Interleukin 5 and phenotypically altered eosinophils in the blood of patients with the idiopathic hypereosinophilic syndrome

Unmet needs and evidence gaps in hypereosinophilic syndrome and eosinophilic granulomatosis with polyangiitis

Hypereosinophilic syndrome (HES) and eosinophilic granulomatosis with polyangiitis (EGPA) are rare systemic inflammatory disorders with overlapping symptoms, elevated eosinophil counts, and heterogenous clinical presentations. Although progress has been made in recent years, there are substantial gaps in our understanding of the pathologic mechanisms involved in these diseases, as well as numerous unmet needs relating to both diagnosis and patient management. For example, in most cases of HES, the underlying cause of hypereosinophilia is unknown, while in EGPA, although a polygenic genetic susceptibility has been found, understanding of the pathogenic mechanisms remains largely elusive. Delineating differences between certain disease variants may be challenging, and there are no reliable predictive markers of disease course. In addition, the current diagnostic criteria for HES and classification criteria for EGPA are not easy to implement in a nonspecialist setting, and specialist referral pathways need to be signposted more clearly. Furthermore, disease-specific activity scores need to be developed to aid the assessment of treatment effects, and improved biomarkers are needed to aid with treatment stratification. In this review, we outline the limitations of our current understanding of HES and EGPA and highlight areas for future work, which ultimately should help improve patient management and outcomes.

Potent CCR3 Receptor Antagonist, SB328437, Suppresses Colonic Eosinophil Chemotaxis and Inflammation in the Winnie Murine Model of Spontaneous Chronic Colitis

Eosinophils and their regulatory molecules have been associated with chronic intestinal inflammation and gastrointestinal dysfunctions; eosinophil accumulation in the gut is prominent in inflammatory bowel disease (IBD). The chemokine receptor CCR3 plays a pivotal role in local and systemic recruitment and activation of eosinophils. In this study, we targeted CCR3-ligand interactions with a potent CCR3 receptor antagonist, SB328437, to alleviate eosinophil-associated immunological responses in the Winnie model of spontaneous chronic colitis. Winnie and C57BL/6 mice were treated with SB328437 or vehicle. Clinical and histopathological parameters of chronic colitis were assessed. Flow cytometry was performed to discern changes in colonic, splenic, circulatory, and bone marrow-derived leukocytes. Changes to the serum levels of eosinophil-associated chemokines and cytokines were measured using BioPlex. Inhibition of CCR3 receptors with SB328437 attenuated disease activity and gross morphological damage to the inflamed intestines and reduced eosinophils and their regulatory molecules in the inflamed colon and circulation. SB328437 had no effect on eosinophils and their progenitor cells in the spleen and bone marrow. This study demonstrates that targeting eosinophils via the CCR3 axis has anti-inflammatory effects in the inflamed intestine, and also contributes to understanding the role of eosinophils as potential end-point targets for IBD treatment.

Relationship between Neutrophil Gelatinase-Associated Lipocalin, Eosinophil Cationic Protein, Cytokines, and Atopic Sensitization in Patients with Allergic Diseases

The effect of neutrophil gelatinase-associated lipocalin (NGAL) on eosinophil activation, atopic sensitization, and systemic inflammation in allergic diseases has rarely been investigated. This study aimed to investigate the relationship between NGAL, eosinophil cationic protein (ECP), cytokines, and allergen-specific immunoglobulin E (sIgE) in allergic diseases. A total of 136 patients with allergies and 58 healthy individuals were evaluated. The concentrations of NGAL, ECP, tumor necrosis factor-α (TNF-α), interleukin-5 (IL-5), sIgE, total IgE (tIgE), and high-sensitivity C-reactive protein (hsCRP) were measured. The transforming growth factor-β1 (TGF-β1) level was measured as a profibrotic marker of bronchial asthma. Allergic patients had significantly higher NGAL, ECP, and hsCRP levels than healthy individuals. However, there was no significant difference in NGAL levels between patients with positive and negative ECP tests and those with high and low sIgE scores. Asthmatic patients with elevated NGAL exhibited a significantly higher TGF-β1 level than those without elevated NGAL. However, no significant difference was observed in the ECP, IL-5, and sIgE levels between the two groups. Among the patients with a positive ECP test, subjects with elevated hsCRP had two times higher NGAL levels than those without elevated hsCRP. NGAL was positively correlated with TNF-α, TGF-β1, and hsCRP, but not with ECP, IL-5, tIgE, and sIgE. An elevated NGAL level led to a 1.3-fold increase in the prevalence of high TGF-β1 (odds ratio: 1.31; 95% CI: 1.04–2.58; P < 0.001). In conclusion, NGAL elevation may be more closely linked to allergic inflammation and a possible fibrotic change in the airways than to the severity of eosinophil activation and atopic sensitization.

Eosinophils in Inflammatory Bowel Disease

Clinical investigations in inflammatory bowel disease (IBD) patients have provided increasing evidence that eosinophils contribute to chronic intestinal inflammation. Accumulation of eosinophils in the gastrointestinal tract correlates with the variations of eosinophil regulatory molecules; however, their role in gastrointestinal dysfunction in IBD has not been fully elucidated. This review will describe the development and characterization of gastrointestinal eosinophils, mechanisms of eosinophil recruitment to the gastrointestinal tract. Moreover, the eosinophil-induced changes to the enteric nervous system associated with disease severity and gastrointestinal dysfunction will be analyzed with suggestive molecular pathways for enteric neuronal injury. Current and potential therapeutic interventions targeting eosinophils will be discussed.

Dysregulated fatty acid metabolism in nasal polyp-derived eosinophils from patients with chronic rhinosinusitis

BACKGROUND

Eosinophils are multifunctional granulocytes capable of releasing various cytokines, chemokines, and lipid mediators. We previously reported dysregulated fatty acid metabolism in peripheral blood-derived eosinophils from patients with severe asthma. However, functional characteristics of eosinophils present in allergic inflammatory tissues remain largely uncharacterized.

METHODS

We established a method for isolating CD69^hi CCR3^low CXCR4^- siglec-8^int eosinophils from nasal polyps of patients with eosinophilic rhinosinusitis (NP-EOS). Multi-omics analysis including lipidomics, proteomics, and transcriptomics was performed to analyze NP-EOS as compared to peripheral blood-derived eosinophils from healthy subjects (PB-EOS).

RESULTS

Lipidomic analysis revealed impaired synthesis of prostaglandins and 15-lipoxygenase (15-LOX)-derived mediators, and selective upregulation of leukotriene D₄ production. Furthermore, proteomics and transcriptomics revealed changes in the expression of specific enzymes (GGT5, DPEP2, and 15-LOX) responsible for dysregulated lipid metabolism. Ingenuity pathway analysis indicated the importance of type 2 cytokines and pattern recognition receptor pathways. Stimulation of PB-EOS with eosinophil activators IL-5, GM-CSF, and agonists of TLR2 and NOD2 mimicked the observed changes in lipid metabolism.

CONCLUSION

Inflammatory tissue-derived eosinophils possess a specific phenotype with dysregulated fatty acid metabolism that may be targeted therapeutically to control eosinophilic inflammatory diseases.

Discovery of novel 3-(hydroxyalkoxy)-2-alkylchromen-4-one analogs as interleukin-5 inhibitors

A series of novel chromen-4-one analogs 9a-d and 10a-u was designed, synthesized and evaluated for their IL-5 inhibitory activity. Most of the chromen-4-one analogs showed strong inhibitory activity in low micro molar potency. Among them, 5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-2-isopropyl-4H-chromen-4-one (10t, 90.0% inhibition at 30 μM, IC₅₀ = 5.5 μM, CLogP = 4.76887) and 2-cyclohexyl-5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-4H-chromen-4-one (10u, 95.5% inhibition at 30 μM, IC₅₀ = 3.0 μM, CLogP = 5.96187) showed the best inhibition. The structure activity relationship reveals that the hydrophobic cyclohexylmethoxy group at the position 5 of the chromen-4-one ring A is preferable than at position 6 and the dual hydrogen bonding acceptor property on the chromen-4-one ring should be important for the inhibitory activity. In addition, the optimum length of the side chain at position 3 of chromen-4-one ring is critical for the donation of hydrogen to the binding site and the 3-hydroxypropoxy group showed the best activity. Moreover, the conformational restrictor (isopropyl, cyclohexyl group) at position 2 is much more favorable for the formation of effective conformer of side chain with hydrogen bonding donor property of these chromen-4-one analogs.

The Eosinophil in Health and Disease: from Bench to Bedside and Back

Historically, eosinophils have been considered as end-stage cells involved in host protection against parasitic infection and in the mechanisms of hypersensitivity. However, later studies have shown that this multifunctional cell is also capable of producing immunoregulatory cytokines and soluble mediators and is involved in tissue homeostasis and modulation of innate and adaptive immune responses. In this review, we summarize the biology of eosinophils, including the function and molecular mechanisms of their granule proteins, cell surface markers, mediators, and pathways, and present comprehensive reviews of research updates on the genetics and epigenetics of eosinophils. We describe recent advances in the development of epigenetics of eosinophil-related diseases, especially in asthma. Likewise, recent studies have provided us with a more complete appreciation of how eosinophils contribute to the pathogenesis of various diseases, including hypereosinophilic syndrome (HES). Over the past decades, the definition and criteria of HES have been evolving with the progress of our understanding of the disease and some aspects of this disease still remain controversial. We also review recent updates on the genetic and molecular mechanisms of HES, which have spurred dramatic developments in the clinical strategies of diagnosis and treatment for this heterogeneous group of diseases. The conclusion from this review is that the biology of eosinophils provides significant insights as to their roles in health and disease and, furthermore, demonstrates that a better understanding of eosinophil will accelerate the development of new therapeutic strategies for patients.

Humanized Anti-IL-5 Antibody Therapy

Eosinophils are suppressed by a new class of drugs targeting Interleukin-5 (IL-5), an eosinophil growth, activation, and survival factor. Humanized anti-IL-5 antibodies are effective in treating asthma patients with the severe eosinophilic form of the disease and are the first new class of asthma drugs approved in 12 years.

Zingiber officinale ameliorates allergic asthma via suppression of Th2-mediated immune response

CONTEXT

Ginger has been used commonly in the traditional system of medicine for the treatment of respiratory disorders.

OBJECTIVE

The present study investigates the immunosuppressive activity of ginger by using the mouse model of ovalbumin-induced allergic asthma.

MATERIALS AND METHODS

Treatment with ethanol extract (500 mg/kg) and aqueous extract (720 mg/kg) of rhizomes, and methylprednisolone (5 mg/kg) was initiated 1 week after second sensitization of mice with ovalbumin and continued for 7 d. RT-PCR followed by gel electrophoresis and ELISA were used for the evaluation of mRNA expression levels and protein levels of Th2 type markers, respectively. Lung tissue histopathology was conducted by using H&E and PAS staining.

RESULTS

We observed significant reduction in goblet cell hyperplasia (0.83 ± 0.17 and 1.0 ± 0.26), infiltration of inflammatory cells in airways (0.67 ± 0.33 and 1.0 ± 0.37), and edema with vascular congestion (1.0 ± 0.26 and 1.2 ± 0.17) by both ethanol and aqueous extracts, respectively. A highly significant reduction of total and differential count of eosinophils and neutrophils in BALF, and eosinophil count in blood were also observed. Both extracts significantly inhibited Th2-mediated immune response, which is evident by a decrease in mRNA expression levels of IL-4 and IL-5. Protein levels of IL-4 and IL-5 in BALF, along with total serum IgE levels, were also significantly suppressed by both extracts.

DISCUSSION AND CONCLUSION

Our study validated the traditional use of ginger in respiratory disorders and suggests that ginger reduces allergic airway inflammation, possibly by the suppression of Th2-mediated immune response.

Balance of apoptotic cell death and survival in allergic diseases

Allergic diseases result from over-reaction of the immune system in response to exogenous allergens, where inflammatory cells have constantly extended longevity and contribute to an on-going immune response in allergic tissues. Here, we review disequilibrium in the death and survival of epithelial cells and inflammatory cells in the pathological processes of asthma, atopic dermatitis, and other allergic diseases.

Expression and functional roles of G-protein-coupled estrogen receptor (GPER) in human eosinophils

Sexual dimorphism in asthma links the estrogen and allergic immune responses. The function of estrogen was classically believed to be mediated through its nuclear receptors, i.e., estrogen receptors (ERs). However, recent studies established the important roles of G-protein-coupled estrogen receptor (GPER/GPR30) as a novel membrane receptor for estrogen. To date, the role of GPER in allergic inflammation is poorly understood. The purpose of this study was to examine whether GPER might affect the functions of eosinophils, which play an important role in the pathogenesis of asthma. Here, we demonstrated that GPER was expressed in purified human peripheral blood eosinophils both at the mRNA and protein levels. Although GPER agonist G-1 did not induce eosinophil chemotaxis or chemokinesis, preincubation with G-1 enhanced eotaxin (CCL11)-directed eosinophil chemotaxis. G-1 inhibited eosinophil spontaneous apoptosis and caspase-3 activities. The anti-apoptotic effect was not affected by the cAMP-phospodiesterase inhibitor rolipram or phosphoinositide 3-kinase inhibitors. In contrast to resting eosinophils, G-1 induced apoptosis and increased caspase-3 activities when eosinophils were co-stimulated with IL-5. No effect of G-1 was observed on eosinophil degranulation in terms of release of eosinophil-derived neurotoxin (EDN). The current study indicates the functional capacities of GPER on human eosinophils and also provides the previously unrecognized mechanisms of interaction between estrogen and allergic inflammation.

CCL26/eotaxin-3 is more effective to induce the migration of eosinophils of asthmatics than CCL11/eotaxin-1 and CCL24/eotaxin-2

CCL11, CCL24, and CCL26 are chemokines involved in the recruitment of eosinophils into tissues and mainly activate CCR3. Whereas the genomic or pharmacological inhibition of CCR3 prevents the development of experimental asthma in rodents, it only impairs the recruitment of eosinophils by ∼40% in humans. As humans, but not rodents, express CCL26, we investigated the impact of CCL11, CCL24, and CCL26 on human eosinophils recruitment and evaluated the involvement of CCR3. The migration of eosinophils of healthy volunteers was similar for the three eotaxins. Eosinophils of mild asthmatics had a greater response to CCL11 and a much greater response to CCL26. Whereas all eotaxins induced the migration of eosinophil of asthmatics from 0 to 6 h, CCL26 triggered a second phase of migration between 12 and 18 h. Given that the CCR3 antagonists SB 328437 and SB 297006 inhibited the 5-oxo-eicosatetraenoate-induced migration of eosinophils and that the CCR3 antagonist UCB 35625 was not specific for CCR3, CCR3 blockade was performed with the CCR3 mAb. This antibody completely blocked the effect of all eotaxins on eosinophils of healthy subjects and the effect of CCL24 on the eosinophils of asthmatics. Interestingly, CCR3 blockade did not affect the second migration phase induced by CCL26 on eosinophils of asthmatics. In conclusion, CCL26 is a more effective chemoattractant than CCL11 and CCL24 for eosinophils of asthmatics. The mechanism of this greater efficiency is not yet defined. However, these results suggest that CCL26 may play a unique and important role in the recruitment of eosinophils in persistent asthma.

An alternate STAT6-independent pathway promotes eosinophil influx into blood during allergic airway inflammation

Background

Enhanced eosinophil responses have critical roles in the development of allergic diseases. IL-5 regulates the maturation, migration and survival of eosinophils, and IL-5 and eotaxins mediate the trafficking and activation of eosinophils in inflamed tissues. CD4⁺ Th2 cells are the main producers of IL-5 and other cells such as NK also release this cytokine. Although multiple signalling pathways may be involved, STAT6 critically regulates the differentiation and cytokine production of Th2 cells and the expression of eotaxins. Nevertheless, the mechanisms that mediate different parts of the eosinophilic inflammatory process in different tissues in allergic airway diseases remain unclear. Furthermore, the mechanisms at play may vary depending on the context of inflammation and microenvironment of the involved tissues.

Methodology/Principal Findings

We employed a model of allergic airway disease in wild type and STAT6-deficient mice to explore the roles of STAT6 and IL-5 in the development of eosinophilic inflammation in this context. Quantitative PCR and ELISA were used to examine IL-5, eotaxins levels in serum and lungs. Eosinophils in lung, peripheral blood and bone marrow were characterized by morphological properties. CD4⁺ T cell and NK cells were identified by flow cytometry. Antibodies were used to deplete CD4⁺ and NK cells. We showed that STAT6 is indispensible for eosinophilic lung inflammation and the induction of eotaxin-1 and -2 during allergic airway inflammation. In the absence of these chemokines eosinophils are not attracted into lung and accumulate in peripheral blood. We also demonstrate the existence of an alternate STAT6-independent pathway of IL-5 production by CD4⁺ and NK cells that mediates the development of eosinophils in bone marrow and their subsequent movement into the circulation.

Conclusions

These results suggest that different points of eosinophilic inflammatory processes in allergic airway disease may be differentially regulated by the activation of STAT6-dependent and -independent pathways.

Current strategies in the management of hypereosinophilic syndrome, including mepolizumab

BACKGROUND

Patients with hypereosinophilic syndrome (HES) vary considerably in their clinical presentation with regard to the severity and pattern of end-organ involvement. Clinical manifestations range from nonspecific symptoms to life-threatening, multisystem damage caused by eosinophil infiltration and local release of proinflammatory mediators and toxic granule products from these invading cells. The primary objective of treatment is to reduce blood and tissue eosinophilia and prevent eosinophil-mediated tissue damage as safely as possible. Systemic corticosteroids, such as prednisone, are first-line therapy for the management of patients with symptomatic HES who lack the Fip1-like 1-platelet-derived growth factor receptor-alpha (FIP1L1-PDGFRA) gene fusion mutation. The tyrosine kinase inhibitor, imatinib, is first-line treatment for FIP1L1-PDGFRA-positive patients). Because of the toxicity and serious side-effects that can occur with oral corticosteroids, alternative therapies may need to be introduced to reduce the cumulative corticosteroid exposure while maintaining disease control.

SCOPE

Among corticosteroid-sparing agents are cytotoxic drugs and interferon-alpha; anti-interleukin-5 (IL-5) monoclonal antibodies are also currently under investigation for the treatment of HES. This manuscript reviews the available treatments for HES and the range of side-effects associated with long-term corticosteroid use, and then focuses on the anti-IL-5 monoclonal antibodies, mepolizumab and reslizumab. Of these, only mepolizumab has been studied in a randomized, placebo-controlled trial. Literature search methodology utilized www.pubmed.gov and www.clinicaltrials.gov with search terms including hypereosinophilic syndrome and corticosteroid side-effects coupled with search terms including eosinophils, mepolizumab and reslizumab through March 2010.

FINDINGS

Three case studies are presented that demonstrate the limitations of corticosteroid therapy in terms of tolerability and quality of life, and the subsequent use of mepolizumab as a corticosteroid-sparing agent in these individuals.

CONCLUSION

Targeted eosinophil-directed therapy with an anti-IL-5 neutralizing monoclonal antibody reduced the need for corticosteroids in these three HES patients without disease exacerbations.

2007 E. Mead Johnson award: scientific pursuit of the allergy problem

My research has focused on elucidating the allergy problem over the past two decades. The primary approach has been to uncover critical mechanisms of allergic inflammation, with particular focus on eosinophils, a hallmark cellular constituent of allergic responses. Molecular processes that bridge T helper cell type 2 (TH2) immunity with eosinophilia and key checkpoints for regulating eosinophilia have been uncovered. Notably, interleukin (IL)-5 (derived from TH2 cells) has been identified as the chief hematopoietin responsible for eosinophil expansion in the circulation. Pathways for selective eosinophil mobilization from the blood stream to the tissue have been uncovered by defining the role of the eotaxin subfamily of chemokines in eosinophil chemoattraction and activation. Finally, TH2 cell derived IL-4 and IL-13 have been defined as chief inducers of the eotaxins, and upstream orchestrators of eosinophilic inflammation. These translational studies have formulated novel therapeutic strategies (currently being tested) for a variety of eosinophilic conditions, with particular attention on hypereosinophilic syndromes and eosinophil-associated gastrointestinal disorders such as eosinophilic esophagitis.

Idiopathic eosinophilic gastrointestinal diseases in adults

This review focuses on the latest cognitions, diagnosis and treatment strategies of the three main representatives of the eosinophilic gastrointestinal disorders (EGID): idiopathic eosinophilic oesophagitis (EE), idiopathic eosinophilic gastroenteritis (EGE) and idiopathic hypereosinophilic syndromes (HES) with gastrointestinal involvement. These disorders share important similarities: their origin is unknown and their pathogenesis is due to a histological inflammatory response characterised by eosinophilic tissue infiltration. In spite of these parallels, the courses and prognoses of the diseases differ radically: EE is restricted to the oesophagus, and though it may significantly decrease the patient's quality of life, it has a favourable long-term prognosis. In EGE, the inflammatory process involves several segments of the gastrointestinal tract but this chronic inflammation may also be considered a benign disorder. In contrast, HES is primarily a multisystem disorder that may involve several organs, including the digestive tract, and often has a fatal outcome.

Anti-IL-5 (mepolizumab) therapy reduces eosinophil activation ex vivo and increases IL-5 and IL-5 receptor levels

BACKGROUND

Anti-IL-5 might be a useful therapeutic agent for eosinophilic disorders, yet its immunologic consequences have not been well characterized.

OBJECTIVE

We sought to characterize the hematologic and immunologic effects of anti-IL-5 in human subjects.

METHODS

The effects of 3-month infusions of mepolizumab were assessed in 25 patients with a variety of eosinophilic syndromes. Samples with increased IL-5 levels after therapy were analyzed by using size exclusion filtration. Immunoreactive IL-5 fraction and plasma samples were subsequently precipitated with saturating concentrations of protein A/G.

RESULTS

Twenty-three patients responded to anti-IL-5 therapy with a decrease in blood eosinophil counts and a reduced percentage of CCR3(+) cells by 20- and 13-fold, respectively (P < .0001). Responsiveness was not related to the levels of baseline plasma IL-5 or the presence of FIP1L1-PDGFRA fusion gene. Persistently decreased blood eosinophilia remained for 3 months after final infusion in 76% of subjects. Therapy was associated with a large increase in blood IL-5 levels, likely because of a circulating IL-5/mepolizumab complex precipitated with protein A/G, a significant increase in eosinophil IL-5 receptor alpha expression, and increased percentage of CD4(+) and CD8(+) cells producing intracellular IL-5 (P < .05). Additionally, anti-IL-5 therapy decreased eotaxin-stimulated eosinophil shape change ex vivo.

CONCLUSIONS

Anti-IL-5 therapy induces a dramatic and sustained decrease in blood eosinophilia (including CCR3(+) cells), decreased eosinophil activation, and increased circulating levels of IL-5 in a variety of eosinophilic disorders. Increased levels of IL-5 receptor alpha and lymphocyte IL-5 production after anti-IL-5 therapy suggest an endogenous IL-5 autoregulatory pathway.

Eosinophils: biological properties and role in health and disease

Eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of diverse inflammatory responses, as well as modulators of innate and adaptive immunity. In this review, the biology of eosinophils is summarized, focusing on transcriptional regulation of eosinophil differentiation, characterization of the growing properties of eosinophil granule proteins, surface proteins and pleiotropic mediators, and molecular mechanisms of eosinophil degranulation. New views on the role of eosinophils in homeostatic function are examined, including developmental biology and innate and adaptive immunity (as well as their interaction with mast cells and T cells) and their proposed role in disease processes including infections, asthma, and gastrointestinal disorders. Finally, strategies for targeted therapeutic intervention in eosinophil-mediated mucosal diseases are conceptualized.

Origin, regulation and physiological function of intestinal oeosinophils

Oeosinophils are pleiotropic multi-functional leukocytes that are typically associated with the initiation and propagation of inflammatory responses, particularly helminth infection and allergic disease. However, expanding evidence supports a broader role for oeosinophils in homoeostatic function and organ development and modulation of local immune responses via interaction with other effector cells. In this review, the biology of oeosinophils in the healthy gut is summarised. In particular, the molecular steps involved in oeosinophil development and trafficking are described, with special attention to the important role of the transcription factor GATA-1, the oeosinophil-selective cytokine IL-5 and the eotaxin subfamily of chemokines. In addition, the regulation of oeosinophil survival by inhibitory and death receptors and the expanding role for oeosinophils in health and disease are reviewed.

Pharmacologic treatment of eosinophilic esophagitis

There are several treatment options available for patients who have eosinophilic esophagitis (EE). These options include dilatation for mechanical esophageal abnormalities, pharmacologic therapy, and dietary management. Providing the appropriate therapy depends on the significance of clinical symptoms, association of abnormal anatomy, and histologic involvement of underlying the esophageal tissue. This article focuses on the pharmacotherapy of EE.

Mechanisms of eosinophilia in the pathogenesis of hypereosinophilic disorders

The increased numbers of activated eosinophils in the blood and tissues that typically accompany hypereosinophilic disorders result from a variety of mechanisms. Exciting advances in translating discoveries achieved from mouse models and molecular strategies to the clinic have led to a flurry of new therapeutics specifically designed to target eosinophil-associated diseases. So far, this form of hypothesis testing in humans in vivo through pharmacology generally has supported the paradigms generated in vitro and in animal models, raising hopes that a spectrum of novel therapies soon may become available to help those who have eosinophil-associated diseases.

Current concepts on the pathogenesis of the hypereosinophilic syndrome/chronic eosinophilic leukemia

Chronic eosinophilic leukemia is a clonal disease characterized by hypereosinophilia and eosinophilia-related pathologic manifestations. Recently, the fusion gene FIP1L1/PDGFRA was found in the long arm of chromosome 4 and its expression has been shown to be associated with development of a clinical hypereosinophilic syndrome (HES) in a significant proportion of patients. FIP1L1/PDGFRα, the product of the gene FIP1L1/PDGFRA, is a constitutively activated tyrosine kinase and can be inhibited by imatinib mesylate. Several investigations have tried to dissect the mechanism of leukemogenesis and signaling induced by FIP1L1/PDGFRα in cell lines, primary human eosinophils and in murine myeloproliferative models. In this review, we analyzed the current knowledge on the relationship between FIP1L1/PDGFRα-induced signaling and eosinophil proliferation, survival and activation, specially focusing on its possible role in the modulation of cytokine and chemoattractant signaling pathways.

Selective priming of peripheral blood eosinophils in patients with idiopathic hypereosinophilic syndrome

The idiopathic hypereosinophilic syndrome (HES) is characterised by blood eosinophilia associated with organ involvement. Elevated numbers of blood neutrophils have been observed during episodes of active HES. However, an increased responsiveness of eosinophils to chemotactic and chemokinetic stimuli may explain the selective eosinophil infiltration of the tissue. We have studied the migratory responses of blood eosinophils and neutrophils from 9 patients with HES and from 13 healthy control subjects. Chemokinetic and chemotactic responses to factors acting on both cell types were analysed by means of a modification of the Boyden chamber technique. We found increased migratory responses of the eosinophils, but not of the neutrophils, from the patients with HES. Increased blood neutrophil counts in three of the patients did not coincide with alterations of the neutrophil migratory responses. Our finding of increased migratory responses of eosinophils from patients with HES towards non-specific chemoattractants suggests selective priming of eosinophils in this disease. Interleukin (IL)-5 has previously been shown to prime eosinophils for migratory responses, and successful anti-IL-5 therapy of patients with HES indicates an important role for this cytokine in the development of hypereosinophilia.

cIAP-2 and survivin contribute to cytokine-mediated delayed eosinophil apoptosis

The exact molecular mechanisms leading to delayed apoptosis, a phenomenon frequently observed in eosinophil inflammatory responses, remain largely unknown. Here, we show that cultured eosinophils purified from blood of hypereosinophilic syndrome (HES) patients exhibit delayed spontaneous death and relative resistance towards ceramide- but not CD95-mediated death. The subsequent investigation of members of the inhibitor of apoptosis (IAP) family revealed that HES but not normal eosinophils expressed high levels of cellular IAP-2 (cIAP-2) and survivin. The eosinophil hematopoietins IL-3, IL-5, and GM-CSF increased the expression of cIAP-2 and survivin in normal eosinophils in vitro. In the blood of HES patients, we observed increased concentrations of IL-3 and/or IL-5, suggesting that these cytokines are, at least partially, responsible for the elevated levels of cIAP-2 and survivin in the eosinophils of these patients. Utilizing a cell-free system in which caspase-3 was activated in eosinophil cytosolic extracts by addition of cytochrome c and immunodepletion of cIAP-2 or survivin resulted in accelerated caspase activation. These data suggest that some members of the IAP family including survivin are regulated by survival cytokines and inhibit the caspase cascade in HES eosinophils. The cytokine-dependent mechanism of delayed eosinophil apoptosis described here may also apply to other eosinophilic diseases.

The eosinophil

Eosinophils have been considered end-stage cells involved in host protection against parasites. However, numerous lines of evidence have now changed this perspective by showing that eosinophils are pleiotropic multifunctional leukocytes involved in initiation and propagation of diverse inflammatory responses, as well as modulators of innate and adaptive immunity. In this review, we summarize the biology of eosinophils, focusing on the growing properties of eosinophil-derived products, including the constituents of their granules as well as the mechanisms by which they release their pleiotropic mediators. We examine new views on the role of eosinophils in homeostatic function, including developmental biology and innate and adaptive immunity (as well as interaction with mast cells and T cells). The molecular steps involved in eosinophil development and trafficking are described, with special attention to the important role of the transcription factor GATA-1, the eosinophil-selective cytokine IL-5, and the eotaxin subfamily of chemokines. We also review the role of eosinophils in disease processes, including infections, asthma, and gastrointestinal disorders, and new data concerning genetically engineered eosinophil-deficient mice. Finally, strategies for targeted therapeutic intervention in eosinophil-mediated mucosal diseases are conceptualized.

Potential adverse events with biologic response modifiers

In recent years, an explosion of biologic response modifiers has entered the market to combat a variety of immune-mediated diseases. These can be in the form of recombinant cytokines, as in the case of interferon beta in the treatment of multiple sclerosis, or novel engineered antibodies constructed by combining non-human determinants with a human immunoglobulin scaffold, as in the case of omalizumab in the treatment of allergic asthma. More recently, completely human monoclonal antibodies have also been constructed. Adverse reactions related to these agents can be classified as expected or unexpected events. A number of case studies and a handful of randomized trials have demonstrated the potential toxicities with the use of biologic response modifiers. This article aims to review adverse event profiles of select biologic response modifiers for which the most data is available and are common to a rheumatology, allergy/immunology, and dermatology patient population.

Activation of neutrophils in cutaneous T-cell lymphoma

PURPOSE

Cutaneous T-cell lymphoma (CTCL) is a spectrum of disease of unknown etiology defined by infiltrates of activated and malignant T cells in the skin. In working with blood from CTCL patients, we noticed frequent activation of neutrophils; therefore, we tested the hypothesis that neutrophils are activated in CTCL subjects compared with normal healthy controls.

EXPERIMENTAL DESIGN

Using peripheral blood of 44 subjects with CTCL and 15 normal controls, we examined three measures of neutrophil activation. These are the presence of neutrophils of reduced buoyant density, the presence of primed neutrophils in a stimulated chemiluminescence assay, and changes in surface markers by flow cytometry. In addition, we tested plasma interleukin-8 (IL-8) and leukotriene B4 (LTB4) levels using ELISA.

RESULTS

A significantly larger fraction of hypodense neutrophils was observed in CTCL subjects compared with normals (10.6 +/- 1.7% versus 1.5 +/- 0.4%). Stimulated chemiluminescence was also significantly increased in CTCL, and analysis of neutrophil surface markers using flow cytometry showed significantly increased CD11b and CD66b and decreased CD62L, consistent with neutrophil activation. These changes were present even in early stages of CTCL. We further found that plasma IL-8 and LTB4 levels are elevated in CTCL, which could form a feedback loop contributing to disease pathophysiology.

CONCLUSIONS

CTCL is associated with systemic neutrophil activation, even in early disease, and a feedback loop between neutrophils and T cells mediated by IL-8 and LTB4 is a potential contribution to the pathophysiology of CTCL.

Rheumatologic disease with peripheral eosinophilia

Eosinophilia is not common in connective tissue diseases, so the frequency and clinical importance of eosinophilia in rheumatologic disease are not known. The purpose of the present review was to explore its prevalance in rheumatologic disease together with a MEDLINE database search.

Clonal T-helper lymphocytes and elevated IL-5 levels in episodic angioedema and eosinophilia (Gleich's syndrome)

A patient with marked chronic eosinophilia and episodic angioedema (Gleich's syndrome) with a concomitant clonal proliferation of helper T-lymphocytes is described. This association has not previously been documented. The symptoms and clinical course differ markedly from the idiopathic hypereosinophilic syndrome, including an absence of end organ involvement. However, the disease appears to have a similar pathogenesis, with elevated levels of the eosinophil-specific cytokine interleukin-5 (IL-5) produced by the T-cell clone.

Familial eosinophilia: a benign disorder?

Familial eosinophilia (FE) is an autosomal dominant disorder characterized by marked eosinophilia and progression to end organ damage in some, but not all, affected family members. To better define the pathogenesis of FE, 13 affected and 11 unaffected family members (NLs) underwent a detailed clinical evaluation at the National Institutes of Health (NIH). No clinical abnormalities were more frequent in the family members with FE compared with the NLs. There was, however, a decreased prevalence of asthma in family members with FE compared with unaffected family members. Eosinophil morphology as assessed by either light or transmission electron microscopy was normal in family members with and without FE. Although levels of eosinophil-derived neurotoxin (EDN) and major basic protein (MBP) were elevated in patients with FE compared with NL, levels of both granule proteins were lower than in nonfamilial hypereosinophilic syndrome (HES). Similarly, increased surface expression of the activation markers CD69, CD25, and HLA-DR was detected by flow cytometry on eosinophils from patients with FE compared with NL, albeit less than that seen in HES. These data suggest that, despite prolonged marked eosinophilia, FE can be distinguished from HES by a more benign clinical course that may be related to a relative lack of eosinophil activation.

Eosinophilic fasciitis and eosinophilic cellulitis in a patient with abnormal circulating clonal T cells: increased production of interleukin 5 and inhibition by interferon alfa

Eosinophilic fasciitis (Shulman's syndrome) and eosinophilic cellulitis are part of a spectrum of diseases characterized by tissue and peripheral blood eosinophilia. Eosinophils are implicated directly in the lesional process that characterizes these conditions, because signs of eosinophil activation and degranulation are observed at the sites of tissue injury. The cause and pathogenesis of eosinophilic fasciitis and cellulitis are presently unclear. Herein, we report a patient manifesting rapidly progressive localized cutaneous induration of the arms and legs with eosinophilia, no signs of systemic sclerosis, and histopathologic features compatible with the diagnosis of eosinophilic fasciitis. Four years after the onset of eosinophilic fasciitis, the patient had recurrent episodes of eosinophilic cellulitis. Blood screening for clonal T-cell receptor gamma gene rearrangements revealed several amplified clonal populations of circulating T cells. Furthermore, in vitro analysis of cytokine production by the patient's peripheral blood mononuclear cells demonstrated strongly increased production of interleukin 5, the synthesis of which could be completely blocked by interferon (IFN)-alpha. The coexistence of eosinophilic fasciitis and cellulitis in a patient with an abnormal circulating T-cell clone and increased IL-5 production are unique and might be responsible for the eosinophilia and eosinophil-mediated tissue injury. Although not assessed in vivo in this patient, our in vitro data provide a rationale for the use of IFN-alpha in eosinophilic fasciitis and/or cellulitis.

The physiological and pathophysiological roles of eosinophils in the gastrointestinal tract

Eosinophils and the gastrointestinal tract interact in an intimate and enigmatic relationship. Under healthy conditions, the presence of eosinophils is limited almost exclusively to the digestive tract mucosa where they exert several effector and immunoregulatory functions. While their precise function in the gastrointestinal tract is not completely understood, it is likely that, together with different T cell subsets, eosinophils are involved in maintaining the immunologic homeostastis across the mucosal barrier under resting conditions. Eosinophils also play a role in several inflammatory conditions, such as intestinal infections, hypersensitivity reactions, primary eosinophilic inflammations and several other chronic intestinal disorders. Depending on the responsible trigger, their effects may be beneficial or detrimental. Here, we discuss the available information regarding the physiological and pathological functions of eosinophils within the gastrointestinal tract.

Dermal endothelial cells express eotaxin in hypereosinophilic syndrome

We describe a patient with hypereosinophilic syndrome, who had severe cutaneous eruptions. Immunohistochemical study revealed that dermal endothelial cells in the lesional skin of this patient expressed eotaxin, which indicates eotaxin plays a part in inducing eosinophil migration into cutaneous tissue in hypereosinophilic syndrome.

Idiopathic hypereosinophilic syndrome associated with cutaneous infarction and deep venous thrombosis

We report a case of idiopathic hypereosinophilic syndrome (HES) presenting with cutaneous infarction and subsequent extensive deep vein thrombosis. The eosinophilia improved dramatically with systemic corticosteroid therapy. A variety of skin disorders have been associated with HES, although there are no previous reports of HES associated with cutaneous infarction. HES is a rare disorder characterized by a sustained overproduction of eosinophils and multisystem disease. The aetiology of the eosinophilia remains uncertain but clonal populations of abnormal T-cells producing interleukin 5 may be implicated.

Wilms tumor gene (WT1) expression as a panleukemic marker

The Wilms tumor gene (WT1) is expressed in blasts of patients with acute leukemia, irrespective of lineage, and WT1 nuclear protein is detectable in the majority of such blasts. Only very few physiologic hematopoietic progenitors express WT1, but the WT1 expression level of these progenitors and that of leukemic blasts are comparable. Although not specific for acute hematologic malignant diseases, continuous WT1 expression in almost all leukemic blasts strikingly contrasts to its rather transient expression in very few physiologic hematopoietic progenitors. Quantitative and semiquantitative WT1 reverse transcriptase polymerase chain reaction (RT-PCR) protocols have limitations in discriminating physiologic from pathologic overall WT1 expression levels in mononuclear cell preparations. Because of these limitations, reports conflict on the usefulness of long-term monitoring of WT1 expression in patients with acute leukemia. Real-time quantitative WT1 RT-PCR protocols, however, have been developed and tested in small series of patients with acute leukemia. Such protocols hold promise to enable evaluation of the individual treatment response (short-term monitoring) and early diagnosis of imminent relapse through the detection and long-term monitoring of minimal residual disease in patients with acute leukemia. These protocols also should facilitate the notoriously difficult distinction between eosinophilic leukemia and hypereosinophilic syndromes. Data on WT1 expression in leukemic blasts and their physiologic counterparts are discussed in light of clinical relevance.

New diagnostic tool for differentiation of idiopathic hypereosinophilic syndrome (HES) and secondary eosinophilic states

The hypereosinophilic syndrome (HES) is a very rare disease, characterized by persistent eosinophilia with tissue involvement and organ dysfunction which often precedes a subsequent T cell lymphoma. Interleukin-5 secreted by a T lymphocyte subpopulation has been described in previous reports as the most important factor responsible for the prolonged lifespan of the eosinophils. The goal of the present study was to describe a fast, simple diagnostic method for the differentiation of HES and secondary eosinophilic states. Beside the surface marker analysis of peripheral blood mononuclear cells (PBMC) we measured surface bound IgE molecules on lymphocytes and eosinophil cells, intracellular cytokines (IL-5, INFgamma) in CD4+ lymphocytes and eosinophil major basic protein (MBP) in eosinophils using flow cytometric detection method. The appearance of an IL-5 producing cell population with a decreased number of INFgamma positive lymphocytes was characteristic for the blood samples of HES patients. Predominance of Th2 cells with the appearance of a CD8+/CD3 /CD56+ cell population was restricted for the HES cases and could not be detected in secondary eosinophilic individuals. Our flow cytometric cytokine detection method (with parallel cell surface marker analysis) does not require cell separation or long term cell culture steps previously described for the detection of IL-5 producing cells. Therefore it seems to be a more appropriate approach for the differential diagnosis of primary and secondary eosinophilic states.

Neutralizing monoclonal antibodies can potentiate IL-5 signaling

IL-5 is a major determinant in the survival, differentiation and effector-functions of eosinophils. It mediates its effect upon binding and activation of a membrane bound receptor (R), composed of a ligand-specific alpha-chain and a beta-chain, shared with the receptors for IL-3 and granulocyte-macrophage colony-stimulating factor. We have generated and mapped the epitopes of three monoclonal antibodies (mAb) directed against this cytokine: the strong neutralizing mAb 5A5 and 1E1, and the very weak neutralizing mAb H30. We found that H30 as well as 5A5 can increase proliferation above the level induced by human (h)IL-5 alone, in a JAK-2-dependent manner, and at every sub-optimal hIL-5 concentration analyzed. This effect is dependent on mAb-mediated cross-linking of IL-5R complexes, and is only observed on cell lines expressing a hybrid human/mouse IL-5Ralpha-chain. We discuss these findings in view of the stoichiometric and topological requirements for an activated IL-5R. Since humanized anti-IL-5 mAb are currently in clinical testing, our findings imply that such mAb should be carefully evaluated for their potentiating effects.

The cytokine profile in a transient variant of angioedema with eosinophilia

Episodic angioedema with eosinophilia is characterized by recurrent angioedema, fever and weight gain with a remarkable eosinophilia. A transient type, predominantly reported in Japan, in which the disease is limited to a single attack, is usually less severe than the episodic type described in the U.S.A. and Europe, and provides an ideal disease model in which to study the mechanisms for resolution of eosinophilic inflammation. The aim of this study was to evaluate the relationship between cytokine responses and clinical course in three patients with the transient type. Serum levels of interleukin (IL) -5 were only marginally elevated even during an attack, unlike those in reported cases of the episodic type. Significant elevations in granulocyte-macrophage colony-stimulating factor levels were also noted during an attack in two cases in which it was measured. A dramatic increase in tumor necrosis factor (TNF) -alpha levels was subsequently observed in relation to resolution of clinical symptoms. No major changes in the serum levels of soluble Fas and soluble Fas ligand were found throughout the course. These results suggest that relatively lower levels of IL-5 and a subsequent increase in TNF-alpha levels are characteristic features of the transient type. The differences in clinical symptoms and course observed between the two types may be partly explained by the differences in the cytokine profiles.