Marta Ferrer

Comparative studies of functional and binding assays for IgG anti-FcϵRIα (α-subunit) in chronic urticaria ☆ ☆☆ ★ ★★

Abstract Background: Recent data suggest that a subpopulation of patients with chronic urticaria have an autoimmune disorder that is caused by the presence of antibodies to the IgE receptor. The actual incidence of these antibodies is uncertain. Objective: We sought to assess the incidence of autoimmunity to the IgE receptor in patients with chronic urticaria and to compare functional and binding assays. Methods: We isolated skin mast cells and studied a large number of patient sera (68) for their ability to activate these cells and isolated basophils. We then compared the results with those obtained by immunoblotting using cloned α-subunit of the IgE receptor. Results: Sera from patients with chronic urticaria released significant histamine (>15% of basal) on incubation with basophils (48%) and mast cells (46%). By immunoblotting we obtained positive results in 64% of subjects tested and also identified a small subpopulation that is active on cells but does not bind Fc ϵ RI α . Conclusion: Our data suggest that approximately 45% to 50% of patients with chronic urticaria have a cutaneous autoimmune disorder. Immunoblotting may provide a rapid screening method for anti-Fc ϵ RI α detection in such patients. (J Allergy Clin Immunol 1998;101:672-6.)

The clinical utility of basophil activation testing in diagnosis and monitoring of allergic disease

The basophil activation test (BAT) has become a pervasive test for allergic response through the development of flow cytometry, discovery of activation markers such as CD63 and unique markers identifying basophil granulocytes. Basophil activation test measures basophil response to allergen cross‐linking IgE on between 150 and 2000 basophil granulocytes in <0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In addition to clinical history, skin prick test, and specific IgE determination, BAT can be a part of the diagnostic evaluation of patients with food‐, insect venom‐, and drug allergy and chronic urticaria. It may be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti‐IgE treatment or in the natural resolution of allergy. Basophil activation test may use fewer resources and be more reproducible than challenge testing. As it is less stressful for the patient and avoids severe allergic reactions, BAT ought to precede challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. In this EAACI task force position paper, we provide an overview of the practical and technical details as well as the clinical utility of BAT in diagnosis and management of allergic diseases.

Complement dependence of histamine release in chronic urticaria

BACKGROUND IgG autoantibodies directed to the alpha-subunit of the IgE receptor have been identified in 30% to 45% of patients with chronic urticaria. However, the exact mechanism by which histamine secretion is initiated is uncertain. OBJECTIVE Histamine release from cutaneous mast cells may occur by cross-linking the IgE receptor or by activation of complement. Our goal is to distinguish these 2 possibilities. METHODS We incubated human cutaneous mast cells with patient sera, decomplemented sera, or purified patient IgG. The IgG was also added to pooled normal serum or to sera deficient in either C2 or C5, and its ability to activate mast cells was assessed. Mast cells were incubated with human IgE myeloma to saturate alpha-subunits to determine the effect on histamine release. RESULTS Patient sera released histamine (18.26% +/- 4.39%), but purified IgG from patients (5.5% +/- 4.3%) did not. Addition of the patient IgG to normal sera rendered the sera positive for histamine-releasing activity (18.4% +/- 4.3%), whereas control IgG or patient IgG added to C2- or C5-deficient sera did not release histamine. Histamine release with decomplemented patient sera was also diminished (8.34% +/- 4.3%). Preincubation of mast cells with a C5-blocking peptide decreased histamine release but was not statistically significant; there was a significant decrease after preincubating mast cells with IgE myeloma. CONCLUSION The degranulation of mast cells by IgG autoantibodies in patients with chronic urticaria requires binding to the IgE receptor and activation of the classical complement cascade. Saturation of the IgE receptor with IgE inhibits such degranulation, presumably by preventing binding of the requisite IgG.

EAACI taskforce position paper: evidence for autoimmune urticaria and proposal for defining diagnostic criteria

An autoimmune subset of chronic spontaneous urticaria is increasingly being recognized internationally, based on laboratory and clinical evidence that has accrued over the last 20 years. This evidence has been reviewed by a taskforce of the Dermatology section of the European Academy of Allergy and Clinical Immunology. Functional autoantibodies in chronic urticaria (CU) patient sera have been demonstrated against IgE and FcεRIα by basophil and mast cell histamine release assays and by basophil activation assays. Antibody specificity has been confirmed by immunoassay, but there is a poor correlation between functionality and immunoreactivity. Approximately 25% of CU patients have a positive basophil histamine release assay and show autoreactivity (a positive autologous serum skin test), whereas 50% are negative regarding both. Functionality of CU sera appears to be complement dependent on mast cells but not exclusively on basophils. Basophil activation by CU sera is predominantly restricted to IgG1 and IgG3 subclasses. Circumstantial evidence for CU being an autoimmune disease comes from an observed association with other autoimmune diseases, a strong association between serum functionality and HLA‐DR4 haplotype and the good response of CU patients to immunotherapies. It was proposed that a study should be undertaken to prospectively validate potentially relevant clinical criteria (from the history, examination and routinely available clinical investigations) against a new ‘gold standard’ for the diagnosis of ACU (positive autoreactivity, functional bioassay and immunoassay) to define preliminary criteria sets for the diagnosis of ACU based on clinical and laboratory features with highest individual sensitivity and specificity.

Exercise‐induced hypersensitivity syndromes in recreational and competitive athletes: a PRACTALL consensus report (what the general practitioner should know about sports and allergy)

Exercise‐induced (EI) hypersensitivity disorders are significant problems for both recreational and competitive athletes. These include EI‐asthma, EI‐bronchoconstriction, EI‐rhinitis, EI‐anaphylaxis and EI–urticaria. A group of experts from the European Academy of Allergology and Clinical Immunology and the American Academy of Allergy Asthma and Immunology met to discuss the pathogenesis of these disorders and how to diagnose and treat them, and then to develop a consensus report. Key words (exercise with asthma, bronchoconstriction, rhinitis, urticaria or anaphylaxis) were used to search Medline, the Cochrane database and related websites through February 2008 to obtain pertinent information which, along with personal reference databases and institutional experience with these disorders, were used to develop this report. The goal is to provide physicians with guidance in the diagnosis, understanding and management of EI‐hypersensitivity disorders to enable their patients to safely return to exercise‐related activities.

Secretion of Cytokines, Histamine and Leukotrienes in Chronic Urticaria

Background: Approximately 35–40% of patients with chronic urticaria have an IgG autoantibody to the IgE receptor which can activate basophils and mast cells so that they release histamine. In this study we assessed the cytokine profile present in chronic urticaria sera, and then measured cytokine and leukotriene release from basophils and mast cells upon incubation with chronic urticaria sera. Finally we assessed cytokine expression at the single-cell level and characterized the T cell subpopulations involved in their production. We chose IL-4 as representative of Th2 lymphocytes and IFN-γ for Th1 lymphocytes. Methods: We analyzed IL-4, IL-5 and IFN-γ in 60 chronic urticaria sera versus 51 controls. Sera were incubated with purified human basophils and cutaneous mast cells and the release of histamine, IL-4 and leukotrienes (C4, D4, E4) was quantitated. Immunoblotting was performed to identify IgG antibody to FcΕRIα, α subunit. We measured intracellular cytokine production in peripheral blood mononuclear cells of 17 chronic urticaria patients compared to 50 healthy controls. Results: We found higher IL-4 levels (p = 0.028) in the sera of chronic urticaria patients (1.03 pg/ml) versus healthy donors (0.20 pg/ml) but no difference between urticaria sera and atopic control sera (0.52 pg/ml). We did not detect IFN-γ or IL-5 in any serum. However, sera that activated basophils so that they released histamine also produced leukotriene and IL-4, and leukotriene production by cutaneous mast cells and basophils was closely correlated. However, there was no correlation between immunoblotting and the functional ability to induce either histamine or IL-4. After stimulating with PMA-ionomycin we found significant differences in CD4+ lymphocyte production of IL-4 and IFN-γ with no differences in CD8+ lymphocyte production of either cytokine. Conclusion: Our data support the presence of basophil and mast cell activators in the sera of patients with chronic urticaria which can lead to the production of leukotrienes and IL-4 in addition to the histamine. IL-4 levels are similar to those seen in atopic subjects. We found that CD4+ T cells from patients with chronic urticaria are activated and tend to produce higher cytokine levels than CD4+ T cells from healthy controls. There were no differences when cytokine production by CD8+ lymphocytes was similarly assessed. These results are consistent with the histology found in biopsies of chronic urticaria lesions, where a CD4+-predominant infiltrate is found with cytokine production suggesting either a Th0 response or a mixture of Th1 and Th2 lymphocytes.

Validation of ARIA (Allergic Rhinitis and its Impact on Asthma) classification in a pediatric population: The PEDRIAL study

To cite this article: Jáuregui I, Dávila I, Sastre J, Bartra J, del Cuvillo A, Ferrer M, Montoro J, Mullol J, Molina X, Valero A. Validation of ARIA (Allergic Rhinitis and its Impact on Asthma) classification in a pediatric population: The PEDRIAL study. Pediatr Allergy Immunol 2011; 22: 388–392.

Nanoparticulate adjuvants and delivery systems for allergen immunotherapy

In the last decades, significant progress in research and clinics has been made to offer possible innovative therapeutics for the management of allergic diseases. However, current allergen immunotherapy shows limitations concerning the long-term efficacy and safety due to local side effects and risk of anaphylaxis. Thus, effective and safe vaccines with reduced dose of allergen have been developed using adjuvants. Nevertheless, the use of adjuvants still has several disadvantages, which limits its use in human vaccines. In this context, several novel adjuvants for allergen immunotherapy are currently being investigated and developed. Currently, nanoparticles-based allergen-delivery systems have received much interest as potential adjuvants for allergen immunotherapy. It has been demonstrated that the incorporation of allergens into a delivery system plays an important role in the efficacy of allergy vaccines. Several nanoparticles-based delivery systems have been described, including biodegradable and nondegradable polymeric carriers. Therefore, this paper provides an overview of the current adjuvants used for allergen immunotherapy. Furthermore, nanoparticles-based allergen-delivery systems are focused as a novel and promising strategy for allergy vaccines.

Increased responsiveness of basophils of patients with chronic urticaria to sera but hypo-responsiveness to other stimuli

Background Although it has been shown that basophils from patients with chronic ordinary urticaria (CU) are less responsive than normal basophils when stimulated with anti‐IgE, very few studies have examined the response of those cells to alternative stimuli.

Serum total tryptase levels are increased in patients with active chronic urticaria

Background We have demonstrated previously mast cell histamine release upon incubation with chronic urticaria (CU) sera, presumably by degranulation.