGata mice were more susceptible to IgE-mast cell-mediated oral antigen induced anaphylaxis. The increased allergic response was associated with increased Type 2 immunity (antigen-specific IgE, and CD4+ TH2 cells), MMC9 cells and small intestine (SI) mast cell load.

CONCLUSION

Diminished GATA-1 activity results in reduced in vitro mast cell FcεRIα expression, proliferation, and degranulation activity. However, in vivo, diminished GATA-1 activity results in normal homeostatic tissue mast cell levels and increased antigen-induced CD4+ Th2 and iMMC9 cell levels and heightened IgE-mast cell mediated reactions.

Combinatorial diversity of Syk recruitment driven by its multivalent engagement with FcεRIγ

Syk/Zap70 family kinases are essential for signaling via multichain immune-recognition receptors such as tetrameric (αβγ2) FcεRI. Syk activation is generally attributed to cis binding of its tandem SH2 domains to dual phosphotyrosines within FcεRIγ-ITAMs (immunoreceptor tyrosine-based activation motifs). However, the mechanistic details of Syk docking on γ homodimers are unresolved. Here, we estimate that multivalent interactions for WT Syk improve cis-oriented binding by three orders of magnitude. We applied molecular dynamics (MD), hybrid MD/worm-like chain polymer modeling, and live cell imaging to evaluate relative binding and signaling output for all possible cis and trans Syk-FcεRIγ configurations. Syk binding is likely modulated during signaling by autophosphorylation on Y130 in interdomain A, since a Y130E phosphomimetic form of Syk is predicted to lead to reduced helicity of interdomain A and alter Syk's bias for cis binding. Experiments in reconstituted γ-KO cells, whose γ subunits are linked by disulfide bonds, as well as in cells expressing monomeric ITAM or hemITAM γ-chimeras, support model predictions that short distances between γ ITAM pairs are required for trans docking. We propose that the full range of docking configurations improves signaling efficiency by expanding the combinatorial possibilities for Syk recruitment, particularly under conditions of incomplete ITAM phosphorylation.

Nothofagin suppresses mast cell-mediated allergic inflammation

Mast cells play a major role in immunoglobulin E-mediated allergic inflammation, which is involved in asthma, atopic dermatitis, and allergic rhinitis. Nothofagin has been shown to ameliorate various inflammatory responses such as the septic response and vascular inflammation. In this study, we assessed the inhibitory effect of nothofagin on allergic inflammation using cultured/isolated mast cells and an anaphylaxis mouse model. Nothofagin treatment prevented histamine and β-hexosaminidase release by reducing the influx of calcium into the cytosol in a concentration-dependent manner. Nothofagin also inhibited the gene expression and secretion of pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-4 by downregulating the phosphorylation of Lyn, Syk, Akt and nuclear translocation of nuclear factor-κB. To confirm these effects of nothofagin in vivo, we used a passive cutaneous anaphylaxis mouse model. Topical administration of nothofagin suppressed local pigmentation and ear thickness. Taken together, these results suggest nothofagin as a potential candidate for the treatment of mast cell-involved allergic inflammatory diseases.

Immunoglobulin G; structure and functional implications of different subclass modifications in initiation and resolution of allergy

IgE and not IgG is usually associated with allergy. IgE lodged on mast cells in skin or gut and basophils in the blood allows for the prolonged duration of allergy through the persistent expression of high affinity IgE receptors. However, many allergic reactions are not dependent on IgE and are generated in the absence of allergen specific and even total IgE. Instead, IgG plasma cells are involved in induction of, and for much of the pathogenesis of, allergic diseases. The pattern of IgG producing plasma cells in atopic children and the tendency for direct or further class switching to IgE are the principle factors responsible for long-lasting sensitization of mast cells in allergic children. Indirect class switching from IgG producing plasma cells has been shown to be the predominant pathway for production of IgE while a Th2 microenvironment, genetic predisposition, and the concentration and nature of allergens together act on IgG plasma cells in the atopic tendency to undergo further immunoglobulin gene recombination. The seminal involvement of IgG in allergy is further indicated by the principal role of IgG4 in the natural resolution of allergy and as the favourable immunological response to immunotherapy. This paper will look at allergy through the role of different antibodies than IgE and give current knowledge of the nature and role of IgG antibodies in the start, maintenance and resolution of allergy.

Allergens displayed on virus-like particles are highly immunogenic but fail to activate human mast cells

BACKGROUND

The goal of allergen-specific immunotherapy is the induction of protective immune responses in the absence of anaphylactic reactions. We have previously shown that Fel d 1, the major cat allergen, displayed in a repetitive fashion on virus-like particles (VLPs) may fulfill these criteria. Specifically, Fel d 1 on VLPs induced strongly increased protective IgG responses compared to free allergen in mice while anaphylactic reactions were essentially abolished. Here we extend these findings to human mast cells and offer a mechanistic explanation for the reduced anaphylactic activity.

METHODS

We differentiated human mast cells in vitro from blood-derived stem cell progenitors and sensitized the cells with a monoclonal Fel d 1-specific IgE. We compared the capability of Fel d 1 to induce mast cell activation in its free form versus displayed on VLPs and we performed allergen binding studies by surface plasmon resonance as well as flow cytometry.

RESULTS

We show that free Fel d 1 induces degranulation of IgE-sensitized mast cells whereas Fel d 1 displayed on VLPs fails to induce mast cell activation. We demonstrate that this inability to activate mast cells is based on a biophysical as well as a biochemical mechanism. Firstly, Fel d 1 on VLPs showed a strongly impaired ability to bind to surface-bound IgE. Secondly, despite residual binding, repetitively displayed allergen on VLPs failed to cause mast cell activation.

CONCLUSION

These findings indicate that repetitively displaying allergens on VLPs increases their immunogenicity while reducing their potential to cause anaphylactic reactions by essentially eliminating IgE-mediated activation of mast cells.

Omalizumab, the first available antibody for biological treatment of severe asthma: more than a decade of real-life effectiveness

Omalizumab was the first, and for a long time the only available monoclonal antibody for the add-on treatment of severe allergic asthma. In particular, omalizumab selectively targets human immunoglobulin (Ig)E, forming small-size immune complexes that inhibit IgE binding to its high- and low-affinity receptors. Therefore, omalizumab effectively blunts the immune response in atopic asthmatic patients, thus significantly improving the control of asthma symptoms and successfully preventing disease exacerbations. These very positive effects of omalizumab make it possible to drastically decrease both referrals to the emergency room and hospitalizations for asthma exacerbations. Such important therapeutic actions of omalizumab have been documented by several randomized clinical trials, and especially by more than 10 years of real-life experience in daily clinical practice. Omalizumab can also interfere with airway remodelling by inhibiting the activation of IgE receptors located on structural cells such as bronchial epithelial cells and airway smooth muscle cells. Moreover, omalizumab is characterized by a very good safety and tolerability profile. Hence, omalizumab represents a valuable therapeutic option for the add-on biological treatment of severe allergic asthma.

Targeted therapy in severe asthma today: focus on immunoglobulin E

Asthma is a complex chronic inflammatory disease of multifactorial etiology. International guidelines increasingly recognize that a standard "one size fits all" approach is no longer an effective approach to achieve optimal treatment outcomes, and a number of disease phenotypes have been proposed for asthma, which has the potential to guide treatment decisions. Among the many asthma phenotypes, allergic asthma represents the widest and most easily recognized asthma phenotype, present in up to two-thirds of adults with asthma. Immunoglobulin E (IgE) production is the primary and key cause of allergic asthma leading to persistent symptoms, exacerbations and a poor quality of life. Therefore, limiting IgE activity upstream could stop the entire allergic inflammation cascade in IgE-mediated allergic asthma. The anti-IgE treatment omalizumab has an accepted place in the management of severe asthma (Global Initiative for Asthma [GINA] step 5) and represents the first (and, currently, only) targeted therapy with a specific target in severe allergic asthma. This review summarizes current knowledge of the mechanisms and pathogenesis of severe asthma, examines the actual role of IgE in asthma and the biological rationale for targeting IgE in allergic asthma and reviews the data for the efficacy and safety of omalizumab in the treatment of severe asthma. Current knowledge of the role of IgE in asthma, extensive clinical trial data and a decade of use in clinical practice has established omalizumab as a safe and effective targeted therapy for the treatment of patients with severe persistent IgE-mediated allergic asthma.

Innate immunity as the orchestrator of allergic airway inflammation and resolution in asthma

The respiratory system is constantly in direct contact with the environment and, has therefore, developed strong innate and adaptive immune responses to combat pathogens. Unlike adaptive immunity which is mounted later in the course of the immune response and is naive at the outset, innate immunity provides the first line of defense against microbial agents, while also promoting resolution of inflammation. In the airways, innate immune effector cells mainly consist of eosinophils, neutrophils, mast cells, basophils, macrophages/monocytes, dendritic cells and innate lymphoid cells, which attack pathogens directly or indirectly through the release of inflammatory cytokines and antimicrobial peptides, and coordinate T and B cell-mediated adaptive immunity. Airway epithelial cells are also critically involved in shaping both the innate and adaptive arms of the immune response. Chronic allergic airway inflammation and linked asthmatic disease is often considered a result of aberrant activation of type 2 T helper cells (Th2) towards innocuous environmental allergens; however, innate immune cells are increasingly recognized as key players responsible for the initiation and the perpetuation of allergic responses. Moreover, innate cells participate in immune response regulation through the release of anti-inflammatory mediators, and guide tissue repair and the maintenance of airway homeostasis. The scope of this review is to outline existing knowledge on innate immune responses involved in allergic airway inflammation, highlight current gaps in our understanding of the underlying molecular and cellular mechanisms and discuss the potential use of innate effector cells in new therapeutic avenues.

Activation of the ileal neuroendocrine tumor cell line P-STS by acetylcholine is amplified by histamine: role of H3R and H4R

Neuroendocrine tumors may present with pseudoallergic reactions like diarrhea and idiopathic anaphylaxis. Here we present the P-STS human ileal neuroendocrine cell line as a model cell line for these tumors. Neuroendocrine markers and changes in cytoplasmic calcium concentration ([Ca2+]i) in response to several possible activators of 5-hydroxytryptamine (5-HT) release were analyzed. P-STS cells still expressed chromogranin A and synaptophysin after 2 years of culture. Tryptophan hydroxylase 1 mRNA and a low amount of 5-HT were also detected. Acetylcholine (ACh) caused a rise in [Ca2+]i. Somatostatin inhibited, whereas histamine (HA) but not the HA receptor ligand betahistine enhanced activation by ACh. The [Ca2+]i response to ACh/HA was inhibited by the HA receptor H3 (H3R) agonist methimepip and by the antidepressant imipramine. Further [Ca2+]i response studies indicated the presence of H4Rs and of a functional calcium sensing receptor. High or low affinity IgE receptor protein or mRNA were not detected. Taken together, neuroendocrine markers and response to intestinal neurotransmitters approve the P-STS cell line as a valuable model for enterochromaffin cells. Enhancement of their ACh-induced pro-secretory response by HA, with a role for H3R and H4R, suggests an amplifying role of neuroendocrine cells in allergen-induced diarrhea or anaphylaxis.

Basophil Activation-Dependent Autoantibody and Interleukin-17 Production Exacerbate Systemic Lupus Erythematosus

Objective

Autoantibody and inflammatory cytokines play crucial roles in the development of systemic lupus erythematosus (SLE); however, the regulation of their production warrants further investigation. This study aimed to investigate the role of basophil activation in the development of SLE based on studies in patients with SLE and spontaneous lupus-prone MRL-lpr/lpr mice.

Methods

The phenotypes of peripheral basophils and the production of autoantibody and interleukin (IL)-17 in patients with SLE were determined by flow cytometry and enzyme-linked immunosorbent assay, and also their correlations were investigated by statistical analysis. Thereafter, the effect of basophils on autoantibody production by B cells and Th17 differentiation in SLE were evaluated in vitro. Finally, the effect of basophil depletion on the development of autoimmune disorders in spontaneous lupus-prone MRL-lpr/lpr mice was examined.

Results

The decreased numbers and an increased activation of peripheral basophils were found to be correlated with increased autoantibody production and disease activity in patients with SLE. Correspondingly, in vitro coculture studies showed that basophils obtained from patients with SLE promoted autoantibody production by SLE B cells and promoted Th17 differentiation from SLE naïve CD4⁺ T cells. The decrease of peripheral basophils in patients with SLE might be due to their migration to lymph nodes post their activation mediated by (autoreactive) IgE as supported by their increased CD62L and CCR7 expressions and accumulation in the lymph nodes of MRL-lpr/lpr mice. Furthermore, an increased activation of peripheral basophils was identified in MRL-lpr/lpr mice. Importantly, basophil-depleted MRL-lpr/lpr mice exhibited an extended life span, improved renal function, and lower serum levels of autoantibodies and IL-17, while basophil-adoptive-transferred mice exhibited the opposite results.

Conclusion

These finding suggest that basophil activation-dependent autoantibody and IL-17 production may constitute a critical pathogenic mechanism in SLE.

Allergen Valency, Dose, and FcεRI Occupancy Set Thresholds for Secretory Responses to Pen a 1 and Motivate Design of Hypoallergens

Ag-mediated crosslinking of IgE-FcεRI complexes activates mast cells and basophils, initiating the allergic response. Of 34 donors recruited having self-reported shrimp allergy, only 35% had significant levels of shrimp-specific IgE in serum and measurable basophil secretory responses to rPen a 1 (shrimp tropomyosin). We report that degranulation is linked to the number of FcεRI occupied with allergen-specific IgE, as well as the dose and valency of Pen a 1. Using clustered regularly interspaced palindromic repeat-based gene editing, human RBL^rαKO cells were created that exclusively express the human FcεRIα subunit. Pen a 1-specific IgE was affinity purified from shrimp-positive plasma. Cells primed with a range of Pen a 1-specific IgE and challenged with Pen a 1 showed a bell-shaped dose response for secretion, with optimal Pen a 1 doses of 0.1-10 ng/ml. Mathematical modeling provided estimates of receptor aggregation kinetics based on FcεRI occupancy with IgE and allergen dose. Maximal degranulation was elicited when ∼2700 IgE-FcεRI complexes were occupied with specific IgE and challenged with Pen a 1 (IgE epitope valency of ≥8), although measurable responses were achieved when only a few hundred FcεRI were occupied. Prolonged periods of pepsin-mediated Pen a 1 proteolysis, which simulates gastric digestion, were required to diminish secretory responses. Recombinant fragments (60-79 aa), which together span the entire length of tropomyosin, were weak secretagogues. These fragments have reduced dimerization capacity, compete with intact Pen a 1 for binding to IgE-FcεRI complexes, and represent a starting point for the design of promising hypoallergens for immunotherapy.

Concealing Emotions at Work Is Associated with Allergic Rhinitis in Korea

Concealing emotions at work can cause considerable psychological stress. While there is extensive research on the adverse health effects of concealing emotions and the association between allergic diseases and stress, research has not yet investigated whether concealing emotions at work is associated with allergic rhinitis. Allergic rhinitis is a common disease in many industrialized countries, and its prevalence is increasing. Thus, our aim was to determine the strength of this association using data from three years (2007-2009) of the 4th Korean National Health and Nutrition Examination Survey. Participants (aged 20-64) were 8,345 individuals who were economically active and who had completed the questionnaire items on concealing emotions at work. Odds ratio (OR) and 95% confidence intervals (95% CIs) were calculated for allergic rhinitis using logistic regression models. Among all participants, 3,140 subjects (37.6%) reported concealing their emotions at work: 1,661 men and 1,479 women. The OR (95% CIs) for allergic rhinitis among those who concealed emotions at work versus those who did not was 1.318 (1.148-1.512). Stratified by sex, the OR (95% CIs) was 1.307 (1.078-1.585) among men and 1.346 (1.105-1.639) among women. Thus, individuals who concealed their emotions at work were significantly more likely to have a diagnosis of AR in comparison to those who did not. Because concealing emotions at work has adverse health effects, labor policies that aim to reduce this practice are needed.

Anti-IgE treatment, airway inflammation and remodelling in severe allergic asthma: current knowledge and future perspectives

Asthma is a disorder of the airways involving various inflammatory cells and mediators and characterised by bronchial hyperresponsiveness, chronic inflammation and structural alterations in the airways, also known as remodelling. IgE is an important mediator of allergic reactions and has a central role in allergic asthma pathophysiology, as it is implicated in both the early and late phase allergic response. Moreover, clinical and mechanistic evidence has lately emerged, implicating IgE in the development of airway remodelling. The use of monoclonal antibodies targeting IgE, such as omalizumab, has proven very effective in improving respiratory symptoms and quality of life, while reducing asthma exacerbations, emergency room visits and the use of systemic corticosteroids in allergic severe asthma. These effects are believed to be mainly mediated by omalizumab's inhibitory effect on the initiation and further propagation of the allergic inflammation cascade. However, there is evidence to suggest that anti-IgE treatment remains effective long after it has been discontinued. In part, these findings could be attributed to the possible ameliorating effects of anti-IgE treatment on airway remodelling. In this review, we discuss recent findings supporting the notion that anti-IgE treatment modulates the complex immune responses that manifest clinically as asthma and ameliorates airway remodelling changes often observed in allergic severe asthma phenotypes.

Immunotherapy using algal-produced Ara h 1 core domain suppresses peanut allergy in mice

Peanut allergy is an IgE-mediated adverse reaction to a subset of proteins found in peanuts. Immunotherapy aims to desensitize allergic patients through repeated and escalating exposures for several months to years using extracts or flours. The complex mix of proteins and variability between preparations complicates immunotherapy studies. Moreover, peanut immunotherapy is associated with frequent negative side effects and patients are often at risk of allergic reactions once immunotherapy is discontinued. Allergen-specific approaches using recombinant proteins are an attractive alternative because they allow more precise dosing and the opportunity to engineer proteins with improved safety profiles. We tested whether Ara h 1 and Ara h 2, two major peanut allergens, could be produced using chloroplast of the unicellular eukaryotic alga, Chlamydomonas reinhardtii. C. reinhardtii is novel host for producing allergens that is genetically tractable, inexpensive and easy to grow, and is able to produce more complex proteins than bacterial hosts. Compared to the native proteins, algal-produced Ara h 1 core domain and Ara h 2 have a reduced affinity for IgE from peanut-allergic patients. We further found that immunotherapy using algal-produced Ara h 1 core domain confers protection from peanut-induced anaphylaxis in a murine model of peanut allergy.

Possible Mechanism of Action of the Antiallergic Effect of an Aqueous Extract of Heliotropium indicum L. in Ovalbumin-Induced Allergic Conjunctivitis

Heliotropium indicum is used traditionally as a remedy for conjunctivitis in Ghana. This study therefore evaluated the antiallergic potential of an aqueous whole plant extract of Heliotropium indicum (HIE) in ovalbumin-induced allergic conjunctivitis and attempted to predict its mode of action. Clinical scores for allergic conjunctivitis induced by intraperitoneal ovalbumin sensitization (100 : 10 μg OVA/Al(OH)3 in phosphate-buffered saline [PBS]) and topical conjunctival challenge (1.5 mg OVA in 10 μL PBS) in Dunkin-Hartley guinea pigs were estimated after a week's daily treatment with 30-300 mg kg(-1) HIE, 30 mg kg(-1) prednisolone, 10 mg kg(-1) chlorpheniramine, or 10 mL kg(-1) PBS. Ovalbumin-specific IgG and IgE and total IgE in serum were estimated using Enzyme-Linked Immunosorbent Assay. Histopathological assessment of the exenterated conjunctivae was also performed. The 30 and 300 mg kg(-1) HIE treatment resulted in a significantly (p ≤ 0.001) low clinical score of allergic conjunctivitis. Ovalbumin-specific IgG and IgE as well as total serum IgE also decreased significantly (p ≤ 0.01-0.001). The conjunctival tissue in HIE treated guinea pigs had mild mononuclear infiltration compared to the PBS-treated ones, which had intense conjunctival tissue inflammatory infiltration. HIE exhibited antiallergic effect possibly by immunomodulation or immunosuppression.

Anti-IgE treatment, airway inflammation and remodelling in severe allergic asthma: current knowledge and future perspectives

Asthma is a disorder of the airways involving various inflammatory cells and mediators and characterised by bronchial hyperresponsiveness, chronic inflammation and structural alterations in the airways, also known as remodelling. IgE is an important mediator of allergic reactions and has a central role in allergic asthma pathophysiology, as it is implicated in both the early and late phase allergic response. Moreover, clinical and mechanistic evidence has lately emerged, implicating IgE in the development of airway remodelling. The use of monoclonal antibodies targeting IgE, such as omalizumab, has proven very effective in improving respiratory symptoms and quality of life, while reducing asthma exacerbations, emergency room visits and the use of systemic corticosteroids in allergic severe asthma. These effects are believed to be mainly mediated by omalizumab's inhibitory effect on the initiation and further propagation of the allergic inflammation cascade. However, there is evidence to suggest that anti-IgE treatment remains effective long after it has been discontinued. In part, these findings could be attributed to the possible ameliorating effects of anti-IgE treatment on airway remodelling. In this review, we discuss recent findings supporting the notion that anti-IgE treatment modulates the complex immune responses that manifest clinically as asthma and ameliorates airway remodelling changes often observed in allergic severe asthma phenotypes.

The therapeutic potential of orphan GPCRs, GPR35 and GPR55

The G protein-coupled receptor (GPCR) superfamily of integral proteins is the largest family of signal transducers, comprised of ∼1000 members. Considering their prevalence and functional importance, it’s not surprising that ∼60% of drugs target GPCRs. Regardless, there exists a subset of the GPCR superfamily that is largely uncharacterized and poorly understood; specifically, more than 140 GPCRs have unknown endogenous ligands—the so-called orphan GPCRs. Orphan GPCRs offer tremendous promise, as they may provide novel therapeutic targets that may be more selective than currently known receptors, resulting in the potential reduction in side effects. In addition, they may provide access to signal transduction pathways currently unknown, allowing for new strategies in drug design. Regardless, orphan GPCRs are an important area of inquiry, as they represent a large gap in our understanding of signal transduction at the cellular level. Here, we focus on the therapeutic potential of two recently deorphanized GPCRs: GPR35/CXCR8 and GPR55. First, GPR35/CXCR8 has been observed in numerous tissues/organ systems, including the gastrointestinal tract, liver, immune system, central nervous system, and cardiovascular system. Not surprisingly, GPR35/CXCR8 has been implicated in numerous pathologies involving these tissues/systems. While several endogenous ligands have been identified, GPR35/CXCR8 has recently been observed to bind the chemokine CXCL17. Second, GPR55 has been observed to be expressed in the central nervous system, adrenal glands, gastrointestinal tract, lung, liver, uterus, bladder, kidney, and bone, as well as, other tissues/organ systems. Likewise, it is not surprising that GPR55 has been implicated in pathologies involving these tissues/systems. GPR55 was initially deorphanized as a cannabinoid receptor and this receptor does bind many cannabinoid compounds. However, the GPR55 endogenous ligand has been found to be a non-cannabinoid, lysophophatidylinositol (LPI) and subsequent high throughput assays have identified other GPR55 ligands that are not cannabinoids and do not bind to either the cannabinoid CB1 and CB2 receptors. Here, we review reports that suggest that GPR35/CXCR8 and GPR55 may be promising therapeutic targets, with diverse physiological roles.

BODIPY(®) FL histamine as a new modality for quantitative detection of histamine receptor upregulation upon IgE sensitization in murine bone marrow-derived mast cells

Flow cytometry is one of the most widely used methods for the qualitative and quantitative analysis of cell surface expressed proteins by making use of fluorescent specific antibodies. Lacking an antibody validated for flow cytometry, an alternative approach for labeling cell surface receptors is the use of fluorescently tagged ligands. In this study, histamine H4 receptor transfected Chinese hamster ovary cells and murine bone marrow-derived mast cells (mBMMCs) were selected for studying the possibility of staining individual histamine receptors using BODIPY(®) FL histamine and selective antagonists. Flow cytometric measurements and supporting calculations showed that BODIPY FL histamine is suitable tool for quantitating cell surface histamine receptors. The binding, and competitive inhibition of this fluorescent ligand were characterized, which were in good agreement with a semi-empirical model constructed from fundamental protein-binding relationships. Using this method it was shown for the first time that even though mature mBMMCs express H2R and H4R to the same extent, immunoglobulin E sensitization results in H4R upregulation only, while the surface expression of H2R remains unchanged.

Role of basophils in the pathogenesis of minimal change nephrotic syndrome: A literature review

A number of studies have verified that minimal change nephrotic syndrome (MCNS) may result from the dysfunction of T cells and B cells, although the precise mechanisms are yet to be elucidated. It is widely recognized that MCNS is a T helper (Th)2-dominant glomerular disease caused by an imbalanced Th1/Th2 immune response. Increased levels of the Th2 cytokines, interleukin (IL)-4 and IL-13, have been demonstrated to be closely associated with disease activity. In addition, basophils can affect the Th1/Th2 balance by enhancing the Th2 response and impairing the Th1 response, which are then involved in the development of numerous diseases. However, whether basophils are vital in the pathogenesis of MCNS remains unknown. Frequent positivity of the human basophil degranulation test in patients with MCNS has been observed. Thus, basophils should be analyzed in order to determine their role in the pathogenesis of MCNS.

IgG-mediated down-regulation of IgE bound to mast cells: a potential novel mechanism of allergen-specific desensitization

BACKGROUND

Allergen-specific IgGs are known to inhibit IgE-mediated mast cell degranulation by two mechanisms, allergen-neutralization and engagement of the inhibitory FcγRIIB recruiting the phosphatase SHIP-1. Here we unravel an additional mechanism of IgG-mediated mast cell desensitization in mice: down-regulation of allergen-specific IgE.

METHODS

Mast cells were loaded in vitro and in vivo with monoclonal IgE antibodies specific for Fel d1 and exposed to immune complexes consisting of Fel d1-specific IgG antibodies recognizing different epitopes. Down regulation of IgE was followed by flow cytometry.

RESULTS

Mast cells loaded with 2 different IgE antibodies efficiently internalized the IgE antibodies if exposed to recombinant Feld d1. In contrast, no down-regulation occurred if mast cells were loaded with IgE antibodies exhibiting a single specificity before stimulation with recombinant Fel d1 [corrected]. Interestingly, however, IgEs of a single specificity were rapidly down-regulated in vitro and in vivo in the presence of Fel d1-specific monoclonal IgGs recognizing another epitope on Fel d1. Despite FceRI-internalization, little calcium flux or mast cell degranulation occurred. FcγRIIB played a dual role in the process since it enhanced IgE internalization and prevented cellular activation as documented by the inhibited calcium flux and mast cell degranulation. Similar observations were made in the presence of low concentrations of IgEs recognizing several epitopes on Fel d1.

CONCLUSION

We demonstrate here that Fel d1-specific IgG antibodies interact with FcγRIIB which (i) promotes IgE internalization; and (ii) inhibits mast cell activation. These results broaden our understanding of allergen-specific desensitization and may provide a mechanism for long-term desensitization of mast cells by selective removal of long-lived IgE antibodies on mast cells.

The tetraspanin CD63 is required for efficient IgE-mediated mast cell degranulation and anaphylaxis

Mast cell (MC) activation through the high-affinity IgE receptor FcεRI leads to the release of mediators involved in immediate-type allergic reactions. Although Abs against the tetraspanins CD63 and CD81 inhibit FcεRI-induced MC degranulation, the intrinsic role of these molecules in FcεRI-induced MC activation is unknown. In MCs, CD63 is expressed at the cell surface and in lysosomes (particularly secretory lysosomes that contain allergic mediators). In this study, we investigated the role of CD63 in MC using a CD63 knockout mouse model. CD63-deficiency did not affect in vivo MC numbers and tissue distribution. Bone marrow-derived MC developed normally in the absence of CD63 protein. However, CD63-deficient bone marrow-derived MC showed a significant decrease in FcεRI-mediated degranulation, but not PMA/ionomycin-induced degranulation, as shown by β-hexosaminidase release assays. The secretion of TNF-α, which is both released from granules and synthesized de novo upon MC activation, was also decreased. IL-6 secretion and production of the lipid mediator leukotriene C₄ were unaffected. There were no ultrastructural differences in granule content and morphology, late endosomal/lysosomal marker expression, FcεRI-induced global tyrosine phosphorylation, and Akt phosphorylation. Finally, local reconstitution in genetically MC-deficient Kit(w/w-v) mice was unaffected by the absence of CD63. However, the sites reconstituted with CD63-deficient MC developed significantly attenuated cutaneous anaphylactic reactions. These findings demonstrate that the absence of CD63 results in a significant decrease of MC degranulation, which translates into a reduction of acute allergic reactions in vivo, thus identifying CD63 as an important component of allergic inflammation.

Polydatin attenuated food allergy via store-operated calcium channels in mast cell

AIM: To investigate the effect of polydatin (PD), a resveratrol glucoside, on mast cell degranulation and anti-allergic activity.

METHODS: After the rats were orally sensitized with ovalbumin (OVA) for 48 d and underwent PD treatment for 4 d, all the rats were stimulated by 100 mg/mL OVA for 24 h and then sacrificed for the following experiments. The small intestines from all the groups were prepared for morphology examination by hematoxylin and eosin staining. We also used a smooth muscle organ bath to evaluate the motility of the small intestines. The OVA-specific immunoglobulin E (IgE) production and interleukin-4 (IL-4) levels in serum or supernatant of intestinal mucosa homogenates were analyzed by enzyme-linked immunosorbent assay (ELISA). Using toluidine blue stain, the activation and degranulation of isolated rat peritoneal mast cells (RPMCs) were analyzed. Release of histamine from RPMCs was measured by ELISA, and regulation of PD on intracellular Ca²⁺ mobilization was investigated by probing intracellular Ca²⁺ with fluo-4 fluorescent dye, with the signal recorded and analyzed.

RESULTS: We found that intragastric treatment with PD significantly reduced loss of mucosal barrier integrity in the small intestine. However, OVA-sensitization caused significant hyperactivity in the small intestine of allergic rats, which was attenuated by PD administration by 42% (1.26 ± 0.13 g vs OVA 2.18 ± 0.21 g, P < 0.01). PD therapy also inhibited IgE production (3.95 ± 0.53 ng/mL vs OVA 4.53 ± 0.52 ng/mL, P < 0.05) by suppressing the secretion of Th2-type cytokine, IL-4, by 34% (38.58 ± 4.41 pg/mL vs OVA 58.15 ± 6.24 pg/mL, P < 0.01). The ratio of degranulated mast cells, as indicated by vehicles (at least five) around the cells, dramatically increased in the OVA group by 5.5 fold (63.50% ± 15.51% vs phosphate-buffered saline 11.15% ± 8.26%, P < 0.001) and fell by 65% after PD treatment (21.95% ± 4.37% vs OVA 63.50% ± 15.51%, P < 0.001). PD mediated attenuation of mast cell degranulation was further confirmed by decreased histamine levels in both serum (5.98 ± 0.17 vs OVA 6.67 ± 0.12, P < 0.05) and intestinal mucosa homogenates (5.83 ± 0.91 vs OVA 7.35 ± 0.97, P < 0.05). Furthermore, we demonstrated that administration with PD significantly decreased mast cell degranulation due to reduced Ca²⁺ influx through store-operated calcium channels (SOCs) (2.35 ± 0.39 vs OVA 3.51 ± 0.38, P < 0.01).

CONCLUSION: Taken together, our data indicate that PD stabilizes mast cells by suppressing intracellular Ca²⁺ mobilization, mainly through inhibiting Ca²⁺ entry via SOCs, thus exerting a protective role against OVA-sensitized food allergy.

Histamine receptor H4 regulates mast cell degranulation and IgE induced FcεRI upregulation in murine bone marrow-derived mast cells

There is increasing evidence that histamine regulates the immune system via histamine H4 receptors, therefore we sought to investigate the functions of the H4 receptor on mast cells. Mast cells were differentiated from murine bone marrow stem cells, and the expression of mast cell surface markers FcεRI and CD117 were measured using flow cytometry. Real-time qRT-PCR was used to determine the expression of mH4R; as a measure of antigen-dependent degranulation, β-hexosaminidase release assay was carried out using IgE sensitized mast cells. We determined that the expression kinetics of FcεRI and mH4R can be described with a function that has one maximum value in the time range of the culture's differentiation. Antigen-dependent degranulation of murine bone marrow-derived mast cells could be inhibited by a selective H4 antagonist/inverse agonist only when it was present during the IgE sensitization phase of degranulation. In addition, flow cytometric analysis revealed that the H4 antagonist/inverse agonist also inhibited IgE induced FcεRI upregulation. The inhibition percentage of H4 antagonist on IgE induced FcεRI upregulation was determined to be dependent upon the maturity of the mast cell cultures, and this time-dependency was consistent with the expression kinetics of both mH4R and FcεRI. These results imply that H4R has regulatory roles in FcεRI expression and FcεRI mediated functions in mast cells. In conclusion the present study shows that H4 receptors potentially play a role in IgE induced FcεRI upregulation and in the sensitization phase but not the effector phase of mast cell degranulation.

A Rat Basophilic Leukaemia cell sensor for the detection of pathogenic viruses

A Rat Basophilic Leukemia (RBL) cell sensor is developed for the detection and identification of pathogenic viruses. Recombinant sdAb-Fc antibodies were constructed by linking virus-specific single domain antibody to mouse IgE-Fc fragment. The sdAb-Fc can bind to FcεRI receptors on RBL cells and can be cross-linked by target viruses leading to cell activation and Ca(2+) influx reflected by the increase of intracellular fluorescence. The responses of RBL cells to viruses in real time could be observed using fluorescence microscopy. 10(3) TCID50 of H5N1 viruses and 10 LD50 of rabies viruses could be detected in less than three minutes. An excess quantity of non-relevant viruses did not interfere with the recognition of target viruses.

Immunomodulatory Effects of Danshen (Salvia miltiorrhiza) in BALB/c Mice

Danshen, the root and rhizome of Salvia miltiorrhiza Bge, a Traditional Chinese Medicine, especially for cardiovascular and cerebrovascular diseases, has unique immunomodulatory effects. Danshen is capable of anti-inflammation and antiallergy, which are immunosuppressive activities, whereas it is also able to promote immunity against cancer, viruses, and bacteria. Most previous reports were performed with use of a purified compound or compounds of Danshen. Since there are more than twenty active compounds in Danshen, it is very difficult to predict that one compound will act the same way when it is combined with other compounds. In order to overcome this limitation, we used the crude form of Danshen to study its immunomodulatory effects in a mouse model. The mice were fed daily diet supplements of Danshen for three months and then tested for their immunity, including leukocyte subsets in peripheral blood, humoral and cell-mediated immune responses, and host defenses against a Listeria monocytogenes (LM) infection. Different doses of Danshen caused different immunomodulatory effects. Danshen at 0.5% decreased serum IgE production in BALB/c mice; 1% Danshen promoted cell-mediated immunity; Danshen at 0.5 and 1% inhibited the production of oxygen free radicals in liver and spleen and NO production in liver; 2% Danshen enhanced the host resistance against LM with increased numbers of peripheral monocytes and natural killer (NK) cells and decreased production of IL-1 β and NO.

Polydatin (PD) inhibits IgE-mediated passive cutaneous anaphylaxis in mice by stabilizing mast cells through modulating Ca²⁺ mobilization

Mast cells play a key role in the pathogenesis of asthma and are a promising target for therapeutic intervention in asthma. This study investigated the effects of polydatin (PD), a resveratrol glucoside, on mast cell degranulation upon cross-linking of the high-affinity IgE receptors (FcεRI), as well as the anti-allergic activity of PD in vivo. Herein, we demonstrated that PD treatment for 30 min suppressed FcεRI-mediated mast cell degranulation in a dose-dependent manner. Concomitantly, PD significantly decreased FcεRI-mediated Ca²⁺ increase in mast cells. The suppressive effects of PD on FcεRI-mediated Ca²⁺ increase were largely inhibited by using LaCl₃ to block the Ca²⁺ release-activated Ca²⁺ channels (CRACs). Furthermore, PD significantly inhibited Ca²⁺ entry through CRACs evoked by thapsigargin (TG). Knocking down protein expression of Orai1, the pore-forming subunit of CRACs, significantly decreased PD suppression of FcεRI-induced intracellular Ca²⁺ influx and mast cell degranulation. In a mouse model of mast cell-dependent passive cutaneous anaphylaxis (PCA), in vivo PD administration suppressed mast cell degranulation and inhibited anaphylaxis. Taken together, our data indicate that PD stabilizes mast cells by suppressing FcεRI-induced Ca²⁺ mobilization mainly through inhibiting Ca²⁺ entry via CRACs, thus exerting a protective effect against PCA.

Nanostructures of designed geometry and functionality enable regulation of cellular signaling processes

Extracellular matrices (ECM) triggered cellular signaling processes often begin with the clustering of the cellular receptors such as integrin and FcεRI. The sizes of these initial protein complexes or clusters are tens to 100 nm in dimension; therefore, engineered nanostructures could provide effective mimics of ECM for investigation and control of the initial and downstream specific signaling processes. This current topic discusses recent advances in nanotechnology in the context of design and production of matching chemical functionality and geometry for control of specific cellular signaling processes. Two investigations are reported to demonstrate this concept: (a) how the presentation of antigen at the nanometer scale would influence the aggregation of FcεRI, which would impact the formation of activation complexes, leading to the rearrangement of actin in cytoskeleton and degranulation or activation of mast cells; (b) how the engineered nanostructure could guide the initial integrin clustering, which would impact the formation of focal adhesion and downstream cell signaling cascades, leading to polarization, migration, and morphological changes. Complementary to engineered ECMs using synthetic ligands or peptides, or topographic control at the micrometer scale, nanostructures of designed geometry and chemical functionality provide new and effective biochemical cues for regulation of cellular signaling processes and downstream behaviors.

Deciphering the structure and function of FcεRI/mast cell axis in the regulation of allergy and anaphylaxis: a functional genomics paradigm

Allergy and anaphylaxis are inflammatory disorders caused by immune reactions mainly induced by immunoglobulin-E that signal through the high-affinity FcεRI receptor to release the inflammatory mediators from innate immune cells. The FcεRI/mast cell axis is potently involved in triggering various intracellular signaling molecules to induce calcium release from the internal stores, induction of transcription factors such as NF-kB, secretion of various cytokines as well as lipid mediators, and degranulation, resulting in the induction of allergy and anaphylaxis. In this review, we discuss various cellular and molecular mechanisms triggered through FcεRI/mast cell axis in allergy and anaphylaxis with a special emphasis on the functional genomics paradigm.