Evidence of in vivo basophil activation in chronic idiopathic urticaria

Basophils in pruritic skin diseases

Basophils are rare cells in the peripheral blood which have the capability to infiltrate into the skin. Invasion of basophils has been detected in pruritic skin diseases, including atopic dermatitis, bullous pemphigoid, chronic spontaneous urticaria and contact dermatitis. In the skin, basophils are important players of the inflammatory immune response, as they release Th2 cytokines, including interleukin (IL)-4 and IL-13, subsequently inducing the early activation of T-cells. Further, basophils release a multitude of mediators, such as histamine and IL-31, which both play an important role in the initiation of the pruritic response via activation of sensory nerves. Chronic pruritus significantly affects the quality of life and the working capability of patients, though its mechanisms are not fully elucidated yet. Since basophils and neurons share many receptors and channels, bidirectional interaction mechanisms, which drive the sensation of itch, are highlighted in this review.

Basophil Characteristics as a Marker of the Pathogenesis of Chronic Spontaneous Urticaria in Relation to the Coagulation and Complement Systems

Chronic spontaneous urticaria (CSU) is a common skin disorder characterized by daily or almost daily recurring skin edema and flare with itch and pruritus anywhere on the body for more than 6 weeks. Although basophil- and mast cell-released inflammatory mediators, such as histamine, play important roles in the pathogenesis of CSU, the detailed underlying mechanism is not clear. Since several auto-antibodies, IgGs which recognize IgE or the high-affinity IgE receptor (FcεRI) and IgEs against other self-antigens, are detected in CSU patients, they are considered to activate both mast cells in the skin and basophils circulating in the blood. In addition, we and other groups demonstrated that the coagulation and complement system also contribute to the development of urticaria. Here, we summarized the behaviors, markers and targets of basophils in relation to the coagulation-complement system, and for the treatment of CSU.

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.

Urticaria and basophils

Chronic spontaneous urticaria (CSU) is a common skin disease without an etiology in the vast majority of cases. The similarity of symptoms and pathology to allergen-induced skin reactions supports that skin mast cell IgE receptor activation is also involved in CSU. Accumulating evidence also supports a role for blood basophils in disease expression. Blood basopenia is noted in active CSU disease with the recruitment of blood basophils to skin lesion sites. Blood basophils further display altered IgE receptor mediated degranulation patterns in two phenotypes that improve in remission. In active CSU subjects, changes in IgE receptor signaling molecule expression levels accompany the altered degranulation function in blood basophils. The success of therapies targeting IgE in CSU patients have also shown that altered blood basophil phenotypes and enumeration have potential use as a disease biomarker.

miRNAs' Cross-Involvement in Skin Allergies: A New Horizon for the Pathogenesis, Diagnosis and Therapy of Atopic Dermatitis, Allergic Contact Dermatitis and Chronic Spontaneous Urticaria

Skin inflammation is a common underlying feature of atopic dermatitis, allergic contact dermatitis and chronic spontaneous urticaria. The pathogenetic mechanisms have not been fully elucidated. The purpose of this study was to examine whether miRNA, by regulating inflammatory mechanisms through the modulation of innate and adaptive immune responses, could play a major role in the pathogenesis of these skin conditions. We conducted a narrative review using the Pubmed and Embase scientific databases and search engines to find the most relevant miRNAs related to the pathophysiology, severity and prognosis of skin conditions. The studies show that miRNAs are involved in the pathogenesis and regulation of atopic dermatitis and can reveal an atopic predisposition or indicate disease severity. In chronic spontaneous urticaria, different miRNAs which are over-expressed during urticaria exacerbations not only play a role in the possible response to therapy or remission, but also serve as a marker of chronic autoimmune urticaria and indicate associations with other autoimmune diseases. In allergic contact dermatitis, miRNAs are upregulated in inflammatory lesions and expressed during the sensitization phase of allergic response. Several miRNAs have been identified as potential biomarkers of these chronic skin conditions, but they are also possible therapeutic targets.

Basophils from allergy to cancer

Human basophils, first identified over 140 years ago, account for just 0.5-1% of circulating leukocytes. While this scarcity long hampered basophil studies, innovations during the past 30 years, beginning with their isolation and more recently in the development of mouse models, have markedly advanced our understanding of these cells. Although dissimilarities between human and mouse basophils persist, the overall findings highlight the growing importance of these cells in health and disease. Indeed, studies continue to support basophils as key participants in IgE-mediated reactions, where they infiltrate inflammatory lesions, release pro-inflammatory mediators (histamine, leukotriene C₄: LTC₄) and regulatory cytokines (IL-4, IL-13) central to the pathogenesis of allergic diseases. Studies now report basophils infiltrating various human cancers where they play diverse roles, either promoting or hampering tumorigenesis. Likewise, this activity bears remarkable similarity to the mounting evidence that basophils facilitate wound healing. In fact, both activities appear linked to the capacity of basophils to secrete IL-4/IL-13, with these cytokines polarizing macrophages toward the M2 phenotype. Basophils also secrete several angiogenic factors (vascular endothelial growth factor: VEGF-A, amphiregulin) consistent with these activities. In this review, we feature these newfound properties with the goal of unraveling the increasing importance of basophils in these diverse pathobiological processes.

Basophils activation of patients with chronic spontaneous urticaria in response to C5a despite failure to respond to IgE-mediated stimuli

Urticaria is characterized by the occurrence of wheals and flares in response to vasoactive mediators, such as histamine. Various studies have suggested the involvement of basophils in the pathogenesis of chronic spontaneous urticaria (CSU). However, histamine release from peripheral basophils in response to stimuli acting on the high affinity IgE receptor (FcϵRI) is impaired in many patients with CSU (non/low responders). We previously demonstrated that tissue factor (TF)s expressed on vascular endothelial cells in response to a combination of various stimuli, such as that of histamine and lipopolysaccharide (LPS), activates the extrinsic coagulation pathway and produces anaphylatoxin, complement 5a (C5a), which then activates basophils and mast cells via the C5a receptor (C5aR). We have revealed that histamine release was induced in response to C5a and formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLP), regardless of the response to anti-IgE antibody, the reduced numbers of basophils and severity of urticaria. Moreover, we found that spontaneous release of histamine ex vivo from basophils of patients with CSU is higher than that from healthy individuals. These results suggest that basophils and the complement system, which could be activated by coagulation factors, may play a critical role in the pathogenesis of CSU, especially in cases refractory to treatment involving the IgE/FcϵRI pathway.

Clarithromycin-treated chronic spontaneous urticaria with the negative regulation of FcεRΙ and MRGPRX2 activation via CD300f

Mast cells (MCs) are main effector cells in chronic spontaneous urticaria (CSU). Both Fc epsilon RI (FcεRΙ)- and MAS-related G coupled receptor-X2 (MRGPRX2)-mediated MC activations affect CSU course. Leukocyte mono-immunoglobulin-like receptor 3 (CD300f) has been shown to regulate FcεRΙ activation. However, no study has verified CD300f is a target to cure CSU. Therefore this study aimed to verify whether clarithromycin (CLA) regulates FcεRΙ- and MRGPRX2-mediated MC activations via CD300f and shows therapeutic effect on CSU. The target of CLA was verification. CLA inhibited FcεRΙ- and MRGPRX2-mediated MC activations were shown in vivo and in vitro. A single-center, self-comparison study was performed, and CLA-treated CSU was investigated in 28 patients who were not sensitive to the third-generation antihistamines. Serum inflammatory mediators in patients before and after CLA administration were analyzed. CLA effectively inhibited type Ι anaphylactic reactions and pseudo-allergic reactions in mice. Moreover, CLA inhibited FcεRΙ- and MRGPRX2-mediated MC signaling pathway activation. Regulatory effects of CLA were decreased significantly after CD300f knockdown. CLA effectively alleviated the symptoms of wheal and itch and reduced serum cytokine levels in patients. CLA negatively regulated FcεRΙ- and MRGPRX2-mediated MC activation via CD300f and showed significant therapeutic effect on CSU.

IgG Autoantibodies Against IgE from Atopic Dermatitis Can Induce the Release of Cytokines and Proinflammatory Mediators from Basophils and Mast Cells

IgE-mediated release of proinflammatory mediators and cytokines from basophils and mast cells is a central event in allergic disorders. Several groups of investigators have demonstrated the presence of autoantibodies against IgE and/or FcεRI in patients with chronic spontaneous urticaria. By contrast, the prevalence and functional activity of anti-IgE autoantibodies in atopic dermatitis (AD) are largely unknown. We evaluated the ability of IgG anti-IgE from patients with AD to induce the in vitro IgE-dependent activation of human basophils and skin and lung mast cells. Different preparations of IgG anti-IgE purified from patients with AD and rabbit IgG anti-IgE were compared for their triggering effects on the in vitro release of histamine and type 2 cytokines (IL-4, IL-13) from basophils and of histamine and lipid mediators (prostaglandin D₂ and cysteinyl leukotriene C₄) from human skin and lung mast cells. One preparation of human IgG anti-IgE out of six patients with AD induced histamine release from basophils, skin and lung mast cells. This preparation of human IgG anti-IgE induced the secretion of cytokines and eicosanoids from basophils and mast cells, respectively. Human monoclonal IgE was a competitive antagonist of both human and rabbit IgG anti-IgE. Human anti-IgE was more potent than rabbit anti-IgE for IL-4 and IL-13 production by basophils and histamine, prostaglandin D₂ and leukotriene C₄ release from mast cells. Functional anti-IgE autoantibodies rarely occur in patients with AD. When present, they induce the release of proinflammatory mediators and cytokines from basophils and mast cells, thereby possibly contributing to sustained IgE-dependent inflammation in at least a subset of patients with this disorder.

Aeroallergens in Atopic Dermatitis and Chronic Urticaria

PURPOSE OF REVIEW

While aeroallergens are a well-established trigger of asthma and allergic rhinitis, their role in allergic skin diseases such as atopic dermatitis and chronic urticaria remains controversial. This paper reviews the pathophysiology and clinical evidence for aeroallergens in these allergic skin diseases and summarizes current strategies for evaluation and management.

RECENT FINDINGS

Current evidence implicates aeroallergens as triggers of cutaneous reactions in atopic dermatitis. Direct skin contact is the likely route of trigger. Aeroallergens may also trigger chronic urticaria, though mechanistic studies are limited. These allergens may cross the skin barrier and directly trigger neurons to release substance P, resulting in mast cell degranulation and dumping of histamine and prostaglandin D2. Many studies link aeroallergen sensitization to chronic urticaria, and case reports suggest the utility of avoidance strategies. The role of aeroallergens as a trigger is clear in atopic dermatitis and becoming emergent in chronic urticaria. Skin prick testing or serum-specific immunoglobulin E testing may be used to determine sensitivities. Management at this time centers on avoidance, and further studies are necessary to evaluate the efficacy of aeroallergen immunotherapy for both conditions.

Development and Evaluation of an In-House ELISA to Detect Anti-FcεR1α IgG Autoantibodies in Chronic Spontaneous Urticaria Patients

Background

Association between chronic spontaneous urticaria (CSU) and autoimmunity has been well documented. Autologous serum skin testing could support the autoimmune etiology of CSU, whereas it is difficult to interpret and could not be performed on antihistamine omitted patients. It was found that immunoglobulin G (IgG) autoantibodies (autoAbs) against high-affinity IgE receptor (FcεR1) were suggested as a potential trigger in the pathogenesis of CSU. Although many ELISA protocols have been developed to detect these autoAbs, they lacked validation or a reliable cut-off point. We, therefore, aimed to develop a validated ELISA with a reliable cut-off point to quantitate IgG anti-FcεR1α autoAbs for CSU.

Methods

We developed an in-house ELISA to quantitate IgG anti-FcεR1α autoAbs. Sera from 233 CSU patients and 25 healthy people were used to test with ELISA. The cut-off point was obtained from the results subjected to analyze with receiver operating characteristic (ROC) analysis. ELISA was validated with 116 CSU patients and 150 healthy donors.

Results

ELISA revealed that healthy people had a basal level of IgG anti-FcεR1α autoAbs, whereas their levels were significantly lower than autoAbs levels in CSU patients. ROC analysis of ELISA determined the cut-off point at 936.7 ng/ml. Our ELISA was validated and provided excellent sensitivity and specificity at 98.28% and 92.67%, respectively.

Conclusion

Our ELISA could detect significant levels of IgG anti-FcεR1α autoAbs in CSU, supporting that these autoAbs were associated with CSU etiology. Our validated ELISA with the reliable cut-off point provided excellent accuracy at 95.11% (98.28% sensitivity and 92.67% specificity). Our ELISA could be an alternative test benefit for the patient who is unable to omit antihistamine treatment.

Immunological Targets of Biologic Drugs in Allergic Skin Diseases in Children

Atopic dermatitis and urticaria are two invalidating skin disorders that are very common in children. Recent advances in the understanding of their specific intracellular molecular pathways have permitted the development of precise biological molecules, targeting inflammatory mediators and arresting the pathogenetic pathways of skin diseases. Many biologics with promising results have been studied, although few are currently approved in children. In this review, we aim to provide the latest evidence about the use, indications, efficacy and safety of biologic therapies to treat atopic dermatitis and chronic urticaria in children and adolescents.

Innate Immune Regulation of Dermatitis

Dermatitis encompasses a spectrum of inflammatory skin disorders with aberrant immune responses classified as type 1, type 2, and/or type 3. Major advances in the understanding of the pathogenesis of atopic dermatitis (AD) have shed new light on how innate immune responses critically regulate type 2 inflammation and itch. This article highlights the diverse ways by which type 2 immune cells regulate diseases beyond AD. The discovery of human Mas-related G protein-coupled receptor X2 on mast cells has revealed novel T cell-independent and immunoglobulin E-independent mechanisms of allergic contact dermatitis-associated and urticarial itch, respectively.

The Pathogenesis of Chronic Spontaneous Urticaria: The Role of Infiltrating Cells

Chronic spontaneous urticaria is characterized by a perivascular non-necrotizing cellular infiltrate around small venules of the skin. It consists primarily of CD4(+) lymphocytes, a prominence of the T helper (Th)2 subtype but also Th1 cells, with Th17 cell-derived cytokines elevated in plasma. There are also neutrophils, eosinophils, basophils, and monocytes. Chemokines derived from mast cells and activated endothelial cells drive the process. Although the role of the cellular infiltrate has not previously been addressed, each constituent can contribute to the overall pathogenesis. It is of interest that CSU responds to corticosteroid, yet, short-term steroids do not affect autoimmunity or degranulation of mast cells, and act on margination of cells along the endothelium and chemotaxis to enter the surrounding dermis. In this review, we address each cell's contribution to the overall inflammatory response, as it is currently understood, with a view toward development of therapeutic options that impede the function of critical cells and/or their secretory products.

Factitious Disorder Masquerading as a Life-Threatening Anaphylaxis

Factitious disorder is a psychiatric disorder in which sufferers intentionally fabricate physical or psychological symptoms in order to assume the role of the patient, without any obvious gain. We present a case of a 23-year-old female with chronic urticaria who presented with dyspnea, dysphasia, mild generalized erythema, abdominal cramps, and headache. She was tachypneic and hypotensive. This was her third admission with similar symptoms within the last 7 months. Tryptase, complement, anti-SM/RNP, Sjogren, Scl-70, C3, and C4 were negative. Computed tomography–guided bone marrow biopsy showed no mast cells. Flow cytometry did not show any immunophenotypic reaction. Other possible differentials including pregnancy, autoimmune disorders, and infections including hepatitis, thyroid disorder, and age-related malignancies were ruled out. After a thorough review, malingering disorder was ruled out, but we noticed the patient’s intent of assuming a sick role. Later, the patient was diagnosed with major depressive disorder. Factitious anaphylaxis can present with multiple presentations including a life-threatening condition that mimics true anaphylaxis. A better approach would be thorough clinical evaluation and early multidisciplinary involvement. This case highlights the importance of further evidence-based studies in factitious disorder to decrease the disease burden and reduce the health care cost.

Response of peripheral blood basophils in subjects with chronic spontaneous urticaria during treatment with omalizumab

BACKGROUND

Treatment of patients with asthma or food allergy with omalizumab results in several consistent changes in circulating basophils. The multiple basophil phenotypes observed in patients with chronic spontaneous urticaria (CSU) present some unique attributes that may not respond in a similar fashion to patients with asthma or food allergy. As part of a clinical study on the therapeutic outcomes of omalizumab treatment in CSU, the basophil compartment was examined for changes in characteristics predicted by prior studies.

OBJECTIVE

This study sought to examine the changes in basophil function and its relationship to auto-antibodies in serum during treatment with omalizumab.

METHODS

At multiple time points before and during omalizumab treatment of patients with CSU, basophil surface IgE and FcεRI expression, cellular spleen tyrosine kinase (SYK) expression, IgE-mediated histamine release (HR), and the presence of auto-antibodies in serum were determined.

RESULTS

Three basophil phenotypes were enumerated in the clinical study and used to group results in this basophil study: subjects with (1) basopenia, (2) normal basophil numbers with normal IgE-mediated HR, and (3) normal basophil numbers with poor HR. Basopenia was highly associated with the presence of auto-antibodies to unoccupied FcεRI and basophil numbers did not change during treatment. Likewise, subjects who are basopenic showed no changes in SYK expression or HR during treatment. In basophils of subjects who are nonbasopenic, increases in SYK expression and HR showed the expected inverse relationship to starting SYK and HR levels. Treatment with omalizumab resulted in similar kinetics for decreases in surface FcεRI and IgE in all 3 groups.

CONCLUSIONS

A unifying interpretation of the results revolves around the presence of auto-antibodies to FcεRI in CSU. If present, basopenia and an absence of changes in basophils during omalizumab treatment are observed. If auto-antibodies are absent, the changes in the basophil compartment are consistent with prior studies of asthma and food allergy. These group differences also are related to efficacy of the treatment for clinical outcomes, as found in the parent clinical study.

Decreased intracellular histamine concentration and basophil activation in anaphylaxis

BACKGROUND

Histamine is a crucial mediator in the development of anaphylaxis. Although histamine is promptly degraded because of its short half-life in plasma, basophils, which release histamine, remain in the blood for days. To explore basophils as a potential marker and their involvement in the pathogenesis of anaphylaxis, we evaluated the intracellular histamine concentration and the degree of basophil activation in anaphylaxis patients.

METHODS

We conducted a case-control study enrolling anaphylaxis patients and healthy controls. Basophil activation was evaluated by flow cytometry using up-regulation of CD203c expression.

RESULTS

We enrolled 23 patients and measured their blood histamine concentration. Basophil activation was analyzed in seven of 23 patients. The median intracellular histamine concentrations at admission were significantly lower in patients compared with controls (16.4 ng/mL [interquartile range {IQR}, 2.70 to 34.0] vs. 62.3 ng/mL [IQR, 46.0 to 85.1]; p < 0.0001). The median basophil number at admission was also significantly lower in patients compared with controls (2.21 cell/μL [IQR, 0.75 to 12.3] vs. 21.0 cell/μL [IQR, 19.5 to 28.9]; p = 0.027). CD203c expression was not up-regulated in any of the seven patients in vitro, but it was up-regulated in response to anti-IgE stimulation in vitro in two patients at admission and four patients at follow-up.

CONCLUSIONS

Anaphylaxis is associated with a decrease in intracellular histamine, and a reduced number and reactivity of peripheral basophils. Impaired basophil function and a decrease in their number and intracellular histamine levels in the circulation may reflect the underlying mechanism, suggesting that basophils may be a marker of anaphylaxis.

Differentiation between control subjects and patients with chronic spontaneous urticaria based on the ability of anti-IgE autoantibodies (AAbs) to induce FcεRI crosslinking, as compared to anti-FcεRIα AAbs

BACKGROUND

The reported prevalences of IgG autoantibodies (AAbs) to FcεRIα and IgE in sera from patients with chronic spontaneous urticaria (CSU) have varied, and these AAbs are also often observed in healthy control subjects. Regarding the histamine release activity of purified IgG from patients with CSU, the number of examined patients has been small. Thus, we sought to determine the prevalence and FcεRI crosslinking ability of these AAbs in a large number of patients with CSU and non-atopic control (NC) subjects.

METHODS

We compared the concentrations of anti-IgE and anti-FcεRIα AAbs and the abilities of these AAbs to cause FcεRI aggregation in patients with CSU (n = 134) and NC subjects (n = 55) using ELISA and an in vitro elicitation test, respectively.

RESULTS

The concentration of anti-IgE AAbs was significantly different between the NC subjects and the CSU patients (P < 0.0001, cutoff value: 0.558 μg/mL), whereas the concentration of anti-FcεRIα AAbs was not. A significant difference in the duration of illness was noted between patients with lower and those with higher concentrations of anti-IgE AAbs relative to the cutoff value. The abilities of anti-IgE AAbs, but not anti-FcεRIα AAbs, to induce FcεRI crosslinking were significantly higher in CSU patients than in NC subjects (P = 0.0106).

CONCLUSIONS

In the Japanese population of CSU patients studied, the ability of the anti-IgE AAbs to induce FcεRI crosslinking differed significantly between NC subjects and CSU patients, suggesting the involvement of anti-IgE AAbs in the pathogenesis of CSU in the Japanese population.

Autoimmune Theories of Chronic Spontaneous Urticaria

Urticaria (hives) is a highly prevalent skin disorder that can occur with or without associated angioedema. Chronic spontaneous urticaria (CSU) is a condition which persists for more than 6 weeks in duration and occurs in the absence of an identifiable provoking factor. CSU results from pathogenic activation of mast cells and basophils, which gives rise to the release of proinflammatory mediators that support the generation of urticaria. Several theories have been put forth regarding the pathogenesis of CSU with much evidence pointing toward a potential autoimmune etiology in up to 50% of patients with this condition. In this review, we highlight the evidence surrounding the autoimmune pathogenesis of chronic urticaria including recent data which suggests that CSU may involve contributions from both immunoglobin G (IgG)-specific and immunoglobulin E (IgE)-specific autoantibodies against a vast array of antigens that can span beyond those found on the surface of mast cells and basophils.

Biomarkers for evaluation of mast cell and basophil activation

Mast cells and basophils play a pathogenetic role in allergic, inflammatory, and autoimmune disorders. These cells have different development, anatomical location and life span but share many similarities in mechanisms of activation and type of mediators. Mediators secreted by mast cells and basophils correlate with clinical severity in asthma, chronic urticaria, anaphylaxis, and other diseases. Therefore, effective biomarkers to measure mast cell and basophil activation in vivo could potentially have high diagnostic and prognostic values. An ideal biomarker should be specific for mast cells or basophils, easily and reproducibly detectable in blood or biological fluids and should be metabolically stable. Markers of mast cell and basophil include molecules secreted by stimulated cells and surface molecules expressed upon activation. Some markers, such as histamine and lipid mediators are common to mast cells and basophils whereas others, such as tryptase and other proteases, are relatively specific for mast cells. The best surface markers of activation expressed on mast cells and basophils are CD63 and CD203. While these mediators and surface molecules have been associated to a variety of diseases, none of them fulfills requirements for an optimal biomarker and search for better indicators of mast cell/basophil activation in vivo is ongoing.

Emerging Therapies in Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is characterized by typically short-lived and fleeting wheals, angioedema or both, which occur spontaneously and persist for longer than 6 weeks. This term is applied to the most common subtype of chronic urticaria. The underlying pathophysiology for CSU involves mast cell and basophil degranulation with release of histamine, leukotrienes, prostaglandins and other inflammatory mediators. Although a variety of treatments exist, many patients do not tolerate or benefit from the existing therapies and even require more effective treatments. Omalizumab is currently the only licensed biologic for antihistamine-refractory CSU, and novel drugs are under development. This article reviews its current status regarding pathogenesis and approach to treatment as well as therapeutic agents that are under development for the treatment of CSU.

Assessment of circulating FCεRIa in Chronic Spontaneous Urticaria patients and its correlation with clinical and immunological variables

Chronic spontaneous urticaria (CSU) is a chronic type characterized by episodes of wheals with or without angioedema. Autoantibody against the alpha subunit of Fc epsilon receptor (FcεRIa) was detected in CSU patients' sera. The study aims to evaluate the clinical utility of skin tests in CSU patients. In addition, it assesses the presence of circulating FcεRIa in CSU patients and their correlation with other clinical and immunological variables. The study includes 40 healthy controls and 40 CSU patients who had urticaria symptoms for at least 8 weeks. All subjects underwent the following tests: autologous serum skin test (ASST), autologous plasma skin test (APST), immunoglobulin E (IgE), antinuclear antibodies (ANA), antithyroid antibodies (ATA). An in-house enzyme-linked immunosorbent assay was used for FcεRIa detection. The prevalence of ANA and ATA in CSU was 7.5% and 20% respectively. Total IgE was significantly higher in CSU than in controls (p < 0.0001). The study detected circulating antibody to FcεRIα in 2.5% of controls and 52.5% of CSU patients (p < 0.0001). The prevalence of antibody to FcεRIa was 27.3% and 83.3% of ASST negative and positive patients respectively (p = 0.0004). But the prevalence was 17.6% and 78.3% of APST negative and positive patients respectively (p = 0.0002). In conclusion, Circulating antibody to FcεRIa has a role in the pathogenic mechanisms of CSU.

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.

Important and specific role for basophils in acute allergic reactions

IgE‐mediated allergic reactions involve the activation of effector cells, predominantly through the high‐affinity IgE receptor (FcεRI) on mast cells and basophils. Although the mast cell is considered the major effector cell during acute allergic reactions, more recent studies indicate a potentially important and specific role for basophils and their migration which occurs rapidly upon allergen challenge in humans undergoing anaphylaxis. We review the evidence for a role of basophils in contributing to clinical symptoms of anaphylaxis and discuss the possibility that basophil trafficking during anaphylaxis might be a pathogenic (to target organs) or protective (preventing degranulation in circulation) response. Finally, we examine the potential role of basophils in asthma exacerbations. Understanding the factors that regulate basophil trafficking and activation might lead to new diagnostic and therapeutic strategies in anaphylaxis and asthma.

Chronic urticaria: a focus on pathogenesis

Chronic urticaria is a spontaneous or inducible group of diseases characterized by the occurrence of wheals (and, in about half of cases, angioedema) for more than 6 weeks. These are rather frequent conditions that may severely affect patients’ quality of life and sometimes represent a challenge for doctors as well. The causes of chronic urticaria are still poorly defined, although there is growing evidence that different biologic systems including immunity, inflammation, and coagulation may take part in the pathomechanism eventually leading to mast cell and basophil degranulation and hence to wheal formation. This review will discuss the main findings that are (slowly) shedding light on the pathogenesis of this disorder.

Identification of a Th2- and Th17-skewed immune phenotype in chronic urticaria with Th22 reduction dependent on autoimmunity and thyroid disease markers

BACKGROUND

Chronic urticaria is a condition with many inciting factors and often presents a therapeutic challenge to clinicians. In addition to a central role for mast cells, an immune dysregulated state related to cytokine/chemokine alterations is increasingly being recognized.

METHODS

Biopsies of chronic urticaria (n = 11) and normal skin (n = 5) were evaluated with immunostains for CD117, CD3 and dual stains for CD4/T-bet, GATA-3, STAT-3 or BNC-2 (transcription factors specific and mutually exclusive for Th1, Th2, Th17 and Th22 cells, respectively). Clinical data, including autoantibodies and thyroid function tests, and the number of CD117+ mast cells and percent of Th1, Th2, Th17 and Th22 of CD3+ T-cells were compared.

RESULTS

Th2 cells and Th17 cells were significantly more frequent in chronic urticaria than controls. In contrast, there was no significant difference in mast cells, Th1 cells or Th22 cells. Three of nine chronic urticaria patients had evidence of autoimmune disease; biopsies from these patients trended toward a greater number of mast cells and decreased percent of Th-cell subtypes as compared with those without autoimmunity markers, with significantly less Th22 cells.

CONCLUSIONS

These findings provide novel insight into the role of Th2 and Th17 in chronic urticaria pathophysiology and may impact therapy.

Chlorpheniramine-induced anaphylaxis diagnosed by basophil activation test

Chlorpheniramine is a widely prescribed H1-antihistamine for relieving urticaria or histamine-mediated allergic reactions. However, although rare, it may cause immediate hypersensitivity reactions. The diagnosis is usually made by provocation test, but its application is often limited due to comorbidities or potential risk of severe reactions. In those cases, skin tests and basophil activation tests can be considered as additional diagnostic tests for the drug allergy. Here, we report a 33-year-old female with underlying chronic urticaria, who recurrently developed anaphylaxis after chlorpheniramine administration. Intradermal test showed positive responses in the patient at 0.02 mg/mL of chlorpheniramine, but not in healthy controls. Basophil activation test showed significant up-regulation of CD63 and CD203c by chlorpheniramine. The present case reminds the rare but potential allergic risk of chlorpheniramine, and also suggests the potential utility of basophil activation test in making the diagnosis.

Peripheral basophil reactivity, CD203c expression by Cryj1 stimulation, is useful for diagnosing seasonal allergic rhinitis by Japanese cedar pollen

Measuring specific IgE can yield direct, accurate, and objective data. Nevertheless, clinical symptoms of allergy are often inconsistent with these data. Recently, the expression of CD203c, a surface marker of basophils, has been reported as capable of distinguishing allergic patients. This study compared specific IgE in serum and skin tests against antigen to assess CD203c as a biomarker correlated with allergic rhinitis (AR). We asked 3,453 subjects whether they experienced any AR related symptom. All subjects were assessed for six specific IgEs for common aeroallergens. Skin tests were also conducted for six aeroallergens. We observed the reactivity of peripheral basophil by measuring the levels of CD203c by Cryj1 stimulation using flow cytometry. Of the 3,453 participants, 1,987 (57.5%) possessed Japanese cedar pollen (JCP) specific IgE in their serum. Among those 1,987 JCP specific IgE positive participants, 552 (27.8%) had not experienced any allergic symptom during the JCP season. The levels of CD203c in the peripheral basophil by Cryj1 stimulation were significantly higher in SAR-JCP subjects than in non-SAR-JCP subjects (Cryj1 0.5 ng/ml: 2.25 ± 0.90% vs. 60.2 ± 27.4%, p < 0.01, Cryj1 50 ng/ml: 1.89 ± 0.90% vs. 68.0 ± 21.2%, p < 0.01). Our results indicate that the levels of CD203c in peripheral basophils by Cryj1 stimulation is a more objective and reliable marker that better reflects the allergic reaction by SAR-JCP in vivo than measuring specific IgE in serum or skin tests.

Expression profiling of human basophils: modulation by cytokines and secretagogues

Human basophils are an accessible participant of the human allergic reaction. There is natural variation in various functional endpoints and in signaling molecule expression but there has been only a limited effort to place this information in the context of mRNA expression profiles. This study examined the hypothesis that unique mRNA signatures could be identified during the response of human basophils to several known forms of stimulation. Highly purified human basophils were cultured in vitro and exposed to IL-3, IL-5, NGF, IL-33, IL-2, anti-IgE Ab, or FMLP and the mRNA profiles examined by microarrays. The response to IL-3 and anti-IgE Ab were examined on 2–3 time frames and the response to IL-3 examined at several concentrations. In addition, the mRNA signatures of 3 different potential phenotypes were examined. These included basophils with the so-called non-releaser phenotype, and basophils from atopic and non-atopic subjects. Given the role of IL-3 in basophil maturation and the known profound effects on mature basophil function, it was not surprising that IL-3 showed the greatest influence on the basophil transcriptome. However, it also became apparent that the act of isolating and culturing basophils was sufficient to induce a large number of changes in the transcriptome, despite high viability and recovery. These “culture-effect” changes dominated the changes in mRNA profiles induced by other stimuli. Unique signatures for anti-IgE antibody and IL-33 could be identified although the number of gene transcripts (6–30) that were unique to these two stimuli was very limited. There were no apparent unique profiles for IL-5, NGF, IL-2 or FMLP. Therefore, a potential tool for screening basophil phenotypes was limited to changes that could be induced by IL-3 (or no IL-3), IL-33 and anti-IgE Ab.

Pathogenic intracellular and autoimmune mechanisms in urticaria and angioedema

Urticaria and angioedema are common disorders. Chronic urticaria is defined as lasting longer than 6 weeks. Causes of chronic urticaria fall into the following categories: physical, allergic, hereditary, autoimmune, and idiopathic. Basophils and mast cells are the primary effector cells responsible for clinical symptoms and signs. These cells produce and secrete a variety of mediators including histamine, leukotrienes, prostaglandins, cytokines, chemokines, and other pro-inflammatory mediators. This leads to vasodilation, fluid exudation, increased vascular permeability, and accumulation of additional secondary inflammatory cells. Two mechanisms have been investigated as possibly contributing to the pathogenesis of chronic urticaria. One is the development of autoantibodies to FcεRI or IgE on mast cells and basophils. This appears to be responsible for 30-50 % of cases. The other is dysregulation of intracellular signaling pathways involving Syk, SHIP-1, or SHIP-2 in basophils and mast cells. The primary treatment for chronic urticaria is to treat the underlying pathology, if any can be identified. Otherwise, in idiopathic cases, H1 antihistamines, H2 antihistamines, antileukotrienes, and corticosteroids constitute the main pharmacologic treatment modalities. In severe and recalcitrant cases of chronic and autoimmune urticaria, immunosuppressive drugs have been used, most commonly cyclosporin. More recent experimental studies have also suggested that omalizumab, an anti-IgE therapy, may be of benefit. Currently, inhibitors of Syk are also being developed and tested in the laboratory and in animal models. As our understanding of the pathogenesis of idiopathic urticaria increases, development of additional drugs targeting these pathways may provide relief for the significant physical and psychological morbidity experienced by patients with this disorder.

Therapy of chronic urticaria: a simple, modern approach

OBJECTIVE

To examine the available treatment choices for chronic spontaneous urticaria (CSU) and discuss a new paradigm for treating such patients.

DATA SOURCES

The literature regarding treatment is reviewed, including considerations of published guidelines. Attention is focused on the most recent evidence indicating particular efficacy of omalizumab.

RESULTS

Omalizumab has been found to have considerable efficacy in phase 2 and phase 3 trials in which more than 900 patients have been studied. A response rate of 65% is seen in patients resistant to antihistamines as well as to histamine2 blockers and leukotriene antagonists, and 40% of patients are completely free of hives as long as therapy is continued. In addition, serious adverse events have not been seen. Only cyclosporine can match this response rate (excluding steroids), but the adverse effect profile (blood pressure and renal function) is substantial by comparison. Double-blind, placebo-controlled studies of other agents often listed as alternatives are lacking (ie, whether their success rate exceeds the 25%-30% placebo response is uncertain). The mechanism by which omalizumab works in CSU is not clear because the response rate is unrelated to the autoimmune profile and can occur rapidly (ie, within a few days).

CONCLUSION

Omalizumab has exceptional efficacy for antihistamine-resistant CSU with an excellent adverse effect profile.

Increased level of basophil CD203c expression predicts severe chronic urticaria

Increased FcεR1α expression with upregulated CD203c expression on peripheral basophils is seen in patients with chronic urticaria (CU). However, there has been no published report on the association between CD203c expression level and clinical disease activity in CU patients. To investigate whether the increase of basophil activation is associated with the disease activity of CU, we measured basophil CD203c expression using a tricolor flow cytometric method in 82 CU patients and 21 normal controls. The relationship between the percentage of CD203c-expressing basophils and clinical parameters was analyzed. The mean basophil CD203c expression was significantly higher in CU patients than in healthy controls (57.5% vs 11.6%, P < 0.001). The basophil CD203c expression in severe CU patients was significantly higher than in non-severe CU (66.5% ± 23.3% vs 54.0% ± 23.3%, P = 0.033). Multiple logistic regression analysis indicated that both ≥ 72% basophil CD203c expression and urticaria activity score (UAS)≥ 13 were significant predictors of severe CU (P = 0.005 and P = 0.032, respectively). These findings suggest that the quantification of basophil activation with CD203c at baseline may be used as a potential predictor of severe CU requiring another treatment option beyond antihistamines.

Chronic spontaneous urticaria: etiology and pathogenesis

Urticaria affects individuals of all ages and is commonplace. Nearly 1 in 5 individuals will experience an episode of urticaria in their lifetime, while the chronic form of disease has an estimated annual prevalence of approximately 1% of the population. Given the similarity of chronic urticaria symptoms to those seen in patients suffering an allergic reaction, the condition often leads to a search for an external cause. In most cases, no external trigger factor is identified. At present several theories of pathogenesis exist, none of which is firmly established.

Basophil activation testing

Both the treatment of patients with allergic diseases and the study of allergic disease mechanisms depend on a wide variety of assays that in various ways assess the presence and function of IgE antibody. The study of allergic diseases could benefit from the study of its 2 principle cellular participants, mast cells and basophils, but the basophil is more accessible than mast cells for ex vivo studies. Its functionality is tested by using 2 predominant methodologies: the secretion of mediators of allergic inflammation and the expression of proteins on the plasma membrane after stimulation. Each approach has benefits. There are also many operational details to consider regardless of which general approach is taken, and proper interpretation of the methods requires a good understanding of the reagents used and the receptors expressed on basophils and a detailed understanding of the factors regulating aggregation of cell-surface IgE.

The role of focal infections in the pathogenesis of psoriasis and chronic urticaria

INTRODUCTION

The Focal Infection Theory, originally presented at the beginning of the 20(th) century, postulates that systemic diseases can be caused by microorganisms that arise from the focus of infection. Foci of infections have been described as sinuses, adenoids, tonsils, teeth, genitourinary tract, gall bladder and kidneys. A focus of infection is defined as the area that can occur in any part of the body, contains a pathogen (microorganism) and is usually asymptomatic. There are discordant opinions about the role of focal infections in the pathogenesis of psoriasis and urticaria.

AIM

To establish whether there is a higher incidence of focal infections in patients with chronic urticaria and psoriasis.

MATERIAL AND METHODS

We retrospectively reviewed 129 patients with a history of psoriasis and chronic urticaria: 58 women and 71 men treated in the Department of Dermatology of the Jagiellonian University Medical College in Krakow.

RESULTS

In the analyzed group, 11 patients had a dental consultation, 58 - laryngological consultation and 29 women had a gynecological consultation. The most common examples of focal infection were tonsillitis, upper respiratory tract infections, sinusitis, dental caries and genitourinary tract infections. Aggravating factors were similar to previously described.

CONCLUSIONS

A high incidence of focal infections in patients with psoriasis and urticaria suggests that infections may play a significant role in the pathogenesis of these skin disorders. Treatment of infection foci may play the key role in the remission of skin changes.

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.

Development of a microarray-based method to detect exposure of human basophils to IL-3

Human basophils are an accessible participant of the human allergic reaction. There is natural variation in various functional endpoints and in signaling molecule expression but there has been only a limited effort to place this information in the context of mRNA expression profiles. The goal of these studies was to develop gene transcript profiles associated with IL-3 exposure for use in probing basophil phenotypes. Highly purified human basophils were cultured under several conditions and the cells subsequently analyzed by microarray analysis of gene transcript expression. Basophils were cultured with or without IL-3 for 24 h and the expression profile, relative to pre-culture, analyzed for transcripts that act in a reciprocal fashion depending on the condition. A 51-gene transcript set was identified that was composed of 34 transcripts that increased with IL-3 and decreased without IL-3 and a further 17 transcripts that did the reverse. This set of transcripts was validated on two microarray chips. The changes induced by IL-3 were stable in time, with 3 day cultures generating a signature concordant with 1 day cultures. The inverted nature of the response to ±IL-3 suggested that the normal circulating basophil is balanced between a state of high and low IL-3 exposure and thus is very sensitive to changes in IL-3. For example, the basophil could detect the early generation of IL-3 that follows IgE-mediated stimulation of basophils. When this signature tool was applied to freshly isolated basophils, it was observed that the signature was similar for the same subjects' basophil sampled weeks apart. It was also shown that the 51-gene transcript was insensitive to the method of preparing purified basophils. Finally, these studies provided an estimate for the normal in vivo exposure of circulating basophils to IL-3 or IL-3-like functionality. These studies identified an IL-3 signature to probe changes in basophils occurring in vivo.

Antibody repertoire complexity and effector cell biology determined by assays for IgE-mediated basophil and T-cell activation

Effector cell activation and T-cell activation, the latter mediated by facilitated antigen presentation, are immunological mechanisms that play crucial roles in the manifestation and maintenance of allergic disease. In addition to their relevance for the pathogenesis of allergy in-vivo, in-vitro assays based on these immunological mechanisms have been established and used for diagnostics, for monitoring the progression of disease and for the effect of specific immunotherapy as well as for basic research purposes. Here we review different parameters that affect effector cell activation and facilitated antigen uptake and presentation, including assay designs, readout parameters and critical experimental conditions. Central to the two immunological mechanisms is complex formation between allergen-specific IgE, allergen, and cell surface-anchored immunoglobulin receptor; the high affinity IgE-receptor FcεRI on basophils and mast cells, and the low affinity IgE-receptor FcεRII (CD23) on B-cells. Accordingly, the effect of IgE repertoire complexity and allergen diversity on effector cell and facilitated antigen presentation is discussed in detail.

Assessing basophil functional measures during monoclonal anti-IgE therapy

Assessing the impact of therapeutic interventions on the clinical and immunologic responses of allergic subjects is a topic of extensive investigation. Available approaches include the measurement of in vivo allergen challenge responses, serologic measures, or in vitro studies of cells that participate in the allergic reaction. Several decades of work support that measures of allergen responses of IgE-bearing peripheral blood basophils can reflect clinical expression of allergic disease. In the last decade, an immune-based therapy targeting IgE, omalizumab, has emerged as an adjunct treatment for a variety of allergic diseases. This monoclonal humanized IgG antibody specifically binds circulating IgE at a region in the Fc tail that prevents IgE attachment to high affinity IgE receptor (FcεRI) bearing cell types such as tissue mast cells and blood basophils. This review focuses on methods to monitor changes of basophil allergen reactivity with a focus on omalizumab therapy and the implications for clinical disease management.

Chronic spontaneous urticaria: an autoimmune disease? A revision of the literature

The cause of chronic spontaneous urticaria has been an enigma for decades, but the recognition of functional autoantibodies in some patients with the spontaneous chronic urticaria has opened up a new concept of autoimmune urticaria. Clinical and laboratory features are in keeping with an autoimmune aetiology for many patients with otherwise inexplicable disease, but there is still debate about the importance of functional autoantibodies in the disease pathogenesis, how to test them and the clinical implications for treatment and prognosis. This review will look at the evidence for there being an autoimmune subset of urticaria, the strengths and weaknesses of the available tests in current use.

Basophils: emerging roles in the pathogenesis of allergic disease

After approximately 130 years since their discovery as rare granulocytes that circulate in blood, basophils are just now gaining respect as significant contributors in the pathogenesis underlying allergic inflammation and disease. While long known for secreting preformed and newly synthesized mediators and for selectively infiltrating tissue during immunoglobulin E (IgE)-mediated inflammation, their role has largely been viewed as redundant to that of tissue mast cells in functioning as effector cells. This line of thought has persisted even though it has been known in humans for approximately 20 years that basophils additionally produce relatively large quantities of cytokines, e.g. interleukin-4 (IL-4)/IL-13, that are central for the manifestations of allergic disease. Studies using novel IL-4 reporter mice have significantly added to the in vivo importance of basophils as IL-4 producing cells, with recent findings indicating that these cells also function as antigen-presenting cells essential in initiating T-helper 2 responses. If confirmed and translated to humans, these provocative findings will give new meaning to the role basophils have in allergic disease, and in immunology overall.