Recombinant human interleukin 5 is an eosinophil differentiation factor but has no activity in standard human B cell growth factor assays

Chronic rhinosinusitis with nasal polyps: eosinophils versus B lymphocytes in disease pathogenesis

PURPOSE OF REVIEW

To highlight the current evidence that supports the view that eosinophils may not drive disease in chronic rhinosinusitis with nasal polyps (CRSwNP) and the emerging evidence for B cells as an important player in this disease.

RECENT FINDINGS

Eosinophil depletion studies in CRSwNP do not fully support a critical role for eosinophils in CRSwNP. Almost complete eosinophil depletion with dexpramipexole had no impact on polyp size reduction or clinical improvement. Anti-interleukin (IL)-5 and IL-5Rα inhibition were more effective though with less clinical impact when compared to anti-immunoglobulin E (IgE) or IL-4Rα inhibition strategies. As IL-5Rα is also expressed on CRSwNP derived IgE+ and IgG4+ plasma cells to the same extent as eosinophils, improvements in CRSwNP with IL-5 inhibition may suggest a role for B cells over eosinophils in CRSwNP. We review both eosinophils and B cells in the context of CRSwNP and highlight the current evidence that supports an emerging role for B cells.

SUMMARY

Despite many aspects of immunopathology in CRSwNP explainable by B cell dysfunction, B cells have so far been ignored in CRSwNP. Further work is needed, as targeting B cells may offer an exciting new therapeutic option in the future.

Macrophages Orchestrate Airway Inflammation, Remodeling, and Resolution in Asthma

Asthma is a heterogenous chronic inflammatory lung disease with endotypes that manifest different immune system profiles, severity, and responses to current therapies. Regardless of endotype, asthma features increased immune cell infiltration, inflammatory cytokine release, and airway remodeling. Lung macrophages are also heterogenous in that there are separate subsets and, depending on the environment, different effector functions. Lung macrophages are important in recruitment of immune cells such as eosinophils, neutrophils, and monocytes that enhance allergic inflammation and initiate T helper cell responses. Persistent lung remodeling including mucus hypersecretion, increased airway smooth muscle mass, and airway fibrosis contributes to progressive lung function decline that is insensitive to current asthma treatments. Macrophages secrete inflammatory mediators that induce airway inflammation and remodeling. Additionally, lung macrophages are instrumental in protecting against pathogens and play a critical role in resolution of inflammation and return to homeostasis. This review summarizes current literature detailing the roles and existing knowledge gaps for macrophages as key inflammatory orchestrators in asthma pathogenesis. We also raise the idea that modulating inflammatory responses in lung macrophages is important for alleviating asthma.

Involvement of CD40-CD40L and ICOS-ICOSL in the development of chronic rhinosinusitis by targeting eosinophils

Background

Chronic rhinosinusitis (CRS), whose prevalence and pathogenesis are age-related, is characterized by nasal tissue eosinophil infiltration. CD40-CD40 ligand (CD40L) pathway involves in the eosinophil-mediated inflammation, and inducible co-stimulator (ICOS)-ICOS ligand (ICOSL) signal can strengthen CD40-CD40L interaction. Whether CD40-CD40L and ICOS-ICOSL have a role in the development of CRS remains unknown.

Objectives

The aim of this study is to investigate the association of CD40-CD40L and ICOS-ICOSL expression with CRS and underlying mechanisms.

Methods

Immunohistology detected the expression of CD40, CD40L, ICOS, and ICOSL. Immunofluorescence was performed to evaluate the co-localizations of CD40 or ICOSL with eosinophils. Correlations between CD40-CD40L and ICOS-ICOSL as well as clinical parameters were analyzed. Flow cytometry was used to explore the activation of eosinophils by CD69 expression and the CD40 and ICOSL expression on eosinophils.

Results

Compared with the non-eCRS subset, ECRS (eosinophilic CRS) subset showed significantly increased CD40, ICOS, and ICOSL expression. The CD40, CD40L, ICOS, and ICOSL expressions were all positively correlated with eosinophil infiltration in nasal tissues. CD40 and ICOSL were mainly expressed on eosinophils. ICOS expression was significantly correlated with the expression of CD40-CD40L, whereas ICOSL expression was correlated with CD40 expression. ICOS-ICOSL expression positively correlated with blood eosinophils count and disease severity. rhCD40L and rhICOS significantly enhanced the activation of eosinophils from patients with ECRS. Tumor necrosis factor-α (TNF-α) and interleukin-5 (IL-5) obviously upregulated CD40 expression on eosinophils, which was significantly inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor.

Conclusions

Increased CD40-CD40L and ICOS-ICOSL expressions in nasal tissues are linked to eosinophils infiltration and disease severity of CRS. CD40-CD40L and ICOS-ICOSL signals enhance eosinophils activation of ECRS. TNF-α and IL-5 regulate eosinophils function by increasing CD40 expression partly via p38 MAPK activation in patients with CRS.

Immune cells and immune cell-targeted therapy in chronic pancreatitis

In recent years, studies have attempted to understand the immune cells and mechanisms underlying the pathogenesis of chronic pancreatitis (CP) by constructing a model of CP. Based on these studies, the innate immune response is a key factor in disease pathogenesis and inflammation severity. Novel mechanisms of crosstalk between immune and non-immune pancreatic cells, such as pancreatic stellate cells (PSC), have also been explored. Immune cells, immune responses, and signaling pathways in CP are important factors in the development and progression of pancreatitis. Based on these mechanisms, targeted therapy may provide a feasible scheme to stop or reverse the progression of the disease in the future and provide a new direction for the treatment of CP. This review summarizes the recent advances in research on immune mechanisms in CP and the new advances in treatment based on these mechanisms.

Eosinophils and eosinophil-associated disorders: immunological, clinical, and molecular complexity

Eosinophils and their mediators play a crucial role in various reactive states such as bacterial and viral infections, chronic inflammatory disorders, and certain hematologic malignancies. Depending on the underlying pathology, molecular defect(s), and the cytokine- and mediator-cascades involved, peripheral blood and tissue hypereosinophilia (HE) may develop and may lead to organ dysfunction or even organ damage which usually leads to the diagnosis of a HE syndrome (HES). In some of these patients, the etiology and impact of HE remain unclear. These patients are diagnosed with idiopathic HE. In other patients, HES is diagnosed but the etiology remains unknown — these patients are classified as idiopathic HES. For patients with HES, early therapeutic application of agents reducing eosinophil counts is usually effective in avoiding irreversible organ damage. Therefore, it is important to systematically explore various diagnostic markers and to correctly identify the disease elicitors and etiology. Depending on the presence and type of underlying disease, HES are classified into primary (clonal) HES, reactive HES, and idiopathic HES. In most of these patients, effective therapies can be administered. The current article provides an overview of the pathogenesis of eosinophil-associated disorders, with special emphasis on the molecular, immunological, and clinical complexity of HE and HES. In addition, diagnostic criteria and the classification of eosinophil disorders are reviewed in light of new developments in the field.

Immune cell infiltration and related core genes expression characteristics in eosinophilic and non-eosinophilic chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) refers to chronic inflammation of the sinonasal mucosa. It can either be eosinophilic (ECRSwNP) or non-eosinophilic (non-ECRSwNP). However, immune cell infiltration in the microenvironment and pathogenesis of ECRSwNP and non-ECRSwNP are still unclear. The aim of the present study was to assess the immune cell infiltration and molecular mechanisms of ECRSwNP and non-ECRSwNP. In the present study, 22 immune cell types in ECRSwNP and non-ECRSwNP were investigated by CIBERSORT based on transcriptome data. The core gene related pathophysiology of CRSwNP was analyzed using Weighted Gene Correlation Network Analysis according to the phenotype of the infiltrated eosinophils and nasal polyps (NP). A total of four types of immune cells (mast cells, activated dendritic cells, M2 macrophages and activated natural killer cells) were demonstrated to have a direct and indirect correlation with eosinophilic infiltration in ECRSwNP. M1 macrophages and activated CD4⁺ memory T cells were correlated with major immune cell types in non-ECRSwNP. NP could affect the expression of ‘olfactory receptor activity’ and ‘channel activity’ genes to impair the olfactory signaling pathway and neuroactive ligand receptor pathway. ‘Cell adhesion molecule binding’, ‘cytokine receptor binding’ and ‘glucocorticoid receptor binding’ were significantly enriched in ECRSwNP, whereas epithelial cell injury, autophagy and the mTOR pathway (hsa04140 and hsa04150) may serve an important role in the pathogenesis of non-ECRSwNP. There were significantly different immune cell infiltration and related core genes expression characteristics between ECRSwNP and non-ECRSwNP. The results of the present study provide an improved basis for elucidation of the mechanism and treatment of CRSwNP.

Mepolizumab for the treatment of eosinophilic granulomatosis with polyangiitis

INTRODUCTION

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis characterized by asthma, hypereosinophilia, and progressive multiorgan involvement. Although not fully elucidated, advancement in our understanding of the pathophysiology of EGPA has led to the development of multiple new treatment targets.

AREAS COVERED

Herein we review the epidemiology, clinical manifestations, pathophysiology, treatments, and ongoing research in the management of EGPA. The central role of Interleukin-5 (IL-5) in the development and maintenance of hypereosinophilia will be discussed. The value of mepolizumab, an anti-IL-5 monoclonal antibody, in the treatment of EGPA is reviewed in detail.

EXPERT OPINION

The available literature supports the use of mepolizumab for the induction and maintenance of remission of refractory, relapsing, or glucocorticoid-dependent EGPA with potentially greater benefit in those who are ANCA-positive or those with greater eosinophilia ( ≥ 150 cells/ μ L). Despite these positive results, relapses remain frequent, and the need for both short- and long-term glucocorticoid use remains common. More research is needed to address these needs and determine the precise role of mepolizumab.

Role of eosinophils in the initiation and progression of pancreatitis pathogenesis

Eosinophilic pancreatitis (EP) is reported in humans; however, the etiology and role of eosinophils in EP pathogenesis are poorly understood and not well explored. Therefore, it is interesting to examine the role of eosinophils in the initiation and progression of pancreatitis pathogenesis. Accordingly, we performed anti-major basic protein immunostaining, chloroacetate esterase, and Masson's trichrome analyses to detect eosinophils, mast cells, and collagen in the tissue sections of mouse and human pancreas. Induced eosinophils accumulation and degranulation were observed in the tissue sections of human pancreatitis, compared with no eosinophils in the normal pancreatic tissue sections. Similarly, we observed induced tissue eosinophilia along with mast cells and acinar cells atrophy in cerulein-induced mouse model of chronic pancreatitis. Additionally, qPCR and ELISA analyses detected induced transcript and protein levels of proinflammatory and profibrotic cytokines, chemokines like IL 5, IL-18, eotaxin-1, eotaxin-2, TGF-β1, collagen-1, collagen-3, fibronectin, and α-SMA in experimental pancreatitis. Mechanistically, we show that eosinophil-deficient GATA1 and endogenous IL-5-deficient mice were protected from the induction of proinflammatory and profibrotic cytokines, chemokines, tissue eosinophilia, and mast cells in a cerulein-induced murine model of pancreatitis. These human and experimental data indicate that eosinophil accumulation and degranulation may have a critical role in promoting pancreatitis pathogenesis including fibrosis. Taken together, eosinophil tissue accumulation needs appropriate attention to understand and restrict the progression of pancreatitis pathogenesis in humans. NEW & NOTEWORTHY The present study for the first time shows that eosinophils accumulate in the pancreas and promote disease pathogenesis, including fibrosis in earlier reported cerulein-induced experimental models of pancreatitis. Importantly, we show that GATA-1 and IL-5 deficiency protects mice form the induction of eosinophil active chemokines, and profibrotic cytokines, including accumulation of tissue collagen in an experimental model of pancreatitis. Additionally, we state that cerulein-induced chronic pancreatitis is independent of blood eosinophilia.

Integrated Cellular and Plasma Proteomics of Contrasting B-cell Cancers Reveals Common, Unique and Systemic Signatures

Approximately 800,000 leukemia and lymphoma cases are diagnosed worldwide each year. Burkitt's lymphoma (BL) and chronic lymphocytic leukemia (CLL) are examples of contrasting B-cell cancers; BL is a highly aggressive lymphoid tumor, frequently affecting children, whereas CLL typically presents as an indolent, slow-progressing leukemia affecting the elderly. The B-cell-specific overexpression of the myc and TCL1 oncogenes in mice induce spontaneous malignancies modeling BL and CLL, respectively. Quantitative mass spectrometry proteomics and isobaric labeling were employed to examine the biology underpinning contrasting Eμ-myc and Eμ-TCL1 B-cell tumors. Additionally, the plasma proteome was evaluated using subproteome enrichment to interrogate biomarker emergence and the systemic effects of tumor burden. Over 10,000 proteins were identified (q<0.01) of which 8270 cellular and 2095 plasma proteins were quantitatively profiled. A common B-cell tumor signature of 695 overexpressed proteins highlighted ribosome biogenesis, cell-cycle promotion and chromosome segregation. Eμ-myc tumors overexpressed several methylating enzymes and underexpressed many cytoskeletal components. Eμ-TCL1 tumors specifically overexpressed ER stress response proteins and signaling components in addition to both subunits of the interleukin-5 (IL5) receptor. IL5 treatment promoted Eμ-TCL1 tumor proliferation, suggesting an amplification of IL5-induced AKT signaling by TCL1. Tumor plasma contained a substantial tumor lysis signature, most prominent in Eμ-myc plasma, whereas Eμ-TCL1 plasma contained signatures of immune-response, inflammation and microenvironment interactions, with putative biomarkers in early-stage cancer. These findings provide a detailed characterization of contrasting B-cell tumor models, identifying common and specific tumor mechanisms. Integrated plasma proteomics allowed the dissection of a systemic response and a tumor lysis signature present in early- and late-stage cancers, respectively. Overall, this study suggests common B-cell cancer signatures exist and illustrates the potential of the further evaluation of B-cell cancer subtypes by integrative proteomics.

Pathogenesis of eosinophilic chronic rhinosinusitis

Eosinophilic chronic rhinosinusitis (ECRS) is considered a refractory and intractable disease. Patients with ECRS present with thick mucus production, long-term nasal congestion, loss of sense of smell, and intermittent acute exacerbations secondary to bacterial infections. Despite medical and surgical interventions, there is a high rate of recurrence with significant impairment to quality of life. The recent increasing prevalence of ECRS in south Asian countries and the strong tendency of ECRS to reoccur after surgery should be considered. The majority of cases need repeat surgery, and histological examinations of these cases show eosinophilic-dominant inflammation. The degradation and accumulation of eosinophils, release of cytokines, and mucus secretion have important roles in the pathogenesis of ECRS. ECRS differs from non-ECRS, in which eosinophils are not involved in the pathogenesis of the disease, and also in terms of many clinical characteristics, blood examination and nasal polyp histological findings, clinical features of the disease after surgery, efficacy of medications, and computed tomography findings. This review describes the clinical course, diagnosis, and treatment of ECRS as well as its pathophysiology and the role of eosinophils, mucus, cytokines, and other mediators in the pathogenesis of ECRS.

Helminth Products Protect against Autoimmunity via Innate Type 2 Cytokines IL-5 and IL-33, Which Promote Eosinophilia

Epidemiologic studies in humans have demonstrated that infection with helminth parasites is associated with a reduced risk of developing autoimmune diseases. Mechanistic studies in mice have linked the protective effect of helminths on autoimmunity to the suppressive activity of helminth-induced regulatory T cells (Tregs) or Th2 cells. In this study, we demonstrate that treatment of mice with Fasciola hepatica excretory-secretory products (FHES) attenuated the clinical signs of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. Protection was associated with a significant reduction in the infiltration of pathogenic Th1 and Th17 cells into the brain. Although FHES enhanced anti-inflammatory cytokine and Th2 responses, protection against EAE was independent of IL-4, IL-10, and Tregs. However, administration of FHES induced production of the type 2 cytokines IL-33 and IL-5, which promoted accumulation of eosinophils. FHES-induced expansion of eosinophils and protection against EAE was lost in IL-33(-/-) mice and upon neutralization of IL-5. Furthermore, transfer of FHES-induced or IL-33-induced eosinophils conferred protection against EAE. In addition, treatment of mice with recombinant IL-33 attenuated autoimmunity, and this was dependent on IL-5. To our knowledge, this study is the first to report a role for helminth-induced IL-5 and IL-33 in protection against autoimmunity.

Elements Involved In Promoting Eosinophilic Gastrointestinal Disorders

Eosinophilic gastrointestinal disorders (EGID) are food allergen-induced allergic gastrointestinal disorders, characterized by accumulation of highly induced eosinophils in different segments of gastrointestinal tract along with eosinophil microabssess and extracellular eosinophilic granules in the epithelial layer. EGID are both IgE- and cell-mediated group of diseases that include eosinophilic esophagitis (EoE), eosinophilic gastritis (EG), eosinophilic gastroenteritis (EGE) and eosinophilic colitis (EC). Despite the increased incidences and considerable progress made in understanding EGID pathogenesis. The mechanism is still not well understood. It has been shown that IL-4, IL-5, IL-13, IL-15, IL-18, eotaxin-1, eotaxin-2 and eotaxin-3 play a critical role in EGID pathogenesis. Currently, the only criterion for diagnosing EoE, EGE and EC are repetitive endoscopic and histopathological evaluation of biopsies along with other clinical characteristics/manifestations. Antigen elimination and corticosteroid therapies are the most effective therapies currently in practice for the treatment of EGID. The cytokines (anti-IL-5 and anti-IL-13) therapy trials were not very successful in case of EoE. Most recently, a clinical trial using anti-IL-13 reported only 60% reduced esophageal eosinophilia without achieving primary endpoint. This clinical finding is not surprising and is in accordance with our earlier report indicating that IL-13 is not critical in the initiation of EoE. Notably, EGID still has no reliable noninvasive diagnostic biomarkers. Hence, there is a great necessity to identify novel noninvasive diagnostic biomarkers that can easily diagnose EGID and provide an effective therapy. Now, the attention is required to target cell types like iNKT cells that produce eosinophil active cytokines and is found induced in the pathogenesis of both experimental and human EoE. iNKT cell neutralization is shown to protect allergen-induced EoE in experimental model. In this review, we have discussed the key elements that are critical in the disease initiation, progression, pathogenesis and important for future diagnostic and therapeutic interventions for EGID.

B cells secrete eotaxin-1 in human inflammatory bowel disease

BACKGROUND

Our previous studies have demonstrated that B cells in human inflammatory bowel disease (IBD) are highly activated and produce copious amounts of chemokines. Here, we showed that B cells produce eotaxin-1, a selective chemokine for acute eosinophilia. Increased levels of activated eosinophils have been found in the intestinal mucosa in patients with IBD, but their role(s) and the regulation of their migration patterns remain poorly defined.

METHODS

To determine how B-cell secretion of eotaxin-1 influences eosinophil activation and migration, we performed immunoepidemiological approaches coupled with in vitro studies. B cells and eosinophils from patients with Crohn's disease and ulcerative colitis were isolated, and responses to Toll-like receptor ligands (TLR) were measured and assessed for the relationship with clinical disease.

RESULTS

Eotaxin-1 from recirculating B cells, and TLR ligands, regulated eosinophil homing mechanisms in IBD. B cells stimulated with hypo-acylated lipopolysaccharide (LPS) produced copious amounts of eotaxin-1, which influenced eosinophil activation profiles in the bloodstream. We also found that hexa-acylated LPS, such Escherichia coli LPS, directly activated TLR2-expressing and TLR4-expressing eosinophils from patients with IBD to express a different repertoire of mucosal homing receptors, namely CCR9 and CCR10. Whereas B-cell production of eotaxin-1 was correlated with reduced disease activity, eosinophil activation by hexa-acylated LPS was associated with increased disease activity.

CONCLUSIONS

These results suggest that systemic TLR ligands influence eosinophil migration patterns, both directly and indirectly, through B cells. Our report uncovers unexpected mechanisms of cross talk between certain immune cells that shed new light on IBD immunology.

Ste20-like kinase SLK, at the crossroads: a matter of life and death

Reorganization of the cytoskeleton is necessary for apoptosis, proliferation, migration, development and tissue repair. However, it is well established that mutations or overexpression of key regulators contribute to the phenotype and progression of several pathologies such as cancer. For instance, c-src mutations and the overexpression of FAK have been implicated in the invasive and metastatic process, suggesting that components of the motility system may represent a new class of therapeutic targets. Over the last several years, we and others have established distinct roles for the Ste20-like kinase SLK, encompassing apoptosis, growth, motility and development. Here, we review the SLK field from its initial cloning to the most recent findings from our laboratory. We summarize the various roles of SLK and the biochemical mechanisms that regulate its activity. These various findings reveal very complex functions and pattern of regulation for SLK in development and cancer, making it a potential therapeutic target.

Identification of novel chromenone derivatives as interleukin-5 inhibitors

A series of (E)-5-alkoxy-3-(3-phenyl-3-oxoprop-1-enyl)-4H-chromen-4-ones (4) and (E)-5-alkoxy-3-(3-hydroxy-3-phenylprop-1-enyl)-4H-chromen-4-ones (5) were synthesized and evaluated for their IL-5 inhibitory activity. Propenone analogs 4 possess some of the structurally important characteristics of isoflavone 2 and chalcone 3 previously known as potent IL-5 inhibitor. However, the inhibitory activity of 4 was weak and therefore this structural hybridization appears to be ineffective for the design of IL-5 inhibitor. Meanwhile the potent activity profile of compounds 5 was discovered. This enhanced activity of 5 compared to 4 could be due to the effective location of hydroxyl group of allylic alcohol moiety of 5 in the 3D structure. The electron withdrawing substituents at position 4 of phenyl ring of 5 enhances the activity possibly due to an increase in the strength of hydrogen bonding property of hydroxyl group of allylic alcohol moiety.

Pathogenesis and classification of eosinophil disorders: a review of recent developments in the field

Eosinophils and their products play an essential role in the pathogenesis of various reactive and neoplastic disorders. Depending on the underlying disease, molecular defect and involved cytokines, hypereosinophilia may develop and may lead to organ damage. In other patients, persistent eosinophilia is accompanied by typical clinical findings, but the causative role and impact of eosinophilia remain uncertain. For patients with eosinophil-mediated organ pathology, early therapeutic intervention with agents reducing eosinophil counts can be effective in limiting or preventing irreversible organ damage. Therefore, it is important to approach eosinophil disorders and related syndromes early by using established criteria, to perform all appropriate staging investigations, and to search for molecular targets of therapy. In this article, we review current concepts in the pathogenesis and evolution of eosinophilia and eosinophil-related organ damage in neoplastic and non-neoplastic conditions. In addition, we discuss classifications of eosinophil disorders and related syndromes as well as diagnostic algorithms and standard treatment for various eosinophil-related disorders.

Controversies and open questions in the definitions and classification of the hypereosinophilic syndromes and eosinophilic leukemias

Eosinophilia is frequently detectable in certain myeloid neoplasms and various reactive conditions, but it may also occur in the absence of an apparent underlying disease, or, rarely, as a paraneoplastic feature with solid tumors. In myeloid neoplasms, eosinophils are considered to belong to the malignant clone in most cases, whereas in all other conditions, eosinophilia is a reactive process triggered by eosinopoietic cytokines. Excessive accumulation of eosinophils, also termed hypereosinophilia (HE), is typically seen in eosinophilic leukemias, but it may also occur in other neoplasms and reactive disorders. HE-related end organ damage may develop in patients with reactive HE but also in those with hematologic malignancies. During the past few years, our knowledge about HE and HE-related organ damage in hematologic and nonhematologic disorders has improved considerably. Moreover, proposals for the definition and classification of eosinophil disorders have been generated by various expert groups and by the World Health Organization (WHO). However, several questions related to eosinophils and HE remain open, and many aspects of the definition and classification of eosinophil disorders and related pathologies remain controversial. In the current article, these open issues are discussed with special reference to the 2008 WHO classification of myeloid neoplasms and other classifications proposed by immunologists and various expert panels, as well as definitions and criteria recently proposed in a multidisciplinary consensus proposal.

Mepolizumab in eosinophilic disorders

Mepolizumab (Bosatria(®), GlaxoSmithKline) is a biologic agent developed to treat asthma. It represents a humanized monoclonal antibody of IgG1 κ type, which targets human IL-5 and thus prevents its interaction with the α-chain of the IL-5 receptor. To date, it has not been approved for use in any eosinophil-related disorder; however, several studies have suggested some therapeutic benefit across a spectrum of eosinophil-related disorders. This article evaluates the currently available preclinical and clinical studies, and the impact of mepolizumab against a variety of eosinophilic disorders.

Eosinophils in health and disease: the LIAR hypothesis

Discussions of eosinophils are often descriptions of end-stage effector cells with destructive capabilities mediated predominantly by released cytotoxic cationic granule proteins. Moreover, eosinophils in the medical literature are invariably associated with the pathologies linked with helminth infections or allergic diseases such as asthma. This has led to an almost fatalist view of eosinophil effector functions and associated therapeutic strategies targeting these cells that would make even William of Ockham proud - eosinophil effector functions have physiological consequences that increase patient morbidity/mortality and 'the only good eosinophils are dead eosinophils'. Unfortunately, the strengths of dogmas are also their greatest weaknesses. Namely, while the repetitive proclamation of dogmatic concepts by authoritative sources (i.e. reviews, meeting proceedings, textbooks, etc.) builds consensus within the medical community and lower the entropies surrounding difficult issues, they often ignore not easily explained details and place diminished importance on alternative hypotheses. The goal of this perspective is twofold: (i) we will review recent observations regarding eosinophils and their activities as well as reinterpret earlier data as part of the synthesis of a new paradigm. In this paradigm, we hypothesize that eosinophils accumulate at unique sites in response to cell turnover or in response to local stem cell activity(ies). We further suggest that this accumulation is part of one or more mechanisms regulating tissue homeostasis. Specifically, instead of immune cells exclusively mediating innate host defence, we suggest that accumulating tissue eosinophils are actually regulators of Local Immunity And/or Remodeling/Repair in both health and disease - the LIAR hypothesis; (ii) we want to be inflammatory (pun intended!) and challenge the currently common perspective of eosinophils as destructive end-stage effector cells. Our hope is to create more questions than we answer and provoke everyone to spend countless hours simply to prove us wrong!

What targeting eosinophils has taught us about their role in diseases

Eosinophil-associated disease is a term used to encompass a range of disorders from hypereosinophilic syndrome to asthma. Despite the longstanding belief that eosinophils can be primary contributors to disease pathophysiology, it is only in recent years that direct and selective reduction or elimination of eosinophils can be achieved in animals or human subjects. These developments have been made possible in mice through clever targeting of eosinophil production. Antibodies and other agents that target soluble eosinophil-related molecules, such as IL-5, or cell-surface structures, such as CCR3, have also proved useful in reducing blood and tissue eosinophil counts. In human subjects the only eosinophil-selective agents tested in clinical trials thus far are neutralizing antibodies to IL-5, with promising but mixed results. At the very least, such forms of pharmacologic hypothesis testing of the role of eosinophils in certain airway, gastrointestinal, and hematologic diseases has finally provided us with new insights into disease pathogenesis. At its optimistic best, these and other targeted agents might someday become available for those afflicted with eosinophil-associated disorders. This review summarizes what has been learned in vivo in both preclinical and clinical studies of eosinophil-directed therapies, with an emphasis on recent advances.

Acute stress affects the physiology and behavior of allergic mice

Physical and psychological stressors have been implicated in acute asthma exacerbation. The objective of the current study was to determine the effects of forced swimming stress (FST) on allergic pulmonary inflammation in BALB/c mice. Eighty female mice were allocated to one of four treatments arranged in a 2 x 2 factorial consisting of two levels of allergy and two levels of stress. The effects of stress and allergy were assessed by examination of cytokines and leukocyte differentials in the bronchoalveolar lavage fluid, corticosterone and immunoglobulin (Ig) E in the plasma, leukocyte differentials in the peripheral blood, natural killer cytotoxicity, and histopathology of the lungs. Behavior was recorded during the FST. Stress and allergy increased plasma corticosterone in mice. Allergy increased IgE concentrations and pulmonary inflammation. Interleukin-4 was greater among allergic stressed and non-stressed mice and stressed, non-allergic mice compared with non-stressed, non-allergic mice. Interleukin-5 (IL-5) and 6 (IL-6) were greater among allergic stressed and non-stressed mice compared with non-allergic mice. Interleukin-5 and 6 were reduced among stressed-allergic mice compared with non-stressed, allergic mice. Stress and allergy shifted mice towards a T-helper 2 response as shown by increased interleukin-4. Stress reduced IL-5 and IL-6 in allergic mice but not non-allergic mice. Pulmonary inflammation was not reduced among allergic stressed mice in spite of elevated glucocorticoids. Mice induced to be allergic responded to FST differently than non-allergic mice. Our findings suggest that stress induces a differential response among allergic and non-allergic mice.

Pathogenesis, classification, and therapy of eosinophilia and eosinophil disorders

Eosinophilia is a recurrent feature and diagnostic clue in several hematologic malignancies. In stem cell- and myelopoietic neoplasms, eosinophils are derived from the malignant clone, whereas in lymphoid neoplasms and reactive states, eosinophilia is usually triggered by eosinopoietic cytokines. Myeloid neoplasms typically presenting with eosinophilia include chronic myeloid leukemia, chronic eosinophilic leukemia (CEL), other myeloproliferative neoplasms, some acute leukemias, advanced mast cell disorders, and rare forms of myelodysplastic syndromes. Diagnostic evaluations in unexplained eosinophilia have to take these diagnoses into account. In such patients, a thorough hematologic work-up including bone marrow histology and immunohistochemistry, cytogenetics, molecular markers, and a complete staging of potentially affected organ systems has to be initiated. Endomyocardial fibrosis, the most dangerous cardiovascular complication of the hypereosinophilic state, is frequently detected in PDGFR-mutated neoplasms, specifically in FIP1L1/PDGFRA+ CEL, but is usually not seen in other myeloid neoplasms or reactive eosinophilia, even if eosinophilia is recorded for many years. Treatment of hypereosinophilic patients depends on the variant of disease, presence of end organ damage, molecular targets, and the overall situation in each case. In a group of patients, oncogenic tyrosine kinases (TK) such as FIP1L1/PDGFRA, can be employed as therapeutic targets by using imatinib or other TK-blocking agents.

Allergy, asthma, and inflammation: which inflammatory cell type is more important?

: A recent review in Allergy, Asthma, and Clinical Immunology suggested that eosinophils play a minor role, if any, in the inflammatory spectrum of asthma and allergic inflammation. The article that dealt with mast cells suggested that the presence of these important cells within the smooth muscle layer in asthmatic airways renders this cell type primal in asthma and an obvious and important target for therapy. This article proposes that in a complex inflammatory milieu characterizing the complex syndromes we call asthma, no single cell phenotype is responsible for the condition and thus should be a sole target for therapeutic strategies. Our reductionist approach to research in asthma and related conditions has provided us with convincing evidence for multiple roles that immune, inflammatory, and structural cell types can play in complex diseases. The next stage in understanding and ameliorating these complex conditions is to move away from the simplistic notion of one cell type being more important than another. Instead, what is needed is to acquire knowledge of intricate and exquisite biological systems that regulate such conditions in both health and disease involving various cell types, mediators, pharmacologically active products, their multifaceted capacities, and their socio-biological networking.

Measurement of Feline Serum Interleukin-5 Level

A bioassay was developed to measure feline interleukin-5 (IL-5). Human IL-5 receptor alpha chain transfected murine Ba/F3 cells (Ba/F3-IL-5R) showed feline IL-5-dependent proliferation in a dose-dependent manner. IL-5 levels in serum samples from 54 cats with suspected allergic dermatitis and from 11 control cats could be successfully measured using Ba/F3-IL-5R cells. The number of eosinophils in peripheral blood was not correlated with serum IL-5 level.

Sublingual immunotherapy in children modulates allergen-induced in vitro expression of cytokine mRNA in PBMC

BACKGROUND

During subcutaneous immunotherapy (SCIT), there is a local mucosal shift from Th2 to Th1 type cytokine predominance and downregulation of interleukin (IL)-5 and eosinophilia. According to recent studies IL-10- and transforming growth factor (TGF)-beta-induced tolerance is another key phenomenon in SCIT. Few data to date is available on mechanisms and roles of these cytokines in sublingual immunotherapy (SLIT).

SCOPE

This study was undertaken to analyse the allergen-induced in vitro mRNA expression of IL-4, IL-5, IL-10, TGF-beta and interferon (IFN)-gamma during SLIT in peripheral blood mononuclear cells (PBMC) of children with allergic rhinitis (AR).

METHODS

Ten patients with AR undergoing pollen SLIT with a weekly dose of 200,000 SQ-U, 10 with a weekly dose of 24,000 SQ-U of glycerinated mixture of Betula verrucosa, Corylus avellana and Alnus glutinosa and 10 with placebo were included in the study. Peripheral blood mononuclear cell samples were collected and stimulated with pollen allergen extract prior to the treatment, after 1 and 2 years of the treatment. The cytokine mRNA expression was assessed using kinetic real time reverse transcription polymerase chain reaction (RT-PCR; TaqMan).

RESULTS

The in vitro allergen-induced mRNA expression of IL-5 by PBMC in the placebo group at 1 (P = 0.0065) and 2 (P = 0.013) years of therapy were increased in comparison with the highest dose. The expression of IL-10 mRNA was increased in the highest dose group (P = 0.0016) and the lower dose group (P = 0.034) at 2 years of therapy when compared with placebo. The change in the expression of allergen-induced TGF-beta had an inversed correlation with the change of IL-5 (r = -0.38, P = 0.036) and positive correlation with the change of IL-10 (r = 0.58, P = 0.0019).

CONCLUSIONS

Sublingual immunotherapy induced a dose-dependent systemic allergen-specific immunological response in children with AR. During high-dose SLIT, there was activation of regulatory cytokine IL-10 and an inhibitory effect on IL-5 expression increase that was associated with TGF-beta.

The rise of the phoenix: the expanding role of the eosinophil in health and disease

We have entered a new phase in the evolution of our understanding of the role of the eosinophil with a greater appreciation of novel potential functions that may be ascribed to this enigmatic cell type. This review not only provides an update to our current understanding of the various immunobiological roles for the eosinophil, but also attracts attention to some novel observations predicting functions beyond its putative effector role. These observations include the intriguing possibility that the eosinophil may possess the capacity to regulate the immune and inflammatory responses in diseases such as asthma.

Interleukin-13-dependent expression of matrix metalloproteinase-12 is required for the development of airway eosinophilia in mice

We investigated the expression and function of matrix metalloproteinase-12 (MMP-12) in a model of allergic airway inflammation. Mice were sensitized mucosally by exposure to aerosolized ovalbumin (OVA) daily over a period of 10 d in the context of adenovirus-mediated granulocyte macrophage colony-stimulating factor (GM-CSF) expression. The ensuing inflammatory response is characterized by a Th2 cytokine profile, OVA-specific IgE, and airway eosinophilia. Using real-time, quantitative reverse transcriptase-polymerase chain reaction we assessed MMP-12 mRNA expression in whole lung tissue. We observed a 12- and 70-fold increase in expression at Days 7 and 11, respectively, in OVA-exposed mice when compared with naive controls. Immunoblot analysis revealed an increase in MMP-12 protein in the bronchoalveolar lavage fluid of mice exposed to OVA in the context of GM-CSF. No such elevation was observed in mice exposed to saline only in the context of GM-CSF. To assess functional role of MMP-12, MMP-12 knockout (KO) mice were subjected to the aforementioned protocol. We observed an 80% reduction in eosinophils in the bronchoalveolar lavage fluid of KO mice compared with their wild-type littermates. Using interleukin-13 KO mice, we demonstrated that expression of MMP-12 is interleukin-13-dependent. Collectively, our data indicate a novel function for MMP-12 in the process of airway eosinophil accumulation.

Constitutive activation of the SRC family kinase Hck results in spontaneous pulmonary inflammation and an enhanced innate immune response

To identify the physiological role of Hck, a functionally redundant member of the Src family of tyrosine kinases expressed in myelomonocytic cells, we generated Hck(F/F) "knock-in" mice which carry a targeted tyrosine (Y) to phenylalanine (F) substitution of the COOH-terminal, negative regulatory Y(499)-residue in the Hck protein. Unlike their Hck(-/-) "loss-of-function" counterparts, Hck(F/F) "gain-of-function" mice spontaneously acquired a lung pathology characterized by extensive eosinophilic and mononuclear cell infiltration within the lung parenchyma, alveolar airspaces, and around blood vessels, as well as marked epithelial mucus metaplasia in conducting airways. Lungs from Hck(F/F) mice showed areas of mild emphysema and pulmonary fibrosis, which together with inflammation resulted in altered lung function and respiratory distress in aging mice. When challenged transnasally with lipopolysaccharide (LPS), Hck(F/F) mice displayed an exaggerated pulmonary innate immune response, characterized by excessive release of matrix metalloproteinases and tumor necrosis factor (TNF)alpha. Similarly, Hck(F/F) mice were highly sensitive to endotoxemia after systemic administration of LPS, and macrophages and neutrophils derived from Hck(F/F) mice exhibited enhanced effector functions in vitro (e.g., nitric oxide and TNFalpha production, chemotaxis, and degranulation). Based on the demonstrated functional association of Hck with leukocyte integrins, we propose that constitutive activation of Hck may mimic adhesion-dependent priming of leukocytes. Thus, our observations collectively suggest an enhanced innate immune response in Hck(F/F) mice thereby skewing innate immunity from a reversible physiological host defense response to one causing irreversible tissue damage.

Synergistic effect of theophylline and procaterol on interleukin-5-induced degranulation from human eosinophils

Inhibiting the release of toxic granule proteins from eosinophils is a possible means of treating allergic inflammation. This study was performed to examine whether procaterol and theophylline, commonly used bronchodilators in asthma, inhibit eosinophil degranulation induced by interleukin (IL)-5. Purified eosinophils from patients with asthma were incubated with IL-5 for 24 hr in the presence of theophylline, procaterol, combinations of theophylline and procaterol, or dexamethasone. Levels of eosinophil-derived neurotoxin (EDN) in the supernatants were measured with radioimmunoassay. Theophylline inhibited IL-5-induced release of EDN in a concentration-dependent manner. Procaterol inhibited degranulation only at high concentrations. However, procaterol at 10(-9) M and 10(-8) M, which are physiologic concentrations, together with theophylline at 10(-5) M, which is a concentration commonly found in the serum of patients receiving low-dose theophylline, inhibited degranulation by 43.8%. This finding indicates that theophylline and procaterol have synergistic effects. The inhibition was comparable to that with dexamethasone at 10(-9) M. Our results suggest that a combination of low-dose theophylline and procaterol exhibits antiinflammatory effects in asthma by inhibiting eosinophil-effector functions.

Cloning of the rat IL-5Ralpha gene: analysis of 5'-upstream region and expression by B cells

Although rats are widely used for the analysis of allergic reactions and parasitic infections where IL-5 is involved, nothing is currently known of the expression of IL-5 receptor in this species. In this study, the cDNA sequence, genomic structure and the transcriptional regulation of the rat IL-5Ralpha were analyzed. The rat IL-5Ralpha gene, which we localized to chromosome 4q34-q41, spans more than 25 kb and consists of 12 exons. Promoter activity was seen in different cell lines and analysis by deletion experiments allowed to identify two negative regulatory regions which did not differ when tested either with IL-5Ralpha-negative or positive cells. Finally, the investigation of the expression of IL-5Ralpha showed that it is expressed in lung, spleen, liver, and purified rat B cells from normal rat. This can provide an explanation for the role of rat IL-5 as B-cell growth factor and a relevant model in order to better understand the activity of IL-5 on human B cells.

Th2 cytokines and asthma. The role of interleukin-5 in allergic eosinophilic disease

Interleukin-5 is produced by a number of cell types, and is responsible for the maturation and release of eosinophils in the bone marrow. In humans, interleukin-5 is a very selective cytokine as a result of the restricted expression of the interleukin-5 receptor on eosinophils and basophils. Eosinophils are a prominent feature in the pulmonary inflammation that is associated with allergic airway diseases, suggesting that inhibition of interleukin-5 is a viable treatment. The present review addresses the data that relate interleukin-5 to pulmonary inflammation and function in animal models, and the use of neutralizing anti-interleukin-5 monoclonal antibodies for the treatment of asthma in humans.

Identification of regions within the third FnIII-like domain of the IL-5Ralpha involved in IL-5 interaction

Previously, two binding sites for interleukin 5 (IL-5) were identified on the IL-5 receptor alpha chain (IL-5Ralpha). They are located within the CD loop of the first fibronectin type III (FnIII)-like domain and the EF loop of the second FnIII-like domain. The first binding site was identified by exploiting the different abilities of human IL-5Ralpha (hIL-5Ralpha) and mouse IL-5Ralpha (mIL-5Ralpha) to bind hIL-5. Here we show that ovine IL-5 (oIL-5) has the ability to activate the hIL-5Ralpha but not the mIL-5Ralpha. By using chimeras of the mIL-5Ralpha and hIL-5Ralpha we demonstrate that residues within the first and third FnIII-like domains of mIL-5Ralpha are responsible for this lack of activity. Furthermore, mutation of residues on hIL-5Ralpha to mIL-5Ralpha within the predicted DE and FG loop regions of the third FnIII domain reduces oIL-5 activity. These results show that regions of the third FnIII domain of IL-5Ralpha are involved in binding, in addition to the regions in domains one and two of the IL-5Ralpha that were identified in an earlier study.

Inhibition of antigen-induced eosinophilia and late phase airway hyperresponsiveness by an IL-5 antisense oligonucleotide in mouse models of asthma

Chronic airway eosinophilia is associated with allergic asthma and is mediated in part by secretion of IL-5 from allergen-specific Th2 lymphocytes. IL-5 is a known maturation and antiapoptotic factor for eosinophils and stimulates release of nascent eosinophils from bone marrow into the peripheral circulation. An antisense oligonucleotide found to specifically inhibit IL-5 expression in vitro was observed to significantly reduce experimentally induced eosinophilia in vivo, in both the murine OVA lung challenge and allergic peritonitis models. Intravenous administration resulted in sequence-dependent inhibition of eosinophilia coincident with reduction of IL-5 protein levels, supporting an antisense mechanism of action. Potent suppression of lung eosinophilia was observed up to 17 days after cessation of oligonucleotide dosing, indicating achievement of prolonged protection with this strategy. Furthermore, sequence-specific, antisense oligonucleotide-mediated inhibition of Ag-mediated late phase airway hyperresponsiveness was also observed. These data underscore the potential utility of an antisense approach targeting IL-5 for the treatment of asthma and eosinophilic diseases.

Could the airway epithelium play an important role in mucosal immunoglobulin A production?

Immunoglobulin (Ig) A is the major immunoglobulin of the healthy respiratory tract and is thought to be the most important immunoglobulin for lung defence. The basis for the preferential generation of IgA-secreting cells in the airway mucosa remains unclear. Given the half-life of 5 days for the majority of IgA plasma cells, many IgA plasma cells must develop daily from B cells to guarantee a continuous supply of IgA antibodies in the airway mucosa. For this, the surrounding cells must provide a constant supply of cytokines necessary for B-cell isotype switch, growth and differentiation into IgA-secreting plasma cells. Studies with CD4+ T-cell knockout mice, T-cell receptor knockout mice and mice made transgenic for CTLA4-Ig demonstrate normal mucosal IgA isotype switch, differentiation and IgA production, thereby suggesting that T cells are not critical for mucosal IgA production, and that other cell sources may be more important. Also, the bronchus-associated lymphoid tissue (BALT), which is believed to be the major site where IgA isotype switch and differentiation of B cells into plasma cells occur with the help of cytokines released by T cells, is not a constitutive feature of the normal human lung. This indicates that other parts of the respiratory tract must carry out the BALT function. We have recently demonstrated that healthy human airway epithelial cells constitutively produce IL-5, a major cytokine implicated in the growth and differentiation of post-switch mIgA+ B cells to IgA-producing plasma cells. Several studies have recently reported that the human airway epithelium also constitutively produces IL-2, TGFbeta, IL-6 and IL-10, factors which are essential for B-cell clonal proliferation, IgA isotype switch and differentiation into IgA-producing plasma cells. The close proximity of B cells to the airway epithelium probably ensures a constant supply of growth and differentiation factors necessary for mucosal IgA production. In addition, the epithelial cells produce a glycoprotein, called the secretory component, which not only confers increased stability to S-IgA, but is also quantitatively the most important receptor of the mucosal immune system, since it is responsible for the external transport of locally produced polymeric IgA and IgM. Recent studies also suggest a possible role for epithelial cells in antigen presentation. Dendritic cells situated within the airway epithelium could directly present antigens to B cells and direct their isotype switch towards IgA1 and IgA2 with the help of cytokines produced by epithelial cells. Airway epithelial cells could therefore play a major role in the production of mucosal IgA antibodies which are essential for airway mucosal defence.

Preparation of recombinant rat interleukin-5 by baculovirus expression system and analysis of its biological activities

Rat interleukin-5 (IL-5) cDNA was subcloned from peritoneal cells collected 4 h after intraperitoneal injection of Ascaris suum antigen solution into the immunized rats. Cysteine proteinase-deleted (CPd) rat IL-5 recombinant virus was constructed by inserting rat IL-5 cDNA into CPd virus having a deletion in the cysteine proteinase gene of the silkworm Bombyx mori nuclear polyhedrosis virus. On infection with the CPd rat IL-5 recombinant virus, the silkworm B. mori larvae produced rat IL-5 as a dimeric form in hemolymph. Recombinant rat IL-5 was purified more than 95.5% by anion-exchange chromatography and hydrophobic chromatography. The purified recombinant rat IL-5 promoted the proliferation of T88-M cells in a concentration-dependent manner, and its effect was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. When bone marrow cells from normal rats were incubated with recombinant rat IL-5 in medium containing methylcellulose, the colony formation by eosinophilic cells was induced. Furthermore, when rat peritoneal eosinophils were incubated with recombinant rat IL-5, the spontaneous decrease in the eosinophil viability was inhibited in time- and concentration-dependent manners. In addition, the recombinant rat IL-5-induced eosinophil survival was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. These findings suggest that rat IL-5 acts as B-cell growth factor II (BCGF-II), eosinophil differentiation factor (EDF), and eosinophil survival-enhancing factor.

Biology of IL-5 in health and disease

LEARNING OBJECTIVES

Reading this article will increase the readers' knowledge of the biology of interleukin-5 (IL-5), an important cytokine. The immune and inflammatory responses of any organism are the basis of the defense mechanism ensuring its survival. The role of IL-5 in these processes, as well as in the pathogenesis of various diseases has been discussed along with the effects of various pharmacologic agents on the production and function of IL-5.

DATA SOURCES

A detailed literature search was performed. Studies considered relevant and important, in all languages, which involved humans and animals were used.

STUDY SELECTION

Information was obtained only from peer reviewed journals.

RESULTS

Interleukin-5 is normally produced by T-cells, mast cells, and eosinophils while Reed Sternberg and Epstein Barr virus (EBV) transformed cells also produce IL-5. Monoclonal antibodies (mAb) to IL-5 are potent inhibitors of IL-5 mediated tissue damage, secondary to eosinophil infiltration. The majority of the studies on IL-5 are preliminary, often the information is obtained from animal studies or in vitro systems and occasionally from pathologic tissue analysis. This along with the absence of confirmatory studies is a limiting factor. Nonetheless, the role of IL-5 in allergic and immunologic disease and asthma may be central to their pathogenesis.

CONCLUSIONS

Interleukin-5 is an important molecule that is participant to many processes that maintain health and are involved directly or indirectly in the pathogenesis of disease. Some pharmacologic agents can modify IL-5 production in vivo. Development of selective inhibitors of IL-5 may have a potential use for specific therapy of certain autoimmune, inflammatory, and neoplastic diseases.

Biological and molecular characteristics of interleukin-5 and its receptor

Interleukin-5 (IL5) is a T cell-derived cytokine involved in the pathogenesis of atopic diseases. It specifically controls the production, the activation and the localization of Eosinophils. The Eosinophils are the major cause of tissue damage resulting in the symptoms of asthma and related allergic disorders. T cells purified from bronchoalveolar lavage and peripheral blood of asthmatics secrete elevated amount of IL5. Therefore IL5 emerges to be an attractive target for the generation of new anti-allergic drugs. Agents which inhibit either the production or the activity of IL5 could be expected to ameliorate the pathological effects of the allergic response. A better understanding of the biology of IL5 and the regulation of its expression is, however, a prerequisite for the development of new therapeutic agents. This review covers the major biological, molecular and structural aspects of IL5 research since the identification of this cytokine ten years ago.

Percutaneous sensitization with allergens through barrier-disrupted skin elicits a Th2-dominant cytokine response

We investigated whether percutaneous sensitization with different allergens through barrier-disrupted skin regulates the balance of Th1/Th2 cytokine expression. When mice were sensitized with the typical hapten picryl chloride (PiCl) by a single topical application to intact skin, there was an up-regulation in the lymph nodes (LN) of mRNA expression for the Th1 cytokines IL-2 or IFN-gamma, and for the Th2 cytokine IL-4. In contrast, sensitization with PiCl after barrier disruption of the skin down-regulated the expression of mRNA for IFN-gamma in a tape-stripping number-dependent manner without changing the expression of mRNA for IL-4. When mice were sensitized with house dust mite antigens (MA) by a single topical application to barrier-disrupted abdominal skin, there was a tape-stripping number-dependent up-regulation in the LN of mRNA expression for IL-4 but not for IL-2 or IFN-gamma. In the LN, mRNA for the IL-4-inducible immunoglobulins IgE and IgG1, but not for the IFN-gamma-inducible IgG2a, were up-regulated after sensitization with MA, while all three immunoglobulin mRNA were augmented after PiCl sensitization through intact skin. Antigenic elicitation by a topical application of PiCl in aural skin of mice sensitized through intact skin consistently increased the expression of mRNA for all three cytokines in the challenged skin, whereas elicitation in mice sensitized through barrier-disrupted skin decreased the expression of mRNA for IL-2 and IFN-gamma, but not for IL-4. Antigenic elicitation by subcutaneous injection of MA in aural skin consistently increased the expression of mRNA for IL-4, but not for IL-2 or IFN-gamma in the challenged skin. Infiltration of eosinophils in the dermis was more prominent following elicitation with MA in mice sensitized through barrier disruption than with PiCl in mice sensitized through intact skin. These findings suggest that the percutaneous entry of environmental allergens through barrier-disrupted skin is strongly associated with the induction of Th2-dominant immunological responses, as is seen in atopic dermatitis.

Molecular cloning and characterization of a novel putative STE20-like kinase in guinea pigs

Protein kinases play a key role in cell growth and differentiation. We have isolated the cDNA of a novel protein serine/threonine kinase (referred to as STE20-like kinase (SLK) from a guinea pig liver cDNA library with a probe generated by a cloning approach based on the polymerase chain reaction. The encoded polypeptide (1231 amino acids, M(r) 141,079) contains all conserved subdomains characteristic of the protein serine threonine kinase family. A hemagglutinin-tagged SLK expressed artificially in COS7 cells was hyperphosphorylated by anisomycin. By Northern blot analysis, SLK mRNA was detected in all organs examined: brain, lung heart, liver, kidney, spleen, testis, and eosinophils. Sequence comparisons of its catalytic domain related SLK to p21-activated kinase family of protein serine/threonine kinases. Its noncatalytic domain comprises several intriguing structural features, including the acidic region and the nuclear targeting sequence. This noncatalytic domain exhibited no extended similarity with other proteins. Thus, SLK is a protein serine/threonine kinase which contains an unknown regulatory domain(s).

Modulation of apoptosis with cytokines in B-cell chronic lymphocytic leukaemia

In B chronic lymphocytic leukaemia (B-CLL) non-proliferating peripheral blood (PB) B cells have a long life span in vivo. In cultures, these cells die spontaneously by apoptosis. Interleukin (IL) 4 inhibits spontaneous apoptosis (SA) and promotes survival of B-CLL B cells in vitro. No such effect is observed in PB B cells from normal healthy donors. The anti-apoptotic effect of IL4 is independent of mitogen-induced cell activation but depends on the concentration of IL4. The protective effect of IL4 is specific and it is significantly reduced or abolished with anti-IL4 antibody. Interferon (IFN)-gamma and alpha- IFN also protect B-CLL B cells from apoptosis in vitro. Sera from B-CLL patients have increased levels of IFN-gamma when compared with sera from healthy donors. In addition, B-cells in B-CLL express detectable levels of IFN-gamma mRNA. Other cytokines, namely ILl, IL2, IL6 and IL7 do not affect SA of B-CLL B cells. By contrast, IL5 and antibody to apolipoprotein-1 (APO- 1) receptor increase SA significantly and in a dose-dependent manner. Interleukin 4 protects B-CLL B cells from IL5-, anti(alpha) APO-1- and steroid-induced apoptosis. The mode of action of the cytokines inducing apoptosis or protecting B-CLL B cells from dying is largely unknown. Recently the bcl-2 proto-oncogene has been associated with prolonged cell survival. However, the involvement of bel-2 in spontaneous, cytokine-induced or steroid-induced apoptosis in B-CLL has been controversial. Some authors have reported down-regulation of bcl-2 protein expression in B-CLL B-cells undergoing SA or in steroid-treated cells with IL4 preventing this down-regulation. By contrast, others observed no significant loss of bcl-2 protein expression in steroid-, alpha-APO-1 - and IL5-treated cells when compared with untreated or fresh cells. Also, no correlation between bcl-2 protein expression and protection with IL4 has been reported. In conclusion, in B-CLL IL4, IFN-gamma and alpha-IFN promote the survival of the leukaemic cells. These cytokines may therefore be involved in the pathogenesis of the B-CLL.

Interleukin-5 receptor alpha subunit gene regulation in human eosinophil development: identification of a unique cis-element that acts lie an enhancer in regulating activity of the IL-5R alpha promoter

Further functional and biochemical characterization of the nuclear factor(s) which interacts with the EOS1 enhancer-like element in the IL-5R alpha promoter is currently in progress. Since different transcription factors recognize and interact with DNA in distinct fashions and with distinct structural motifs, we have modeled potential binding of the EOS1 factor to its cis-element based upon its methylation interference pattern (Fig. 2), using a cylindrical DNA helical projection (Fig. 6). Over a length of two helical turns, all nuclear protein contacts indicated by methylation interference map to one side of the DNA helix, suggesting that EOS1 binds in the major groove, across the minor groove, and on only one side of the helix. Further review of the model also reveals a potential diad symmetry for the binding site, suggestive of binding by a homodimer and consistent with the formation of the two DNA-protein complexes in our electrophoretic mobility shift experiments that could represent interactions with monomer versus dimer. Comparison of the EOS1 binding motif to similar models for the binding of other transcription factor families for which structural crystallographic and/or binding data is available suggests a similarity of the EOS1 complex to that of the bacterial helix-turn-helix phage lambda and 434 repressor-operator complexes, and the Cys4 zinc finger glucocorticoid response element (GRE) DNA-binding motifs, all of which show similar diad symmetry and binding in the major groove on one side of the DNA. The possibility that EOS1 functions as a GRE is being investigated, especially since there is a consensus AP-1 site at bp -440 to -432 of the IL-5R alpha promoter, immediately adjacent to the EOS1 binding site (see Fig. 5 in reference [36]) and AP-1/GRE interactions have been identified for composite response elements in the regulation of a number of different genes. The identification or cloning of EOS1, a potentially novel and eosinophil lineage-active transcription factor, should enhance our understanding of the processes involved in eosinophil development in particular and myeloid lineage commitment and differentiation in general.

In vitro impairment of interleukin-5 production in HLA-B8, DR3-positive individuals implications for immunoglobulin A synthesis dysfunction

Healthy subjects carrying the HLA-B8,DR3 haplotype may show a large number of immune dysfunctions. Concerning T-cell dysfunctions, the most intriguing is a defect of the early phases of T-cell activation, responsible for the impairment of in vitro mitogen-stimulated cytokine production. Regarding B-cell dysfunctions, one the most fascinating topics is the association between this haplotype and IgA deficiency in healthy blood donors. Accordingly, HLA-B8,DR3-positive healthy subjects show significantly lower values of serum IgA than HLA-B8,DR3-negative ones. Because IL-5 is a stimulating factor for the secretion of IgA by committed B cells, we have analyzed the in vitro mitogen-stimulated IL-5 production by MNCs from healthy HLA-B8,DR3-positive individuals to study whether they display an impaired production of IL-5. The results clearly demonstrate that MNCs from HLA-B8,DR3-positive individuals display significant reduction of IL-5 production, suggesting that IgA synthesis dysregulation observed in HLA-B8,DR3-positive subjects could be due to an impairment of IL-5 production.

Binding interactions of human interleukin 5 with its receptor alpha subunit. Large scale production, structural, and functional studies of Drosophila-expressed recombinant proteins

Human interleukin 5 (hIL5) and soluble forms of its receptor alpha subunit were expressed in Drosophila cells and purified to homogeneity, allowing a detailed structural and functional analysis. B cell proliferation confirmed that the hIL5 was biologically active. Deglycosylated hIL5 remained active, while similarly deglycosylated receptor alpha subunit lost activity. The crystal structure of the deglycosylated hIL5 was determined to 2.6-A resolution and found to be similar to that of the protein produced in Escherichia coli. Human IL5 was shown by analytical ultracentrifugation to form a 1:1 complex with the soluble domain of the hIL5 receptor alpha subunit (shIL5R alpha). Additionally, the relative abundance of ligand and receptor in the hIL5.shIL5R alpha complex was determined to be 1:1 by both titration calorimetry and SDS-polyacrylamide gel electrophoresis analysis of dissolved cocrystals of the complex. Titration microcalorimetry yielded equilibrium dissociation constants of 3.1 and 2.0 nM, respectively, for the binding of hIL5 to shIL5R alpha and to a chimeric form of the receptor containing shIL5R alpha fused to the immunoglobulin Fc domain (shIL5R alpha-Fc). Analysis of the binding thermodynamics of IL5 and its soluble receptor indicates that conformational changes are coupled to the binding reaction. Kinetic analysis using surface plasmon resonance yielded data consistent with the Kd values from calorimetry and also with the possibility of conformational isomerization in the interaction of hIL5 with the receptor alpha subunit. Using a radioligand binding assay, the affinity of hIL5 with full-length hIL5R alpha in Drosophila membranes was found to be 6 nM, in accord with the affinities measured for the soluble receptor forms. Hence, most of the binding energy of the alpha receptor is supplied by the soluble domain. Taken with other aspects of hIL5 structure and biological activity, the data obtained allow a prediction for how 1:1 stoichiometry and conformational change can lead to the formation of hIL5.receptor alpha beta complex and signal transduction.