FcεRI Expression Research Articles

Didox (3,4-dihydroxybenzohydroxamic acid) suppresses IgE-mediated mast cell activation through attenuation of NFκB and AP-1 transcription

Mast cell activation via the high-affinity IgE receptor (FcεRI) elicits production of inflammatory mediators central to allergic disease. As a synthetic antioxidant and a potent ribonucleotide reductase (RNR) inhibitor, Didox (3,4-dihyroxybenzohydroxamic acid) has been tested in clinical trials for cancer and is an attractive therapeutic for inflammatory disease. We found that Didox treatment of mouse bone marrow-derived mast cells (BMMC) reduced IgE-stimulated degranulation and cytokine production, including IL-6, IL-13, TNF and MIP-1a (CCL3). These effects were consistent using BMMC of different genetic backgrounds and peritoneal mast cells. While the RNR inhibitor hydroxyurea had little or no effect on IgE-mediated function, high concentrations of the antioxidant N-acetylcysteine mimicked Didox-mediated suppression. Furthermore, Didox increased expression of the antioxidant genes superoxide dismutase and catalase, and suppressed DCFH-DA fluorescence, indicating reduced reactive oxygen species production. Didox effects were not due to changes in FcεRI expression or cell viability, suggesting it inhibits signaling required for inflammatory cytokine production. In support of this, we found that Didox reduced FcεRI-mediated AP-1 and NFκB transcriptional activity. Finally, Didox suppressed mast cell-dependent, IgE-mediated passive systemic anaphylaxis in vivo. These data demonstrate the potential use for Didox asa means of antagonizing mast cell responses in allergic disease.

Spontaneous food allergy in Was-/- mice occurs independent of FcεRI-mediated mast cell activation.

Food allergies are a growing health problem, and the development of therapies that prevent disease onset is limited by the lack of adjuvant-free experimental animal models. We compared allergic sensitization in patients with food allergy or Wiskott-Aldrich syndrome (WAS) and defined whether spontaneous disease in Was-/- mice recapitulates the pathology of a conventional disease model and/or human food allergy. Comparative ImmunoCAP ISAC microarray was performed in patients with food allergy or WAS. Spontaneous food allergy in Was-/- mice was compared to an adjuvant-based model in wild-type mice (WT-OVA/alum). Intestinal and systemic anaphylaxis was assessed, and the role of the high-affinity IgE Fc receptor (FcεRI) in allergic sensitization was evaluated using Was-/- Fcer1a-/- mice. Polysensitization to food was detected in both WAS and food-allergic patients which was recapitulated in the Was-/- model. Oral administration of ovalbumin (OVA) in Was-/- mice induced low titers of OVA-specific IgE compared to the WT-OVA/alum model. Irrespectively, 79% of Was-/- mice developed allergic diarrhea following oral OVA challenge. Systemic anaphylaxis occurred in Was-/- mice (95%) with a mortality rate >50%. Spontaneous sensitization and intestinal allergy occurred independent of FcεRI expression on mast cells (MCs) and basophils. Was-/- mice provide a model of food allergy with the advantage of mimicking polysensitization and low food-antigen IgE titers as observed in humans with clinical food allergy. This model will facilitate studies on aberrant immune responses during spontaneous disease development. Our results imply that therapeutic targeting of the IgE/FcεRI activation cascade will not affect sensitization to food.

Phospholipid scramblase 1 amplifies anaphylactic reactions in vivo.

Mast cells are critical actors of hypersensitivity type I (allergic) reactions by the release of vasoactive and proinflammatory mediators following their activation by aggregation of the high-affinity receptor for immunoglobulin E (FcεRI). We have previously identified Phospholipid Scramblase 1 (PLSCR1) as a new molecular intermediate of FcεRI signaling that amplifies degranulation of the rat mast cell line RBL-2H3. Here we characterized primary mast cells from Plscr1-/- mice. The absence of PLSCR1 expression did not impact mast cell differentiation as evidenced by unaltered FcεRI expression, general morphology, amount of histamine stored and expression of FcεRI signal effector molecules. No detectable mast cell deficiency was observed in Plscr1-/- adult mice. In dose-response and time-course experiments, primary cultures of mast cells (bone marrow-derived mast cells and peritoneal cell-derived mast cells) generated from Plscr1-/- mice exhibited a reduced release of β-hexosaminidase upon FcεRI engagement as compared to their wild-type counterparts. In vivo, Plscr1-/- mice were protected in a model of passive systemic anaphylaxis when compared to wild-type mice, which was consistent with an observed decrease in the amounts of histamine released in the serum of Plscr1-/- mice during the reaction. Therefore, PLSCR1 aggravates anaphylactic reactions by increasing FcεRI-dependent mast cell degranulation. PLSCR1 could be a new therapeutic target in allergy.

Endothelial integrity may be regulated by a specific antigen via an IgE-mediated mechanism.

Human vascular endothelial function and integrity may be regulated by many non-specific factors. However, the potential influence of specific antigens via an IgE-mediated mechanism remains unknown. The aim of the study was to determine the expression of the IgE receptors FcεRI and FcεRII in the human vascular endothelium and to assess their relevance in the IgE-mediated regulation of endothelial integrity. FcεRI and FcεRII expression in human umbilical vein endothelial cells (HUVEC) was genetically assessed by PCR with respective primers and sequencing. HUVEC were cultured with IL-4, and changes in FcεRI and FcεRII mRNA expression were analyzed by real-time PCR. Changes in the integrity of endothelium pre-treated with anti-BSA-DNP IgE following exposure to the specific BSA-DNP antigen was assessed using the Real-time Cell Electric Impedance Sensing system (RTCA-DP). PCR and sequencing revealed the expression of FcεRI and FcεRII receptors in the human vascular endothelium. IL-4 caused respective 2- and 3-fold increases in FcεRI and FcεRII mRNA expression. Exposure of endothelium pre-treated with anti-BSA-DNP IgE to specific BSA-DNP antigen led to a 20% increase of endothelial integrity (p<0.05) after 24 hours, but only in cells pre-incubated with IL-4. The presence of FcεRI and FcεRII may allow the human vascular endothelium to respond to a specific antigen by increasing its integrity via an IgE-mediated mechanism.

Retinoic Acid Negatively Impacts Proliferation and MCTC Specific Attributes of Human Skin Derived Mast Cells, but Reinforces Allergic Stimulability.

The Vitamin-A-metabolite retinoic acid (RA) acts as a master regulator of cellular programs. Mast cells (MCs) are primary effector cells of type-I-allergic reactions. We recently uncovered that human cutaneous MCs are enriched with RA network components over other skin cells. Yet, direct experimental evidence on the significance of the RA-MC axis is limited. Here, skin-derived cultured MCs were exposed to RA for seven days and investigated by flow-cytometry (BrdU incorporation, Annexin/PI, FcεRI), microscopy, RT-qPCR, histamine quantitation, protease activity, and degranulation assays. We found that while MC size and granularity remained unchanged, RA potently interfered with MC proliferation. Conversely, a modest survival-promoting effect from RA was noted. The granule constituents, histamine and tryptase, remained unaffected, while RA had a striking impact on MC chymase, whose expression dropped by gene and by peptidase activity. The newly uncovered MRGPRX2 performed similarly to chymase. Intriguingly, RA fostered allergic MC degranulation, in a way completely uncoupled from FcεRI expression, but it simultaneously restricted MRGPRX2-triggered histamine release in agreement with the reduced receptor expression. Vitamin-A-derived hormones thus re-shape skin-derived MCs numerically, phenotypically, and functionally. A general theme emerges, implying RA to skew MCs towards processes associated with (allergic) inflammation, while driving them away from the skin-imprinted MCTC (“MCs containing tryptase and chymase”) signature (chymase, MRGPRX2). Collectively, MCs are substantial targets of the skin retinoid network.

Peroxisome proliferator-activated receptor γ agonist suppresses mast cell maturation and induces apoptosis.

Peroxisome proliferator-activated receptor gamma (PPAR γ), is important in the immunoregulation of the allergic response. Mast cells are the most important inflammatory cells in immediate hypersensitivity and allergic diseases. However, there is limited information regarding the effects of PPAR γ on mast cell maturation. In the present study, mouse bone marrow-derived mast cells (BMMCs) were cultured in interleukin (IL)-3 and stem cell factor (SCF), in the presence or absence of the PPAR γ agonist, pioglitazone (PIO). The expression levels of the tyrosine kinase receptor CD117 and the high affinity IgE receptor FcεRI α, were assessed by flow cytometry, cell viability was assessed by Alamar-Blue assay and histamine release was determined by measuring the activity of β-hexosaminidase. IL-3 and SCF are required for the development of mast cells in vitro. PIO dose-dependently inhibited the expression of CD117 and FcεRI α, and the maturation of BMMCs. Treatment with PIO additionally inhibited the formation of granules and reduced the expression of β-hexosaminidase. In addition, reverse transcription-polymerase chain reaction analysis revealed that BMMCs treated with PIO expressed a lower level of mast cell protease (MCP)-6 mRNA and PIO treatment enhanced the level of PPAR γ mRNA. Furthermore, PIO induced mast cell progenitor apoptosis. PPAR γ agonists may maintain mast cell homeostasis by inhibiting maturation of their precursors. The inhibitory effects of PPAR γ agonists include suppression of the activation of mast cells and a decrease in mast cell function in the inflammatory response. Therefore, PPAR γ agonists may serve as effective anti-inflammatory reagents in the treatment of allergic reactions.

Clinical efficacy of omalizumab in chronic spontaneous urticaria is associated with a reduction of FcεRI-positive cells in the skin

Background. Treatment with omalizumab, a humanized recombinant monoclonal anti-IgE antibody, results in clinical efficacy in patients with Chronic Spontaneous Urticaria (CSU). The mechanism of action of omalizumab in CSU has not been elucidated in detail.Objectives. To determine the effects of omalizumab on levels of high affinity IgE receptor-positive (FcεRI+) and IgE-positive (IgE+) dermal cells and blood basophils. Treatment efficacy and safety were also assessed.Study design. In a double-blind study, CSU patients aged 18‑75 years were randomized to receive 300 mg omalizumab (n=20) or placebo (n=10) subcutaneously every 4 weeks for 12 weeks. Changes in disease activity were assessed by use of the weekly Urticaria Activity Score (UAS7). Circulating IgE levels, basophil numbers and levels of expression of FcεRI+ and IgE+ cells in the skin and in blood basophils were determined.Results. Patients receiving omalizumab showed a significantly greater decrease in UAS7 compared with patients receiving placebo. At Week 12 the mean difference in UAS7 between treatment groups was -14.82 (p=0.0027), consistent with previous studies.Total IgE levels in serum were increased after omalizumab treatment and remained elevated up to Week 12. Free IgE levels decreased after omalizumab treatment.Mean levels of FcεRI+ skin cells in patients treated with omalizumab 300 mg were decreased at Week 12 compared with baseline in the dermis of both non-lesional and lesional skin, reaching levels comparable with those seen in healthy volunteers (HVs). There were no statistically significant changes in mean FcɛRI+ cell levels in the placebo group. Similar results were seen for changes in IgE+ cells, although the changes were not statistically significant.The level of peripheral blood basophils increased immediately after treatment start and returned to Baseline values after the follow-up period. The levels of FcεRI and IgE expression on peripheral blood basophils were rapidly reduced by omalizumab treatment up to Week 12.Conclusions. Treatment with omalizumab resulted in rapid clinical benefits in patients with CSU. Treatment with omalizumab was associated with reduction in FcɛRI+ and IgE+ basophils and intradermal cells.

Characteristics of the eosinophilic fenotype of bronchial asthma in children

The purpose of the work is clinical and laboratory examination of children with an eosinophilic phenotype of bronchial asthma. Materials and methods. 160 children aged 5 to 18 years were examined: 130 patients with atopic bronchial asthma, 30 children of the control group. During the work, the level of eosinophils, the level of eosinophils carrying FcεRI+ and CD23+IgE+ receptor, the level of total IgE, IgE antibodies to domestic and epidermal allergens in the blood serum were determined, clinical and anamnestic data were studied. Results. In children with atopic bronchial asthma, the relative and absolute content of eosinophils, as well as eosinophils carrying FcεRI+ and CD23+IgE+ receptors, is statistically significantly higher than in the control group (p&lt;0.001). In 71 (54.62%) children with bronchial asthma, eosinophilia was detected, with 58 (81.69%) patients having a high level of eosinophils bearing the FcεRI + receptor and 56 (78.87%) children with a high level of eosinophils carrying CD23+IgE+ receptor. In the group of children with bronchial asthma, a correlation was established between the level of total IgE and the level of eosinophils carrying FcεRI+ (r=+0.389; p&lt;0.01) and CD23+IgE+ receptors (r=+ 0.677; p&lt;0.0001). In children with eosinophilia, in most cases, the hereditary nature of the disease is observed, the first manifestations of allergy are already present in the first year of life, concomitant allergopathology has been established. The optimal effect in the treatment of patients with eosinophilia was obtained with the appointment, as a basic therapy, of inhaled glucocorticosteroids, as well as short-acting β2-agonists for arresting episodes of bronchial obstruction. In most patients with asthma who have eosinophilia, serum levels of IgE antibodies to Dermatophagoides pteronyssinus, to the coat of the cat and the dog's coat are revealed, and positive skin scarification tests with these allergens are detected. Conclusion. In children with atopic bronchial asthma, there are signs of an eosinophilic phenotype: eosinophilia, high expression of FcεRI+ and CD23+IgE+ receptors, increased levels of total IgE and IgE antibodies, positive skin tests with domestic and epidermal allergens, hereditary predisposition, effectiveness of inhaled glucocorticosteroids.

Basophil FcεRI Expression in Chronic Spontaneous Urticaria: A Potential Immunological Predictor of Response to Omalizumab Therapy.

Although the efficacy of omalizumab has been clearly demonstrated in the treatment of chronic spontaneous urticaria (CSU), its mechanism of action, which results in improvement in CSU symptoms, is not entirely understood. This study investigated the effect of omalizumab on expression of the high-affinity IgE receptor (FcεRI) on blood basophils from patients with active CSU, and its association with the clinical response. Patients exhibiting significant clinical improvement showed a sharp reduction in the levels of basophil FcεRI after 4 weeks, which was maintained throughout the total duration of the treatment. Such evolution was not observed in non-responder patients. Furthermore, non-responders showed significantly lower baseline levels of FcεRI than responders. Baseline basophil FcεRI expression was found to be a potential immunological predictor of response to omalizumab (100% sensitivity and 73.2% specificity). The results of this study contribute to our knowledge of the therapeutic benefit and mechanism of action of anti-IgE therapy in CSU.

Exon skipping of FcεRIβ eliminates expression of the high-affinity IgE receptor in mast cells with therapeutic potential for allergy

Allergic diseases are driven by activation of mast cells and release of mediators in response to IgE-directed antigens. However, there are no drugs currently available that can specifically down-regulate mast cell function in vivo when chronically administered. Here, we describe an innovative approach for targeting mast cells in vitro and in vivo using antisense oligonucleotide-mediated exon skipping of the β-subunit of the high-affinity IgE receptor (FcεRIβ) to eliminate surface high-affinity IgE receptor (FcεRI) expression and function, rendering mast cells unresponsive to IgE-mediated activation. As FcεRIβ expression is restricted to mast cells and basophils, this approach would selectively target these cell types. Given the success of exon skipping in clinical trials to treat genetic diseases such as Duchenne muscular dystrophy, we propose that exon skipping of FcεRIβ is a potential approach for mast cell-specific treatment of allergic diseases.

Neuronal Fc-epsilon receptor I contributes to antigen-evoked pruritus in a murine model of ocular allergy

Pruritus is the major symptom of ocular allergy but currently available treatments are often ineffective. Previous studies demonstrated that subpopulations of primary sensory neurons express Fc receptors and may contribute to antigen-specific pain. We investigated the role of neuronal Fc-epsilon Receptor I (FcεRI) in allergic ocular pruritus. Ovalbumin (OVA) was used as allergen together with alum adjuvant (OVA+alum) to produce a mouse model of ocular allergy with a significant elevation in the serum levels of both antigen-specific IgE and IgG. Mice sensitized by OVA without alum only induced elevation of serum IgG but not IgE. Scratching behavior toward the eyes with the hindlimb was used as an indicator of ocular itch. Topical OVA challenging to the eye dose-dependently induced scratching toward the eye in the OVA+alum sensitized mice, but not those sensitized by OVA only. The antigen-induced scratching was largely abolished by topical application of the blocking antibody to FcεRIα, but was only partially alleviated by pretreatment of mast cell stabilizer or histamine I receptor antagonist. The expression of FcεRI was detected in subpopulations of trigeminal ganglion (TG) neurons including those expressing pruriceptive markers and innervating the conjunctiva in the naïve mice. Moreover, FcεRI was found significantly upregulated in small-sized TG neurons in the OVA+alum sensitized mice. In acutely dissociated TG neurons, IgE-immune complex (IC), but not the antibody or antigen alone, induced intracellular calcium increase. The neuronal responses to IgE-IC could be specifically blocked by pre-application of a siRNA for FcεRIα. Our results indicate that FcεRI expressed on peripheral nociceptive neurons in the TG may be directly activated by IgE-IC and contribute to allergic ocular pruritus. This study may suggest a novel mechanism for the development of pathological itch in allergic diseases.

Characterization of the potential allergenicity of irradiated bovine α-lactalbumin in a BALB/c mouse model

Bovine α-lactalbumin (ALA) is a known food allergen present in milk to induce anaphylaxis. A previous study demonstrated that irradiated ALA (iALA) decreased the IgE-binding properties and weakened the degranulation capacity of basophils in vitro. The present study aimed to further assess the potential allergenicity of iALA in vivo in a BALB/c mouse model. The mice (n = 10/group) were intragastrically sensitized and orally challenged with either iALA or ALA using cholera toxin as adjuvant. In contrast to the ALA group, the iALA group did not show anaphylactic shock symptoms. A tendency toward decreased serum allergen-specific IgG/IgG1/IgE levels, plasma histamine levels and mast cell protease-1 (mMCP-1) concentrations in the iALA group were also observed, accompanied by a decrease in Th2-related cytokine levels and an increase of IFN-γ production in spleen cell cultures. Moreover, the peritoneal mast cell surface expression of FcεRI and peripheral blood basophil CD200R+ expression were decreased by 64.3% and 35.19%, respectively. Conversely, the percentage of CD4+CD25+Foxp3+ regulatory T cells increased in the iALA group. All of these findings indicated that iALA induces a shift toward the Th1 response, which ultimately reduces its potential allergenicity.

IL-10 Enhances IgE-Mediated Mast Cell Responses and Is Essential for the Development of Experimental Food Allergy in IL-10-Deficient Mice.

IL-10 is a key pleiotropic cytokine that can both promote and curb Th2-dependent allergic responses. In this study, we demonstrate a novel role for IL-10 in promoting mast cell expansion and the development of IgE-mediated food allergy. Oral OVA challenge in sensitized BALB/c mice resulted in a robust intestinal mast cell response accompanied by allergic diarrhea, mast cell activation, and a predominance of Th2 cytokines, including enhanced IL-10 expression. In contrast, the development of intestinal anaphylaxis, including diarrhea, mast cell activation, and Th2 cytokine production, was significantly attenuated in IL-10(-/-) mice compared with wild-type (WT) controls. IL-10 also directly promoted the expansion, survival, and activation of mast cells; increased FcεRI expression on mast cells; and enhanced the production of mast cell cytokines. IL-10(-/-) mast cells had reduced functional capacity, which could be restored by exogenous IL-10. Similarly, attenuated passive anaphylaxis in IL-10(-/-) mice could be restored by IL-10 administration. The adoptive transfer of WT mast cells restored allergic symptoms in IL-10(-/-) mice, suggesting that the attenuated phenotype observed in these animals is due to a deficiency in IL-10-responding mast cells. Lastly, transfer of WT CD4 T cells also restored allergic diarrhea and intestinal mast cell numbers in IL-10(-/-) mice, suggesting that the regulation of IL-10-mediated intestinal mast cell expansion is T cell dependent. Our observations demonstrate a critical role for IL-10 in driving mucosal mast cell expansion and activation, suggesting that, in its absence, mast cell function is impaired, leading to attenuated food allergy symptoms.

The effects of D3R on TLR4 signaling involved in the regulation of METH-mediated mast cells activation

Accumulating studies have revealed that the dopamine D3 receptor (D3R) plays an important role in methamphetamine (METH) addiction. However, the action of D3R on METH-mediated immune response and the underlying mechanism remain unclear. Mast cells (MCs) are currently identified as effector cells in many processes of immune responses, and MC activation is induced by various stimuli such as lipopolysaccharide (LPS). Moreover, CD117 and FcεRI are known as MC markers due to their specific expression in MCs. To investigate the effects of D3R on METH-mediated alteration of LPS-induced MCs activation and the underlying mechanism, in this study, we examined the expression of CD117 and FcεRI in the intestines of wild-type (D3R+/+) and D3R-deficient (D3R−/−) mice. We also measured the production of MC-derived cytokines, including TNF-α, IL-6, IL-4, IL-13 and CCL-5, in the bone marrow-derived mast cells (BMMCs) of WT and D3R−/− mice. Furthermore, we explored the effects of D3R on METH-mediated TLR4 and downstream MAPK and NF-κB signaling induced by LPS in mouse BMMCs. We found that METH suppressed MC activation induced by LPS in the intestines of D3R+/mice. In contrast, LPS-induced MC activation was less affected by METH in D3R−/− mice. Furthermore, METH altered LPS-induced cytokine production in BMMCs of D3R+/+ mice but not D3R−/− mice. D3R was also involved in METH-mediated modulation of LPS-induced expression of TLR4 and downstream MAPK and NF-κB signaling molecules in mouse BMMCs. Taken together, our findings demonstrate that the effect of D3R on TLR4 signaling may be implicated in the regulation of METH-mediated MCs activation induced by LPS.

IgE and FcεRI are highly expressed on innate cells in psoriasis.

Although elevated serum IgE levels have been reported in psoriasis, the role of IgE in psoriasis still needs to be clarified. To analyse serum total IgE levels in addition to the presence and distribution of IgE and FcεRI in psoriatic lesions, and to investigate alteration of IgE and FcεRI after successful systemic treatment. Total serum IgE levels were determined using enzyme-linked immunosorbent assay. The expression and localization of IgE and FcεRI was investigated using immunohistochemistry and double immunofluorescence. Elevated total serum IgE levels were found in 39% of patients with psoriasis. The levels of total serum IgE were significantly higher in male patients compared with female patients. Furthermore, total serum IgE levels decreased after successful systemic treatment. A positive correlation between IgE+ and FcεRI+ cells and a significant increase of these cells was found in psoriatic lesions when compared with normal skin. Interestingly, IgE+ and FcεRI+ cells decreased significantly after successful therapy with ustekinumab. IgE and FcεRI were coexpressed on mast cells, epidermal Langerhans cells, dermal dendritic cells, macrophages and a small number of neutrophils. IgE might participate in the development of psoriasis by activating FcεRI-bearing cells.

Efficacy and safety of multiple doses of QGE031 (ligelizumab) versus omalizumab and placebo in inhibiting allergen-induced early asthmatic responses

Omalizumab is an established anti-IgE therapy for the treatment of allergic diseases that prevents IgE from binding to its receptor. QGE031 is an investigational anti-IgE antibody that binds IgE with higher affinity than omalizumab. This study compared the effects of QGE031 with those of omalizumab on clinical efficacy, IgE levels, and FcεRI expression in a clinical model of allergic asthma. Thirty-seven patients with mild allergic asthma were randomized to subcutaneous omalizumab, placebo, or QGE031 at 24, 72, or 240mg every 2weeks for 10weeks in a double-blind, parallel-group multicenter study. Inhaled allergen challenges and skin tests were conducted before dosing and at weeks 6, 12, and 18, and blood was collected until 24weeks after the first dose. QGE031 elicited a concentration- and time-dependent change in the provocative concentration of allergen causing a 15% decrease in FEV1 (allergen PC15) that was maximal and approximately 3-fold greater than that of omalizumab (P=.10) and 16-fold greater than that of placebo (P=.0001) at week 12 in the 240-mg cohort. Skin responses reached 85% suppression at week 12 in the 240-mg cohort and were maximal at week 18. The top doses of QGE031 consistently suppressed skin test responses among subjects but had a variable effect on allergen PC15 (2-fold to 500-fold change). QGE031 was well tolerated. QGE031 has greater efficacy than omalizumab on inhaled and skin allergen responses in patients with mild allergic asthma. These data support the clinical development of QGE031 as a treatment of asthma.

The dendritic cell high-affinity IgE receptor is overexpressed in both asthma and severe COPD.

The reduction of asthma exacerbations following omalizumab treatment has been related to the suppression of the high-affinity IgE receptor (FcεRI) on plasmacytoid dendritic cells (DCs). However, the FcεRI expression on DCs in chronic obstructive pulmonary disease (COPD) is unknown. To compare FcεRI expression on DCs in COPD with patients with allergic asthma and healthy controls, and to relate the findings to clinical parameters, blood eosinophil concentrations and serum immunoglobin E (IgE) concentrations. Using four-colour flow cytometry, FcεRI expression on blood myeloid DCs and plasmacytoid DCs was analyzed in 64 patients with COPD, 20 patients with allergic asthma, 41 asymptomatic never smokers and 21 asymptomatic current smokers. As compared with never smokers, current smokers displayed an increased expression of the FcεRI on myeloid and plasmacytoid DCs. In patients with COPD, the expression of the FcεRI on plasmacytoid DCs, but not myeloid DCs, increased from spirometric GOLD stage 2 to GOLD stage 4, and was correlated with several lung function parameters. Patients with severe COPD and patients with allergic asthma displayed a similar FcεRI overexpression on plasmacytoid DCs. In all groups, there was a positive correlation between total IgE serum concentrations and the FcεRI expression on plasmacytoid DCs. Severe COPD and allergic asthma are characterized by a similar overexpression of the high-affinity IgE receptor on plasmacytoid DCs. In view of the effect of anti-IgE on exacerbations in asthma, trials investigating the effect of anti-IgE on exacerbations in severe COPD appear to be warranted.

Phenotypic variability in human skin mast cells.

Mast cells (MCs) are unique constituents of the human body. While inter-individual differences may influence the ways by which MCs operate in their skin habitat, they have not been surveyed in a comprehensive manner so far. We therefore set out to quantify skin MC variability in a large cohort of subjects. Pathophysiologically relevant key features were quantified and correlated: transcripts of c-kit, FcεRIα, FcεRIβ, FcεRIγ, histidine decarboxylase, tryptase, and chymase; surface expression of c-Kit, FcεRIα; activity of tryptase, and chymase; histamine content and release triggered by FcεRI and Ca(2+) ionophore. While there was substantial variability among subjects, it strongly depended on the feature under study (coefficient of variation 33-386%). Surface expression of FcεRI was positively associated with FcεRIα mRNA content, histamine content with HDC mRNA, and chymase activity with chymase mRNA. Also, MC signature genes were co-regulated in distinct patterns. Intriguingly, histamine levels were positively linked to tryptase and chymase activity, whereas tryptase and chymase activity appeared to be uncorrelated. FcεRI triggered histamine release was highly variable and was unrelated to FcεRI expression but unexpectedly tightly correlated with histamine release elicited by Ca(2+) ionophore. This most comprehensive and systematic work of its kind provides not only detailed insights into inter-individual variability in MCs, but also uncovers unexpected patterns of co-regulation among signature attributes of the lineage. Differences in MCs among humans may well underlie clinical responses in settings of allergic reactions and complex skin disorders alike.

IL-6 promotes an increase in human mast cell numbers and reactivity through suppression of suppressor of cytokine signaling 3

IL-6, levels of which are reported to be increased in association with mastocytosis, asthma, and urticaria, is used in conjunction with stem cell factor to generate CD34(+) cell-derived primary human mast cell (HuMC) cultures. Despite these associations, the effects on and mechanisms by which prolonged exposure to IL-6 alters HuMC numbers and function are not well understood. We sought to study the effect of IL-6 on HuMC function, the mechanisms by which IL-6 exerts its effects, and the relationship of these findings to mastocytosis. HuMCs were cultured in stem cell factor with or without IL-6. Responses to FcεRI aggregation and expression of proteases and receptors, including the soluble IL-6 receptor (sIL-6R), were then quantitated. Epigenetic changes in suppressor of cytokine signaling 3 (SOCS3) were determined by using methylation-specific PCR. Serum samples from healthy control subjects and patients with mastocytosis were assayed for IL-6, tryptase, and sIL-6R. IL-6 enhanced mast cell (MC) proliferation, maturation, and reactivity after FcεRI aggregation. IL-6 reduced expression of SOCS3, which correlated with methylation of the SOCS3 promoter and increased expression and activation of signal transducer and activator of transcription 3. IL-6 also suppressed constitutive production of sIL-6R, and serum levels of sIL-6R were similarly reduced in patients with mastocytosis. IL-6 increases MC proliferation and formation of a more reactive phenotype enabled by suppressing proteolytic cleavage of sIL-6R from IL-6R and downregulation of the SOCS3 autoinhibitory pathway. We suggest IL-6 blockade might ameliorate MC-related symptoms and pathology in patients with MC-related diseases associated with increased IL-6 levels, including mastocytosis.

Asthma phenotypes and IgE responses.

The discovery of IgE represented a major breakthrough in allergy and asthma research, whereas the clinical interest given to IgE in asthma has been blurred until the arrival of anti-IgE biotherapy. Novel facets of the complex link between IgE and asthma have been highlighted by the effect of this treatment and by basic research. In parallel, asthma phenotyping recently evolved to the concept of endotypes, relying on identified/suspected pathobiological mechanisms to phenotype patients, but has not yet clearly positioned IgE among biomarkers of asthma.In this review, we first summarise recent knowledge about the regulation of IgE production and its main receptor, FcεRI. In addition to allergens acting as classical IgE inducers, viral infections as well as air pollution may trigger the IgE pathway, notably resetting the threshold of IgE sensitivity by regulating FcεRI expression. We then analyse the place of IgE in different asthma endo/phenotypes and discuss the potential interest of IgE among biomarkers in asthma.