The immunoglobulin superfamily member CD200R identifies cells involved in type 2 immune responses

Disease modification in inflammatory skin disorders: opportunities and challenges

Progress in understanding of the mechanisms underlying chronic inflammatory skin disorders, such as atopic dermatitis and psoriasis vulgaris, has led to new treatment options with the primary goal of alleviating symptoms. In addition, this knowledge has the potential to inform on new strategies aimed at inducing deep and therapy-free remission, that is, disease modification, potentially impacting on associated comorbidities. However, to reach this goal, key areas require further exploration, including the definitions of disease modification and disease activity index, further understanding of disease mechanisms and systemic spillover effects, potential windows of opportunity, biomarkers for patient stratification and successful intervention, as well as appropriate study design. This Perspective article assesses the opportunities and challenges in the discovery and development of disease-modifying therapies for chronic inflammatory skin disorders.

23ME-00610, a genetically informed, first-in-class antibody targeting CD200R1 to enhance antitumor T cell function

Immune checkpoint inhibition (ICI) has revolutionized cancer treatment; however, only a subset of patients benefit long term. Therefore, methods for identification of novel checkpoint targets and development of therapeutic interventions against them remain a critical challenge. Analysis of human genetics has the potential to inform more successful drug target discovery. We used genome-wide association studies of the 23andMe genetic and health survey database to identify an immuno-oncology signature in which genetic variants are associated with opposing effects on risk for cancer and immune diseases. This signature identified multiple pathway genes mapping to the immune checkpoint comprising CD200, its receptor CD200R1, and the downstream adapter protein DOK2. We confirmed that CD200R1 is elevated on tumor-infiltrating immune cells isolated from cancer patients compared to the matching peripheral blood mononuclear cells. We developed a humanized, effectorless IgG1 antibody (23ME-00610) that bound human CD200R1 with high affinity (KD <0.1 nM), blocked CD200 binding, and inhibited recruitment of DOK2. 23ME-00610 induced T-cell cytokine production and enhanced T cell-mediated tumor cell killing in vitro. Blockade of the CD200:CD200R1 immune checkpoint inhibited tumor growth and engaged immune activation pathways in an S91 tumor cell model of melanoma in mice.

Expression of CCR8 and CCX-CKR on Basophils in Chronic Urticaria Is Amplified by IgE-Mediated Activation

Recruitment to the local tissue and alerted phenotype are the hallmarks of basophils in chronic urticaria (CU). Chemokine receptors such as chemokine (C-C motif) receptor 4 (CCR4) or CCR8 have been studied in skin diseases, e.g., atopic dermatitis, but not in CU. In this study, we aimed to define CU's basophil homing potential and receptor profile and the effect of Omalizumab treatment on these. Unstimulated and activated (anti-IgE, fMLP, C5a, and Substance P) whole blood basophils from 11 Omalizumab-treated CU patients and 10 healthy subjects were investigated with flow cytometry. Unstimulated basophils in CU showed higher expression of the skin-associated (CCR8) and scavenger (CCX-CKR) receptors and lower expression of the lung-associated (CCR3) receptor in contrast to healthy ones. IgE-mediated activation increased the percentage of CCR8 and CCX-CKR in CU compared to healthy group and elevated the expression of the lung-associated chemokine receptor, XCR1, in all groups. A trend of augmented expression of the coagulation cascade (CD87) and fMLP (FPR1) receptors was seen on basophils in CU, while a tendency of reduced expression was seen for itch (IL-31RA) and immunotolerance (CD109) receptors. fMLP and C5a increased the expression of CCR4, CCR8, CCX-CKR, and CD87 and decreased CCR2 and CCR3, though no changes between the groups were found. In conclusion, CU basophils exhibit skin-homing potential amplified by IgE-mediated stimulation.

CD200R1 promotes interleukin-17 production by group 3 innate lymphoid cells by enhancing signal transducer and activator of transcription 3 activation

Psoriasis is a common chronic inflammatory skin disease with no cure. It is driven by the interleukin (IL)-23/IL-17A axis and type 17 T helper cells; however, recently, group 3 innate lymphoid cells (ILC3s) have also been implicated. Despite being the focus of much research, factors regulating the activity of ILC3s remain incompletely understood. Immune regulatory pathways are particularly important at barrier sites, such as the skin, gut, and lungs, which are exposed to environmental substances and microbes. CD200R1 is an immune regulatory cell surface receptor that inhibits proinflammatory cytokine production in myeloid cells. CD200R1 is also highly expressed on ILCs, where its function remains largely unexplored. We previously observed reduced CD200R1 signaling in psoriasis-affected skin, suggesting that dysregulation may promote disease. Here, we show that contrary to this, psoriasis models are less severe in CD200R1-deficient mice due to reduced IL-17 production. Here, we uncover a key cell-intrinsic role for CD200R1 in promoting IL-23-driven IL-17A production by ILC3s by promoting signal transducer and activator of transcription 3 activation. Therefore, contrary to its inhibitory role in myeloid cells, CD200R1 is required on ILC3 to promote IL-23-stimulated signal transducer and activator of transcription 3 activation, triggering optimal IL-17 production.

Immune checkpoint molecules in prevention and development of asthma

Allergic asthma is a respiratory disease initiated by type-2 immune responses characterized by secretion of alarmins, interleukin-4 (IL-4), IL-5, and IL-13, eosinophilic inflammation, and airway hyperresponsiveness (AHR). Immune checkpoints (ICPs) are inhibitory or stimulatory molecules expressed on different immune cells, tumor cells, or other cell types that regulate immune system activation and maintain immune homeostasis. Compelling evidence indicates a key role for ICPs in both the progression and prevention of asthma. There is also evidence of asthma development or exacerbation in some cancer patients receiving ICP therapy. The aim of this review is to provide an updated overview of ICPs and their roles in asthma pathogenesis, and to assess their implications as therapeutic targets in asthma.

Long Non-Coding RNAs Expressed in the Peanut Allergy for Understanding the Pathophysiology of Peanut Allergy Rat Model

BACKGROUND

Peanut allergy (PA) has become a clinical and public health problem, which is mainly regulated by genetics, immune responses, and environmental factors. Diagnosis and treatment for PA have always remained huge challenges due to its multiple triggers. Studies have shown that long non-coding RNAs (lncRNAs) play a critical role in the development of allergic diseases.

METHOD AND RESULTS

In the current study, we examined the plasma lncRNA expression profiles of peanut allergy Brown Norway rats and healthy controls and 496 differently expressed lncRNAs were identified, including 411 up-regulated genes and 85 down-regulated genes. We screened 8 lncRNAs based on the candidate principle and the candidates were verified in individual samples by quantitative real-time PCR. Then, the four lncRNA-based diagnostic model was established by least absolute shrinkage and selection operator (LASSO) and logistic regression, which was proved by area under the receiver operating characteristic curve (AUC).

CONCLUSIONS

In summary, we assessed the correlation between lncRNA expression levels and the diagnosis of peanut allergy, which may perform a vital role in guiding the management of peanut allergy.

Th2A cells: The pathogenic players in allergic diseases

Proallergic type 2 helper T (Th2A) cells are a subset of memory Th2 cells confined to atopic individuals, and they include all the allergen-specific Th2 cells. Recently, many studies have shown that Th2A cells characterized by CD3+ CD4+ HPGDS+ CRTH2+ CD161high ST2high CD49dhigh CD27low play a crucial role in allergic diseases, such as atopic dermatitis (AD), food allergy (FA), allergic rhinitis (AR), asthma, and eosinophilic esophagitis (EoE). In this review, we summarize the discovery, biomarkers, and biological properties of Th2A cells to gain new insights into the pathogenesis of allergic diseases.

Monoclonal Antibodies in Treating Chronic Spontaneous Urticaria: New Drugs for an Old Disease

Background: H1-antihistamines (H1AH) represent the current mainstay of treatment for chronic spontaneous urticaria (CSU). However, the response to H1AH is often unsatisfactory, even with increased doses. Therefore, guidelines recommend the use of omalizumab as an add-on treatment in refractory CSU. This paved the way for the investigation of targeted therapies, such as monoclonal antibodies (mAbs), in CSU. Methods: A literature review was conducted including papers published between 2009 and 2022 and ongoing trials about the efficacy and safety of mAbs as treatment for CSU. Results: Twenty-nine articles, a trial with preliminary results, and seventeen ongoing or completed clinical trials on the use of mAbs in CSU were included. Randomized controlled trials (RCTs), meta-analysis, and real-life studies have proven the effectiveness and safety of omalizumab as a third-line treatment in refractory CSU. However, a percentage of patients remain unresponsive to omalizumab. Therefore, other mAbs, targeting different pathways, have been used off-label in case series and others are under investigation in RCTs. Most of them have showed promising results. Conclusions: Omalizumab remains the best choice to treat refractory CSU. Although results from other mAbs seem to be encouraging to achieve symptom control in refractory CSU, thus improving patients’ QoL, RCTs are needed to confirm their effectiveness and safety.

Phenotype, function and clinical significance of innate lymphoid cells in immunoglobulin G4-related disease

OBJECTIVE

Innate immune system participates in immunoglobulin G4 related disease (IgG4-RD). While the role of innate lymphoid cells (ILCs) in IgG4-RD remains to be elucidated, we aimed to evaluate the phenotype, function and clinical significance of ILCs in IgG4-RD patients.

METHODS

Sixty-seven untreated IgG4-RD patients, age and sex matched healthy controls (HCs) were enrolled. Circulating and tissue infiltration of ILCs were detected by flow cytometry. Serum suppression of tumorigenicity 2 (sST2) was detected by ELISA and membrane-bound ST2 (ST2L) was detected by flow cytometry. Tissue infiltration of IL-33 was measured by immunohistochemistry staining. RT-qPCR was performed to analyze the expression pattern of ILC2 associated genes between HCs and IgG4-RD patients. In addition, correlation analysis was performed in order to evaluate clinical significance of ILCs in IgG4-RD.

RESULTS

The frequency of circulating pan ILCs in IgG4-RD patients was lower than in HCs. ILC2s was higher in IgG4-RD compared with HCs, whereas ILC1s was lower in IgG4-RD. sST2 and ST2L were increased in IgG4-RD than HC. Infiltration of ILC1s in submandibular glands of IgG4-RD was more prominent than ILC2s. Intracellular secretion of IL-9 was increased in ILC2s of IgG4-RD than in HCs. Circulating ILC2s correlated positively with Treg cells, the surface expression of CD154, PD-1 and CXCR5 in ILC2s correlated positively with CD19+B cells, serum IgG4 level and serum IgE, respectively.

CONCLUSION

ILCs and their subsets were significantly altered in IgG4-RD. We demonstrated the dysfunction of ILC2s in IgG4-RD by phenotype, correlation analysis, and function investigation, revealing ILC2s participated in the pathogenesis of IgG4-RD.

Single-cell analysis pinpoints distinct populations of cytotoxic CD4+ T cells and an IL-10+CD109+ TH2 cell population in nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by a chronic inflammatory process often associated with comorbid asthma. In this study, we analyzed the transcriptomes of single T helper (T_H) cells from nasal polyps of patients with CRSwNP and validated these findings using multiparameter flow cytometry. Polyp tissue contained suppressive T regulatory (T_reg) cells, T_H2 cells, type 2 innate lymphoid cells, and three transcriptionally distinct subsets of cytotoxic CD4⁺ T cells (CD4⁺ CTL). GATA3 expression was a feature of polyp T_reg cells, whereas T_H2 cells highly expressed TCN1, CD200R, and HPGDS and were enriched for genes involved in lipid metabolism. Only a portion of polyp T_H2 cells expressed the prostaglandin D2 receptor CRTH2, whereas a subpopulation of CD109⁺CRTH2^- T_H2 cells expressed mRNA for common inhibitor receptors including LAG3 and TIM3 and produced IL-10. Together, we resolved the complexity of T_H cells in patients with CRSwNP, identifying several distinct clusters of CD4⁺ CTL and a population of CD109⁺CRTH2^- T_H2 cells with putative regulatory potential.

Memory Generation and Re-Activation in Food Allergy

Recent evidence has highlighted the critical role of memory cells in maintaining lifelong food allergies, thereby identifying these cells as therapeutic targets. IgG⁺ memory B cells replenish pools of IgE-secreting cells upon allergen exposure, which contract thereafter due to the short lifespan of tightly regulated IgE-expressing cells. Advances in the detection and highly dimensional analysis of allergen-specific B and T cells from allergic patients have provided insight on their phenotype and function. The newly identified Th2A and Tfh13 populations represent a leap in our understanding of allergen-specific T cell phenotypes, although how these populations contribute to IgE memory responses remains poorly understood. Within, we discuss the mechanisms by which memory B and T cells are activated, integrating knowledge from human systems and fundamental research. We then focus on memory reactivation, specifically, on the pathways of secondary IgE responses. Throughout, we identify areas of future research which will help identify immunotargets for a transformative therapy for food allergy.

Memory T helper cells identify patients with nickel, cobalt, and chromium metal allergy

BACKGROUND

Patch testing is the gold standard for identifying culprit allergens in allergic contact dermatitis; however, it is laborious and positive reactions are difficult to quantitate. Development of complementary in vitro tests is, therefore, of great importance.

OBJECTIVES

This study aimed to improve the in vitro lymphocyte proliferation test (LPT) to detect allergic responses to nickel (Ni), cobalt (Co), and chromium (Cr).

METHODS

Twenty-one metal allergic patients with a positive patch test to Ni (n=16), Co (n=8), and Cr (n=3) and 13 controls were included. All were tested by a flow cytometric LPT.

RESULTS

Metal-reactive cells were identified as T helper (Th) cells with high expression of the memory marker CD45RO. Skin-homing (cutaneous lymphocyte-associated antigen positive [CLA+]) Ni-reactive memory Th (Th_mem ^hi ) cells identified individuals with a positive patch test for Ni with 100% sensitivity (95% confidence interval [CI] 81%-100%) and 92% specificity (95% CI 67%-100%). Moreover, Co-specific Th_mem ^hi cells expressing CCR6 identified patients with a positive patch test for Co with 63% sensitivity (95% CI 31%-86%) and 100% specificity (95% CI 77%-100%). In Cr allergic individuals, Cr-reactive Th_mem ^hi cells tended to increased CLA and CCR6 expression.

CONCLUSION

Metal-reactive Th cells with high expression of CD45RO and coexpression of CLA and CCR6 improved the LPT, making it an attractive supplement to the patch test.

Tumor-Infiltrating T Cells Concurrently Overexpress CD200R with Immune Checkpoints PD-1, CTLA-4, and TIM-3 in Non-Small-Cell Lung Cancer

INTRODUCTION

CD200R has been reported to be the receptor for the immune checkpoint molecule CD200 and can transduce immune-suppressive signals. In this study, we mainly focused on the expression level of CD200R in T cells in pulmonary artery (PA) blood and non-small-cell lung cancer (NSCLC) tumor tissue.

METHODS

Immune cells were isolated from dissected tumor samples and PA blood of NSCLC patients and analyzed with multiparameter flow cytometry. The co-expression of CD200R with other immune checkpoints, including programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), was also investigated.

RESULTS

CD200R expression was observed on the surface of approximately 75% of T cells among tumor-infiltrating leukocytes (TILs). Compared to T cells extracted from TILs, only 55% of T cells extracted from PA blood exhibited CD200R expression. Moreover, with higher expression of CD200R, the expression of other immune checkpoints, including PD-1, CTLA-4, and TIM-3, was also increased in tumor-infiltrating T cells compared to T cells in PA blood.

CONCLUSIONS

Our results showed that those tumors were dominated by T cells expressing CD200R together with other checkpoints, which suggests a phenotypic change after T cell infiltration into the tumor, such as T cell exhaustion.

Advances and novel developments in molecular allergology

The continuous search for new allergens and the design of allergen derivatives improves the understanding of their allergenicity and aids the design of novel diagnostic and immunotherapy approaches. This article discusses the recent developments in allergen and epitope discovery, allergy diagnostics and immunotherapy. Structural information is crucial for the elucidation of cross-reactivity of marker allergens such as the walnut Jug r 6 or that of nonhomologous allergens, as shown for the peanut allergens Ara h 1 and 2. High-throughput sequencing, liposomal nanoallergen display, bead-based assays, and protein chimeras have been used in epitope discovery. The binding of natural ligands by the birch pollen allergen Bet v 1 or the mold allergen Alt a 1 increased the stability of these allergens, which is directly linked to their allergenicity. We also report recent findings on the use of component-resolved approaches, basophil activation test, and novel technologies for improvement of diagnostics. New strategies in allergen-specific immunotherapy have also emerged, such as the use of virus-like particles, biologics or novel adjuvants. The identification of dectin-1 as a key player in allergy to tropomyosins and the formyl peptide receptor 3 in allergy to lipocalins are outstanding examples of research into the mechanism of allergic sensitization.

Children with nut allergies have impaired gene expression of Toll-like receptors pathway

BACKGROUND

Trends in food allergies prompted investigation into the underlying mechanisms. Genetic and epigenetic factors are of high interest, and, in particular, the interplay between genes relating to immune factors directly and indirectly involved in food allergy pathogenesis. We sought to determine potential links between gene expression and epigenetic factors relating to Toll-like receptor (TLR) pathways and childhood food allergies.

METHODS

In a cross-sectional study, samples from 80 children with and without food allergies were analysed for gene expression, DNA methylation and a range of immune factors relating to TLR pathways. TLR2, TLR4, CD14, IL5, IL13 and vitamin D were explored.

RESULTS

The importance of these immune factors appeared to vary between the different types of food allergies. Expression of TLR2 (P < .001), TLR4 (P = .014) and CD14 (P = .028) varied significantly between children with no food allergy, allergy to nuts and peanuts, and allergy to eggs. DNA methylation in the promoter regions of these genes had a significant association with gene expression. These trends persisted when subjects were stratified by nut allergy vs no nut allergy. Furthermore, TLR2 (P = .001) and CD14 (P = .007) expressions were significantly lower in children with food allergies when compared to those without.

CONCLUSION

Gene expression of TLR pathway genes was directly related to food allergy type, and DNA methylation had an indirect effect. TLR2 pathways are of significant interest in nut allergies.

The nonlesional skin surface distinguishes atopic dermatitis with food allergy as a unique endotype

Skin barrier dysfunction has been reported in both atopic dermatitis (AD) and food allergy (FA). However, only one-third of patients with AD have FA. The purpose of this study was to use a minimally invasive skin tape strip sampling method and a multiomics approach to determine whether children with AD and FA (AD FA+) have stratum corneum (SC) abnormalities that distinguish them from AD without FA (AD FA-) and nonatopic (NA) controls. Transepidermal water loss was found to be increased in AD FA+. Filaggrin and the proportion of ω-hydroxy fatty acid sphingosine ceramide content in nonlesional skin of children with AD FA+ were substantially lower than in AD FA- and NA skin. These abnormalities correlated with morphologic changes in epidermal lamellar bilayer architecture responsible for barrier homeostasis. Shotgun metagenomic studies revealed that the nonlesional skin of AD FA+ had increased abundance of Staphylococcus aureus compared to NA. Increased expression of keratins 5, 14, and 16 indicative of hyperproliferative keratinocytes was observed in the SC of AD FA+. The skin transcriptome of AD FA+ had increased gene expression for dendritic cells and type 2 immune pathways. A network analysis revealed keratins 5, 14, and 16 were positively correlated with AD FA+, whereas filaggrin breakdown products were negatively correlated with AD FA+. These data suggest that the most superficial compartment of nonlesional skin in AD FA+ has unique properties associated with an immature skin barrier and type 2 immune activation.

Impact of high-altitude therapy on type-2 immune responses in asthma patients

BACKGROUND

Asthma patients present with distinct immunological profiles, with a predominance of type 2 endotype. The aim of this study was to investigate the impact of high-altitude treatment on the clinical and immunological response in asthma.

METHODS

Twenty-six hospitalized asthma patients (nine eosinophilic allergic; EA, nine noneosinophilic allergic; NEA and eight noneosinophilic nonallergic; NN) and nine healthy controls in high altitude for 21 days were enrolled in the study. We assessed eosinophils, T cells, Tregs, and innate lymphoid cells (ILC) from peripheral blood using flow cytometry.

RESULTS

The number of eosinophils (both resting and activated) and chemoattractant receptor homolog expressed on Th2 cells (CRTH2)-expressing CD4⁺ and CD8⁺ T cells decreased significantly in EA patients after altitude treatment. The frequency of CRTH2⁺ Tregs as decreased significantly in all the asthma phenotypes as well as the frequency of ILC2 was significantly reduced in EA after altitude treatment. After 21 days of altitude therapy, CRTH2-expressing ILC2, CD4⁺ and CD8⁺ T cells and Treg cells showed attenuated responses to exogenous PGD2. Furthermore, PGD2 signaling via CRTH2 was found to diminish the suppressive function of CRTH2⁺ Tregs which partially normalized during high-altitude treatment. Improved asthma control was particularly evident in allergic asthma patients and correlated with decreased frequencies of CRTH2⁺ Treg cells in EA patients. Serum IL-5 and IL-13 decreased during climate treatment in asthma patients with high baseline levels.

CONCLUSIONS

Asthma treatment in high altitude reduced the type 2 immune response, corrected the increased CRTH2 expression and its dysregulated functions.

Recent developments and highlights in food allergy

The achievement of long-lasting, safe treatments for food allergy is dependent on the understanding of the immunological basis of food allergy. Accurate diagnosis is essential for management. In recent years, data from oral food challenges have revealed that routine allergy testing is poor at predicting clinical allergy for tree nuts, almonds in particular. More advanced antigen-based tests including component-resolved diagnostics and epitope reactivity may lead to more accurate diagnosis and selection of therapeutic intervention. Additional diagnostic accuracy may come from cellular tests such as the basophil activation test or mast cell approaches. In the context of clinical trials, cellular tests have revealed specific T-cell and B-cell populations that are more abundant in food-allergic individuals with distinct mechanistic features. Awareness of clinical markers, such as the ability to eat baked forms of milk and egg, continues to inform the understanding of natural tolerance development. Mouse models have allowed for investigation into multiple mechanisms of food allergy including modification of epithelial metabolism, and the induction of regulatory cell subsets and the microbiome. Increasing numbers of children who underwent food immunotherapy enlarged the body of evidence on mechanisms and predictors of treatment success. Experimental immunological markers in conjunction with clinical determinants such as lower age and lower initial specific IgE appear to be of benefit. More research on the optimal dose, preparation, and route of application integrating a high-level safety and efficacy is demanded. Alternatively, biologics blocking TSLP, IL-33, IL-4 and IL-13, or IgE may help to achieve that.

Single-Cell RNA Sequencing of the T Helper Cell Response to House Dust Mites Defines a Distinct Gene Expression Signature in Airway Th2 Cells

Naive CD4⁺ T cells differentiate into functionally diverse T helper (Th) cell subsets. Th2 cells play a pathogenic role in asthma, yet a clear picture of their transcriptional profile is lacking. We performed single-cell RNA sequencing (scRNA-seq) of T helper cells from lymph node, lung, and airways in the house dust mite (HDM) model of allergic airway disease. scRNA-seq resolved transcriptional profiles of naive CD4⁺ T, Th1, Th2, regulatory T (Treg) cells, and a CD4⁺ T cell population responsive to type I interferons. Th2 cells in the airways were enriched for transcription of many genes, including Cd200r1, Il6, Plac8, and Igfbp7, and their mRNA profile was supported by analysis of chromatin accessibility and flow cytometry. Pathways associated with lipid metabolism were enriched in Th2 cells, and experiments with inhibitors of key metabolic pathways supported roles for glucose and lipid metabolism. These findings provide insight into the differentiation of pathogenic Th2 cells in the context of allergy.

KLRG1 and NKp46 discriminate subpopulations of human CD117+CRTH2- ILCs biased toward ILC2 or ILC3

Recently, human ILCs that express CD117 and CD127 but lack CRTH2 and NKp44 have been shown to contain precursors of ILC1, ILC2, and ILC3. However, these ILCs have not been extensively characterized. We performed an unbiased hierarchical stochastic neighbor embedding (HSNE) analysis of the phenotype of peripheral blood CD117⁺ ILCs, which revealed the presence of three major subsets: the first expressed NKp46, the second expressed both NKp46 and CD56, and the third expressed KLRG1, but not NKp46 or CD56. Analysis of their cytokine production profiles and transcriptome revealed that NKp46⁺ ILCs predominantly develop into ILC3s; some of them can differentiate into ILC1/NK-like cells, but they are unable to develop into ILC2s. In contrast, KLRG1⁺ ILCs predominantly differentiate into ILC2s. Single-cell cultures demonstrate that KLRG1⁺ ILCs can also differentiate into other ILC subsets depending on the signals they receive. Epigenetic profiling of KLRG1⁺ ILCs is consistent with the broad differentiation potential of these cells.

CD200 in asthma

Constant exposure to foreign particles in the airways requires tight immune regulation in order to maintain sufficient anti-microbial defences, while preventing immunopathological responses that could impair gas exchange. Dysregulation of immunoregulatory pathways has been associated with asthma and allergy. This review will focus on the CD200 regulatory pathway and its role in the asthmatic cascade. CD200 and its receptors are highly expressed in the lung, on epithelial cells and leukocytes, and emerging evidence links dysregulation of the CD200 pathway with asthma. Moreover, pharmacological modulation of CD200 receptors was shown to improve clinical and inflammatory outcomes of preclinical asthma models. Therefore, the involvement of CD200 in asthma is increasingly recognized and preclinical studies support the contention that it could constitute an additional target to alleviate asthma exacerbation and/or reduce disease severity.

A comparative study on basophil activation test, histamine release assay, and passive sensitization histamine release assay in the diagnosis of peanut allergy

BACKGROUND

Allergy can be diagnosed using basophil tests. Several methods measuring basophil activation are available. This study aimed at comparing basophil activation test (BAT), histamine release assay (HR), and passive sensitization histamine release assay (passive HR) in the diagnosis of peanut allergy.

METHODS

BAT, HR, and passive HR were performed on 11 peanut-allergic and 14 nonallergic subjects. Blood was incubated with peanut extract or anti-IgE and tests were performed as follows: BAT-CD63 upregulation was assessed by flow cytometry; HR-released histamine was quantified by a glass fiber-based fluorometric method; passive HR-IgE-stripped donor basophils were incubated with participants' serum and histamine release was quantified as HR.

RESULTS

CDsens, a measure of basophil allergen sensitivity, was significantly higher for BAT (80.1±17.4) compared to HR (23.4±10.31) and passive HR (11.1±2.0). BAT, HR, and passive HR had a clinical sensitivity of 100%, 100%, and 82% and specificity of 100%, 100%, and 100%, respectively, when excluding inconclusive results. BAT identified 11 of 11 allergic patients, HR 10, and passive HR 9. Likewise, BAT recognized 12 of 14 nonallergic subjects, HR 10, and passive HR 13. However, the tests' diagnostic performances were not statistically different. Interestingly, nonreleasers in HR but not in BAT had lower basophil count compared to releasers (249 vs 630 counts/min).

CONCLUSION

BAT displayed a significantly higher CDsens compared to HR and passive HR. The basophil tests' diagnostic performances were not significantly different. Still, BAT could diagnose subjects with low basophil number in contrast to HR.