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.

Tolerance to cephalosporins and carbapenems in penicillin-allergic patients

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CD300c costimulates IgE-mediated basophil activation, and its expression is increased in patients with cow's milk allergy.

BACKGROUND: Basophils express high-affinity IgE receptors (FcεRI), which play an essential role in allergic diseases. It is important to characterize new cell-surface receptors that modulate IgE-mediated basophil activation threshold to design promising immunomodulatory therapies. OBJECTIVES: We sought to analyze the expression of CD300 receptors on human basophils and their implication in IgE-mediated basophil activation processes. METHODS: Blood samples from healthy subjects and patients with cow's milk allergy were collected through the Basque Biobank under an institutional review board-approved protocol. PBMCs were obtained by means of density centrifugation, basophils were purified with a specific isolation kit, and phenotypic and functional studies were performed by using flow cytometry. RESULTS: We demonstrate that basophils express the activating receptor CD300c, which is specifically upregulated in response to IL-3. CD300c works as a costimulatory molecule during IgE-mediated basophil activation, as shown by a significant increase in degranulation and cytokine production when basophils are activated in the presence of CD300c cross-linking compared with activation through the IgE/FcεRI axis alone. Coligation of FcεRI and CD300c increased intracellular calcium mobilization and phosphorylation of signaling intermediates evoked only by FcεRI ligation. We show that the natural ligands of CD300c, phosphatidylserine and phosphatidylethanolamine, modulate IgE-mediated basophil activation. Furthermore, we have observed that CD300c expression in children with cow's milk allergy is increased compared with that in healthy control subjects and that the intensity of expression correlates with the severity of the hypersensitivity symptoms. CONCLUSION: CD300c could be considered a biomarker and therapeutic target in patients with IgE-mediated allergic diseases because it seems to be involved in the modulation of IgE-mediated basophil activation.

Lipid Transfer Protein Syndrome in a Non-Mediterranean Area.

BACKGROUND: Plant food allergies associated with lipid transfer protein (LTP) have been widely described in the Mediterranean Basin. OBJECTIVE: The aim of this work was to describe the clinical profile and pollen sensitization of plant food- allergic patients sensitized to LTP in a non-Mediterranean area. METHODS: Patients with clear IgE-mediated symptoms associated with plant foods and a positive skin prick test (SPT) to Pru p 3 were included in a prospective study in the north of Spain. Reported symptoms were analyzed together with a battery of food and pollen SPTs and specific IgE components by ISAC microarray. Cross-inhibition studies were performed by ImmunoCAP with plane tree, mugwort and rPru p 3. RESULTS: Among the 72 patients included, the most frequent food allergy reported was to peaches (69%) followed by nuts (walnuts 55%, peanuts 54% and hazelnuts 43%). Most patients suffered from symptoms with multiple plant foods (a median of 6 foods per patient). Regarding the patients' pollen sensitization, 36% were sensitized to mugwort pollen (72% showing sIgE to Art v 3), 33% to grass pollen and 24% to plane tree pollen (94% with sIgE to Pla a 3). Inhibition studies showed that specific IgEs against mugwort and plane tree pollen are inhibited by Pru p 3 in a strong manner, whereas Pru p 3 was less inhibited by pollen extracts. CONCLUSIONS: LTP syndrome occurs in a non-Mediterranean area and is related to multiple sensitizations to foods and pollens such as plane tree and mugwort. In these pollen sensitizations, Pru p 3 seems to be the primary sensitizer.

Decrease in antigen-specific CD63 basophil expression is associated with the development of tolerance to egg by SOTI in children.

BACKGROUND: In the last decade, there have been an increasing number of studies on achieving tolerance to foods by specific oral tolerance induction (SOTI). Still, the underlying mechanism of SOTI is unknown. Our aim was to describe changes in CD63 expression on basophils following in vitro Ag-specific stimulation by basophil activation test (BAT), after SOTI with egg in a pediatric population. METHODS: Ten children with persistent allergy to egg were included. Skin prick tests (SPTs) and open food challenges (OFCs) were performed before SOTI. Specific IgE determination and BAT with egg white (EW), ovomucoid (OM), and ovalbumin (OVA) were performed before and after 1 month of the buildup phase of SOTI. RESULTS: Total tolerance to egg was achieved in 9 cases and partial in one. After SOTI, there was a significant decrease in mean specific IgE levels (p < 0.05). CD63 expression also decreased (p < 0.05) in all patients. CONCLUSION: Decrease in Ag-specific basophil responsiveness is associated with the development of clinical tolerance by SOTI.

An overview of the novel H1-antihistamine bilastine in allergic rhinitis and urticaria.

Currently available second-generation H1-antihistamines include a wide group of drugs with a better therapeutic index (or risk-benefit ratio) than the classic antihistamines, although their properties and safety profiles may differ. Bilastine is a newly registered H1-antihistamine for the oral treatment of allergic rhinitis and urticaria, with established antihistaminic and antiallergic properties. Clinical studies in allergic rhinitis and chronic urticaria show that once-daily treatment with bilastine 20 mg is effective in managing symptoms and improving patient's quality of life, with at least comparable efficacy to other nonsedative H1-antihistamines. As far as studies in healthy volunteers, clinical assays and clinical experience can establish, bilastine's safety profile is satisfactory, since it lacks anticholinergic effects, does not impair psychomotor performance or actual driving, and appears to be entirely free from cardiovascular effects.

Basophil activation tests in the evaluation of immediate drug hypersensitivity.

PURPOSE OF REVIEW: The aim of this study was to confirm the applicability of the basophil activation test (BAT) in the in-vitro diagnosis of drug allergy reactions. RECENT FINDINGS: The results obtained in terms of sensitivity and specificity with BAT are encouraging and in significant number of cases can establish the diagnosis. SUMMARY: BAT sensitivity in beta-lactam allergy was 50%, and specificity ranged from 89 to 97%. There are several studies to validate the BAT in allergy to muscle relaxants showing a sensitivity ranging from 54 to 64% with a specificity of 100 and 93%. The sensitivity of a test for evaluating immediate allergic reactions to drugs may decrease over time. To date, the BAT is the only in-vitro diagnostic method that has been validated for the diagnosis of both IgE-mediated and hypersensitivity reactions to NSAIDs. With respect to other drugs, they are nonetheless interesting as they include the evaluation of allergy to drugs that cannot be studied by other in-vitro techniques. All these data suggest that although a full validation of the test is required, BAT is a potential diagnostic method for evaluating immediate allergic reactions to drugs and NSAID hypersensitivity reactions.

Cellular tests in the diagnosis of drug hypersensitivity.

The application of flowcytometry in the study of basophil activation for the diagnosis of allergic diseases has given interesting results in recent years. The quantification of basophil activation by flowcytometry has been proven to be a useful tool for the assessment of the immediate-type response to allergens mediated by IgE or by other mechanisms in drug allergic patients. Up to now, most basophil activation test studies reported in the literature have used CD69 or CD203c as markers to quantify basophil activation after antigen-specific stimulation. Some technical variations such as the use of whole blood or isolated leukocytes, the addition of IL-3, the conditions of storage of the blood sample, the time of incubation with allergens and their concentration can affect the results of the basophil activation tests. The basophil activation test is more sensitive and specific than other in vitro diagnostic techniques in drug allergy. In various studies, its sensitivity in allergy to muscle relaxant drugs ranges between 36 and 97.7%, with a specificity around 95%. For betalactam antibiotics, basophil activation test sensitivity is 50% and its specificity 90%. For NSAIDs, sensitivity varies between 66% and 75%; specificity is about 93%. Basophil activation test reproduces in vitro hypersensitivity mechanisms involved in immediate-type allergic reactions, allows the diagnosis of allergic and pseudo-allergic reactions particularly for drugs, which are often not detectable by serological techniques, such as determination of specific IgE.

Drug hypersensitivities: which room for biological tests?

Drug allergic reactions frequently represent a serious diagnostic problem. In this paper we summarise the most relevant data published in recent years on the diagnostic reliability of the in vitro techniques in drug allergy diagnosis. The lymphocyte transformation test (LTT) offers a sensitivity of 58% in the diagnosis of late allergic reactions to betalactams and 64.5% in the immediate allergic reactions. The basophil activation test and the antigen-specific sulphidoleukotriene determination have an acceptable diagnostic reliability in muscle relaxant drug-induced reactions and in betalactam allergy. BAT sensitivity in betalactam allergy was 50.7% and its specificity 93.3%, whereas CAP had a sensitivity of 36.7% and a specificity of 83.3%, and CAST, a sensitivity of 47.7% and a specificity of 83.3%. For NSAID hypersensitivity, BAT sensitivity was 63.3% and specificity 93.3%, CAST sensitivity was 38.3% and specificity 76.6%. BAT sensitivity in metamizol allergy was 42.3% and the specificity 100% and CAP was negative in all the 17 cases in which it was performed. The joint use of BAT and CAP (specific IgE) allows diagnosis of 65.2% of the betalactam allergic patients with a specificity of 83.3%. The combined use of CAST and BAT in metamizol allergy detects 76% of the cases and 76.9% when associating the skin tests. In NSAID hypersensitivity, the joint use of BAT and CAST does not increase the diagnostic reliability of BAT alone. BAT is a non-invasive useful technique in the in vitro diagnosis of betalactam and metamizol allergy, and NSAID hypersensitivity.

Recombinant Pru p 3 and natural Pru p 3, a major peach allergen, show equivalent immunologic reactivity: a new tool for the diagnosis of fruit allergy.

BACKGROUND: The peach lipid transfer protein Pru p 3 has been identified as a major allergen from this fruit. Homologous cross-reactive allergens have been found in several plant foods and pollens. Recombinant Pru p 3 has been recently produced in the yeast Pichia pastoris. OBJECTIVE: We sought to evaluate the potential role of recombinant Pru p 3 as a novel tool for the diagnosis of fruit allergy. METHODS: Circular dichroism analysis was used to compare the protein folding of natural Pru p 3 and recombinant Pru p 3. IgE binding by both molecular forms was quantified by means of ELISA and ELISA inhibition assays, and their biologic activity was estimated by using basophil activation, histamine release, and sulphidoleukotriene production tests. Individual sera or blood samples from patients with peach allergy (up to 17) were used in the assays. RESULTS: A nearly identical circular dichroism spectra was shown by using natural Pru p 3 and recombinant Pru p 3, indicating that both protein forms are similarly folded. No difference was detected in the IgE-binding capacity of the 2 mo-lecular versions. Basophil activation and induction of sulphidoleukotriene production were positive in 9 of 10 patients, and histamine release was induced in at least half of the patients, with similar effects of the natural and recombinant forms in the 3 assays. CONCLUSION: Recombinant Pru p 3 shows a strong immunologic activity equivalent to that of its natural counterpart, and therefore it can be a useful tool for diagnosis (and future immunotherapy) of fruit allergy.

Flow-cytometric cellular allergen stimulation test in latex allergy.

BACKGROUND: The use of flow-cytometric basophil activation to different allergens has been recommended in recent years. In this study, we analyzed the diagnostic reliability of the flow-cytometric allergen stimulation test (FAST) after latex-specific stimulation in vitro. The diagnostic reliability of the technique was assessed as well as its correlation with other in vitro diagnostic parameters. METHODS: 43 patients allergic to latex with a positive history and skin test participated in the study. Thirty subjects (20 of them exposed to latex) with a negative history, skin tests and serum-specific IgE determination to latex were used as controls. In FAST the percentage of basophils that express CD63 as an activation marker after in vitro stimulation with allergen (latex) is determined by flow cytometry, following double labelling with the monoclonal antibodies anti-CD63-PE and anti-IgE FITC. RESULTS: Intraclass correlation coefficient in FAST with latex was 0.995 (p < 0.0001), which demonstrates the excellent reproducibility of this technique. Taking a cutoff point of 10% by means of ROC curves, FAST yields a sensitivity of 93% and a specificity of 100%. The FAST positive predictive value in latex allergy was 100% and the negative predictive value was 99.9%. We found a positive and significant correlation between FAST and specific IgE (CAP) with the histamine release test and specific sulphidoleukotriene production [cellular allergen stimulation test (CAST); p < 0.05]. CONCLUSIONS: FAST is a highly reliable technique (93% sensitivity and 100% specificity) in the in vitro diagnosis of IgE-mediated latex allergy.