Basophil Expression Research Articles

Omalizumab reduces allergic rhinitis symptoms due to Japanese cedar pollen by improving eosinophilic inflammation.

Seasonal allergic rhinitis caused by Japanese cedar pollen (SAR-JCP) is a serious social problem in Japan, affecting 38.8% of the population (1). Omalizumab, a recombinant humanised monoclonal anti-immunoglobulin (Ig)E antibody, reduces serum-free IgE levels by 84-99% (2). The reduction of serum-free IgE levels induced by omalizumab ultimately downregulates FcεRI expression in basophils and mast cells (3). Omalizumab significantly reduces nasal symptoms and improves the quality of life in patients with allergic rhinitis (4,5); however, other than a decrease in free IgE, its biomarker activity is unclear. Allergic rhinitis reactions are more pronounced in nasal secretions and mucosa than in serum; however, no studies have examined the changes in proteins in nasal secretions after omalizumab administration. In this study, we aimed to elucidate the pathophysiology of the effect of omalizumab. This may serve as a basis for the identification of new biomarkers through the examination of proinflammatory proteins in nasal secretions, which may reflect the pathophysiology more accurately than peripheral blood.

Increased expression of formyl peptide receptor-1 by basophils from patients with mastocytosis

BackgroundSymptoms in patients with systemic mastocytosis (SM) are associated with an increase in mast cell burden and release of mast cell-derived mediators. The most frequent presentation of SM is indolent (ISM), with moderate symptoms and prognosis. Basophil numbers in these patients are generally normal. However, when examining basophil activation in patients with ISM, we noted an abnormal response to N-formylmethione-leucyl-phenylalanine (fMLP). ObjectiveTo compare basophil responsiveness to fMLP and anti-IgE in healthy volunteers and patients with ISM and relate findings to fMLP receptor (FPR) expression. MethodsBasophils isolated from peripheral blood of fifteen patients with ISM and fourteen healthy volunteers were stimulated with fMLP or anti-IgE. CD63 expression to assess basophil activation and expression of FPRs were assessed by flow cytometry. ResultsBaseline expression of CD63 on basophils was similar between healthy volunteers and patients with ISM. fMLP induced higher expression of CD63 on basophils from patients with ISM, while responses to anti-IgE were similar between groups. Basophils from patients with ISM also had higher fMLP1 receptor (FPR1) expression, while FPR2 and FPR3 were not detected. fMLP blocked the binding of anti-FPR1 antibody to FPR1, consistent with the conclusion that fMLP signals through FPR1. ConclusionsFMLP-induced basophil activation is higher in patients with ISM which is associated with an increase in FPR1 expression. Further investigation is needed to determine why FPR1 expression is elevated, whether such expression might serve as an additional surrogate marker in the diagnosis of ISM, and whether enhanced responses of basophils to fMPL might have some relationship to unexplained episodes of mediator release.

Forsythia velutina Nakai extract: A promising therapeutic option for atopic dermatitis through multiple cell type modulation.

Atopic dermatitis (AD) is a complex condition characterized by impaired epithelial barriers and dysregulated immune cells. In this study, we demonstrated Forsythia velutina Nakai extract (FVE) simultaneously inhibits basophils, macrophages, keratinocytes, and T cells that are closely interrelated in AD development. We analyzed the effect of FVE on nitric oxide and reactive oxygen species (ROS) production in macrophages, basophil degranulation, T cell activation, and tight junctions in damaged keratinocytes. Expression of cell-type-specific inflammatory mediators was analyzed, and the underlying signaling pathways for anti-inflammatory effects of FVE were investigated. The anti-inflammatory effects of FVE were validated using a DNCB-induced mouse model of AD. Anti-inflammatory activity of compounds isolated from FVE was validated in each immune cell type. FVE downregulated the expression of inflammatory mediators and ROS production in macrophages through TLR4 and NRF2 pathways modulation. It significantly reduced basophil degranulation and expression of type 2 (T2) and pro-inflammatory cytokines by perturbing FcεRI signaling. Forsythia velutina Nakai extract also robustly inhibited the expression of T2 cytokines in activated T cells. Furthermore, FVE upregulated the expression of tight junction molecules in damaged keratinocytes and downregulated leukocyte attractants, as well as IL-33, an inducer of T2 inflammation. In the AD mouse model, FVE showed superior improvement in inflammatory cell infiltration and skin structure integrity compared to dexamethasone. Dimatairesinol, a lignan dimer, was identified as the most potent anti-inflammatory FVE compound. Forsythia velutina Nakai extract and its constituent compounds demonstrate promising efficacy as a therapeutic option for prolonged AD treatment by independently inhibiting various cell types associated with AD and disrupting the deleterious link between them.

Basophil responses in susceptible AKR mice upon infection with the intestinal helminth parasite Trichuris muris.

Intestinal helminth infection promotes a Type 2 inflammatory response in resistant C57BL/6 mice that is essential for worm clearance. The study of inbred mouse strains has revealed factors that are critical for parasite resistance and delineated the role of Type 1 versus Type 2 immune responses in worm clearance. In C57BL/6 mice, basophils are key innate immune cells that promote Type 2 inflammation and are programmed via the Notch signalling pathway during infection with the helminth Trichuris muris. However, how the host genetic background influences basophil responses and basophil expression of Notch receptors remains unclear. Here we use genetically susceptible inbred AKR/J mice that have a Type 1-skewed immune response during T. muris infection to investigate basophil responses in a susceptible host. Basophil population expansion occurred in AKR/J mice even in the absence of fulminant Type 2 inflammation during T. muris infection. However, basophils in AKR/J mice did not robustly upregulate expression of the Notch2 receptor in response to infection as occurred in C57BL/6 mice. Blockade of the Type 1 cytokine interferon-γ in infected AKR/J mice was not sufficient to elicit infection-induced basophil expression of the Notch2 receptor. These data suggest that the host genetic background, outside of the Type 1 skew, is important in regulating basophil responses during T. muris infection in susceptible AKR/J mice.

A Co-Expressed Natural Antisense RNA FCER1A-AS Controls IgE-Dependent Immunity by Promoting Expression of FcεRIα.

As the α-subunit of the high-affinity receptor for the Fc portion of immunoglobulin E (FcεRIα), FcεRIα plays a central role in IgE-mediated allergic disorders and in the immunity and immunopathology of some parasitic infections. FcεRIα is specifically expressed on basophils and mast cells, but the mechanism that controls FcεRIα expression in these cells is poorly understood. In this study, we found that the natural antisense transcript (NAT) of FcεRIα (FCER1A-AS) is co-expressed with the sense transcript (FCER1A-S) in both interleukin (IL)-3-induced FcεRIα-expressing cells and in the high FcεRIα-expressing cell line MC/9. When FCER1A-AS is selectively knocked down by the CRISPR/RfxCas13d (CasRx) approach in MC/9 cells, the expression of both FCER1A-S mRNA and proteins is markedly decreased. Furthermore, FCER1A-AS deficiency was also found to be associated with a lack of FCER1A-S expression in vivo. Correspondingly, homozygous mice deficient in FCER1A-AS demonstrated a similar phenotype to FCER1A knockout mice in Schistosoma japonicum infection and in IgE-FcεRIα-mediated cutaneous anaphylaxis. Thus, we uncovered a novel pathway for the control of FcεRIα expression by its co-expressed natural antisense transcript. IMPORTANCE FcεRIα is responsible for high-affinity binding with the Fc portion of IgE, which is critical for IgE-dependent disease responses such as allergy responses and anti-parasite immunity. FcεRIα is expressed on a few cell types, including mast cells and basophils. Although the expression of FcεRIα is known to be promoted by the IL-3-GATA-2 pathway during its differentiation, the mechanism by which FcεRIα expression is maintained remains unknown. In this study, we discovered that a natural antisense transcript, FCER1A-AS, is co-expressed with the sense transcript. The presence of FCER1A-AS is essential for sense transcript expression in mast cells and basophils, but not for the differentiation of these cells through cis-regulation. Like FcεRIα knockout mice, mice lacking FCER1A-AS also exhibit reduced survival after Schistosoma japonicum infection and a lack of IgE-mediated cutaneous anaphylaxis. Thus, a novel pathway for regulating IgE-mediated allergic diseases through noncoding RNAs has been revealed.

Abstract 5454: Amdizalisib (HMPL-689), a highly selective PI3Kδ inhibitor, exhibits potent anti-tumor activity in pre-clinical B-cell lymphoma models

Abstract Background: The delta isoform of PI3K (PI3Kδ) plays an important role in B-cell development and function by mediating the signaling of key receptors on B cells. Aberrant activation of PI3Kδ signaling pathway promotes the survival and proliferation of malignant B cells, making selective inhibition of this isoform a promising therapeutic approach for the treatment of B cell malignances. Amdizalisib (HMPL-689, Amdiz), discovered and being currently developed in a pivotal phase II clinical trial (NCT04849351) by HUTCHMED, is a highly potent and selective PI3Kδ inhibitor. Based on encouraging clinical data from the phase Ib study (2021 ESMO, abstract# 8330), Amdiz is a designated breakthrough therapy in China for treatment of relapsed and refractory follicular lymphoma. Herein, we report the pre-clinical anti-tumor activity of Amdiz. Methods: Kinase activity was measured by Transcreener™ Fluorescence Polarization assay. The kinome selectivity profile of Amdiz was evaluated in Eurofins KinaseProfiler™ panel containing 323 kinases. Cell based phosphorylation of AKT was determined by using Acumen Explorer system. CD63 expression in basophils was evaluated by FACS assay. Inhibitory effects of Amdiz alone or in combination with other agents on cell viability were investigated in a panel of B cell lymphoma cell lines by CellTiter-Glo luminescent or CCK-8 assay. The ability of Amdiz to inhibit the activation of B cells in animals was evaluated in naïve rats using an ex vivo assay, and B cell activation was determined by evaluating CD86 expression using FACS analysis. Human B cell lymphoma cell line derived xenograft models were used to determine the anti-tumor activity of Amdiz in combination with other agents such as rituximab, BTK inhibitor, and venetoclax. Results: Amdiz is a highly selective inhibitor of PI3Kδ, showing more than 250-fold selectivity over other PI3K isoforms and no significant inhibition over other 319 protein kinases at the concentration of 1 µM. Amdiz potently inhibited PI3Kδ in biochemical, cellular and human whole blood assays with IC50s ranging from 0.8-3 nM. Its inhibitory effects on cell viability were also evaluated in a panel of B -cell lymphoma cell lines. Results showed that Amdiz potently inhibited cell survival with IC50s from 0.005 to 5 μM. Amdiz showed a long-lasting and strong inhibition on B cell activation in a rat pharmacodynamics (PD) study at a dose as low as 0.1 mg/kg. Moreover, Amdiz significantly improved anti-tumor activity of standard-of-care agents as well as targeted agents in multiple B-cell lymphoma models both in vitro and in vivo. Conclusion: Amdiz is a highly potent and selective PI3Kδ inhibitor with strong activity against B-cell lymphoma in pre-clinical studies, supporting clinical evaluation as either a single agent or in combination with other therapeutic agents for the treatment of B-cell malignancies. Citation Format: Jia Hu, Jianhan Wang, Xiaoming Dai, Jianlin He, Junqing Liang, Ying Yu, Juntao Yu, Na Yang, Linfang Wang, Yu Cai, Xiong Li, Weiguo Qing, Yongxin Ren, Weiguo Su. Amdizalisib (HMPL-689), a highly selective PI3Kδ inhibitor, exhibits potent anti-tumor activity in pre-clinical B-cell lymphoma models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5454.

IFN-γ Induces PD-L1 Expression in Primed Human Basophils.

Programmed death-ligand 1 (PD-L1) plays a key role in maintaining immune tolerance and also in immune evasion of cancers and pathogens. Though the identity of stimuli that induce PD-L1 in various human innate cells and their function are relatively well studied, data on the basophils remain scarce. In this study, we have identified one of the factors, such as IFN-γ, that induces PD-L1 expression in human basophils. Interestingly, we found that basophil priming by IL-3 is indispensable for IFN-γ-induced PD-L1 expression in human basophils. However, priming by other cytokines including granulocyte-macrophage colony-stimulating factor (GM-CSF) and thymic stromal lymphopoietin (TSLP) was dispensable. Analyses of a published microarray data set on IL-3-treated basophils indicated that IL-3 enhances IFNGR2, one of the chains of the IFNGR heterodimer complex, and CD274, thus providing a mechanistic insight into the role of IL-3 priming in IFN-γ-induced PD-L1 expression in human basophils.

IgE and high-affinity IgE receptor in chronic inducible urticaria, pathogenic, and management relevance.

BackgroundIgE and high‐affinity IgE receptor (FcεRI) expression on basophils have been scarcely explored in patients with chronic inducible urticaria (CIndU).ObjectivesTo investigate baseline serum IgE and FcεRI expression on blood basophils in a large cohort of CIndU patients and its relationship to treatment response.MethodsBaseline total serum IgE and basophil FcεRI expression measured by flow cytometry in 165 patients with CIndU was studied. The relationship of both parameters with the response to antihistamine and anti‐IgE (omalizumab) treatment was considered in a subsample of CIndU patients. FcεRI expression in basophils was assessed by mean fluorescence intensity (MFI) and basophil FcεRI standardized density (receptors/cell).ResultsThe median FcεRI expression standardized per density in blood basophils was found significantly higher in patients with CIndU compared to HCs. A positive correlation was found between IgE serum levels and basophil FcεRI expression. Basal FcεRI expression was not related to antihistamine treatment response. However, it was related to omalizumab, and patients responding to omalizumab showed higher basal basophil expression of FcεRI levels. Non‐responders to the antihistamine showed significantly higher IgE serum levels.ConclusionsFcεRI receptor overexpression in patients with CIndU shows almost the same pattern than chronic spontaneous urticaria. It seems to be independent of CIndU subtypes. Although additional studies would be welcome, our work highlights the relevance of FcεRI receptor regulation in CIndU supporting autoimmune basophil and mast cell activation and may be a biomarker for response to anti‐IgE therapy.

Regulation of Trafficking and Signaling of the High Affinity IgE Receptor by FcεRIβ and the Potential Impact of FcεRIβ Splicing in Allergic Inflammation.

Mast cells are tissue-resident immune cells that function in both innate and adaptive immunity through the release of both preformed granule-stored mediators, and newly generated proinflammatory mediators that contribute to the generation of both the early and late phases of the allergic inflammatory response. Although mast cells can be activated by a vast array of mediators to contribute to homeostasis and pathophysiology in diverse settings and contexts, in this review, we will focus on the canonical setting of IgE-mediated activation and allergic inflammation. IgE-dependent activation of mast cells occurs through the high affinity IgE receptor, FcεRI, which is a multimeric receptor complex that, once crosslinked by antigen, triggers a cascade of signaling to generate a robust response in mast cells. Here, we discuss FcεRI structure and function, and describe established and emerging roles of the β subunit of FcεRI (FcεRIβ) in regulating mast cell function and FcεRI trafficking and signaling. We discuss current approaches to target IgE and FcεRI signaling and emerging approaches that could target FcεRIβ specifically. We examine how alternative splicing of FcεRIβ alters protein function and how manipulation of splicing could be employed as a therapeutic approach. Targeting FcεRI directly and/or IgE binding to FcεRI are promising approaches to therapeutics for allergic inflammation. The characteristic role of FcεRIβ in both trafficking and signaling of the FcεRI receptor complex, the specificity to IgE-mediated activation pathways, and the preferential expression in mast cells and basophils, makes FcεRIβ an excellent, but challenging, candidate for therapeutic strategies in allergy and asthma, if targeting can be realized.

Der f 38 Is a Novel TLR4-Binding Allergen Related to Allergy Pathogenesis from Dermatophagoides farinae.

It is difficult to treat allergic diseases including asthma completely because its pathogenesis remains unclear. House dust mite (HDM) is a critical allergen and Toll-like receptor (TLR) 4 is a member of the toll-like receptor family, which plays an important role in allergic diseases. The purpose of this study was to characterize a novel allergen, Der f 38 binding to TLR4, and unveil its role as an inducer of allergy. Der f 38 expression was detected in the body and feces of Dermatophagoides farinae (DF). Electron microscopy revealed that it was located in the granule layer, the epithelium layer, and microvilli of the posterior midgut. The skin prick test showed that 60% of allergic subjects were Der f 38-positive. Der f 38 enhanced surface 203c expression in basophils of Der f 38-positive allergic subjects. By analysis of the model structure of Der p 38, the expected epitope sites are exposed on the exterior side. In animal experiments, Der f 38 triggered an infiltration of inflammatory cells. Intranasal (IN) administration of Der f 38 increased neutrophils in the lung. Intraperitoneal (IP) and IN injections of Der f 38 induced both eosinophils and neutrophils. Increased total IgE level and histopathological features were found in BALB/c mice treated with Der f 38 by IP and IN injections. TLR4 knockout (KO) BALB/c mice exhibited less inflammation and IgE level in the sera compared to wild type (WT) mice. Der f 38 directly binds to TLR4 using biolayer interferometry. Der f 38 suppressed the apoptosis of neutrophils and eosinophils by downregulating proteins in the proapoptotic pathway including caspase 9, caspase 3, and BAX and upregulating proteins in the anti-apoptotic pathway including BCL-2 and MCL-1. These findings might shed light on the pathogenic mechanisms of allergy to HDM.

Human peripheral basophils extended phenotype shows a high expression of CD244 immuno-regulatory receptor

IntroductionBasophils play a major physio-pathological role in hypersensitivity related diseases. Basophils express high affinity Immunoglobulin (Ig) E receptors (FcεRI), IgG and complement regulatory. Basophils also have immunoregulatory activity through interaction with T cells. The aim of this study was to look for the expression of markers reflecting the activation status of peripheral Basophil in healthy donors. Methodthe study was performed on 29 healthy donors, 62% females with a mean age of 50.1 + 17.0 years. Basophils were identified on their expression of CD123 without HLA-DR and/or CD193 in two 8 colors panels including CD46, CD55, CD59, CD203c, CD32 (FcγRII), CD64 (FcγRIII), CD163, CD137L (4-1BBL), CD252 (OX40L), CD244 (2B4) and CD3 on whole blood. Basophil activation with anti IgE was performed on 14 donors. Results and discussionOur results confirmed the Basophil expression of CD123, CD193 and CD203 (the latter is strongly increased under stimulation). Complement regulatory proteins (CD46, CD55, CD59) were expressed at the same levels as on other leukocytes; CD46, CD59 expression being slightly increased under stimulation. CD32 and CD163 scavenger were slightly higher than on lympho and not influenced by activation. CD252 or CD137L were expressed at low levels and significantly induced by stimulation. Most of all, CD244 was highly expressed on Basophils as compared to any other leukocytes in fresh peripheral blood. ConclusionsOur study shows that human resting Basophils express IgE and IgG Fc receptors and check point receptor CD244 that could potentially play a role in their previously reported immunoregulatory activity in sensitization and even in tumor immune escape.

Biomarkers for the Diagnosis of Allergic Bronchopulmonary Aspergillosis in Cystic Fibrosis: A Systematic Review and Meta-Analysis

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity reaction to Aspergillus fumigatus and impacts 10% of individuals with cystic fibrosis (CF). A diagnosis of ABPA is challenging to establish in CF owing to overlapping clinical and radiologic features with CF lung disease. Recent studies have identified blood tests, imaging, and other biomarkers that may be useful for diagnosis. To summarize biomarkers that can aid in the diagnosis of ABPA in CF patients and to quantify their diagnostic accuracy through meta-analysis. We searched MEDLINE, EMBASE, and the Cochrane Controlled Register of Trials and included studies that used a laboratory technique or imaging modality in CF patients diagnosed with ABPA. Pooled sensitivity and specificity were calculated using a hierarchical summary receiver operating characteristic model. We identified 791 articles, of which 29 met our eligibility criteria and 9 were included in the meta-analysis. Hyperattenuating mucus on computed tomography (CT) scan (n= 3 studies; pooled sensitivity 62% and specificity 92%) and serum specific immunoglobulin E against recombinant Aspergillus funigatus antigens f4 (n= 6; 69%, 89%) and f6 (n= 6; 39%, 97%) demonstrated high specificity. Based on single studies, serum thymus and activation regulated chemokine (92%, 94%), stimulated basophil expression of CD203c (94%, 74%), the inverted mucoid impaction signal on magnetic resonance imaging (94%, 100%), and skin prick test with recombinant Aspergillus fumigatus f4 and/or f6 (100%, 100%) showed high sensitivity and specificity. Recent studies have found promising biomarkers for diagnosing ABPA in CF. Further research is needed to improve our understanding of their utility in diagnosis and disease monitoring.

Effects of the Maillard reaction on the epitopes and immunoreactivity of tropomyosin, a major allergen in Chlamys nobilis.

Scallop (Chlamys nobilis) causes an IgE-mediated food allergy; however, studies of the allergens in its musculus are not sufficiently comprehensive. In this context, the target protein was purified from scallops and confirmed to be the major allergen tropomyosin (TM) using proteomic technology and serological testing. Subsequently, seven potential IgE epitopes of TM were obtained using phage display technology with IgE enrichment from the serum of scallop-sensitized patients and identified via inhibition enzyme-linked immunosorbent assays. A method for the Maillard reaction of TM and xylose was established, and Maillard-reacted TM (MR-TM) showed significantly decreased immunobinding activity and CD63 and CD203c expression in basophils compared with TM. Furthermore, shotgun proteomics analysis showed that eleven specific amino acids (K12, R15, K28, K76, R125, R127, K128, R133, R140, K146, and K189) of the six IgE epitopes of TM were modified after the Maillard reaction. Overall, the immunoactivity of MR-TM was reduced, which provides a theoretical reference for the development of hypoallergenic foods.

Epithelial Cell-Associated Galectin-3 Activates Human Dendritic Cell Subtypes for Pro-Inflammatory Cytokines.

There is mounting evidence that galectin-3 is a prognostic and diagnostic biomarker associated with diverse diseases and conditions, including cancer, cardiovascular disease, autoimmunity, wound healing, allergic disease, and chronic inflammation in general. Yet, whether and exactly how galectin-3 may participate in the pathogenesis of these diseases remains poorly understood. Recently, we have linked the expression of galectin-3 on the A549 epithelial cell line –an adenocarcinoma, to the activation of human basophils for the release of histamine and secretion of IL-4 and IL-13. These responses proved dependent on cell-to-cell contact, basophil expression of IgE, were inhibited by n-acetyllactosamine, and were ablated when basophils were co-cultured with A549 clones lacking galectin-3 expression. While recombinant galectin-3 failed to activate basophils when in solution, microspheres expressing this lectin did so by mimicking the responses seen when using A549 cells. Given the IgE dependency of the basophil responses, and the fact that galectin-3 is long known to bind this immunoglobulin, we hypothesize that a similar mode of activation extends to other IgE-bearing cells. To investigate this possibility, we tested epithelial cell-associated galectin-3 for its capacity to activate human dendritic cells, including the plasmacytoid and myeloid subtypes as well as monocytes, all of which bind IgE. Indeed, results indicate that epithelial cell-associated galectin-3 activated these cells for robust production of TNF-α and IL-6 and up-regulated the expression of activation markers found on dendritic cells. Moreover, many of the same parameters previously observed for basophils applied to the findings herein, including evidence that matrix-bound galectin-3 (whether on epithelial cells or microspheres) facilitates this mode of activation. In contrast, IgE expression was dispensable for these galectin-3-dependent cytokine responses, implying that this lectin activates dendritic cells (and monocytes) by binding to a glycoprotein other than this immunoglobulin. Overall, these findings further demonstrate how galectin-3 mediates immune cell activation, providing novel insight into how this lectin may promote chronic inflammation underlying the pathogenesis of many diseases.

A Granulocytic Signature Identifies COVID-19 and Its Severity.

BackgroundAn unbiased approach of SARS-CoV-2-induced immune dysregulation has not been undertaken so far. We aimed to identify previously unreported immune markers able to discriminate COVID-19 patients from healthy controls and to predict mild and severe disease.MethodsAn observational, prospective, multicentric study was conducted in patients with confirmed COVID-19: mild/moderate (n=7) and severe (n=19). Immunophenotyping of whole blood leukocytes was performed in patients upon hospital ward or intensive care unit admission and in healthy controls (n=25). Clinically relevant associations were identified through unsupervised analysis.ResultsGranulocytic (neutrophil, eosinophil and basophil) markers were enriched during COVID-19 and discriminated between mild and severe patients. Increased counts of CD15 +CD16 + neutrophils, decreased granulocytic expression of integrin CD11b, and Th2-related CRTH2 downregulation in eosinophils and basophils established a COVID-19 signature. Severity was associated with the emergence of PDL1 checkpoint expression in basophils and eosinophils. This granulocytic signature was accompanied by monocyte and lymphocyte immunoparalysis. Correlation with validated clinical scores supported pathophysiological relevance.ConclusionPhenotypic markers of circulating granulocytes are strong discriminators between infected and uninfected individuals as well as between severity stages. COVID-19 alters the frequency and functional phenotypes of granulocyte subsets with the emergence of CRTH2 as a disease biomarker.

A new standardized phytoextract from red orange and lemon wastes (red orange and lemon extract) reduces basophil degranulation and activation

Citrus fruits are rich sources of bioactive compounds and their consumption is associated to health-promoting effects. Citrus processing wastes contain bioflavonoids and other high added value compounds. The aim of this study was to evaluate the antiallergic properties of a new phytoextract obtained by citrus wastes and peels. Blood orange and lemon processing wastes were used to produce a Red orange and Lemon Extract (RLE). Blood samples from 30 allergic donors were collected and used to evaluate the basophil activation (CD203c) and degranulation (CD63) by stimulation trough allergen with and without the RLE. Reduced basophil expression of CD203c and CD63 were observed in RLE + Allergen treated samples, with −20.21% of CD203c expression (p < 0.0001) and −54.11% of CD63 expression (p < 0.0001), compared to Allergen treated samples. The RLE evidenced a good antiallergic activity, mainly acting on basophils degranulation, and therefore reducing the key event of pro-inflammatory mediators release after allergic stimuli.

The Expression and Function of CD300 Molecules in the Main Players of Allergic Responses: Mast Cells, Basophils and Eosinophils.

Allergy is the host immune response against non-infectious substances called allergens. The prevalence of allergic diseases is increasing worldwide. However, while some drugs counteract the symptomatology caused by allergic reactions, no completely effective treatments for allergic diseases have been developed yet. In this sense, the ability of surface activating and inhibitory receptors to modulate the function of the main effector cells of allergic responses makes these molecules potential pharmacological targets. The CD300 receptor family consists of members with activating and inhibitory capabilities mainly expressed on the surface of immune cells. Multiple studies in the last few years have highlighted the importance of CD300 molecules in several pathological conditions. This review summarizes the literature on CD300 receptor expression, regulation and function in mast cells, basophils and eosinophils, the main players of allergic responses. Moreover, we review the involvement of CD300 receptors in the pathogenesis of certain allergic diseases, as well as their prospective use as therapeutic targets for the treatment of IgE-dependent allergic responses.

Allergic inflammation is initiated by IL-33-dependent crosstalk between mast cells and basophils.

IgE-primed mast cells in peripheral tissues, including the skin, lung, and intestine, are key initiators of allergen-triggered edema and inflammation. Particularly in severe forms of allergy, this inflammation becomes strongly neutrophil dominated, and yet how mast cells coordinate this type of response is unknown. We and others have reported that activated mast cells––a hematopoietic cell type––can produce IL-33, a cytokine known to participate in allergic responses but generally considered as being of epithelial origin and driving Type 2 immune responses (e.g., ILC2 and eosinophil activation). Using models of skin anaphylaxis, our data reveal that mast cell-derived IL-33 also initiates neutrophilic inflammation. We demonstrate a cellular crosstalk mechanism whereby activated mast cells crosstalk to IL-33 receptor–bearing basophils, driving these basophils to adopt a unique response signature rich in neutrophil-associated molecules. We further establish that basophil expression of CXCL1 is necessary for IgE-driven neutrophilic inflammation. Our findings thus unearth a new mechanism by which mast cells initiate local inflammation after antigen triggering and might explain the complex inflammatory phenotypes observed in severe allergic diseases. Moreover, our findings (i) establish a functional link from IL-33 to neutrophilic inflammation that extends IL-33–mediated biology well beyond that of Type 2 immunity, and (ii) demonstrate the functional importance of hematopoietic cell–derived IL-33 in allergic pathogenesis.

Identifying regulatory pathways of spleen tyrosine kinase expression in human basophils

Expression levels of spleen tyrosine kinase (SYK), a critical signaling tyrosine kinase in basophils, are uniquely low relative to all other circulating leukocytes, and levels are highly variable in the population. We sought to determine whether transcriptional regulation of SYK through unique silencing of the SYK gene determines its basophil-specific expression patterns. Culture-derived basophils (CD34B cells) were derived from cultures of CD34+ progenitor cells by using 2 methods (G1 or G3). Peripheral blood basophils (PBBs; relative SYK protein level= 1), B cells (SYK= 8), CD34B-G1 cells (SYK= 11), and CD34B-G3 cells (SYK= 5) were examined by using assay for transposase-accessible chromatin sequencing (ATAC-seq) methods. In addition, the transcriptomes of 6 cell types, PBBs, peripheral blood eosinophils (SYK= 11), plasmacytoid dendritic cells (SYK= 30), CD34+ progenitors (SYK= 11), CD34B-G1 cells, and CD34B-G3 cells, were analyzed for patterns that matched patterns of SYK expression in these cells, with a focus on transcription factors. ATAC-seq showed that PBBs have multiple open regions in the SYK gene, suggesting a nonsilenced state with 1 region unique to PBBs (low SYK expression), 1 region unique to both PBBs (low SYK expression) and both G1 and G3 CD34B cells (high and moderate SYK expression, respectively), and 5 regions unique to B cells (high SYK expression). SYK expression across the 6 cell types explored showed a unique pattern that was matched to expression patterns of 3 transcription factors: Kruppel-like factor 5 (KLF5), zinc-finger protein 608 (ZNF608), and musculoaponeurotic fibrosarcoma protein (c-MAF). Two new potential regulatory pathways for SYK expression were identified. One appears independent of transcriptional regulation, and one appears to be dependent on transcriptional control in the SYK gene.

Association of Basophil-Expressing Genes with Effectiveness of Sublingual Immunotherapy.

Basophils were reported to be associated with allergy pathogenesis and the efficacy of allergen immunotherapy. Using a purified cedar allergen, we recently studied the effectiveness of sublingual immunotherapy for patients with Japanese cedar pollinosis. Patients were classified as high responders (HR) and nonresponders (NR), and comprehensive microarray analysis was used to examine peripheral basophils in both groups. A total of 153 genes were differentially expressed in HR and NR patients. Most of these differentially expressed genes encoded intracellular molecules, and expression levels were higher in HR patients than in NR patients. mRNA expression of the gene encoding D4, zinc, and double plant homeodomain (PHD) fingers family 2 (DPF2) was significantly correlated with copy number variation (CNV). Genetic variation in the DPF2 gene and its expression in basophils might be associated with the efficacy of sublingual immunotherapy.