Effects of calcineurin inhibitors on an in vitro assay for chronic urticaria

Existing and Investigational Medications for Refractory Chronic Spontaneous Urticaria: Safety, Adverse Effects, and Monitoring

Treatment of chronic spontaneous urticaria (CSU) is responsive to H1 antihistamines administered up to four times the recommended US Food and Drug Administration dose in approximately 50% of patients. However, when patients do not respond to these first-line agents, evidence-based guidelines using Grading of Recommendations, Assessment, Development, and Evaluations methodology have provided direction for second- and third-line treatments that can effectively treat patients with CSU. Some patients remain refractory to these advanced treatments; therefore, alternative treatments with a lower certainty of evidence may be necessary. Regardless of the therapies used to treat CSU patients, it is essential for clinicians to be knowledgeable about the mechanism of action, efficacy, and safety and monitoring recommendations of the treatments prescribed. This review provides a comprehensive review of the adverse effects and monitoring recommendations for agents in use for CSU treatment as well as those currently undergoing investigation for CSU treatment.

Autoimmune chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a debilitating mast cell-driven disease characterized by recurrent wheals and/or angioedema. Substantial progress has been made in dissecting the 2 main autoimmune mechanisms that drive the pathogenesis of CSU. Type I autoimmune (autoallergic) CSU is associated with IgE antibodies against autoantigens, for example, thyroid peroxidase and IL-24. Type IIb autoimmune CSU is mediated by autoantibodies that activate mast cells, for example, via IgE and FcεRI, and is present in less than 10% of patients with CSU when strict criteria are used, that is, triple positivity of autologous serum skin test, immunoassays for IgG autoantibodies, and basophil activation tests. A subpopulation of patients with CSU has both types. Type IIb autoimmune CSU is characterized by higher disease severity, concomitant autoimmune diseases, low levels of total IgE, elevated levels of IgG-anti-thyroid peroxidase, basopenia, eosinopenia, poor response to antihistamines and to omalizumab, and a good response to cyclosporine. Novel targeted therapies for CSU are under development such as ligelizumab, an anti-IgE, fenebrutinib and remibrutinib, Bruton's tyrosine kinase inhibitors, and dupilumab, an anti-IL-4Rα. Further studies should investigate the overlap between autoallergic and type IIb autoimmune CSU, optimize the diagnosis of both autoimmune endotypes using easy-to-perform, noninvasive, and inexpensive markers, and assess differences in response to therapy.

Biologics for the Use in Chronic Spontaneous Urticaria: When and Which

Guidelines for the treatment of chronic spontaneous urticaria (CSU) recommend the use of the IgE-targeted biologic omalizumab in patients with antihistamine-refractory disease. The rationale for this is supported by the key role of IgE and its high-affinity receptor, FcεRI, in the degranulation of skin mast cells that drives the development of the signs and symptoms of CSU, itchy wheals, and angioedema. Here, we review the current understanding of the pathogenesis of CSU and its autoimmune endotypes. We describe the mechanisms of action of omalizumab, the only biologic currently approved for CSU, its efficacy and ways to improve it, biomarkers for treatment response, and strategies for its discontinuation. We provide information on the effects of the off-label use, in CSU, of biologics licensed for the treatment of other diseases, including dupilumab, benralizumab, mepolizumab, reslizumab, and secukinumab. Finally, we discuss targets for novel biologics and where we stand with their clinical development. These include IgE/ligelizumab, IgE/GI-310, thymic stromal lymphopoietin/tezepelumab, C5a receptor/avdoralimab, sialic acid-binding Ig-like lectin 8/lirentelimab, CD200R/LY3454738, and KIT/CDX-0159. Our aim is to provide updated information and guidance on the use of biologics in the treatment of patients with CSU, now and in the near future.

Management of Pediatric Chronic Spontaneous Urticaria: A Review of Current Evidence and Guidelines

Chronic urticaria (CU) is associated with debilitating symptoms such as pruritic wheals and/or angioedema, which can significantly affect patients’ sleep, productivity and quality of life. Chronic spontaneous urticaria (CSU) is defined in cases in which no triggering factor is identified. Various guidelines directing the optimal management of CU in the adult population were published and updated over the recent years with the most accepted and widely used being the EAACI/GA²LEN/EDF/WAO 2017 guidelines. Meanwhile, guidelines specific to the pediatric population are scarce, mainly due to the fact that high quality evidence is lacking for many treatment options in this age group. The objective of this article is to review and synthesize the existing literature regarding the management of pediatric CSU. Our review highlights evidence supporting the EAACI/GA²LEN/EDF/WAO 2017 treatment guidelines with non-sedating second-generation antihistamines (sgAHs) as the mainstay of treatment for pediatric CSU, considering their demonstrated efficacy and reassuring safety profile. Additionally, the use of omalizumab in adolescents is well supported by the current literature. There is limited data available regarding the updosing of sgAHs, omalizumab in children with CSU under 12 years of age and the treatment with cyclosporine and leukotriene receptor antagonists (LTRAs) in pediatric patients of all ages. However, the results from currently available case series and case reports are promising for omalizumab and cyclosporine use in children with CSU, although large and well-designed randomized control trials (RCTs) assessing these treatment options are needed in order to formulate strong recommendations for their use. First-generation antihistamines (fgAHs) remain commonly used in pediatric CSU treatment despite a lack of studies assessing their efficacy and safety in the pediatric population and their widely known inferior safety profile compared to sgAHs.

Urticaria: Collegium Internationale Allergologicum (CIA) Update 2020

This update on chronic urticaria (CU) focuses on the prevalence and pathogenesis of chronic spontaneous urticaria (CSU), the expanding spectrum of patient-reported outcome measures (PROMs) for assessing CU disease activity, impact, and control, as well as future treatment options for CU. This update is needed, as several recently reported findings have led to significant advances in these areas. Some of these key discoveries were first presented at past meetings of the Collegium Internationale Allergologicum (CIA). New evidence shows that the prevalence of CSU is geographically heterogeneous, high in all age groups, and increasing. Several recent reports have helped to better characterize two endotypes of CSU: type I autoimmune (or autoallergic) CSU, driven by IgE to autoallergens, and type IIb autoimmune CSU, which is due to mast cell (MC)-targeted autoantibodies. The aim of treatment in CU is complete disease control with absence of signs and symptoms as well as normalization of quality of life (QoL). This is best monitored by the use of an expanding set of PROMs, to which the Angioedema Control Test, the Cholinergic Urticaria Quality of Life Questionnaire, and the Cholinergic Urticaria Activity Score have recently been added. Current treatment approaches for CU under development include drugs that inhibit the effects of signals that drive MC activation and accumulation, drugs that inhibit intracellular pathways of MC activation and degranulation, and drugs that silence MCs by binding to inhibitory receptors. The understanding, knowledge, and management of CU are rapidly increasing. The aim of this review is to provide physicians who treat CU patients with an update on where we stand and where we will go. Many questions and unmet needs remain to be addressed, such as the development of routine diagnostic tests for type I and type IIb autoimmune CSU, the global dissemination and consistent use of PROMs to assess disease activity, impact, and control, and the development of more effective and well-tolerated long-term treatments for all forms of CU.

Factors Predicting the Response to Cyclosporin Treatment in Patients With Chronic Spontaneous Urticaria: A Systematic Review

Purpose

This study aimed to systemically review literature relating to factors that could potentially predict a favorable response to cyclosporine A (CsA) treatment for chronic spontaneous urticaria (CSU).

Methods

A systematic literature review was done according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis recommendations.

Results

A total of 13 studies (404 patients with CSU and 200 healthy patients) were included. There were only 1 randomized controlled trial (RCT) and 12 non-RCTs. Our systematic review showed that positive autologous serum skin test results, positive baseline basophil histamine release assays, positive baseline basophil activation test responses, elevated baseline plasma D-dimer levels, elevated baseline serum interleukin (IL)-2, IL-5, and tumor necrosis factor-alpha (TNF-α) levels, and low baseline serum IgE levels might assist in predicting favorable CsA responses in CSU patients. Decreased plasma D-dimer levels; and decreased serum IL-2, IL-5, and TNF-α levels were reported to be correlated with clinical improvement after CsA treatment.

Conclusions

Since most positive results were from non-RCT articles and some data were still inconsistent, this systematic review identified no reliable practical biomarker for predicting CsA treatment response in patients with CSU. There were no positive predictors with good consistency and mechanical plausibility.

Chronic Spontaneous Urticaria: The Devil's Itch

Chronic urticaria is defined as the presence of urticaria for a period exceeding 6 weeks, assuming symptoms for most days of the week. It is divided into chronic inducible urticarias and chronic spontaneous urticaria, previously termed chronic idiopathic urticaria. The latter designation emphasizes that patients can experience urticaria independent of any exogenous stimulus even if one can define circumstances that may worsen symptoms. A search for such an external "cause" is fruitless because the underlying abnormality is "intrinsic," whether it is autoimmune, or some unknown process. Approximately 40% of patients with chronic spontaneous urticaria report accompanying episodes of angioedema, whereas 10% have angioedema as their primary manifestation. In most cases, it is a self-limiting disorder, persisting for 2 to 5 years in most cases, although 20% of patients suffer for more than 5 years. The treatment that has evolved is largely empiric, based on double-blind, placebo-controlled studies whenever possible, but is not yet targeted to any particular pathogenic mechanism. In this article, we review the current status regarding pathogenesis, discuss the diagnostic workup, and update the approach to treatment including consideration of published guidelines, our own experience, and guideline updates that are being prepared.

Treatment of chronic spontaneous urticaria: Immunomodulatory approaches

This paper summarizes and reviews the mechanisms of action and data concerning efficacy of recommended treatments as well as other treatments that have been tested, independently of the outcomes, in the management of chronic spontaneous urticaria. Due to the central role of mast cells, basophils and histamine in the pathophysiology of this disease, H₁-antihistamines remain the first-line treatment. However, current knowledge about this complex disease, also recognizes an important role for T lymphocytes, B lymphocytes, and autoantibodies. Implications of these others mediators thus provide further targets for treatment. Indeed, agents previously used to treat other autoimmune and inflammatory diseases, have demonstrated efficacy in chronic spontaneous urticaria and are therefore potential therapeutic alternatives for antihistamine unresponsive patients.

Cyclosporine for Chronic Spontaneous Urticaria: A Meta-Analysis and Systematic Review

BACKGROUND

Despite widely recommended usage of cyclosporine A (CsA) in chronic spontaneous urticaria (CSU), there is no meta-analysis concerning its efficacy and safety.

OBJECTIVE

To meta-analyze and review the efficacy and safety of CsA in CSU.

METHODS

Efficacy was assessed by the relative change in urticaria activity score at 4 weeks and response rates at 4, 8, and 12 weeks. Safety was assessed by analyzing the number of patients with 1 or more adverse event.

RESULTS

Eighteen studies (909 participants) including 2 randomized controlled trials were included, with 125, 363, and 266 patients with CSU receiving very low (<2 mg/kg/d), low (from 2 to< 4 mg/kg/d), and moderate (4-5 mg/kg/d) doses of CsA, respectively. After 4 weeks, the mean relative change in urticaria activity score of CsA-treated patients was -17.89, whereas that of controls was -2.3. The overall response rate to CsA treatment with low to moderate doses at 4, 8, and 12 weeks was 54%, 66%, and 73%, respectively. No studies of very low-dose CsA evaluated response rates at 4, 8, and 12 weeks. Among patients treated with very low, low, and moderate doses of CsA, 6%, 23%, and 57% experienced 1 or more adverse event, respectively.

CONCLUSIONS

Given the limited number and quality of studies, our results should be interpreted with caution. CsA is effective at low to moderate doses. Adverse events appear to be dose dependent and occur in more than half the patients treated with moderate doses of CsA. We suggest that the appropriate dosage of CsA for CSU may range from 1 to 5 mg/kg/d, and 3 mg/kg/d is a reasonable starting dose for most patients.

Update and insights into treatment options for chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is defined as itchy weals, angio-oedema, or both, arising spontaneously without external physical stimuli. Symptoms of the disease continue to develop for more than 6 weeks. It carries a high socioeconomic burden with considerable health care costs. Second generation H1-antihistamines are the mainstay of urticaria treatment and are the only licensed option. However, many patients are resistant to H1-antihistamine therapy. Omalizumab has proven to be an effective therapeutic option in patients with recalcitrant chronic urticaria. Ciclosporin appears to be more beneficial in patients with functional histamine releasing autoantibodies as a cause of their disease. This review article will highlight the major therapeutic options available today for the management of CSU knowing that good quality evidence for efficacy of many agents is scarce except for H1-antihistamines and omalizumab.

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.

Clinical application of development of nonantibiotic macrolides that correct inflammation-driven immune dysfunction in inflammatory skin diseases

BACKGROUND

Inflammation-driven immune dysfunction supports the development of several chronic human disorders including skin diseases. Nonantibiotic macrolides have anti-inflammatory and/or immunomodulatory activity that suggests the exploitation of these in the treatment of skin diseases characterized by inflammatory disorders.

MATERIALS AND METHODS

We performed an extensive review of the nonantibiotic macrolide literature published between 2005 and 2012, including cross-references of any retrieved articles. We also included some data from our own experience.

RESULTS

Calcineurin antagonists such as tacrolimus and ascomycins (e.g., pimecrolimus) act by inhibiting the activation of the nuclear factor for activated T cells (NFAT). There are new applications for these macrolides that have been available for several years and have been applied to skin and hair disorders such as atopic dermatitis, oral lichen planus, vitiligo, chronic autoimmune urticaria, rosacea, alopecia areata, pyoderma gangrenosum, Behcet's disease, neutrophilic dermatosis, and lupus erythematosus. We also reviewed new macrolides, like rapamycin, everolimus, and temsirolimus. In addition to the literature review, we report a novel class of nonantibiotic 14-member macrocycle with anti-inflammatory and immunomodulatory effects.

CONCLUSIONS

This paper summarizes the most important clinical studies and case reports dealing with the potential benefits of nonantibiotic macrolides which have opened new avenues in the development of anti-inflammatory strategies in the treatment of cutaneous disorders.

Calcineurin inhibitors in chronic urticaria

PURPOSE OF REVIEW

The purpose of the review is to review the pathophysiology, available data, and our current recommendations for calcineurin inhibitor (cyclosporine and tacrolimus) treatment in antihistamine refractory chronic idiopathic urticaria (CIU) patients.

RECENT FINDINGS

Low-dose cyclosporine (<5  mg/kg per day) may have unique immunological modulating properties beyond mast cell and basophil stabilization in CIU. Starting CIU treatment with very low cyclosporine dosages (1 mg/kg per day) and titrating based on response and side-effects may decrease adverse events while preserving efficacy. In cyclosporine responsive patients failing cyclosporine taper, case series data support the safety and efficacy of long-term (5-10 years), very low dose (1-2 mg/kg per day) cyclosporine treatment with appropriate clinical monitoring.

SUMMARY

For CIU patients refractory to antihistamines, low-dose cyclosporine therapy (<3 mg/kg per day) with appropriate laboratory monitoring provides an alternative with an acceptable side-effect profile. Long-term (>12 months) moderate-dose (2.5-5 mg/kg per day) cyclosporine treatment may cause longitudinal increases in serum creatinine. However, decreasing or stopping cyclosporine dosing reverses measured nephrotoxicity in the vast majority of patients, and some patients with careful monitoring can tolerate very low-dose cyclosporine (<2 mg/kg per day) for longer periods. Tacrolimus is an alternative to cyclosporine with a slightly different adverse effect profile. Minimal data are available on its use in chronic urticaria.

Methotrexate: a useful steroid-sparing agent in recalcitrant chronic urticaria

Background Reports of methotrexate for chronic urticaria are anecdotal. Objectives To assess the effectiveness of methotrexate in steroid-dependent chronic urticaria, its impact on steroid reduction and any differences in response between patients with and without functional autoantibodies. Methods A retrospective case-note review of 16 patients with steroid-dependent chronic urticaria treated with methotrexate was carried out. Ten patients had chronic ordinary/spontaneous urticaria (CU), including three with associated delayed-pressure urticaria; four patients had normocomplementaemic urticarial vasculitis (UV); and two patients had idiopathic angio-oedema without weals. Median disease duration before methotrexate was 48.5 months (range 12-164). All were unresponsive to antihistamines and second-line agents, except prednisolone. Eleven were assessed for autoimmune urticaria with the basophil histamine release assay (n = 5), autologous serum skin test (n = 5) or both (n = 1). Response to methotrexate was scored: no benefit; some benefit (fewer weals and symptomatic improvement but no steroid reduction); considerable benefit (improvement with steroid reduction); or clear (no symptoms, off steroids but on antihistamines). Results Twelve of 16 patients (eight CU, three UV, one idiopathic angio-oedema) responded. Three showed some benefit, seven considerable benefit and two cleared. Four of eight responders and three out of three nonresponders showed evidence of functional autoantibodies. The dose to achieve a steroid-sparing effect was 10-15 mg weekly (cumulative dose range 15-600 mg, median 135 mg). Methotrexate was well tolerated. Conclusions Methotrexate may be a useful treatment for steroid-dependent chronic urticaria. Functional autoantibodies do not correlate with response. The beneficial effects of methotrexate may be anti-inflammatory and immunosuppressive. It may therefore benefit chronic urticaria independently of the pathogenic mechanism, whether autoimmune or not.

C5a-induced in vitro basophil activation in patients with chronic urticaria: a pilot study

BACKGROUND

Complement component 5a (C5a) might be involved in the formation of wheals in patients with chronic urticaria (CU). We sought to compare the in vitro responsiveness of basophils to C5a in patients with CU and in a control group.

METHODS

Basophil surface expression of activation marker CD63 induced by C5a, anti-FcepsilonRI mAb or anti-IgE pAb was measured using flow cytometry in 17 patients with CU and in 10 healthy controls.

RESULTS

Patients with CU showed significantly greater basophil CD63 surface expression induced by C5a (median [interquartile range]; 16.4% [13-25.1]; P = 0.011) than the group of healthy controls (10.7% [7.2-16.8]). In contrast, basophil CD63 response to anti-IgE and anti-FcepsilonRI was lower in the CU group (12.3% [6-36.3]; 25.9% [12.5-60.5]) than in the control group (51.7% [6.7-84.3]; 62.1% [9.7-89.2]), although not statistically significant.

CONCLUSION

Results of this pilot study suggest that patients with CU might have an enhanced basophil response to stimulation with C5a, indicating that further studies in CU basophil responsiveness are needed.

Experience with cyclosporine in children with chronic idiopathic urticaria

BACKGROUND

The identification of an autoimmune mechanism for many patients with chronic idiopathic urticaria (CIU) was used as a rational for a controlled clinical trial of cyclosporine for adults with CIU not responsive to usual measures. That randomized placebo controlled clinical trial demonstrated clinical efficacy, acceptable safety, and a suggestion of inducing remission in such patients.

OBJECTIVE

To report our experience with cyclosporine in pediatric patients with CIU.

METHODS

Fifty-four patients with CIU were referred to us during the period from 2000 through June of 2005. Seven of those, aged 9-16, failed therapy with high dose antihistamines even with the addition of alternate morning prednisone. Neoral brand of cyclosporine, 3 mg/kg/day divided b.i.d., was initiated in these patients. Cyclosporine serum concentrations, blood urea nitrogen (BUN), creatinine, and blood pressure were routinely monitored.

RESULTS

All had cessation of hives. This occurred after 1-4 weeks for six of the seven and 8 weeks for one. While some experienced relapses, all were eventually off of all medications and free of hives. None of the seven experienced any adverse effects.

CONCLUSIONS

Our experience in children is consistent with a previous controlled clinical trial in adults and supports the efficacy and safety of cyclosporine for CIU. However, we recommend that it be reserved for those whose CIU that is resistant to conventional measures and that patients be carefully monitored with cyclosporine serum concentrations and measures of renal function.

Chronic urticaria: do urticaria nonexperts implement treatment guidelines? A survey of adherence to published guidelines by nonexperts

BACKGROUND

Guidelines including level of evidence and grade of recommendation were recently published for chronic urticaria (CU).

OBJECTIVES

To describe the therapeutic approach in patients with CU, and to depict how recent guidelines are implemented in the daily practice of management of CU.

METHODS

We performed a cross-sectional multicentre study through a questionnaire answered by 139 specialists. In total, 695 patients were evaluated, mean+/-SD age 42.3+/-15 years, 62.1% women. Of the patients, 168 were treated by an allergist, 473 by a dermatologist and in 54 cases the specialist was not stated. The drug prescribed was the main variable, and chi2 and Fisher's tests were utilized for the statistical analysis.

RESULTS

Nonsedating anti-H1 antihistamines taken regularly were the most common drugs prescribed, followed by nonsedating anti-H1 antihistamines taken as needed, corticosteroids, sedating antihistamines taken regularly, sedating antihistamines taken as needed, anti-H2 antihistamines, leukotriene antagonists, ciclosporin and doxepin. Nonsedating antihistamines plus corticosteroids was the most frequent drug combination prescribed. When comparing between allergists and dermatologists we found a positive and significant correlation only between prescription of cetirizine, dexchlorfeniramine, leukotriene antagonists and anti-H2 antihistamines and being treated by an allergist. A positive correlation was found with desloratadine and being seen by a dermatologist. We did not find any difference in CU management in the rest of the treatments studied.

CONCLUSIONS

It is surprising that a large amount of sedating antihistamines was prescribed. In many instances these were prescribed as needed. This fact could have a negative impact on urticaria control and patient satisfaction. It seems difficult for the nonexpert to differentiate between CU and any kind of physical urticaria.

Basophil histamine release activity and disease severity in chronic idiopathic urticaria

BACKGROUND

Altered basophil degranulation phenotypes are found in patients with chronic idiopathic urticaria (CIU).

OBJECTIVE

To evaluate CIU disease severity in relation to basophil histamine release (HR) characteristics.

METHODS

Patients with CIU were recruited from allergy and dermatology clinics. Patients with recent use of systemic corticosteroids or immunosuppressants were excluded. Patients completed disease severity surveys and had blood basophils isolated and stimulated for HR using polyclonal goat anti-human IgE and N-formyl-met-leu-phe. The HR was measured using automated fluorometry. Multivariate linear regression analyses were used to investigate relationships between HR data and CIU disease measures.

RESULTS

Fifty patients completed surveys, of which 34 were further categorized into 2 subgroups based on basophil HR response to anti-IgE stimulation: responders (> or = 10% HR) and nonresponders (< 10% HR). Responders and nonresponders reported similar use of oral corticosteroids, work absences, and quality-of-life impairment but differed in their patterns of medications used for CIU. Basophil responders had a trend of higher use of the emergency department for CIU management. Multivariate regression revealed that patients with the basophil responder phenotype experienced significantly higher current itch scores (P = .02) compared with nonresponders.

CONCLUSIONS

Quality-of-life impairment is similar in CIU basophil subsets. Patients with CIU with a basophil responder phenotype report longer disease duration, a higher frequency of emergency department use, and significantly higher itch severity.

Progress and challenges in the understanding of chronic urticaria

: Chronic urticaria is a skin disorder characterized by transient pruritic weals that recur from day to day for 6 weeks or more. It has a great impact on patients' quality of life. In spite of this prevalence and morbidity, we are only beginning to understand its physiopathology and we do not have a curative treatment. Moreover, a patient with chronic urticaria may undergo extensive laboratory evaluations seeking a cause only to be frustrated when none is found. In recent years there have been significant advances in our understanding of some of the molecular mechanisms responsible for hive formation. The presence and probable role of IgG autoantibodies directed against epitopes expressed on the alpha-chain of the IgE receptor and to lesser extent, to IgE in a subset of patients is generally acknowledged. These autoantibodies activate complement to release C5a, which augments histamine release, and IL4 and leukotriene C4 are released as well. A perivascular cellular infiltrate results without predominance of either Th1 or Th2 lymphocyte subpopulations. Basophils of all chronic urticaria patients (autoimmune or idiopathic) are hyperresponsive to serum, regardless of source, but poorly responsive to anti IgE. In this review we will summarize the recent contributions to this field and try to provide insights to possible future directions for research on this disease.

Autoimmunity and complement in the pathogenesis of chronic urticaria

Chronic urticaria is a debilitating skin disease that is believed to have an underlying autoimmune etiology in 35% to 50% of cases. Patients with autoimmune urticaria have functional antibodies in their sera that release histamine from basophils and mast cells. The C5a component of complement is required for mast cell degranulation in this process and at least augments basophil histamine release. In this article, the evidence that is key to our understanding of autoimmunity and complement in the pathogenesis of a subset of patients with chronic urticaria is outlined. Some of the issues in testing for and treating autoimmune urticaria are discussed.

Serum-induced basophil CD63 expression by means of a tricolour flow cytometric method for the in vitro diagnosis of chronic urticaria

BACKGROUND

Functional autoantibodies against the alpha-chain of the high-affinity IgE receptor (FcepsilonRIalpha) identify a subset of patients with chronic urticaria (CU) due to autoreactivity, as assessed by an in vivo positive response to autologous serum skin test (ASST). We performed a study to standardize the serum-induced basophil activation assay by flow cytometry (FCM) using a new tricolour method, assessing the diagnostic performance of this test in discriminating between ASST+ and ASST- CU patients.

METHODS

Sera of 64 CU patients (22 ASST+ CU and 42 ASST- CU) and 10 healthy subjects were tested for their ability to induce basophil CD63 expression when incubated with whole blood of both atopic (DA) and non-atopic donors (DNA). Using a triple-labelled strategy with anti-CD123, anti-HLA-DR and anti-CD63 antibodies, CD63+ basophils were identified on a selected population of CD123+ HLA-DR- cells. In 3 ASST+ CU patients who underwent cyclosporine therapy, the assay was performed before and after treatment.

RESULTS

The ASST+ CU sera resulted in a significant higher induction of basophil CD63 expression compared with ASST- CU and healthy donors sera; when whole blood from DA was used, sensitivity and specificity of the assay were 95.5% and 90.5% respectively. ASST+ CU serum activity was significantly decreased during cyclosporine A treatment, in parallel with clinical remission.

CONCLUSIONS

Chronic urticaria serum-induced CD63 expression assay performed on DA whole blood by means of our tricolour FCM method could be the most useful tool for identification of a subset of patients with autoimmune CU and may become a promising tool also for monitoring treatment efficacy.

Chronic idiopathic urticaria with functional autoantibodies: 12 years on

It is now recognized that approximately one-third of patients with chronic idiopathic urticaria (CIU) have histamine-releasing autoantibodies directed against either the high-affinity IgE receptor or, less frequently, against IgE. However, there are several unsolved problems relating to the role of such autoantibodies in the disease. Additionally, it is not clear whether CIU with autoantibodies can be classified as an autoimmune disease. The detection of patients with autoantibodies also poses challenges. Firstly, the only in vivo method, the autologous serum skin test, is at best 80% sensitive and specific using in vitro basophil histamine release assays as the verum. Secondly, in vitro tests are only done in a small number of research laboratories, and are not widely commercially available, and thirdly, there is some divergence between results obtained by different methods (functional and immunoassays) used to detect patients with autoantibodies. The presence of autoantibodies may be important clinically in a small group of severely affected, treatment-resistant patients, where immunomodulatory treatments may be helpful.

Autoantibodies to the high-affinity IgE receptor in chronic urticaria: how important are they?

PURPOSE OF REVIEW

Eighty to 90% of patients with chronic urticaria have no specific external cause for their disease, which is therefore labeled 'chronic idiopathic urticaria'. We now know, however, that as many as 30-50% of patients have evidence of an autoantibody to the high-affinity receptor for IgE (FcepsilonRI), which may be pathogenic. The exact prevalence and role of these autoantibodies is still under investigation.

RECENT FINDINGS

The frequency of autoantibodies to FcepsilonRI in chronic urticaria has been estimated at 30-50%, but extensive epidemiological studies have not been done. Recent work has confirmed that autoantibodies to FcepsilonRI can be functional, meaning that they can cause histamine release from basophils in vitro. Evidence increasingly suggests that such autoantibodies are also functional in vivo, but conclusive evidence is still lacking. Approximately 50% of cases of urticaria still have no known cause, but recent studies have demonstrated that some of these patients may have intrinsic abnormalities of basophils or mast cells.

SUMMARY

The recent evidence that is discussed in this review helps to clarify the role of autoantibodies in some cases of urticaria, but also points towards other non-autoimmune mechanisms that might be pathogenic. Further investigation in these areas will help us to understand the cause of urticaria in cases that are still classified as 'idiopathic'.