IgE, IgE Receptors and Anti-IgE Biologics: Protein Structures and Mechanisms of Action.

The evolution of IgE in mammals added an extra layer of immune protection at body surfaces to provide a rapid and local response against antigens from the environment. The IgE immune response employs potent expulsive and inflammatory forces against local antigen provocation, at the risk of damaging host tissues and causing allergic disease. Two well-known IgE receptors, the high-affinity FcεRI and low-affinity CD23, mediate the activities of IgE. Unlike other known antibody receptors, CD23 also regulates IgE expression, maintaining IgE homeostasis. This mechanism evolved by adapting the function of the complement receptor CD21. Recent insights into the dynamic character of IgE structure, its resultant capacity for allosteric modulation, and the potential for ligand-induced dissociation have revealed previously unappreciated mechanisms for regulation of IgE and IgE complexes. We describe recent research, highlighting structural studies of the IgE network of proteins to analyze the uniquely versatile activities of IgE and anti-IgE biologics.

Epithelial damage and tissue γδ T cells promote a unique tumor-protective IgE response.

IgE is an ancient and conserved immunoglobulin isotype with potent immunological function. Nevertheless, the regulation of IgE responses remains an enigma, and evidence of a role for IgE in host defense is limited. Here we report that topical exposure to a common environmental DNA-damaging xenobiotic initiated stress surveillance by γδTCR+ intraepithelial lymphocytes that resulted in class switching to IgE in B cells and the accumulation of autoreactive IgE. High-throughput antibody sequencing revealed that γδ T cells shaped the IgE repertoire by supporting specific variable-diversity-joining (VDJ) rearrangements with unique characteristics of the complementarity-determining region CDRH3. This endogenous IgE response, via the IgE receptor FcεRI, provided protection against epithelial carcinogenesis, and expression of the gene encoding FcεRI in human squamous-cell carcinoma correlated with good disease prognosis. These data indicate a joint role for immunosurveillance by T cells and by B cells in epithelial tissues and suggest that IgE is part of the host defense against epithelial damage and tumor development.

Mast Cells Get on Your Nerves in Itch.

Mast-cell-nerve interactions play an integral role in itch and inflammation. Meixiong et al. (2019) show that the receptors MRGPRB2 and FcεRI mediate distinct types of mast cell activation and nerve interactions and that mast cell activation through MRGPRB2 drives itch in allergic contact dermatitis.

Activation of Mast-Cell-Expressed Mas-Related G-Protein-Coupled Receptors Drives Non-histaminergic Itch.

Classical itch studies have focused on immunoglobulin E (IgE)-mediated mast cell activation and histamine release. Recently, members of the Mas-related G-protein-coupled receptor (Mrgpr) family have been identified as mast cell receptors, but their role in itch is unclear. Here, we report that mast cell activation via Mrgprb2 evoked non-histaminergic itch in mice independently of the IgE-Fc epsilon RI (FcεRI)-histamine axis. Compared with IgE-FcεRI stimulation, Mrgprb2 activation of mast cells was distinct in both released substances (histamine, serotonin, and tryptase) and the pattern of activated itch-sensory neurons. Mrgprb2 deficiency decreased itch in multiple preclinical models of allergic contact dermatitis (ACD), a pruritic inflammatory skin disorder, and both mast cell number and PAMP1-20 concentrations (agonist of the human Mrgprb2 homolog, MRGPRX2) were increased in human ACD skin. These findings suggest that this pathway may represent a therapeutic target for treating ACD and mast-cell-associated itch disorders in which antihistamines are ineffective.

Tyrosine phosphatase SHP-2 mediates C-type lectin receptor-induced activation of the kinase Syk and anti-fungal TH17 responses.

Fungal infection stimulates the canonical C-type lectin receptor (CLR) signaling pathway via activation of the tyrosine kinase Syk. Here we identify a crucial role for the tyrosine phosphatase SHP-2 in mediating CLR-induced activation of Syk. Ablation of the gene encoding SHP-2 (Ptpn11; called 'Shp-2' here) in dendritic cells (DCs) and macrophages impaired Syk-mediated signaling and abrogated the expression of genes encoding pro-inflammatory molecules following fungal stimulation. Mechanistically, SHP-2 operated as a scaffold, facilitating the recruitment of Syk to the CLR dectin-1 or the adaptor FcRγ, through its N-SH2 domain and a previously unrecognized carboxy-terminal immunoreceptor tyrosine-based activation motif (ITAM). We found that DC-derived SHP-2 was crucial for the induction of interleukin 1ß (IL-1ß), IL-6 and IL-23 and anti-fungal responses of the TH17 subset of helper T cells in controlling infection with Candida albicans. Together our data reveal a mechanism by which SHP-2 mediates the activation of Syk in response to fungal infection.

Sialylation of immunoglobulin E is a determinant of allergic pathogenicity.

Approximately one-third of the world's population suffers from allergies1. Exposure to allergens crosslinks immunoglobulin E (IgE) antibodies that are bound to mast cells and basophils, triggering the release of inflammatory mediators, including histamine2. Although IgE is absolutely required for allergies, it is not understood why total and allergen-specific IgE concentrations do not reproducibly correlate with allergic disease3-5. It is well-established that glycosylation of IgG dictates its effector function and has disease-specific patterns. However, whether IgE glycans differ in disease states or affect biological activity is completely unknown6. Here we perform an unbiased examination of glycosylation patterns of total IgE from individuals with a peanut allergy and from non-atopic individuals without allergies. Our analysis reveals an increase in sialic acid content on total IgE from individuals with a peanut allergy compared with non-atopic individuals. Removal of sialic acid from IgE attenuates effector-cell degranulation and anaphylaxis in several functional models of allergic disease. Therapeutic interventions-including removing sialic acid from cell-bound IgE with a neuraminidase enzyme targeted towards the IgE receptor FcεRI, and administering asialylated IgE-markedly reduce anaphylaxis. Together, these results establish IgE glycosylation, and specifically sialylation, as an important regulator of allergic disease.

Multistep IgE Mast Cell Desensitization Is a Dose- and Time-Dependent Process Partially Regulated by SHIP-1.

Multistep mast cell desensitization blocks the release of mediators following IgE crosslinking with increasing doses of Ag. Although its in vivo application has led to the safe reintroduction of drugs and foods in IgE-sensitized patients at risk for anaphylaxis, the mechanisms of the inhibitory process have remained elusive. We sought to investigate the kinetics, membrane, and cytoskeletal changes and to identify molecular targets. IgE-sensitized wild-type murine (WT) and FcεRIα humanized (h) bone marrow mast cells were activated and desensitized with DNP, nitrophenyl, dust mites, and peanut Ags. The movements of membrane receptors, FcεRI/IgE/Ag, actin, and tubulin and the phosphorylation of Syk, Lyn, P38-MAPK, and SHIP-1 were assessed. Silencing SHIP-1 protein was used to dissect the SHIP-1 role. Multistep IgE desensitization of WT and transgenic human bone marrow mast cells blocked the release of ß-hexosaminidase in an Ag-specific fashion and prevented actin and tubulin movements. Desensitization was regulated by the initial Ag dose, number of doses, and time between doses. FcεRI, IgE, Ags, and surface receptors were not internalized during desensitization. Phosphorylation of Syk, Lyn, p38 MAPK, and SHIP-1 increased in a dose-response manner during activation; in contrast, only SHIP-1 phosphorylation increased in early desensitization. SHIP-1 phosphatase function had no impact on desensitization, but silencing SHIP-1 increased ß-hexoxaminidase release, preventing desensitization. Multistep IgE mast cell desensitization is a dose- and time-regulated process that blocks ß-hexosaminidase, impacting membrane and cytoskeletal movements. Signal transduction is uncoupled, favoring early phosphorylation of SHIP-1. Silencing SHIP-1 impairs desensitization without implicating its phosphatase function.

Mast Cell Proteases Cleave Prion Proteins and a Recombinant Ig against PrP Can Activate Human Mast Cells.

IgE Abs, best known for their role in allergic reactions, have only rarely been used in immunotherapies. Nevertheless, they offer a potential alternative to the more commonly used IgGs. The affinity of IgE Ag binding influences the type of response from mast cells, so any immunotherapies using IgEs must balance Ag affinity with desired therapeutic effect. One potential way to harness differential binding affinities of IgE is in protein aggregation diseases, where low-affinity binding of endogenous proteins is preferred, but enhanced binding of clusters of disease-associated aggregated proteins could target responses to the sites of disease. For this reason, we sought to create a low-affinity IgE against the prion protein (PrP), which exists in an endogenous monomeric state but can misfold into aggregated states during the development of prion disease. First, we determined that mast cell proteases tryptase and cathepsin G were capable of degrading PrP. Then we engineered a recombinant IgE Ab directed against PrP from the V region of a PrP-specific IgG and tested its activation of the human mast cell line LAD2. The αPrP IgE bound LAD2 through Fc receptors. Crosslinking receptor-bound αPrP IgE activated SYK and ERK phosphorylation, caused Fc receptor internalization, and resulted in degranulation. This work shows that a recombinant αPrP IgE can activate LAD2 cells to release enzymes that can degrade PrP, suggesting that IgE may be useful in targeting diseases that involve protein aggregation.

Commensal Bacteria and the Lung Environment Are Responsible for Th2-Mediated Memory Yielding Natural IgE in MyD88-Deficient Mice.

IgE Abs are a common mediator of allergic responses and are generally produced in type 2 immune responses to allergens. Allergen stimulation of IgE-bound FcεRI on mast cells or basophils induces the production of chemical mediators and cytokines. In addition, IgE binding to FcεRI without allergen promotes the survival or proliferation of these and other cells. Thus, spontaneously produced natural IgE can increase an individual's susceptibility to allergic diseases. Mice deficient in MyD88, a major TLR signaling molecule, have high serum levels of natural IgE, the mechanism for which remains unknown. In this study, we demonstrated that the high serum IgE levels were maintained from weaning by memory B cells (MBCs). IgE from plasma cells and sera from most Myd88-/- mice, but none of the Myd88+/- mice, recognized Streptococcus azizii, a commensal bacterium overrepresented in the lungs of Myd88-/- mice. IgG1+ MBCs from the spleen also recognized S. azizii. The serum IgE levels declined with the administration of antibiotics and were boosted by challenge with S. azizii in Myd88-/- mice, indicating the contribution of S. azizii-specific IgG1+ MBCs to the natural IgE production. Th2 cells were selectively increased in the lungs of Myd88-/- mice and were activated upon addition of S. azizii in the lung cells ex vivo. Finally, lung nonhematopoietic cells, and CSF1 overproduced therefrom, were responsible for natural IgE production in Myd88-/- mice. Thus, some commensal bacteria may prime the Th2 response and natural IgE production in the MyD88-defective lung environment in general.

The Eotaxin-1/CCR3 Axis and Matrix Metalloproteinase-9 Are Critical in Anti-NC16A IgE-Induced Bullous Pemphigoid.

Bullous pemphigoid (BP) is the most common autoimmune bullous skin disease of humans and is characterized by eosinophilic inflammation and circulating and tissue-bound IgG and IgE autoantibodies directed against two hemidesmosomal proteins: BP180 and BP230. The noncollagenous 16A domain (NC16A) of BP180 has been found to contain major epitopes recognized by autoantibodies in BP. We recently established the pathogenicity of anti-NC16A IgE through passive transfer of patient-derived autoantibodies to double-humanized mice that express the human high-affinity IgE receptor, FcεRI, and human NC16A domain (FcεRI/NC16A). In this model, anti-NC16A IgEs recruit eosinophils to mediate tissue injury and clinical disease in FcεRI/NC16A mice. The objective of this study was to characterize the molecular and cellular events that underlie eosinophil recruitment and eosinophil-dependent tissue injury in anti-NC16A IgE-induced BP. We show that anti-NC16A IgEs significantly increase levels of key eosinophil chemoattractants, eotaxin-1 and eotaxin-2, as well as the proteolytic enzyme matrix metalloproteinase-9 (MMP-9) in the lesional skin of FcεRI/NC16A mice. Importantly, neutralization of eotaxin-1, but not eotaxin-2, and blockade of the main eotaxin receptor, CCR3, drastically reduce anti-NC16A IgE-induced disease activity. We further show that anti-NC16A IgE/NC16A immune complexes induce the release of MMP-9 from eosinophils, and that MMP-9-deficient mice are resistant to anti-NC16A IgE-induced BP. Lastly, we find significantly increased levels of eotaxin-1, eotaxin-2, and MMP-9 in blister fluids of BP patients. Taken together, this study establishes the eotaxin-1/CCR3 axis and MMP-9 as key players in anti-NC16A IgE-induced BP and candidate therapeutic targets for future drug development and testing.

Inhibiting Isoprenylation Suppresses FcεRI-Mediated Mast Cell Function and Allergic Inflammation.

IgE-mediated mast cell activation is a driving force in allergic disease in need of novel interventions. Statins, long used to lower serum cholesterol, have been shown in multiple large-cohort studies to reduce asthma severity. We previously found that statins inhibit IgE-induced mast cell function, but these effects varied widely among mouse strains and human donors, likely due to the upregulation of the statin target, 3-hydroxy-3-methylgutaryl-CoA reductase. Statin inhibition of mast cell function appeared to be mediated not by cholesterol reduction but by suppressing protein isoprenylation events that use cholesterol pathway intermediates. Therefore, we sought to circumvent statin resistance by targeting isoprenylation. Using genetic depletion of the isoprenylation enzymes farnesyltransferase and geranylgeranyl transferase 1 or their substrate K-Ras, we show a significant reduction in FcεRI-mediated degranulation and cytokine production. Furthermore, similar effects were observed with pharmacological inhibition with the dual farnesyltransferase and geranylgeranyl transferase 1 inhibitor FGTI-2734. Our data indicate that both transferases must be inhibited to reduce mast cell function and that K-Ras is a critical isoprenylation target. Importantly, FGTI-2734 was effective in vivo, suppressing mast cell-dependent anaphylaxis, allergic pulmonary inflammation, and airway hyperresponsiveness. Collectively, these findings suggest that K-Ras is among the isoprenylation substrates critical for FcεRI-induced mast cell function and reveal isoprenylation as a new means of targeting allergic disease.

Impaired interferon response in plasmacytoid dendritic cells from children with persistent wheeze.

BACKGROUND: Impaired interferon response and allergic sensitization may contribute to virus-induced wheeze and asthma development in young children. Plasmacytoid dendritic cells (pDCs) play a key role in antiviral immunity as critical producers of type I interferons. pDCs also express the high-affinity IgE receptor through which type I interferon production may be negatively regulated. Whether antiviral function of pDCs is associated with recurrent episodes of wheeze in young children is not well understood. OBJECTIVE: We sought to evaluate the phenotype and function of circulating pDCs in children with a longitudinally defined wheezing phenotype. METHODS: We performed multiparameter flow cytometry on PBMCs from 38 children presenting to the emergency department with an acute episode of respiratory wheeze and 19 controls. RNA sequencing on isolated pDCs from the same individuals was also performed. For each subject, their longitudinal exacerbation phenotype was determined using the Western Australia public hospital database. RESULTS: We observed a significant depletion of circulating pDCs in young children with a persistent phenotype of wheeze. The same individuals also displayed upregulation of the FcεRI on their pDCs. Based on transcriptomic analysis, pDCs from these individuals did not mount a robust systemic antiviral response as observed in children who displayed a nonrecurrent wheezing phenotype. CONCLUSIONS: Our data suggest that circulating pDC phenotype and function are altered in young children with a persistent longitudinal exacerbation phenotype. Expression of high-affinity IgE receptor is increased and their function as major interferon producers is impaired during acute exacerbations of wheeze.

BTK signaling-a crucial link in the pathophysiology of chronic spontaneous urticaria.

Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and basophils are the key pathogenic drivers of CSU; their activation results in histamine and cytokine release with subsequent dermal inflammation. Two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU: type I autoimmunity, also called autoallergy, which is mediated via IgE against various autoallergens, and type IIb autoimmunity, which is mediated predominantly via IgG directed against the IgE receptor FcεRI or FcεRI-bound IgE. Both mechanisms involve cross-linking of FcεRI and activation of downstream signaling pathways, and they may co-occur in the same patient. In addition, B-cell receptor signaling has been postulated to play a key role in CSU by generating autoreactive B cells and autoantibody production. A cornerstone of FcεRI and B-cell receptor signaling is Bruton tyrosine kinase (BTK), making BTK inhibition a clear therapeutic target in CSU. The potential application of early-generation BTK inhibitors, including ibrutinib, in allergic and autoimmune diseases is limited owing to their unfavorable benefit-risk profile. However, novel BTK inhibitors with improved selectivity and safety profiles have been developed and are under clinical investigation in autoimmune diseases, including CSU. In phase 2 trials, the BTK inhibitors remibrutinib and fenebrutinib have demonstrated rapid and sustained improvements in CSU disease activity. With phase 3 studies of remibrutinib ongoing, it is hoped that BTK inhibitors will present an effective, well-tolerated option for patients with antihistamine-refractory CSU, a phenotype that presents a considerable clinical challenge.

Solar urticaria involves rapid mast cell STAT3 activation and neutrophil recruitment, with FcεRI as an upstream regulator.

BACKGROUND: Solar urticaria is a rare photodermatosis characterized by rapid-onset sunlight-induced urticaria, but its pathophysiology is not well understood. OBJECTIVE: We sought to define cutaneous cellular and molecular events in the evolution of solar urticaria following its initiation by solar-simulated UV radiation (SSR) and compare with healthy controls (HC). METHODS: Cutaneous biopsy specimens were taken from unexposed skin and skin exposed to a single low (physiologic) dose of SSR at 30 minutes, 3 hours, and 24 hours after exposure in 6 patients with solar urticaria and 6 HC. Biopsy specimens were assessed by immunohistochemistry and bulk RNA-sequencing analysis. RESULTS: In solar urticaria specimens, there was enrichment of several innate immune pathways, with striking early involvement of neutrophils, which was not observed in HC. Multiple proinflammatory cytokine and chemokine genes were upregulated (including IL20, IL6, and CXCL8) or identified as upstream regulators (including TNF, IL-1ß, and IFN-γ). IgE and FcεRI were identified as upstream regulators, and phosphorylated signal transducer and activator of transcription 3 expression in mast cells was increased in solar urticaria at 30 minutes and 3 hours after SSR exposure, suggesting a mechanism of mast cell activation. Clinical resolution of solar urticaria by 24 hours mirrored resolution of inflammatory gene signature profiles. Comparison with available datasets of chronic spontaneous urticaria showed transcriptomic similarities relating to immune activation, but several transcripts were identified solely in solar urticaria, including CXCL8 and CSF2/3. CONCLUSIONS: Solar urticaria is characterized by rapid signal transducer and activator of transcription 3 activation in mast cells and involvement of multiple chemotactic and innate inflammatory pathways, with FcεRI engagement indicated as an early event.

Carnosic acid inhibits secretion of allergic inflammatory mediators in IgE-activated mast cells via direct regulation of Syk activation.

Mast cells are essential regulators of inflammation most recognized for their central role in allergic inflammatory disorders. Signaling via the high-affinity immunoglobulin E (IgE) receptor, FcεRI, leads to rapid degranulation of preformed granules and the sustained release of newly synthesized proinflammatory mediators. Our group recently established rosemary extract as a potent regulator of mast cell functions, attenuating MAPK and NF-κB signaling. Carnosic acid (CA)-a major polyphenolic constituent of rosemary extract-has been shown to exhibit anti-inflammatory effects in other immune cell models, but its role as a potential modulator of mast cell activation is undefined. Therefore, we sought here to determine the modulatory effects of CA in a mast cell model of allergic inflammation. We sensitized bone marrow-derived mast cells with anti-trinitrophenyl IgE and activated with allergen (TNP-BSA) under stem cell factor potentiation, in addition to treatment with CA. Our results indicate that CA significantly inhibits allergen-induced early phase responses including Ca2+ mobilization, ROS production, and subsequent degranulation. We also show CA treatment reduced late phase responses, including the release of all cytokines and chemokines examined following IgE stimulation and corresponding gene expression excepting that of CCL2. Importantly, we determined that CA mediates its inhibitory effects through modulation of tyrosine kinase Syk and downstream effectors TAK1 (Ser412) and Akt (Ser473) as well as NFκB signaling, while phosphorylation of FcεRI (γ chain) and MAPK proteins remained unaltered. These novel findings establish CA as a potent modulator of mast cell activation, warranting further investigation as a putative anti-allergy therapeutic.

Targeting glycogen synthase kinase 3 with CHIR99021 negatively regulates allergen-induced mast cell activation.

Mast cells are granulated immune sentinels responsible for allergic inflammation. Allergen-induced FcεRI-signaling leads to rapid degranulation in the early-phase and sustained production and release of pro-inflammatory mediators in the late phase. Glycogen synthase kinase 3 (GSK3) is a constitutively active serine/threonine kinase and a central molecular convergence point for several pro-inflammatory pathways. GSK3 inhibition has been shown to reduce inflammation but has not yet been fully characterized in mast cell activation. Therefore, the objective of this study was to evaluate GSK3 as a putative therapeutic target in allergic inflammation using the GSK3 inhibitor, CHIR99021. Here, we found that GSK3 inhibition impaired ROS production and degranulation. Through modulation of MKK4-JNK, c-jun, and NF-κB signaling, GSK3 inhibition reduced the production/release of IL-6, IL-13, TNF, and CCL1, while only the release of CCL2 and CCL3 was impaired. Furthermore, CHIR99021-mediated GSK3 inhibition altered the pro-inflammatory phenotype of mast cells, reducing c-kit receptor levels. This implicated GSK3 in FcεRI signaling, reducing release of IL-6, TNF, and CCL1 when stimulated through FcεRI, while CCL2 and CCL3 remained unaffected, and were increased when stimulated with SCF only. These results identify GSK3 as a potential therapeutic target of utility warranting further consideration in contexts of pathological mast cell activation.

Methiothepin downregulates SNAP-23 and inhibits degranulation of rat basophilic leukemia cells and mouse bone marrow-derived mast cells.

In the present study, we found that methiothepin (a nonselective 5-hydroxytryptamine [5-HT] receptor antagonist) inhibited antigen-induced degranulation in rat basophilic leukemia cells and mouse bone marrow-derived mast cells. Although antigen stimulation induces release of histamine and serotonin (5-HT) by exocytosis and mast cells express several types of 5-HT receptor, the detailed role of these receptors remains unclear. Here, pretreatment of cells with methiothepin attenuated increased intracellular Ca2+ concentration, phosphorylated critical upstream signaling components (Src family tyrosine kinases, Syk, and PLCγ1), and suppressed TNF-α secretion via inhibition of Akt (a Ser/Thr kinase activated by PI3K)and ERK phosphorylation. Furthermore, it inhibited PMA/ionomycin-induced degranulation; this finding suggested that methiothepin affected downstream signaling. IκB kinase ß phosphorylates synaptosomal associated protein 23, which regulates the fusion events of the secretory granule/plasma membrane after mast cell activation, resulting in degranulation. We showed that methiothepin blocked PMA/ionomycin-induced phosphorylation of synaptosomal associated protein 23 by inhibiting its interaction with IκB kinase ß. Together with the results of selective 5-HT antagonists, it is suggested that methiothepin inhibits mast cell degranulation by downregulating upstream signaling pathways and exocytotic fusion machinery through mainly 5-HT1A receptor. Our findings provide that 5-HT antagonists may be used to relieve allergic reactions.

Interleukin-3-dependent potentiation of IgE responsiveness in mouse basophils.

Basophils produce interleukins (IL)-4 in response to various stimuli and may contribute to type 2 immune responses to various infections and allergens. We found that resting basophils freshly isolated from mice produce IL-4 in response to IL-3 but not to high-affinity Fc receptor (FcεRI) cross-linking (CL), yet both required the immunoreceptor tyrosine-based activation motif (ITAM) containing adaptor Fc receptor γ-chain (FcRγ), while basophils activated in vitro by IL-3 become responsive to FcεRI CL. Acquisition of responsiveness to FcεRI CL occurred upon infection with Trichinella spiralis or administration of superantigen. Because cultured basophils return to a quiescent state upon starvation with IL-3 with surface FcεRI levels unchanged, this acquisition is reversible and probably reflects intracellular events requiring protein synthesis. Interestingly, similar activation-associated acquisition was observed for responsiveness to other stimuli, including CD200R3 CL, which is known to signal via DAP-12, and the allergen protease papain. This acquisition of responsiveness to FcεRI CL was inhibited by Jak inhibitor. Thus, the IL-3 signal bifurcates downstream of Jak, into two distinct pathway, one leading to IL-4 production and the other to render basophils competent to respond to stimuli dependent on ITAM-containing adaptors DAP12 and FcRγ for IL-4 production.

Biomarkers of Autologous Whole Blood Injection Efficacy in Patients with Chronic Spontaneous Urticaria with Autoreactivity: A Preliminary Study.

INTRODUCTION: Chronic spontaneous urticaria (CSU) with autoreactivity is often resistant to antihistamines. Autologous whole blood injection (AWBI) has shown potential efficacy in the treatment of this disease, but it is controversial. It is necessary to screen patients who are suitable for this therapy in advance. This study aimed to identify biomarkers that predict the efficacy of AWBI treatment in CSU patients with autoreactivity. METHODS: A total of 30 patients with autologous serum skin test-positive CSU treated with AWBI were included in this study; urticaria activity score (UAS7) was recorded and the treatment response was judged based on it. Levels of total serum IgE, anti-high-affinity IgE receptor (FcεRI) IgG, and basophils CD63 and FcεRI expressions, and D-dimer of all patients were determined and analyzed. RESULTS: Baseline levels of total IgE, D-dimer, basophil FcεRI and CD63 expressions showed good correlations with UAS7 variations. D-dimer, basophil FcεRI and CD63 expressions changed significantly before and after AWBI treatment in AWBI responders, and the basophil FcεRI and CD63 expressions consistently and dynamically decreased in AWBI responders during the treatment. Baseline levels of total IgE, D-dimer, basophil FcεRI and CD63 expressions showed certain predictive values for AWBI response. CONCLUSIONS: Baseline levels of total IgE, D-dimer, basophil FcεRI and CD63 expressions could be biomarkers of predicting AWBI efficacy in patients with CSU with autoreactivity.

The ectoenzyme E-NPP3 negatively regulates ATP-dependent chronic allergic responses by basophils and mast cells.

Crosslinking of the immunoglobulin receptor FcεRI activates basophils and mast cells to induce immediate and chronic allergic inflammation. However, it remains unclear how the chronic allergic inflammation is regulated. Here, we showed that ecto-nucleotide pyrophosphatase-phosphodiesterase 3 (E-NPP3), also known as CD203c, rapidly induced by FcεRI crosslinking, negatively regulated chronic allergic inflammation. Basophil and mast cell numbers increased in Enpp3(-/-) mice with augmented serum ATP concentrations. Enpp3(-/-) mice were highly sensitive to chronic allergic pathologies, which was reduced by ATP blockade. FcεRI crosslinking induced ATP secretion from basophils and mast cells, and ATP activated both cells. ATP clearance was impaired in Enpp3(-/-) cells. Enpp3(-/-)P2rx7(-/-) mice showed decreased responses to FcεRI crosslinking. Thus, ATP released by FcεRI crosslinking stimulates basophils and mast cells for further activation causing allergic inflammation. E-NPP3 decreases ATP concentration and suppresses basophil and mast cell activity.