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

Chronic Spontaneous Urticaria: Etiology and Pathogenesis

Urticaria, also known as hives, is a common condition thought to affect up to 20% of individuals worldwide in their lifetime. This skin condition is characterized by the appearance of pruritic, erythematous papules or plaques with superficial swelling of the dermis. The major complaint is the symptom of pruritus. Angioedema, which involves a deeper swelling of dermal or mucosal tissues, may accompany urticaria. Urticaria can be classified by both time course of symptoms and the underlying etiology.

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.

Unveiling chronic spontaneous urticaria pathophysiology through systems biology

BACKGROUND

Chronic spontaneous urticaria (CSU) is a rare, heterogeneous, severely debilitating, and often poorly controlled skin disease resulting in an itchy eruption that can be persistent. Antihistamines and omalizumab, an anti-IgE mAb, are the only licensed therapies. Although CSU pathogenesis is not yet fully understood, mast cell activation through the IgE:high-affinity IgE receptor (FcεRI) axis appears central to the disease process.

OBJECTIVE

We sought to model CSU pathophysiology and identify in silico the mechanism of action of different CSU therapeutic strategies currently in use or under development.

METHODS

Therapeutic performance mapping system technology, based on systems biology and machine learning, was used to create a CSU interactome validated with gene expression data from patients with CSU and a CSU model that was used to evaluate CSU pathophysiology and the mechanism of action of different therapeutic strategies.

RESULTS

Our models reflect the known role of mast cell activation as a central process of CSU pathophysiology, as well as recognized roles for different therapeutic strategies in this and other innate and adaptive immune processes. They also allow determining similarities and differences between them; anti-IgE and Bruton tyrosine kinase inhibitors play a more direct role in mast cell biology through abrogation of FcεRI signaling activity, whereas anti-interleukins and anti-Siglec-8 have a role in adaptive immunity modulation.

CONCLUSION

In silico CSU models reproduced known CSU and therapeutic strategies features. Our results could help advance understanding of therapeutic mechanisms of action and further advance treatment research by patient profile.

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.

Activated steady status and distinctive FcεRI-mediated responsiveness in basophils of atopic dermatitis

BACKGROUND

Although basophils are considered to play an important role for maintenance of type 2 inflammation in atopic dermatitis (AD), studies on basophils in AD patients are limited. Some studies have reported the activation status, including CD203c and CD63, of peripheral blood basophils in AD patients.

METHODS

We examined the features of circulating basophils in AD patients, assessed cell surface marker expressions and total serum IgE, and compared basophil responsiveness to stimulation between AD patients and healthy controls (HCs). In addition, the correlations among AD severity, laboratory factors, and features of basophils were examined. Blood samples from 38 AD patients and 21 HCs were analyzed. Basophil response markers CD203c and CD63, and expression of surface-bound IgE and FcεRI on basophils were measured. CD203c and CD63 expressions induced by stimulation with anti-IgE and anti-FcεRI antibodies were measured. Clinical/laboratory factors including total serum IgE were examined for correlations with these basophil parameters.

RESULTS

Baseline CD203c and CD63 expression on basophils were significantly higher in AD patients compared with HCs. The CD203c/CD63 response ratio to anti-FcεRI stimulation was higher than that to anti-IgE stimulation in AD patients, but not HCs. FcεRI expression on basophils was higher in AD patients than in HCs, although surface-bound IgE on basophils was equivalent. Total serum IgE had negative correlations with surface-bound IgE and CD63 responsiveness to anti-IgE stimulation.

CONCLUSIONS

Basophils were spontaneously activated under steady-state conditions in AD patients and responsiveness to anti-IgE stimulation was lower than in HCs. Despite high serum IgE and high basophil FcεRI expression, surface-bound IgE on basophils remained relatively low. Basophils might be suppressed or exhausted regarding FcεRI signaling via IgE in severe AD.

A Comparative Study of Sex Distribution, Autoimmunity, Blood, and Inflammatory Parameters in Chronic Spontaneous Urticaria with Angioedema and Chronic Histaminergic Angioedema

BACKGROUND

Recurrent idiopathic histaminergic angioedema is currently classified as a subtype of angioedema, as well as a subtype of chronic spontaneous urticaria (CSU), based on the fact that both are mast cell-mediated and respond to the same treatments.

OBJECTIVE

In the present work, we sought to verify whether chronic histaminergic angioedema (CHA) is an entity distinct from CSU or represents a CSU subtype that lacks hives.

METHODS

We performed a prospective study comparing 68 CHA patients, angioedema without hives, with 63 CSU patients, with hives and angioedema, from whom we collected demographic and clinical data, as well as blood and serum markers.

RESULTS

We found key pathogenic features that differentiate CHA from CSU: gender distribution, basophil number, and antibodies against the IgE receptor. The male/female ratio in CHA was 0.78, whereas in CSU it was 0.36 (P = .0466). Basopenia was more often seen in CSU (n = 13 [20%]) than in CHA (n = 5 [7%]). Finally, 31.15% of CSU sera induced basophil activation, whereas no CHA sera were able to activate normal basophils. By contrast, nonspecific inflammation or immune markers, for example, erythrocyte sedimentation rate, C-reactive protein, or IgG antithyroid antibodies, were very similar between both groups. IgE anti-IL-24 could not be assessed because a control population did not differ from CSU.

CONCLUSIONS

Inclusion of CHA as part of the spectrum of CSU is an assumption not evidence-based, and when studied separately, important differences were observed. Until there is further evidence, CHA and CSU should not necessarily be considered the same disorder, and it is our opinion that review articles and guidelines should reflect that possibility.

Biomarkers of chronic spontaneous urticaria and their clinical implications

Introduction: Chronic spontaneous urticaria (CSU) is a frequent disorder in which activation of effector cells and histamine release can be induced via several distinct pathogenetic mechanisms. Much work has been carried out to identify biomarkers useful for classifying CSU patients, and to predict their response to currently available treatments.Areas covered: The recent literature dealing with CSU biomarkers was screened in PubMed and Google Scholar using 'chronic spontaneous urticaria', 'biomarker', 'diagnosis', 'therapy' and 'treatment response' as key words. The characteristics found in relevant papers were divided into clinical and serological biomarkers of (a) clinical severity/disease activity, and (b) response to treatments.Expert opinion: A diagnostic biomarker for CSU is still missing. Most biomarkers described so far do not seem to possess sufficient specificity for this disease. Basopenia and the activation of the coagulation cascade might be biomarkers of disease activity and severity, but information available so far is insufficient to consider their routine use. Markers suggesting IgG-mediated autoimmunity (autologous serum skin test, basophil activation/histamine release assays, low total IgE) seem to identify patients less prone to respond to omalizumab but responsive to cyclosporine. In contrast, 'autoallergy' (i.e. the presence of IgE to autoallergens), which is often associated with elevated IgE levels seems to identify patients who will respond to omalizumab.

Response of FcεRI-bearing leucocytes to omalizumab in chronic spontaneous urticaria

BACKGROUND

The pathogenesis of chronic spontaneous urticaria (CSU) and the mechanism of action of omalizumab in CSU remain unclear.

OBJECTIVE

In this study, we assessed the responsiveness and FcεRI expression of various subsets of leucocytes in patients with CSU treated with omalizumab.

METHODS

In this prospective cohort study, 30 patients were treated with 6 administrations of 300 mg omalizumab every 4 weeks, followed by a follow-up period of 12 weeks. FcεRI expression and the percentage of basophils, monocytes, and dendritic cell subsets were analysed before and during treatment, and after follow-up. In addition, anti-IgE- and C5a-induced basophil degranulation was measured. The results were correlated with disease activity and response to omalizumab.

RESULTS

In addition to a rapid and significant reduction in FcεRI on basophils, we demonstrated a reduction in FcεRI on plasmacytoid dendritic cells during omalizumab treatment, which persisted until 3 months after discontinuation. FcεRI expression on basophils and its reduction did not correlate with the treatment response. Omalizumab led to an increased percentage of basophils in blood but not of the other FcεRI-bearing leucocytes. Basophil responsiveness was differentially affected; anti-IgE-, but not C5a-induced basophil degranulation increased during the treatment. Apart from clinical non-responders showing a stronger increase in anti-IgE-induced basophil degranulation over a period time, no differences were found in omalizumab responders vs non-responders.

CONCLUSIONS/CLINICAL RELEVANCE

FcεRI expression on basophils decreased rapidly, while anti-IgE-induced degranulation significantly increased due to omalizumab treatment in patients with CSU, persisting at least for 3 months after stopping the treatment. None of the markers were able to predict the effectiveness of treatment. Whether basophils play a role in omalizumab responsiveness in CSU remains unclear.

Platelet-Activating Factor (PAF) in Allergic Rhinitis: Clinical and Therapeutic Implications

Platelet-activating factor (PAF) is a lipid mediator involved in several allergic reactions. It is released from multiple cells of the immune system, such as eosinophils, neutrophils, and mast cells, and also exerts its effect on most of them upon specific binding to its receptor, becoming a pleiotropic mediator. PAF is considered a potential relevant mediator in allergic rhinitis, with a key role in nasal congestion and rhinorrhoea due to its effect on vascular permeability. Interestingly, despite its potential relevance as a therapeutic target, no specific PAF inhibitors have been studied in humans. However, rupatadine, a second-generation antihistamine with dual antihistamine and anti-PAF effects has shown promising results by both blocking nasal symptoms and inhibiting mast cell activation induced by PAF, in comparison to antihistamine receptor drugs. In conclusion, the inhibition of PAF may be an interesting approach in the treatment of allergic rhinitis as part of a global strategy directed at blocking as many relevant inflammatory mediators as possible.

Cutting Edge: Biomarkers for Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is defined by the appearance of wheals and a variable presence of angioedema which persists for at least 6 weeks. It represents the most common subtype of chronic urticaria and is gaining importance in civil society because of its association with impaired quality of life. Moreover, CSU has a growing impact on national health systems representing a great burden due to its variable rate of response to the approved therapies. In this scenario, the identification of clinical and molecular biomarkers is of pivotal importance. Some groups are trying to detect molecules which would be able to help clinicians in reaching a proper diagnosis; additionally, the opportunity to describe disease severity which leads to cluster patients in different groups could fill the gap in the numerous unmet clinical needs. Several biomarkers are currently being studied with the purpose to predict the response to a defined therapy; unfortunately, none of them are ready to be translated from bench to bedside.

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.

Mediators of Inflammation and Angiogenesis in Chronic Spontaneous Urticaria: Are They Potential Biomarkers of the Disease?

In chronic spontaneous urticaria (CSU), different pathophysiological mechanisms, potentially responsible for the development of the disease, have been recently described. It is likely that the activation of skin mast cells with consequent release of histamine and other proinflammatory mediators is responsible for vasodilation in the lesional skin of CSU. However, the underlying causes of mast cell activation in the disease are largely unknown and remain to be identified. Thus, in this review, we discuss new insights in the pathogenesis of CSU, focusing on inflammation and angiogenesis. The understanding of these mechanisms will enable the identification of biomarkers useful for the diagnosis, follow-up, and management of CSU and will allow the development of novel, more specific, and patient-tailored therapies.

Factors linked to disease severity and time to remission in patients with chronic spontaneous urticaria

Biomarkers useful for the evaluation and management of patients with chronic spontaneous urticaria (CSU) are not currently available. A review of various clinical and laboratory markers that have been studied to assess their value for determining the severity or predicting the evolution of disease in adult patients with CSU was carried out. A search of the medical literature on PubMed and MEDLINE including the terms urticaria, chronic urticaria, chronic idiopathic urticaria, CSU, severity, prognosis and treatment was performed. Based on our review of the literature, among the clinical markers studied, higher age at onset, being female, long disease duration and aspirin/NSAID hypersensitivity may be linked to both severe CSU and a long time to spontaneous remission. In addition, a positive autologous serum skin test (ASST) may be associated with severe CSU, and comorbidity of inducible urticaria and concomitant recurrent angio-oedema may be linked to longer CSU duration. Potential biomarkers of CSU severity and/or duration include basophil numbers and susceptibility to activation, inflammatory markers, markers of activation of the extrinsic coagulation pathway, immunoglobulin E and vitamin D. Although the described markers are promising, further studies on representative and well-characterized patient populations are needed to determine the value of these clinical and biological markers for predicting the severity and course of disease in patients with CSU.

Mechanisms of action that contribute to efficacy of omalizumab in chronic spontaneous urticaria

The monoclonal anti-immunoglobulin E (IgE) antibody, omalizumab, was the first drug approved for use in patients with chronic idiopathic/spontaneous urticaria (CIU/CSU) who remain symptomatic despite H₁ -antihistamine treatment. Omalizumab binds to free IgE, which lowers free IgE levels and causes FcεRI receptors on basophils and mast cells to be downregulated. It has been shown to improve symptoms of CIU/CSU, but its mechanism of action is not currently understood. Potential mechanisms in CIU/CSU include reducing mast cell releasability, reversing basopenia and improving basophil IgE receptor function, reducing activity of IgG autoantibodies against FcεRI and IgE, reducing activity of IgE autoantibodies against an antigen or autoantigen that has yet to be definitively identified, reducing the activity of intrinsically 'abnormal' IgE, and decreasing in vitro coagulation abnormalities associated with disease activity. However, none of these theories alone or in combination fully account for the pattern of symptom improvement seen with omalizumab therapy, and therefore, no one mechanism is likely to be the definitive mechanism of action. Additional research is needed to further clarify the involvement of omalizumab in relieving symptoms associated with the complex, multifactorial pathogenesis of CIU/CSU.

Looking forward to new targeted treatments for chronic spontaneous urticaria

The introduction of omalizumab to the management of chronic spontaneous urticaria (CSU) has markedly improved the therapeutic possibilities for both, patients and physicians dealing with this disabling disease. But there is still a hard core of patients who do not tolerate or benefit from existing therapies and who require effective treatment. Novel approaches include the use of currently available drugs off-licence, investigational drugs currently undergoing clinical trials and exploring the potential for therapies directed at pathophysiological targets in CSU. Off-licence uses of currently available drugs include rituximab and tumour necrosis factor inhibitors. Ligelizumab (anti-IgE), canakinumab (anti-IL-1), AZD1981 (a PGD2 receptor antagonist) and GSK 2646264 (a selective Syk inhibitor) are currently in clinical trials for CSU. Examples of drugs that could target potential pathophysiological targets in CSU include substance P antagonists, designed ankyrin repeat proteins, C5a/C5a receptor inhibitors, anti-IL-4, anti-IL-5 and anti-IL-13 and drugs that target inhibitory mast cell receptors. Other mediators and receptors of likely pathogenic relevance should be explored in skin profiling and functional proof of concept studies. The exploration of novel therapeutic targets for their role and relevance in CSU should help to achieve a better understanding of its etiopathogenesis.

Autoreactive IgE in Chronic Spontaneous/Idiopathic Urticaria and Basophil/Mastocyte Priming Phenomenon, as a Feature of Autoimmune Nature of the Syndrome

Recent years of research have shed a new light on the role of IgE in immune reactions. It seems to be more than just a contribution to immediate type of allergic response. It appears that monomeric IgE may enhance mast cell activity without cross-linking of FcεRI by IgE specific allergen or autoreactive IgG anti-IgE antibodies. Monomeric IgE molecules are heterogeneous concerning their ability to induce survival and activation of mast cells only by binding the IgE to FcεRI, but not affecting degranulation of cells. It also turned out that IgE may react to autoantigens occurring in the blood not only in chronic spontaneous urticaria (CSU) but also in other autoimmune diseases. The aforementioned phenomena may promote the activity of mast cells/basophils in CSU that easily degranulate when influenced by various inner (autoreactive IgG against IgE and FcεRI, autoreactive IgE for self-antigens) and outer factors (cold, heat, pressure) or allergens. These findings forced the new approach to the role of autoimmunity, self-antigens and IgE autoantibodies in the pathology of CSU. CSU put in the scheme of autoreactive IgG and autoreactive IgE seems to be either a kind of an autoimmune disease or a clinical manifestation of some other defined autoimmune diseases or both.

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

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

Immunological events in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is a highly debilitating skin disease associated with systemic features. We have made significant progress in several aspects relating to this condition. However, the exact physiopathology remains unknown. There is mounting evidence for an autoimmune basis, demonstrated by the CSU serum ability to activate healthy donors skin mast cells and blood basophils. However, it is only seen among 35–40% of patients. Mast cells and basophils play an important role in this skin condition. Both cells in CSU patients have unique features that differentiate them from basophils and mast cells from healthy donors. In the case of basophils, basopenia is typically found in CSU patients. Basophils from CSU patients also tend to be hyporesponsive to stimuli that act through the IgE receptor, responsive to other stimuli as MCP-1 or C5a, and hyperesponsive when incubated with sera. Eosinophils are also present in CSU skin biopsies, yet their exact role has not yet been defined. Likewise, endothelial cells also play a function, as indirectly demonstrated by an increase of vasoactive peptides in skin and plasma of CSU patients’ samples. All these facts orchestrate a systemic inflammation response producing a significant increase of several inflammatory markers. Unfortunately, we lack a unitary model that could explain the exact role of each of these players. In this review, we will describe the history and discover the pathway to the present knowledge on the immunological facts of this disease.

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.

Interval shifts in basophil measures correlate with disease activity in chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) significantly impacts the quality of life of those affected through symptoms of pruritus and recurrent skin lesions. In active CSU disease, reduced IgE-mediated basophil histamine release (HR) and basopenia are observed. We sought to examine the relationship between interval changes in basophil measures and shifts in patient-reported disease impairment. Simultaneous symptom and basophil evaluations were completed at two sequential study visits, and interval changes in measures were compared between visits for each subject (n = 38). These measures included Skindex-29, current itch and hives scores, total leukocyte histamine content (an indirect measure of blood basophil presence), and basophil HR in response to anti-IgE and formyl-methionine-leucine-phenylalanine. Overall, interval improvements in disease measures in CSU subjects were associated with increased basophil numbers (total leukocyte histamine content) and IgE-mediated HR. This suggests these measures are potential biomarkers for CSU disease improvement and further implicates a role for basophils in CSU.

Pathogenesis of chronic urticaria: an overview

The pathogenesis of chronic urticaria is not well delineated and the treatment is palliative as it is not tied to the pathomechanism. The centrality of mast cells and their inappropriate activation and degranulation as the key pathophysiological event are well established. The triggering stimuli and the complexity of effector mechanisms remain speculative. Autoimmune origin of chronic urticaria, albeit controversial, is well documented. Numerical and behavioral alterations in basophils accompanied by changes in signaling molecule expression and function as well as aberrant activation of extrinsic pathway of coagulation are other alternative hypotheses. It is also probable that mast cells are involved in the pathogenesis through mechanisms that extend beyond high affinity IgE receptor stimulation. An increasing recognition of chronic urticaria as an immune mediated inflammatory disorder related to altered cytokine-chemokine network consequent to immune dysregulation resulting from disturbed innate immunity is emerging as yet another pathogenic explanation. It is likely that these different pathomechanisms are interlinked rather than independent cascades, acting either synergistically or sequentially to produce clinical expression of chronic urticaria. Insights into the complexities of pathogenesis may provide an impetus to develop safer, efficacious, and targeted immunomodulators and biological treatment for severe, refractory chronic urticaria.

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.

Molecular genetic mechanisms of chronic urticaria

Chronic urticaria (CU) is a common allergic skin disease that requires long-term pharmacological treatment. Some patients with severe CU suffer a poor quality of life. Although the pathogenic mechanisms of CU are not clearly understood, several groups have suggested that genetic mechanisms are involved in various CU cohorts. To further understand the molecular genetic mechanisms of CU, we summarize recent genetic data in this review. Although a few HLA alleles were suggested to be candidate markers in different ethnic groups, further replication studies that apply the recent classification are needed. Genetic polymorphisms in histamine-related genes, including FcεRI and HNMT, were suggested to be involved in mast cell activation and histamine metabolism. Several genetic polymorphisms of leukotriene-related genes, such as ALOX5, LTC4S, and the PGE2 receptor gene PTGER4, were suggested to be involved in leukotriene overproduction, a pathogenic mechanism. Further investigations using candidate gene approaches and genome-wide association studies (GWAS) will provide new insights into the molecular genetic mechanisms of CU, which will provide new marker genes for differentiation of CU phenotypes and identification of potential therapeutic targets.

Angioedema

Angioedema can be caused by either mast cell degranulation or activation of the kallikrein-kinin cascade. In the former case, angioedema can be caused by allergic reactions caused by immunoglobulin E (IgE)-mediated hypersensitivity to foods or drugs that can also result in acute urticaria or a more generalized anaphylactic reaction. Nonsteroidal anti-inflammatory drugs (cyclooxygenase 1 inhibitors, in particular) may cause angioedema with or without urticaria, and leukotrienes may have a particular role as a mediator of the swelling. Reactions to contrast agents resemble allergy with basophil and mast cell degranulation in the absence of specific IgE antibody and can be generalized, that is, anaphylactoid. Angioedema accompanies chronic urticaria in 40% of patients, and approximately half have an autoimmune mechanism in which there is IgG antibody directed to the subunit of the IgE receptor (40%) or to IgE itself (5%-10%). Bradykinin is the mediator of angioedema in hereditary angioedema types I and II (C1 inhibitor [INH] deficiency) and the newly described type III disorder some of which are caused bya mutation involving factor XII. Acquired C1 INH deficiency presents in a similar fashion to the hereditary disorder and is due either toC1 INH depletion by circulating immune complexes or to an IgG antibody directed to C1 INH. Although each of these causes excessive bradykinin formation because of activation of the plasma bradykinin-forming pathway, the angioedema due to angiotensin-converting enzyme inhibitors is caused by excessive bradykinin levels due to inhibition of bradykinin degradation. Idiopathic angioedema (ie, pathogenesis unknown) may be histaminergic, that is, caused by mast cell degranulation with histamine release, or nonhistaminergic. The mediator pathways in the latter case are yet to be defined. A minority may be associated with the same autoantibodies associated with chronic urticaria. Angioedema that is likely to be life threatening (laryngeal edema or tongue/pharyngeal edema that obstructs the airway) is seen in anaphylactic/anaphylactoid reactions and the disorders mediated by bradykinin.

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.

Diagnosis and treatment of urticaria and angioedema: a worldwide perspective

: Urticaria and angioedema are common clinical conditions representing a major concern for physicians and patients alike. The World Allergy Organization (WAO), recognizing the importance of these diseases, has contributed to previous guidelines for the diagnosis and management of urticaria. The Scientific and Clinical Issues Council of WAO proposed the development of this global Position Paper to further enhance the clinical management of these disorders through the participation of renowned experts from all WAO regions of the world. Sections on definition and classification, prevalence, etiology and pathogenesis, diagnosis, treatment, and prognosis are based on the best scientific evidence presently available. Additional sections devoted to urticaria and angioedema in children and pregnant women, quality of life and patient-reported outcomes, and physical urticarias have been incorporated into this document. It is expected that this article will supplement recent international guidelines with the contribution of an expert panel designated by the WAO, increasing awareness of the importance of urticaria and angioedema in medical practice and will become a useful source of information for optimum patient management worldwide.

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.

Up-regulation of chemokine C-C ligand 2 (CCL2) and C-X-C chemokine 8 (CXCL8) expression by monocytes in chronic idiopathic urticaria

The disturbed cytokine-chemokine network could play an important role in the onset of diseases with inflammatory processes such as chronic idiopathic urticaria (CIU). Our main objectives were to evaluate the relation between proinflammatory chemokine serum levels from CIU patients and their response to autologous skin test (ASST) and basophil histamine release (BHR). We also aimed to assess the chemokine secretion by peripheral blood mononuclear cells (PBMC) upon polyclonal stimulus and to evaluate chemokine C-C ligand 2/C-X-C chemokine 8 (CCL2/CXCL8) and Toll-like receptor-4 (TLR-4) expression in monocytes. We observed significantly higher serum levels of the CXCL8, CXCL9, CXCL10 and CCL2 in CIU patients compared to the healthy group, regardless of the BHR or ASST response. The basal secretion of CCL2 by PBMC or induced by Staphylococcus aureus enterotoxin A (SEA) was higher in CIU patients than in the control group, as well as for CXCL8 and CCL5 secretions upon phytohaemagglutinin stimulation. Also, up-regulation of CCL2 and CXCL8 mRNA expression was found in monocytes of patients upon SEA stimulation. The findings showed a high responsiveness of monocytes through CCL2/CXCL8 expression, contributing to the creation of a proinflammatory environment in CIU.

Urticaria and infections

Urticaria is a group of diseases that share a distinct skin reaction pattern. Triggering of urticaria by infections has been discussed for many years but the exact role and pathogenesis of mast cell activation by infectious processes is unclear. In spontaneous acute urticaria there is no doubt for a causal relationship to infections and all chronic urticaria must have started as acute. Whereas in physical or distinct urticaria subtypes the evidence for infections is sparse, remission of annoying spontaneous chronic urticaria has been reported after successful treatment of persistent infections. Current summarizing available studies that evaluated the course of the chronic urticaria after proven Helicobacter eradication demonstrate a statistically significant benefit compared to untreated patients or Helicobacter-negative controls without urticaria (p < 0.001). Since infections can be easily treated some diagnostic procedures should be included in the routine work-up, especially the search for Helicobacter pylori. This review will update the reader regarding the role of infections in different urticaria subtypes.

Basophil responsiveness in chronic urticaria

Chronic urticaria is a common skin disease without an etiology in the majority of cases. The similarity of symptoms and pathology to allergen-induced skin reactions supports the idea that skin mast cell and blood basophil IgE receptor activation is involved; however, no exogenous allergen trigger has been identified. Recent evidence supports a role for blood basophils in disease expression. Specifically, blood basopenia is noted in active disease with the recruitment of blood basophils to skin lesional sites. In addition, blood basophils display altered IgE receptor-mediated degranulation that reverts in disease remission. In active chronic idiopathic urticaria (CIU) subjects, changes in IgE receptor-signaling molecule expression levels accompany the altered degranulation function in blood basophils. The arrival of therapies targeting IgE has further shown that altered blood basophil degranulation behavior has potential use as a disease biomarker in CIU.

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.

Cultured peripheral blood mast cells from chronic idiopathic urticaria patients spontaneously degranulate upon IgE sensitization: Relationship to expression of Syk and SHIP-2

Recently, signaling changes in the FcvarepsilonRI pathway involving inositol lipid phosphatases have been identified in the basophils of chronic idiopathic urticaria (CIU) subjects. Based on the profile of basophil FcvarepsilonRI-mediated histamine degranulation, we have segregated CIU subjects into two groups, CIU Responder (CIU R) or CIU Nonresponder (CIU NR). In the present study, we compared expression of SHIP-1, SHIP-2, and Syk protein to histamine release (HR) from mast cells (MC) cultured from the peripheral blood of CIU R, CIU NR, and normal subjects. The MC of CIU R donors contained significantly increased Syk and decreased SHIP-2 as compared to CIU NR (Syk: p=0.038, SHIP-2: p=0.038) and normals (Syk: p=0.042, SHIP-2: p=0.027). Spontaneous HR from CIU donors was increased two-fold compared to normals (p=0.04). In summary, our results suggest a possible predilection for urticarial MC to spontaneously degranulate upon IgE sensitization contributing to the increased pruritus associated with CIU.

Pathogenesis of chronic urticaria

Chronic urticaria is defined as the presence of urticaria (hives) for at least 6 weeks with the assumption that it occurs daily or close to it. If we eliminate physical urticarias and urticarial vasculitis from consideration, the remainder can be divided into autoimmune chronic urticaria (45%) and idiopathic chronic urticaria (55%). The autoimmune subgroup is associated with the IgG anti-IgE receptor alpha subunit in 35-40% of patients and IgG anti-IgE in an additional 5-10%. These autoantibodies have been shown to activate blood basophils and cutaneous mast cells in vitro with augmentation of basophil activation by complement and release of C5a, in particular. Binding methods (immunoblot and ELISA) yield positives in many autoimmune diseases as well as occasional normal subjects or patients with other forms of urticaria but most such sera are non-functional. Activation of basophils or mast cells causing histamine release is quite specific for chronic urticaria and defines the autoimmune subgroup. Although pathogenicity is not formally proven, the antibodies cause wealing upon intradermal injection, and removal of the autoantibody leads to remission. A cellular infiltrate is seen to be characterized by mast cell degranulation and infiltration of CD4+ T lymphocytes, monocytes, neutrophils, eosinophils, and basophils. The intensity of the infiltrate and clinical severity of the disease (including accompanying angio-oedema) is more severe in the autoimmune subpopulation. This latter group also has a higher evidence of human leucocyte antigen DR alleles associated with autoimmunity and a 25% incidence of antithyroid antibodies with diagnosed hypothyroidism in some. Hypo-responsiveness of patients' basophils to anti-IgE and hyperresponsiveness to serum defines another subpopulation (at least 50%) that overlaps the idiopathic and autoimmune subgroups. Hypo-responsiveness to anti-IgE has been shown to be associated with elevated levels of cytoplasmic phosphatases that inhibit degranulation. Reversal of the abnormality is seen with disease remission. Further work will be needed to distinguish whether this is a cause or a consequence of persistent urticaria and to further assess the relationship (or lack thereof) of altered responsiveness (decreased or increased) with the presence or absence of activating autoantibodies.

New concepts in chronic urticaria

Chronic urticaria is a common skin disease without a clear etiology in the vast majority of cases. The similarity of symptoms and lesion pathology to allergen-induced skin reactions supports the idea that skin mast cell and blood basophil IgE receptor activation is involved; however, no exogenous allergen trigger has been identified. The presence of serum IgG autoantibodies targeting IgE or the IgE receptor in approximately 40% of CIU cases supports the theory of an autoimmune basis for the disease. However, issues remain with the assays to detect autoantibodies among other serum factors, the relationship of autoantibodies to CIU disease activity, and the occurrence of autoantibodies in healthy subjects. Other studies have identified altered IgE receptor degranulation that reverts in disease remission and is accompanied by changes in signaling molecule expression and function in mast cells and basophils in active CIU subjects. The arrival of therapies targeting IgE and the IgE receptor pathway elements has potential use in CIU.

Pathophysiology of chronic urticaria

OBJECTIVE

To review the literature on the pathogenesis of chronic urticaria (excluding physical urticaria).

DATA SOURCES

PubMed was searched using the keywords urticaria and either chronic or autoimmune or pathogenesis for articles published from January 1972 to June 2007. All searches were limited to the English language. References from review articles on chronic urticaria were also considered for inclusion in this review.

STUDY SELECTION

The authors selected relevant and current sources for inclusion in this review.

RESULTS

No concise pathogenic mechanism has been identified for all cases of chronic urticaria, although evidence for a serologic mediator that may be autoimmune in nature has been identified in many cases. The activation of basophils and/or mast cells is a central feature in any theory proposed to explain this troubling disease.

CONCLUSION

Further research is needed to better define the mechanism or mechanism(s) responsible for the development of chronic urticaria. Such research will lead to more effective and possibly even curative treatments.

Association of insertion/deletion polymorphism of the angiotensin-converting enzyme gene with angio-oedema accompanying chronic urticaria but not chronic urticaria without angio-oedema or the autologous serum skin test response

BACKGROUND

Chronic urticaria is defined as the daily or almost daily occurrence of weals for more than 6 weeks. The underlying pathophysiology is reported to be mast cell activation, with release of mast cell mediators, predominantly histamine. Substance P is a neuropeptide and has the capacity to provoke histamine release from skin mast cells. Angiotensin-converting enzyme (ACE), widely expressed in skin, is one of the major peptidase for the degradation of substance P. An insertion/deletion polymorphism (I/D) in the ACE gene has been reported to be related to the levels of enzyme.

OBJECTIVE

An increase in substance P levels due to a polymorphism in ACE gene might be related to the pathology. Thus, we aimed to investigate whether there is an association between ACE I/D polymorphism and chronic ordinary urticaria.

METHODS

Ninety-five patients with chronic ordinary urticaria were recruited and divided into two groups according to autologous serum skin test status and accompanying angio-oedema. One hundred and sixty-one healthy subjects were enrolled as control group. All participants were genotyped for I/D polymorphism in intron 16 of the ACE gene by polymerase chain reaction.

RESULTS

A statistically significant association was not found between ACE I/D polymorphism and chronic ordinary urticaria. Further analyses of chronic ordinary urticaria patients showed that ACE I/D polymorphism was not associated with autologous serum skin test status of patients. However, the frequencies of II genotype and I allele were statistically significantly higher in chronic ordinary urticaria patients with accompanying angio-oedema with regard to angio-oedema-negative patients (II genotype: 24% vs. 9%, P = 0.0002; I allele: 58% vs. 27%, P = 0.0001) and control group (II genotype: 24% vs. 19%, P = 0.01; I allele: 58% vs. 41%, P = 0.03).

CONCLUSION

The results of this study suggest no evidence of an association between ACE I/D polymorphism and risk of developing chronic ordinary urticaria. However, it can be a contributing factor to susceptibility of angio-oedema in chronic ordinary urticaria.

Basophil phenotypes in chronic idiopathic urticaria in relation to disease activity and autoantibodies

Potentially pathogenic IgG autoantibodies to IgE or its receptor, Fc epsilonRIalpha, have been detected in approximately 40% of chronic idiopathic urticaria (CIU) patients. CIU patients' basophils display distinct altered Fc epsilonRIalpha-mediated degranulation. CIU patients with basophil histamine release in response to polyclonal goat anti-human IgE > or = 10% are classified as CIU responders (CIU-R) and < 10% are CIU non-responders (CIU-NR). We compared the presence of autoantibodies to basophil degranulation phenotypes and to disease status (active or inactive). Sera were collected from non-CIU subjects and CIU subjects who participated in a longitudinal study of disease severity and had defined basophil degranulation phenotypes. Immunoenzymetric assays (IEMA) quantified IgG anti-Fc epsilonRIalpha and anti-IgE. IgG anti-Fc epsilonRIalpha antibody was detected in 57% of CIU-R (n=35), 55% of CIU-NR (n=29), and 57% of non-CIU subjects (n=23), whereas IgG anti-IgE was present in 43% of CIU-R, 45% of CIU-NR, and 30% of non-CIU subjects. Both the autoantibody levels and the functional basophil phenotype remained stable in subjects with active disease (n=16), whereas there was an enhancement in basophil function as subjects evolved into a state of remission (n=6), which appears independent of the presence of autoantibody. IEMAs detected a similar frequency of autoantibodies in CIU-R, CIU-NR, and non-CIU subjects. Basophil function may be independent of IEMA-detected autoantibodies.

Activated status of basophils in chronic urticaria leads to interleukin-3 hyper-responsiveness and enhancement of histamine release induced by anti-IgE stimulus

BACKGROUND

Basophils and mast cells are the main target cells in chronic idiopathic urticaria (CIU). Besides the basopenia, intrinsic defects of the anti-IgE cross-linking signalling pathway of basophils have been described in CIU.

OBJECTIVES

We sought to investigate the profile of expression of activation markers on basophils of patients with CIU and to explore the effect of interleukin (IL)-3 priming upon anti-IgE cross-linking stimuli through expression of activation markers and basophil histamine releasability.

METHODS

Evaluation of the surface expression of FcepsilonRIalpha, CD63, CD203c and CD123 on whole blood basophils of patients with CIU undergoing autologous serum skin test (ASST) was performed by flow cytometry. The effect of pretreatment with IL-3 in the anti-IgE response was analysed by the expression of basophil activation markers and histamine release using enzyme-linked immunosorbent assay.

RESULTS

Blood basophils of patients with CIU were reduced in number and displayed increased surface expression of FcepsilonRIalpha, which was positively correlated with the IgE serum levels. Upregulation of expression of both surface markers CD203c and CD63 was verified on basophils of patients with CIU, regardless of ASST response. High expression of IL-3 receptor on basophils was detected only in ASST+ patients with CIU. Pretreatment with IL-3 upregulated CD203c expression concomitantly with the excreting function of blood basophils and induced a quick hyper-responsiveness to anti-IgE cross-linking on basophils of patients with CIU compared with healthy controls.

CONCLUSIONS

Basophils of patients with CIU showed an activated profile, possibly due to an in vivo priming. Functionally, basophils have high responsiveness to IL-3 stimulation, thereby suggesting that defects in the signal transduction pathway after IgE cross-linking stimuli are recoverable in subjects with chronic urticaria.

Effect of stress on basophil function in chronic idiopathic urticaria

BACKGROUND

Chronic idiopathic urticaria (CIU) is a distressing skin condition involving recurrent itchy hives lasting 6 weeks or longer. The mechanism involves mast cell and basophil degranulation, which releases inflammatory mediators including histamine. In our clinical practice, we have observed that the onset of CIU is often preceded by a major life event.

OBJECTIVE

To investigate the role of the hormones of the hypothalamic-pituitary-adrenal (HPA) axis in the link between psychological stress and CIU.

METHODS

Thirty people with CIU and 30 normal controls were recruited. A flow cytometric CD63 expression assay was used to quantify basophil activation, and serum cortisol concentrations were measured as an indication of stress.

RESULTS

Both corticotrophin releasing factor (CRF) and adrenocorticotrophic hormone (ACTH) were shown to activate basophils. There was no significant difference between numbers of CIU patients and normal controls responding to CFR, ACTH or cortisol. However, the responses in the CIU patients were stronger than those in normal controls. There was also a trend towards higher serum cortisol concentrations in CIU patients. The basophil response to CRF and ACTH correlated with the serum cortisol concentration in normal controls, but not in CIU patients.

CONCLUSIONS

Although our data have not supported the hypothesis that stress makes a major contribution to CIU, the heightened basophil response to CFR and ACTH and higher levels of serum cortisol do suggest a derangement of the HPA axis in CIU.

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.

Activation of the tissue factor pathway of blood coagulation in patients with chronic urticaria

BACKGROUND

In patients with chronic urticaria (CU), plasma shows signs of thrombin generation and autologous plasma skin tests score positive in as many as 95% of cases.

OBJECTIVE

To evaluate the initiators of blood coagulation that lead to thrombin generation and fibrinolysis in CU.

METHODS

Activated factor VII, activated factor XII, fragment F(1+2), and D-dimer plasma levels were measured in 37 patients with CU and 37 controls. Skin specimens from 10 patients with CU and 10 controls were tested for tissue factor immunohistochemically.

RESULTS

Mean F(1+2) levels were higher in patients than controls (2.54 [SD 2.57] nmol/L vs 0.87 [0.26] nmol/L; P < .001); disease activity was moderate or severe in 9 of 11 (82%) and 9 of 26 (35%) patients showing high or normal F(1+2) levels, respectively (P < .025). Mean D-dimer plasma levels were higher in patients than controls (329 [188] ng/mL vs 236 [81] ng/mL; P < .01); disease activity was moderate or severe in 6 of 8 (75%) and 11 of 29 (38%) showing elevated or normal plasma D-dimer levels (P = NS). Factor VIIa levels were higher in patients than controls (2.86 ng/mL [0.66] vs 1.97 ng/mL [0.65]; P < .001). Activated factor VII and F(1+2) levels were correlated (r = 0.529; P = .008). Tissue factor reactivity was observed only in CU skin specimens.

CONCLUSION

The extrinsic pathway of clotting cascade is activated in CU. Disease severity is associated with the activation of the coagulation cascade.

CLINICAL IMPLICATIONS

The involvement of the coagulation pathway in CU opens new perspectives for a better understanding of the pathogenesis and, possibly, for the treatment of this disease.