The expanding role(s) of eosinophils in health and disease. Blood. 2012;120:3882-3890. [PMID: 22936660 DOI: 10.1182/blood-2012-06-330845]

Challenges and opportunities for checkpoint blockade in T-cell lymphoproliferative disorders

The T-cell lymphoproliferative disorders are a heterogeneous group of non-Hodgkin’s lymphomas (NHL) for which current therapeutic strategies are inadequate, as most patients afflicted with these NHL will succumb to disease progression within 2 years of diagnosis. Appreciation of the genetic and immunologic landscape of these aggressive NHL, including PD-L1 (B7-H1, CD274) expression by malignant T cells and within the tumor microenvironment, provides a strong rationale for therapeutic targeting this immune checkpoint. While further studies are needed, the available data suggests that responses with PD-1 checkpoint blockade alone will unlikely approach those achieved in other lymphoproliferative disorders. Herein, we review the unique challenges posed by the T-cell lymphoproliferative disorders and discuss potential strategies to optimize checkpoint blockade in these T-cell derived malignancies.

CD4 T-cell hyporesponsiveness induced by schistosome larvae is not dependent upon eosinophils but may involve connective tissue mast cells

In areas endemic for schistosomiasis, people can often be in contact with contaminated water resulting in repeated exposures to infective Schistosoma mansoni cercariae. Using a murine model, repeated infections result in IL‐10‐dependent CD4⁺ T‐cell hyporesponsiveness in the skin‐draining lymph nodes (sdLN), which could be caused by an abundance of eosinophils and connective tissue mast cells at the skin infection site. Here, we show that whilst the absence of eosinophils did not have a significant effect on cytokine production, MHC‐II⁺ cells were more numerous in the dermal cell exudate population. Nevertheless, the absence of dermal eosinophils did not lead to an increase in the responsiveness of CD4⁺ T cells in the sdLN, revealing that eosinophils in repeatedly exposed skin did not impact on the development of CD4⁺ T‐cell hyporesponsiveness. On the other hand, the absence of connective tissue mast cells led to a reduction in dermal IL‐10 and to an increase in the number of MHC‐II⁺ cells infiltrating the skin. There was also a small but significant alleviation of hyporesponsiveness in the sdLN, suggesting that mast cells may have a role in regulating immune responses after repeated exposures of the skin to S. mansoni cercariae.

Eosinophil Peroxidase Catalyzed Protein Carbamylation Participates in Asthma

The biochemical mechanisms through which eosinophils contribute to asthma pathogenesis are unclear. Here we show eosinophil peroxidase (EPO), an abundant granule protein released by activated eosinophils, contributes to characteristic asthma-related phenotypes through oxidative posttranslational modification (PTM) of proteins in asthmatic airways through a process called carbamylation. Using a combination of studies we now show EPO uses plasma levels of the pseudohalide thiocyanate (SCN^-) as substrate to catalyze protein carbamylation, as monitored by PTM of protein lysine residues into N^ϵ-carbamyllysine (homocitrulline), and contributes to the pathophysiological sequelae of eosinophil activation. Studies using EPO-deficient mice confirm EPO serves as a major enzymatic source for protein carbamylation during eosinophilic inflammatory models, including aeroallergen challenge. Clinical studies similarly revealed significant enrichment in carbamylation of airway proteins recovered from atopic asthmatics versus healthy controls in response to segmental allergen challenge. Protein-bound homocitrulline is shown to be co-localized with EPO within human asthmatic airways. Moreover, pathophysiologically relevant levels of carbamylated protein either incubated with cultured human airway epithelial cells in vitro, or provided as an aerosolized exposure in non-sensitized mice, induced multiple asthma-associated phenotypes including induction of mucin, Th2 cytokines, IFNγ, TGFβ, and epithelial cell apoptosis. Studies with scavenger receptor-A1 null mice reveal reduced IL-13 generation following exposure to aerosolized carbamylated protein, but no changes in other asthma-related phenotypes. In summary, EPO-mediated protein carbamylation is promoted during allergen-induced asthma exacerbation, and can both modulate immune responses and trigger a cascade of many of the inflammatory signals present in asthma.

A hidden residential cell in the lung

Eosinophils are classically known as proinflammatory cells, as they are equipped with a variety of preformed cytotoxic mediators and have been shown to definitively contribute to asthma. The connection between eosinophils and asthma development has led to a new class of asthma therapeutics based on blocking eosinophils with humanized antibodies that neutralize IL-5, a potent eosinophil growth, activation, and survival factor. Yet, recent studies have led to an increasing appreciation that eosinophils have a variety of homeostatic functions, including immunomodulation. In this issue of the JCI, Mesnil et al. identify a notable population of lung-resident eosinophils and demonstrate that, compared with traditional eosinophils, these cells have distinct characteristics, including nuclear structure, surface markers, IL-5 independence, and immunoregulatory function that is capable of polarizing adaptive immune responses, at least in vitro. Thus, these results reinforce a key homeostatic role for this enigmatic cell population, particularly in residing and regulating immunity in the lung.

Development of a Modular Assay for Detailed Immunophenotyping of Peripheral Human Whole Blood Samples by Multicolor Flow Cytometry

The monitoring of immune cells gained great significance in prognosis and prediction of therapy responses. For analyzing blood samples, the multicolor flow cytometry has become the method of choice as it combines high specificity on single cell level with multiple parameters and high throughput. Here, we present a modular assay for the detailed immunophenotyping of blood (DIoB) that was optimized for an easy and direct application in whole blood samples. The DIoB assay characterizes 34 immune cell subsets that circulate the peripheral blood including all major immune cells such as T cells, B cells, natural killer (NK) cells, monocytes, dendritic cells (DCs), neutrophils, eosinophils, and basophils. In addition, it evaluates their functional state and a few non-leukocytes that also have been associated with the outcome of cancer therapy. This DIoB assay allows a longitudinal and close-meshed monitoring of a detailed immune status in patients requiring only 2.0 mL of peripheral blood and it is not restricted to peripheral blood mononuclear cells. It is currently applied for the immune monitoring of patients with glioblastoma multiforme (IMMO-GLIO-01 trial, NCT02022384), pancreatic cancer (CONKO-007 trial, NCT01827553), and head and neck cancer (DIREKHT trial, NCT02528955) and might pave the way for immune biomarker identification for prediction and prognosis of therapy outcome.

Effect of eosinophils activated with Alternaria on the production of extracellular matrix from nasal fibroblasts

BACKGROUND

Eosinophils and fibroblasts are known to play major roles in the pathogenesis of nasal polyps. Fungi are commonly found in nasal secretion and are associated with airway inflammation.

OBJECTIVE

To investigate whether activated eosinophils by airborne fungi can influence the production of extracellular matrix (ECM) from nasal fibroblasts.

METHODS

Inferior turbinate and nasal polyp fibroblasts were stimulated with Alternaria or Aspergillus, respectively, for 24 hours and ECM messenger RNA (mRNA) and protein expressions were measured. Eosinophils isolated from healthy volunteers were stimulated with Alternaria or Aspergillus for 4 hours then superoxide, eosinophil peroxidase, and transforming growth factor β1 were measured. Then activated eosinophils were cocultured with nasal fibroblasts for 24 hours, and ECM mRNA expressions were measured.

RESULTS

Alternaria strongly enhanced ECM mRNA expression and protein production from nasal fibroblasts. Alternaria also induced the production of superoxide, eosinophil peroxidase, and transforming growth factor β1 from eosinophils, and activated eosinophils enhanced ECM mRNA expression when they were cocultured without the Transwell insert system.

CONCLUSION

Eosinophils activated with Alternaria enhanced ECM mRNA expression from nasal polyp fibroblasts. Alternaria plays an important role in tissue fibrosis in the pathogenesis of nasal polyps by directly or indirectly influencing the production of ECM from nasal fibroblasts.

Tumour-Associated Tissue Eosinophilia in Oral Squamous Cell Carcinoma- A Boon or a Bane?

INTRODUCTION

The infiltration of tumour stroma by eosinophils, Tumour-Associated Tissue Eosinophilia (TATE) is known to modulate the evolution of Oral Squamous Cell Carcinoma (OSCC). Identification of eosinophils in the inflammatory stroma has been proven to be an important factor in prognostication of malignant tumours including cancers of mouth, oesophagus, larynx, pharynx, breast, lung, intestine and genitourinary tract.

AIM

Our study aimed to assess the role of TATE as a prognosticator in OSCC as visualized by Haematoxylin and Eosin (H&E) and congo red staining.

MATERIALS AND METHODS

Thirty histologically-proven cases of OSCC were retrieved from the archives of Department of Oral Pathology, Manipal College of Dental Sciences, Mangalore, Manipal University, Karnataka, India. Two serial sections of 4μm thickness were made and subjected to routine staining with H&E and modified congo red staining, where eosinophil granules stained red and nuclei stained blue. In 40x magnification, 10 HPF at invasive tumour front were assessed for counting eosinophils by placing a 49 square grid (measuring 0.0289 sq mm).

STATISTICAL ANALYSIS

The TATE was compared with the prognosticators using Mann-Whitney U-test. The grades of carcinoma were correlated with TATE using Kruskal-Wallis test followed by Post-hoc Bonferronis correction. Agreement of the number of eosinophils counted in the two staining techniques (H&E and Congo red) in OSCC was achieved using interclass correlation coefficient, and Friedman's test. A value of p< 0.05 was considered statistically significant.

RESULTS

Our results showed that tissue eosinophil counts were higher in well-differentiated cases of OSCC, cases with lymph node involvement, decreased survival, without margin involvement and in cases that did not recur. H&E stain showed significantly better visualization of eosinophils resulting in higher eosinophil counts than when seen with Congo red (p=0.008).

CONCLUSION

Thus, TATE can be used as a surrogate marker in prediction of survival and recurrence in OSCC. H&E proved to be a better stain for evaluation of eosinophils.

Endocannabinoids and Immunity

Over the last 10 years, a great boost of knowledge accumulated on the immunomodulatory and anti-inflammatory properties of endocannabinoids (eCBs). In this scenario, these bioactive lipids, which are produced by most immune cells along with a set of receptors and enzymes that regulate their synthesis and degradation, act as secondary modulators and increase or decrease a plethora of immune functions. In this review, the manifold immunomodulatory effects of the main eCBs in different compartments of innate and adaptive immunity will be discussed, suggesting that they could be considered as master regulators of innate-adaptive immune axis and as potent immunoresolvents.

Immune Mechanisms of Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is a common inflammatory disease that results in a significant decrease in patient quality of life and a large economic burden. However, the lack of population-based epidemiologic studies and robust model systems has made it difficult to fully elucidate the key inflammatory pathways that drive the chronic inflammatory responses observed in CRS. This review will highlight the wide variety of factors that likely contribute to CRS disease pathogenesis. Defects in the innate immune function of the airway epithelium, including decreases in barrier function, mucociliary clearance, and production of antimicrobial peptides, all likely play a role in the initial inflammatory response. Subsequent recruitment and activation of eosinophils, mast cells, and innate lymphoid cells (ILCs) further contributes to the chronic inflammatory response and directly activates adaptive immune cells, including T and B cells. However, development of new tools and model systems is still needed to further understand the chronicity of this inflammatory response and which specific factors are necessary or sufficient to drive CRS pathogenesis. Such studies will be critical for the development of improved therapeutic strategies aimed at treating this highly prevalent and costly disease.

From neutrophils to macrophages: differences in regional adipose tissue depots

Currently, we do not fully understand the underlying mechanisms of how regional adiposity promotes metabolic dysregulation. As adipose tissue expands, there is an increase in chronic systemic low-grade inflammation due to greater infiltration of immune cells and production of cytokines. This chronic inflammation is thought to play a major role in the development of metabolic complications and disease such as insulin resistance and diabetes. We know that different adipose tissue depots contribute differently to the risk of metabolic disease. People who have an upper body fat distribution around the abdomen are at greater risk of disease than those who tend to store fat in their lower body around the hips and thighs. Thus, it is conceivable that adipose tissue depots contribute differently to the inflammatory milieu as a result of varied infiltration of immune cell types. In this review, we describe the role and function of major resident immune cells in the development of adipose tissue inflammation and discuss their regional differences in the context of metabolic disease risk. We find that although initial studies have found regional differences, a more comprehensive understanding of how immune cells interrupt adipose tissue homeostasis is needed.

Eosinophil-Associated Gene Pathways but not Eosinophil Numbers are Differentially Regulated between Synchrotron Microbeam Radiation Treatment and Synchrotron Broad-Beam Treatment by 48 Hours Postirradiation

Synchrotron microbeam radiation treatment (MRT) is a preclinical radiotherapy technique with considerable clinical promise, although some of the underlying radiobiology of MRT is still not well understood. In recently reported studies, it has been suggested that MRT elicits a different tumor immune profile compared to broad-beam treatment (BB). The aim of this study was to investigate the effects of synchrotron MRT and BB on eosinophil-associated gene pathways and eosinophil numbers within and around the tumor in the acute stage, 48 h postirradiation. Balb/C mice were inoculated with EMT6.5 mouse mammary tumors and irradiated with microbeam radiation (112 and 560 Gy) and broad-beam radiation (5 and 9 Gy) at equivalent doses determined from a previous in vitro study. After tumors were collected 24 and 48 h postirradiation, RNA was extracted and quantitative PCR performed to assess eosinophil-associated gene expression. Immunohistochemistry was performed to detect two known markers of eosinophils: eosinophil-associated ribonucleases (EARs) and eosinophil major basic protein (MBP). We identified five genes associated with eosinophil function and recruitment (Ear11, Ccl24, Ccl6, Ccl9 and Ccl11) and all of them, except Ccl11, were differentially regulated in synchrotron microbeam-irradiated tumors compared to broad-beam-irradiated tumors. However, immunohistochemical localization demonstrated no significant differences in the number of EAR- and MBP-positive eosinophils infiltrating the primary tumor after MRT compared to BB. In conclusion, our work demonstrates that the effects of MRT on eosinophil-related gene pathways are different from broad-beam radiation treatment at doses previously demonstrated to be equivalent in an in vitro study. However, a comparison of the microenvironments of tumors, which received MRT and BB, 48 h after exposure showed no difference between them with respect to eosinophil accumulation. These findings contribute to our understanding of the role of differential effects of MRT on the tumor immune response.

Co-Infection and Wild Animal Health: Effects of Trypanosomatids and Gastrointestinal Parasites on Coatis of the Brazilian Pantanal

Wild animals are infected by diverse parasites, but how they influence host health is poorly understood. We examined the relationship of trypanosomatids and gastrointestinal parasites with health of wild brown-nosed coatis (Nasua nasua) from the Brazilian Pantanal. We used coati body condition and hematological parameters as response variables in linear models that were compared using an information theoretic approach. Predictors were high/low parasitemias by Trypanosoma cruzi and T. evansi, and indices representing the abundance of distinct groups of gastrointestinal parasites. We also analyzed how host health changed with host sex and reproductive seasonality. Hemoparasites was best related to coati body condition and hematological indices, whereas abundance of gastrointestinal parasites was relatively less associated with coati health. Additionally, some associations were best predicted by models that incorporated reproductive seasonality and host sex. Overall, we observed a lower health condition during the breeding season, when coatis are under reproductive stress and may be less able to handle infection. In addition, females seem to handle infection better than males. Body condition was lower in coatis with high parasitemias of T. evansi, especially during the reproductive season. Total red blood cell counts, packed cell volume, platelets and eosinophils were also lower in animals with high T. evansi parasitemias. Total white blood cell counts and mature neutrophils were lower in animals with high parasitemias for both Trypanosoma species, with neutrophils decreasing mainly during the reproductive season. Overall, decreases in hematological parameters of females with T. evansi high parasitemias were less evident. For T. cruzi, monocytes decreased in individuals with high parasitemias. High abundances of microfilariae in the bloodstream, and cestode eggs and coccidian oocysts in feces were also associated with coati blood parameters. This study shows the potential value of examining hematological parameters as an approach to better understand the ecological relevance of parasite-host interactions.

Pathogenesis of nasal polyposis

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex inflammatory condition that affects a large proportion of the population world-wide and is associated with high cost of management and significant morbidity. Yet, there is a lack of population-based epidemiologic studies using current definitions of CRSwNP, and the mechanisms that drive pathogenesis in this disease remain unclear. In this review, we summarize the current evidence for the plethora of factors that likely contribute to CRSwNP pathogenesis. Defects in the innate function of the airway epithelial barrier, including diminished expression of antimicrobial products and loss of barrier integrity, combined with colonization by fungi and bacteria likely play a critical role in the development of chronic inflammation in CRSwNP. This chronic inflammation is characterized by elevated expression of many key inflammatory cytokines and chemokines, including IL-5, thymic stromal lymphopoietin and CCL11, that help to initiate and perpetuate this chronic inflammatory response. Together, these factors likely combine to drive the influx of a variety of immune cells, including eosinophils, mast cells, group 2 innate lymphoid cells and lymphocytes, which participate in the chronic inflammatory response within the nasal polyps. Importantly, however, future studies are needed to demonstrate the necessity and sufficiency of these potential drivers of disease in CRSwNP. In addition to the development of new tools and models to aid mechanistic studies, the field of CRSwNP research also needs the type of robust epidemiologic data that has served the asthma community so well. Given the high prevalence, costs and morbidity, there is a great need for continued research into CRS that could facilitate the development of novel therapeutic strategies to improve treatment for patients who suffer from this disease.

IL-1β in eosinophil-mediated small intestinal homeostasis and IgA production

Eosinophils are multifunctional leukocytes that reside in the gastrointestinal (GI) lamina propria, where their basal function remains largely unexplored. In this study, by examining mice with a selective deficiency of systemic eosinophils (by lineage ablation) or GI eosinophils (eotaxin-1/2 double deficient or CC chemokine receptor 3 deficient), we show that eosinophils support immunoglobulin A (IgA) class switching, maintain intestinal mucus secretions, affect intestinal microbial composition, and promote the development of Peyer's patches. Eosinophil-deficient mice showed reduced expression of mediators of secretory IgA production, including intestinal interleukin 1β (IL-1β), inducible nitric oxide synthase, lymphotoxin (LT) α, and LT-β, and reduced levels of retinoic acid-related orphan receptor gamma t-positive (ROR-γt(+)) innate lymphoid cells (ILCs), while maintaining normal levels of APRIL (a proliferation-inducing ligand), BAFF (B cell-activating factor of the tumor necrosis factor family), and TGF-β (transforming growth factor β). GI eosinophils expressed a relatively high level of IL-1β, and IL-1β-deficient mice manifested the altered gene expression profiles observed in eosinophil-deficient mice and decreased levels of IgA(+) cells and ROR-γt(+) ILCs. On the basis of these collective data, we propose that eosinophils are required for homeostatic intestinal immune responses including IgA production and that their affect is mediated via IL-1β in the small intestine.

Targeted treatment of metastatic castration-resistant prostate cancer with sipuleucel-T immunotherapy

Context

Prostate cancer remains highly prevalent and has a poor clinical outcome once metastatic. Sipuleucel-T is an autologous cellular immunotherapy approved for the treatment of metastatic castration-resistant prostate cancer (mCRPC). Sipuleucel-T treatment extends survival but is independent of traditional short-term markers of treatment response observed with chemotherapy and contemporary hormonal treatments. Therefore, it is essential that clinicians understand the mechanism of action of sipuleucel-T and how this can translate in the clinic.

Objective

This article aims to summarize the current knowledge of sipuleucel-T therapy and its effects in mCRPC.

Evidence acquisition

Relevant publications describing sipuleucel-T clinical data and information relating to immunotherapies were identified.

Evidence synthesis

Treatment with sipuleucel-T extends survival, with side effects being usually mild or moderate and manageable within the outpatient setting. The long-term immune responses generated by sipuleucel-T correlate with a survival benefit. Sipuleucel-T shows a greater magnitude of clinical benefit when used in patients earlier in the mCRPC setting.

Conclusions

Sipuleucel-T stimulates long-lived immune responses that translate into long-term clinical benefit. The treatment course (three infusions at weeks 0, 2, and 4) is associated with manageable side effects. Short-term markers of future benefit would be clinically useful, and information on effective treatment combinations or sequences is awaited.

Patient summary

Sipuleucel-T treatment directs the patient’s own immune system to target and remove prostate cancer cells and increases life expectancy. Patients whose cancer is less advanced generally have a more ‘active’ immune system and may benefit the most from this treatment.

Re-defining the unique roles for eosinophils in allergic respiratory inflammation

The role of eosinophils in the progression and resolution of allergic respiratory inflammation is poorly defined despite the commonality of their presence and in some cases their use as a biomarker for disease severity and/or symptom control. However, this ambiguity belies the wealth of insights that have recently been gained through the use of eosinophil-deficient/attenuated strains of mice that have demonstrated novel immunoregulatory and remodelling/repair functions for these cells in the lung following allergen provocation. Specifically, studies of eosinophil-deficient mice suggest that eosinophils contribute to events occurring in the lungs following allergen provocation at several key moments: (i) the initiating phase of events leading to Th2-polarized pulmonary inflammation, (ii) the suppression Th1/Th17 pathways in lung-draining lymph nodes, (iii) the recruitment of effector Th2 T cells to the lung, and finally, (iv) mechanisms of inflammatory resolution that re-establish pulmonary homoeostasis. These suggested functions have recently been confirmed and expanded upon using allergen provocation of an inducible eosinophil-deficient strain of mice (iPHIL) that demonstrated an eosinophil-dependent mechanism(s) leading to Th2 dominated immune responses in the presence of eosinophils in contrast to neutrophilic as well as mixed Th1/Th17/Th2 variant phenotypes in the absence of eosinophils. These findings highlighted that eosinophils are not exclusively downstream mediators controlled by T cells, dendritic cells (DC) and/or innate lymphocytic cells (ILC2). Instead, eosinophils appear to be more aptly described as significant contributors in complex interrelated pathways that lead to pulmonary inflammation and subsequently promote resolution and the re-establishment of homoeostatic baseline. In this review, we summarize and put into the context the evolving hypotheses that are now expanding our understanding of the roles eosinophils likely have in the lung following allergen provocation.

CCR2 deficiency leads to increased eosinophils, alternative macrophage activation, and type 2 cytokine expression in adipose tissue

Adipose tissue (AT) inflammation during obesity is mediated by immune cells and closely correlates with systemic insulin resistance. In lean AT, eosinophils are present in low but significant numbers and capable of promoting alternative macrophage activation in an IL-4/IL-13-dependent manner. In WT mice, obesity causes the proportion of AT eosinophils to decline, concomitant with inflammation and classical activation of AT macrophages. In this study, we show that CCR2 deficiency leads to increased eosinophil accumulation in AT. Furthermore, in contrast to WT mice, the increase in eosinophils in CCR2(-/-) AT is sustained and even amplified during obesity. Interestingly, a significant portion of eosinophils is found in CLSs in AT of obese CCR2(-/-) mice, which is the first time eosinophils have been shown to localize to these inflammatory hot spots. CCR2(-/-) bone marrow precursors displayed increased expression of various key eosinophil genes during in vitro differentiation to eosinophils, suggesting a potentially altered eosinophil phenotype in the absence of CCR2. In addition, the proportion of eosinophils in AT positively correlated with local expression of Il5, a potent eosinophil stimulator. The increase in eosinophils in CCR2(-/-) mice was detected in all white fat pads analyzed and in the peritoneal cavity but not in bone marrow, blood, spleen, or liver. In AT of CCR2(-/-) mice, an increased eosinophil number positively correlated with M2-like macrophages, expression of the Treg marker Foxp3, and type 2 cytokines, Il4, Il5, and Il13. This is the first study to link CCR2 function with regulation of AT eosinophil accumulation.

Carbohydrate–Protein Interactions: A 3D View by NMR

NMR spectroscopy is a key tool for carbohydrate research. In studies with complex oligosaccharides there are limits to the amount of relevant structural information provided by these observables due to problems of signal overlapping, strong coupling and/or the scarcity of the key NOE information. Thus, there is an increasing need for additional parameters with structural information, such as residual dipolar couplings (RDCs), paramagnetic relaxation enhancements (PREs) or pseudo contact shifts (PCSs). Carbohydrates are rather flexible molecules. Therefore, NMR observables do not always correlate with a single conformer but with an ensemble of low free-energy conformers that can be accessed by thermal fluctuations. Depending on the system under study, different NMR approaches can be followed to characterize protein–carbohydrate interactions: the standard methodologies can usually be classified as “ligand-based” or “receptor-based”. The selection of the proper methodology is usually determined by the size of the receptor, the dissociation constant of the complex (KD), the availability of the labelled protein (15N, 13C) and the access to soluble receptors at enough concentration for NMR measurements.

Cellular mechanisms underlying eosinophilic and neutrophilic airway inflammation in asthma

Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th)2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg) lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments.

Endocannabinoid signalling in innate and adaptive immunity

The immune system can be modulated and regulated not only by foreign antigens but also by other humoral factors and metabolic products, which are able to affect several quantitative and qualitative aspects of immunity. Among these, endocannabinoids are a group of bioactive lipids that might serve as secondary modulators, which when mobilized coincident with or shortly after first-line immune modulators, increase or decrease many immune functions. Most immune cells express these bioactive lipids, together with their set of receptors and of enzymes regulating their synthesis and degradation. In this review, a synopsis of the manifold immunomodulatory effects of endocannabinoids and their signalling in the different cell populations of innate and adaptive immunity is appointed, with a particular distinction between mice and human immune system compartments.

Induction of eosinophil apoptosis by hydrogen peroxide promotes the resolution of allergic inflammation

Eosinophils are effector cells that have an important role in the pathogenesis of allergic disease. Defective removal of these cells likely leads to chronic inflammatory diseases such as asthma. Thus, there is great interest in understanding the mechanisms responsible for the elimination of eosinophils from inflammatory sites. Previous studies have demonstrated a role for certain mediators and molecular pathways responsible for the survival and death of leukocytes at sites of inflammation. Reactive oxygen species have been described as proinflammatory mediators but their role in the resolution phase of inflammation is poorly understood. The aim of this study was to investigate the effect of reactive oxygen species in the resolution of allergic inflammatory responses. An eosinophilic cell line (Eol-1) was treated with hydrogen peroxide and apoptosis was measured. Allergic inflammation was induced in ovalbumin sensitized and challenged mouse models and reactive oxygen species were administered at the peak of inflammatory cell infiltrate. Inflammatory cell numbers, cytokine and chemokine levels, mucus production, inflammatory cell apoptosis and peribronchiolar matrix deposition was quantified in the lungs. Resistance and elastance were measured at baseline and after aerosolized methacholine. Hydrogen peroxide accelerates resolution of airway inflammation by induction of caspase-dependent apoptosis of eosinophils and decrease remodeling, mucus deposition, inflammatory cytokine production and airway hyperreactivity. Moreover, the inhibition of reactive oxygen species production by apocynin or in gp91^phox−/− mice prolonged the inflammatory response. Hydrogen peroxide induces Eol-1 apoptosis in vitro and enhances the resolution of inflammation and improves lung function in vivo by inducing caspase-dependent apoptosis of eosinophils.

Eosinophils contribute to the resolution of lung-allergic responses following repeated allergen challenge

BACKGROUND

Eosinophils accumulate at the site of allergic inflammation and are critical effector cells in allergic diseases. Recent studies have also suggested a role for eosinophils in the resolution of inflammation.

OBJECTIVE

To determine the role of eosinophils in the resolution phase of the response to repeated allergen challenge.

METHODS

Eosinophil-deficient (PHIL) and wild-type (WT) littermates were sensitized and challenged to ovalbumin (OVA) 7 or 11 times. Airway inflammation, airway hyperresponsiveness (AHR) to inhaled methacholine, bronchoalveolar lavage (BAL) cytokine levels, and lung histology were monitored. Intracellular cytokine levels in BAL leukocytes were analyzed by flow cytometry. Groups of OVA-sensitized PHIL mice received bone marrow from WT or IL-10(-/-) donors 30 days before the OVA challenge.

RESULTS

PHIL and WT mice developed similar levels of AHR and numbers of leukocytes and cytokine levels in BAL fluid after OVA sensitization and 7 airway challenges; no eosinophils were detected in the PHIL mice. Unlike WT mice, sensitized PHIL mice maintained AHR, lung inflammation, and increased levels of IL-4, IL-5, and IL-13 in BAL fluid after 11 challenges whereas IL-10 and TGF-β levels were decreased. Restoration of eosinophil numbers after injection of bone marrow from WT but not IL-10-deficient mice restored levels of IL-10 and TGF-β in BAL fluid as well as suppressed AHR and inflammation. Intracellular staining of BAL leukocytes revealed the capacity of eosinophils to produce IL-10.

CONCLUSIONS

After repeated allergen challenge, eosinophils appeared not essential for the development of AHR and lung inflammation but contributed to the resolution of AHR and inflammation by producing IL-10.

Mast cells' integrated actions with eosinophils and fibroblasts in allergic inflammation: implications for therapy

Mast cells (MCs) and eosinophils (Eos) are the key players in the development of allergic inflammation (AI). Their cross-talk, named the Allergic Effector Unit (AEU), takes place through an array of soluble mediators and ligands/receptors interactions that enhance the functions of both the cells. One of the salient features of the AEU is the CD48/2B4 receptor/ligand binding complex. Furthermore, MCs and Eos have been demonstrated to play a role not only in AI but also in the modulation of its consequence, i.e., fibrosis/tissue remodeling, by directly influencing fibroblasts (FBs), the main target cells of these processes. In turn, FBs can regulate the survival, activity, and phenotype of both MCs and Eos. Therefore, a complex three players, MCs/Eos/FBs interaction, can take place in various stages of AI. The characterization of the soluble and physical mediated cross talk among these three cells might lead to the identification of both better and novel targets for the treatment of allergy and its tissue remodeling consequences.

Paeoniflorin attenuates allergic inflammation in asthmatic mice

Paeoniflorin (PF), one of the major active ingredients of Chinese peony, has demonstrated anti-inflammatory and immunoregulatory effects. However, it has remained unclear whether PF treatment can inhibit allergic inflammation in asthma. In this study, we evaluated the effects of PF on pulmonary function and airway inflammation in asthmatic mice. The allergic asthma models were established in BALB/c mice. The mice were sensitized and challenged with ovalbumin. Airway hyperresponsiveness was detected by direct airway resistance analysis. Lung tissues were examined for inflammatory cell infiltration. IL-5, IL-13, IL-17, and eotaxin in bronchoalveolar lavage fluid (BALF) and their mRNA expression in lung tissue were examined by ELISA and realtime PCR, respectively. The total IgE level in serum was measured by ELISA. The protein expression of p-ERK and p-JNK was detected by western blot. Our data showed that PF oral administration significantly reduced airway hyperresponsiveness to aerosolized methacholine and decreased IL-5, IL-13, IL-17 and eotaxin levels in the BALF, and decreased IgE level in the serum. Histological studies showed that PF administration markedly decreased inflammatory infiltration. Similarly, treatment with PF significantly inhibited IL-5, IL-13, IL-17 and eotaxin mRNA expression in lung tissues. The protein expression levels of p-ERK and p-JNK were substantially decreased after oral administration of PF. In summary, PF displayed anti-inflammatory effects in the OVA-induced asthmatic model by decreasing the expression of IL-5, IL-13, IL-17 and eotaxin. These effects were mediated at least partially by inhibiting the activation of MAPK pathway.

Novel targeted therapies for eosinophil-associated diseases and allergy

Eosinophil-associated diseases often present with life-threatening manifestations and/or chronic organ damage. Currently available therapeutic options are limited to a few drugs that often have to be prescribed on a lifelong basis to keep eosinophil counts under control. In the past 10 years, treatment options and outcomes in patients with clonal eosinophilic and other eosinophilic disorders have improved substantially. Several new targeted therapies have emerged, addressing different aspects of eosinophil expansion and inflammation. In this review, we discuss available and currently tested agents as well as new strategies and drug targets relevant to both primary and secondary eosinophilic diseases, including allergic disorders.

A transient increase in eosinophils is associated with prolonged survival in men with metastatic castration-resistant prostate cancer who receive sipuleucel-T

Sipuleucel-T is an autologous cellular immunotherapy used to treat asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer (mCRPC). Traditional short-term indicators of clinical response commonly used with chemotherapy have not correlated with survival in patients treated with sipuleucel-T. This retrospective study aimed to evaluate laboratory parameters as possible early biomarkers associated with clinical benefit following sipuleucel-T treatment. Patients treated with sipuleucel-T from three randomized, controlled, phase III clinical trials in mCRPC were considered: IMPACT (NCT00065442; n = 512), D9901 (NCT00005947; n = 127), and D9902A (NCT01133704; n = 98). Patients from these trials were included in this study if their samples were analyzed by the central laboratory and if data were available from baseline and ≥ 1 posttreatment time point (n = 377). We found that sipuleucel-T treatment was associated with a transient increase in serum eosinophil count at week 6 that resolved by week 14 in 28% of patients (105 of 377). This eosinophil increase correlated with induced immune response, longer prostate cancer-specific survival [HR, 0.713; 95% confidence interval (CI), 0.525-0.970; P = 0.031], and a trend in overall survival (HR, 0.753; 95% CI, 0.563-1.008; P = 0.057). Median serum globulin protein levels also increased transiently, which was associated with antigen-specific antibody responses; however, this finding did not correlate with longer survival. We conclude that transient increases in eosinophils at week 6 may be a useful, objective, short-term indicator of global immune activation and survival benefit with sipuleucel-T in patients with mCRPC. This observation warrants prospective evaluation in future clinical trials.

Risk of lymphoma and solid cancer among patients with rheumatoid arthritis in a primary care setting

BACKGROUND

Several studies have demonstrated an association between rheumatoid arthritis (RA) and lymphoproliferative malignancies, but pathogenic mechanisms remain unclear. We investigated 1) the risk of lymphoproliferative malignancies and solid tumors in adults with RA identified in primary care and 2) the possible mediating role of blood eosinophilia in the clonal evolution of cancer in these patients.

METHODS

From the Copenhagen Primary Care Differential Count (CopDiff) Database, we identified 356,196 individuals with at least one differential cell count (DIFF) encompassing the eosinophil count between 2000-2007. From these, one DIFF was randomly chosen (the index DIFF). By linking to the Danish National Patient Register, we categorized the selected individuals according to known longstanding (≥3 years) or recent onset (<3 years) RA prior to the index DIFF. In addition, the cohort was stratified according to management in primary or secondary care. From the Danish Cancer Registry we ascertained malignancies within four years following the index DIFF. Using multivariable logistic regression, odds ratios (OR) were calculated and adjusted for sex, age, year, month, eosinophilia, comorbid conditions and C-reactive protein (CRP).

RESULTS

921 patients had recent onset RA and 2,578 had longer disease duration. Seventy three percent of RA patients were managed in primary care. After adjustment for sex, age, year, and month, neither recent onset nor long-standing RA was associated with incident lymphoproliferative malignancies or solid cancers. These risk estimates did not change when eosinophilia, CRP, and comorbidities were included in the models.

CONCLUSIONS

In this large cohort of patients with RA of short or long duration recruited from a primary care resource, RA was not associated with an increased risk of lymphoproliferative or solid cancers during 4 years of follow-up, when the models were adjusted for confounders. Blood eosinophilia could not be identified as a mediator of cancer development in the present setting.

The immune injury effects and clinical significance of eosinophils in auto-immune-related hematocytopenia

Eosinophils (EOS) quantity, active state, peroxidase activity (POX), and HLA-DR expression in bone marrow of 176 Auto-Immune-Related Hematocytopenia (AIRH) patients were analyzed. Immunofluorescent staining (IF) is performed to observe the expression of immunizing molecules on EOS. In serum of AIRH patients the levels of IL-4, IL-5, IL-6, IL-12, IL-17, and IFN- γ were increased but there was no significance on IL-2 level. In marrow of AIRH, activated EOS expressed POX, and other molecules, it played various cell-mediated immunity injury roles to hemocyte. EOS might be possessed with multiple immunological fuctions, it playes an important immune effect in AIRH autoimmune pathological processes.

Eosinophil activities modulate the immune/inflammatory character of allergic respiratory responses in mice

BACKGROUND

The importance and specific role(s) of eosinophils in modulating the immune/inflammatory phenotype of allergic pulmonary disease remain to be defined. Established animal models assessing the role(s) of eosinophils as contributors and/or causative agents of disease have relied on congenitally deficient mice where the developmental consequences of eosinophil depletion are unknown.

METHODS

We developed a novel conditional eosinophil-deficient strain of mice (iPHIL) through a gene knock-in strategy inserting the human diphtheria toxin (DT) receptor (DTR) into the endogenous eosinophil peroxidase genomic locus.

RESULTS

Expression of DTR rendered resistant mouse eosinophil progenitors sensitive to DT without affecting any other cell types. The presence of eosinophils was shown to be unnecessary during the sensitization phase of either ovalbumin (OVA) or house dust mite (HDM) acute asthma models. However, eosinophil ablation during airway challenge led to a predominantly neutrophilic phenotype (>15% neutrophils) accompanied by allergen-induced histopathologies and airway hyper-responsiveness in response to methacholine indistinguishable from eosinophilic wild-type mice. Moreover, the iPHIL neutrophilic airway phenotype was shown to be a steroid-resistant allergic respiratory variant that was reversible upon the restoration of peripheral eosinophils.

CONCLUSIONS

Eosinophil contributions to allergic immune/inflammatory responses appear to be limited to the airway challenge and not to the sensitization phase of allergen provocation models. The reversible steroid-resistant character of the iPHIL neutrophilic airway variant suggests underappreciated mechanisms by which eosinophils shape the character of allergic respiratory responses.

Mutant mice and animal models of airway allergic disease

Eosinophilia is a hallmark of allergic airway inflammation, and eosinophils represent an integral effector leukocyte through their release of various granule-stored cytokines and proteins. Numerous mouse models have been developed to mimic clinical disease and they have been instrumental in furthering our understanding of the role of eosinophils in disease. Most of these models consist of intranasal (i.n.) administration of antigenic proteases including papain and house dust mite (HDM) or the neo-antigen ovalbumin, with a resulting Th2-biased immune response and airway eosinophilia. These models have been particularly informative when combined with the numerous transgenic mice available that modulate eosinophil frequency or the mechanisms involved in their migration. Here, we describe the current models or allergic airway inflammation and outline some of the transgenic mice available to study eosinophils in disease.

Flow Cytometry Analysis of Pparα Receptors in Metabolic Syndrome / Studiul Receptorilor Pparα prin Metoda Citometriei în Flux în Sindromul Metabolic

Introduction. Metabolic syndrome (MS) is a cluster of distinct metabolic alterations with an increased cardiovascular risk. Peroxisome Proliferator-Activated Receptor - Alpha (PPARα), member of the nuclear receptor superfamily of transcription factors, is critically involved in the management of lipid metabolism during homeostasis or inflammatory stresses in various cell types and represents one of the therapeutic targets in MS. We analysed the PPARα expression in leukocytes of pacients with MS, in order to address PPARα involvement in these group of diseases. Material and method. Our study included 57 adult patients recruited under informed voluntary consent, investigated in order to establish whether they present MS, according to International Diabetes Federation (IDF) European guidelines and grouped in 2 lots: the MS Lot (26 patients) and control group, non-MS Lot (31 subjects). Common clinical and laboratory parameters targeted in MS evaluation were determined for all the studied cases. The expression levels of 2 molecules, PPARα and CD36 were evaluated in various circulating leukocyte populations of these patients by an optimized flow cytometry method. Statistic analysis clarifying the significance of value differences for various parameters measured was performed under SPSS and simple statistical tests (Pearson, t-Student, Chi -test). Results and discussion. The fluorescence staining for PPARα were significantly dimmer when comparing the cellular expression in eosinophils (p<0.05) of MS versus the Control group of subjects. Conclusions: Our study is the first to show that circulating eosinophils display significantly reduced PPARα protein expression in MS patients. The differences in key molecule expression in circulating leukocytes (like PPAR species, CD36, and other) might be evocatory for the endothelial dysfunction and obesity and might be of use in the therapeutic decision.

Brentuximab vedotin for Hodgkin lymphoma and systemic anaplastic large cell lymphoma: a review of clinical experience and future directions

SUMMARY Brentuximab vedotin is a novel agent indicated for the treatment of relapsed and refractory Hodgkin lymphoma and systemic anaplastic large cell lymphoma. Brentuximab vedotin is an antibody–drug conjugate consisting of chimeric anti-CD30 antibody cAC10, linked to four molecules of monomethylauristatin E, a tubulin destabilizer. It was granted US FDA approval in 2011 following two pivotal Phase II studies showing objective responses of 75 and 86% in heavily pretreated relapsed and refractory Hodgkin lymphoma and systemic anaplastic large cell lymphoma, respectively. Brentuximab vedotin can be used as a bridge to more definitive stem cell transplant. There are currently over 30 open clinical studies involving the use of brentuximab vedotin used as single agent or combined with chemotherapy in both front-line and salvage settings. These studies include use in other CD30-positive B- and T-cell lymphomas, as well as in CD30-positive germ cell tumors. In clinical practice brentuximab vedotin has been associated with significant sensory and motor neuropathies and clinicians should be alert to the potential for significant neuropathy and the need for dose reduction. However, the potential for significant neuropathy must be balanced against the remarkable clinical benefit of brentuximab vedotin in patients with heavily pretreated relapsed and refractory lymphomas.

Autotaxin and lysophosphatidic acid signalling in lung pathophysiology

Autotaxin (ATX or ENPP2) is a secreted glycoprotein widely present in biological fluids. ATX primarily functions as a plasma lysophospholipase D and is largely responsible for the bulk of lysophosphatidic acid (LPA) production in the plasma and at inflamed and/or malignant sites. LPA is a phospholipid mediator produced in various conditions both in cells and in biological fluids, and it evokes growth-factor-like responses, including cell growth, survival, differentiation and motility, in almost all cell types. The large variety of LPA effector functions is attributed to at least six G-protein coupled LPA receptors (LPARs) with overlapping specificities and widespread distribution. Increased ATX/LPA/LPAR levels have been detected in a large variety of cancers and transformed cell lines, as well as in non-malignant inflamed tissues, suggesting a possible involvement of ATX in chronic inflammatory disorders and cancer. In this review, we focus exclusively on the role of the ATX/LPA axis in pulmonary pathophysiology, analysing the effects of ATX/LPA on pulmonary cells and leukocytes in vitro and in the context of pulmonary pathophysiological situations in vivo and in human diseases.

Loss of hypoxia-inducible factor 2 alpha in the lung alveolar epithelium of mice leads to enhanced eosinophilic inflammation in cobalt-induced lung injury

Hard metal lung disease (HMLD) is an occupational lung disease specific to inhalation of cobalt-containing particles whose mechanism is largely unknown. Cobalt is a known hypoxia mimic and stabilizer of the alpha subunits of hypoxia-inducible factors (HIFs). Previous work revealed that though HIF1α contrib utes to cobalt toxicity in vitro, loss of HIF1α in the alveolar epithelial cells does not provide in vivo protection from cobalt-induced lung inflammation. HIF1α and HIF2α show unique tissue expression profiles, and HIF2α is known to be the predominant HIF mRNA isoform in the adult lung. Thus, if HIF2α activation by cobalt contributes to pathophysiology of HMLD, we hypothesized that loss of HIF2α in lung epithelium would provide protection from cobalt-induced inflammation. Mice with HIF2α-deficiency in Club and alveolar type II epithelial cells (ATIIs) (HIF2α(Δ/Δ)) were exposed to cobalt (60 µg/day) or saline using a subacute occupational exposure model. Bronchoalveolar lavage cellularity, cytokines, qRT-PCR, and histopathology were analyzed. Results show that loss of HIF2α leads to enhanced eosinophilic inflammation and increased goblet cell metaplasia. Additionally, control mice demonstrated a mild recovery from cobalt-induced lung injury compared with HIF2α(Δ/Δ) mice, suggesting a role for epithelial HIF2α in repair mechanisms. The expression of important cytokines, such as interleukin (IL)-5 and IL-10, displayed significant differences following cobalt exposure when HIF2α(Δ/Δ) and control mice were compared. In summary, our data suggest that although loss of HIF2α does not afford protection from cobalt-induced lung inflammation, epithelial HIF2α signaling does play an important role in modulating the inflammatory and repair response in the lung.

Innate immune pathways in afferent lymph following vaccination with poly(I:C)-containing liposomes

Many modern vaccines use defined adjuvants to stimulate the innate immune system and shape the adaptive immune response. The exact nature of these innate signals and whether immune differentiation can originate within the periphery is not known. Here we used an ovine lymphatic cannulation model to characterise the cellular and transcriptomic profile of the afferent lymph following injection of a liposomal vaccine formulation incorporating diphtheria toxoid and the innate stimulator poly(I:C) over a 78-h period. The response to this vaccine featured an early activation of broad pro-inflammatory pathways (e.g. TLR signalling and inflammasome pathways) and the transient recruitment of granulocytes into the lymph. At 24 h a more monocytic cellular profile arose coinciding with a transition to a specific antiviral response characterised by the up-regulation of genes associated with the receptors typical for the viral mimic, poly(I:C) (e.g. TLR3, RIG-I and MDA5). At the latest time points the up-regulation of IL-17A and IL-17F suggested that Th17 cells may participate in the earliest adaptive response to this vaccine. These data provide the most comprehensive picture of the cellular and molecular mechanisms that link the periphery to the draining lymph node following vaccination, and indicate that the immune response is capable of specialising within the periphery.

The current status and future impact of targeted therapies in non-Hodgkin lymphoma

A number of new, biologic targeted therapies have been developed for the treatment of lymphoid malignancies. These include anti-CD20 monoclonal antibodies designed with greater binding affinities and different mechanisms of action profiles compared with rituximab. Other extracellular antigens on B cells and T cells are also being targeted. Monoclonal antibodies have been conjugated to radioisotopes and cellular toxins. In addition, several exciting new small-molecule kinase inhibitors are in development that target intracellular pathways that contribute to the pathogenesis of these diseases. Drugs that affect the tumor microenvironment are also under investigation. The advantage of these targeted agents compared with standard chemotherapy is greater tumor specificity, a more favorable toxicity profile, and, when combined with scientific rationale, and in the appropriate setting, perhaps a better long-term outcome.

A modified database search strategy leads to improved identification of in vitro brominated peptides spiked into a complex proteomic sample

Inflammation leads to activation of immune cells, resulting in production of hypobromous acid. Few investigations have been performed on protein bromination on a proteomic scale, even though bromination is a relatively abundant protein modification in endogenously brominated proteomes. Such studies have been hampered by the lack of an optimized database search strategy. In order to address this issue, we performed nano-LC-MS/MS analysis of an in vitro generated, trypsin-digested brominated human serum albumin standard, spiked into a complex trypsin-digested proteomic background, in an LTQ-Orbitrap instrument. We found that brominated peptides spiked in at a 1-10% ratio (mass:mass) were easily identified by manual inspection when higher-energy collisional dissociation (HCD) and collision induced dissociation (CID) were employed as the dissociation mode; however, confident assignment of brominated peptides from protein database searches required a novel approach. By addition of a custom modification, corresponding to the substitution of a single bromine with 81Br rather than 79Br for dibromotyrosine (79Br81BrY), the number of validated assignments for peptides containing dibromotyrosine increased significantly when analyzing both high resolution and low resolution MS/MS data. This new approach will facilitate the identification of proteins derived from endogenously brominated proteomes, providing further knowledge about the role of protein bromination in various pathological states.

Update on anticytokine treatment for asthma

Current advances in the knowledge of asthma pathobiology suggest that anticytokine therapies can be potentially useful for the treatment of this complex and heterogeneous airway disease. Recent evidence is accumulating in support of the efficacy of anti-IL-4, anti-IL-5, and anti-IL-13 drugs. Therefore, these new developments are now changing the global scenario of antiasthma therapies, especially with regard to more severe disease. Current findings referring to variability of individual therapeutic responses highlight that the different asthma subtypes need to be well characterized, in order to implement phenotype-targeted treatments which in the near future will hopefully be mainly based on cytokine-directed biologics.

The effectiveness of fish oil supplementation in asthmatic rats is limited by an inefficient action on ASM function

Episodes of acute exacerbation are the major clinical feature of asthma and therefore represent an important focus for developing novel therapies for this disease. There are many reports that the n-3 fatty acids found in fish oil exert anti-inflammatory effects, but there are few studies of the action of fish oil on airway smooth muscle (ASM) function. In the present investigation, we evaluated the effect of fish oil supplementation on smooth muscle force of contraction in ovalbumin-induced asthmatic Wistar rats, and its consequences on static lung compliance, mucus production, leukocyte chemotaxis and production of proinflammatory cytokines. Fish oil supplementation suppressed the infiltration of inflammatory cells into the lung in asthmatic animals (2.04 ± 0.19 × 10(6) cells vs. 3.33 ± 0.43 × 10(6) cells in the control asthmatic group; P < 0.05). Static lung compliance increased with fish oil supplementation in asthmatic rats (0.640 ± 0.053 mL/cm H2O vs. 0.399 ± 0.043 mL/cm H2O; P < 0.05). However, fish oil did not prevent asthma-associated lung eosinophilia and did not affect the concentrations of tumor necrosis factor-α and interleukin-1β in lung tissue or the proportion of the airways obliterated with mucus. Fish oil had no effect on the force of contraction in asthmatic rats in response to acetylcholine (3.026 ± 0.274 mN vs. 2.813 ± 0.364 mN in the control asthmatic group). In conclusion, although fish oil exerts some benefits in this model of asthma, its effectiveness appears to be limited by an inefficient action on airway smooth muscle function.

Expression of the secondary granule proteins major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX) is required for eosinophilopoiesis in mice

Eosinophil activities are often linked with allergic diseases such as asthma and the pathologies accompanying helminth infection. These activities have been hypothesized to be mediated, in part, by the release of cationic proteins stored in the secondary granules of these granulocytes. The majority of the proteins stored in these secondary granules (by mass) are major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX). Unpredictably, a knockout approach targeting the genes encoding these proteins demonstrated that, unlike in mice containing a single deficiency of only MBP-1 or EPX, the absence of both granule proteins resulted in the near complete loss of peripheral blood eosinophils with no apparent impact on any other hematopoietic lineage. Moreover, the absence of MBP-1 and EPX promoted a concomitant loss of eosinophil lineage-committed progenitors in the marrow, identifying a specific blockade in eosinophilopoiesis as the causative event. Significantly, this blockade of eosinophilopoiesis is also observed in ex vivo cultures of marrow progenitors and is not rescued in vivo by adoptive bone marrow engraftment, suggesting a cell-autonomous defect in marrow progenitors. These observations implicate a role for granule protein gene expression as a regulator of eosinophilopoiesis and provide another strain of mice congenitally deficient of eosinophils.

Homologous recombination into the eosinophil peroxidase locus generates a strain of mice expressing Cre recombinase exclusively in eosinophils

Eosinophils are generally linked to innate host defense against helminths, as well as the pathologies associated with allergic diseases, such as asthma. Nonetheless, the activities of eosinophils remain poorly understood, which in turn, has prevented detailed definitions of their role(s) in health and disease. Homologous recombination in embryonic stem cells was used to insert a mammalianized Cre recombinase in the ORF encoding Epx. This knock-in strategy overcame previous inefficiencies associated with eosinophil-specific transgenic approaches and led to the development of a knock-in strain of mice (eoCRE), capable of mediating recombination of "floxed" reporter cassettes in >95% of peripheral blood eosinophils. We also showed that this Cre expression was limited exclusively to eosinophil-lineage committed cells with no evidence of Cre-mediated toxicity. The efficiency and specificity of Cre expression in eoCRE mice were demonstrated further in a cross with a knock-in mouse containing a "(flox-stop-flox)" DTA cassette at the ROSA26 locus, generating yet another novel, eosinophil-less strain of mice. The development of eoCRE mice represents a milestone in studies of eosinophil biology, permitting eosinophil-specific gene targeting and overexpression in the mouse as part of next-generation studies attempting to define eosinophil effector functions.

Eosinophilic inflammation in allergic asthma

Eosinophils are circulating granulocytes involved in pathogenesis of asthma. A cascade of processes directed by Th2 cytokine producing T-cells influence the recruitment of eosinophils into the lungs. Furthermore, multiple elements including interleukin (IL)-5, IL-13, chemoattractants such as eotaxin, Clara cells, and CC chemokine receptor (CCR)3 are already directly involved in recruiting eosinophils to the lung during allergic inflammation. Once recruited, eosinophils participate in the modulation of immune response, induction of airway hyperresponsiveness and remodeling, characteristic features of asthma. Various types of promising treatments for reducing asthmatic response are related to reduction in eosinophil counts both in human and experimental models of pulmonary allergic inflammation, showing that the recruitment of these cells really plays an important role in the pathophysiology of allergic diseases such asthma.

Eosinophil recruitment and activation: the role of lipid mediators

Eosinophils are effector cells that migrate toward several mediators released at inflammatory sites to perform their multiple functions. The mechanisms driving eosinophil selective accumulation in sites of allergic inflammation are well-established and involve several steps controlled by adhesion molecules, priming agents, chemotactic, and surviving factors. Even though the majority of studies focused on role of protein mediators like IL-5 and eotaxins, lipid mediators also participate in eosinophil recruitment and activation. Among the lipid mediators with distinguish eosinophil recruitment and activation capabilities are platelet activating factor and the eicosanoids, including leukotriene B₄, cysteinyl leukotrienes, and prostaglandin D₂. In this review, we focused on the role of these four lipid mediators in eosinophil recruitment and activation, since they are recognized as key mediators of eosinophilic inflammatory responses.

Targeting eosinophils in allergy, inflammation and beyond

Eosinophils can regulate local immune and inflammatory responses, and their accumulation in the blood and tissue is associated with several inflammatory and infectious diseases. Thus, therapies that target eosinophils may help control diverse diseases, including atopic disorders such as asthma and allergy, as well as diseases that are not primarily associated with eosinophils, such as autoimmunity and malignancy. Eosinophil-targeted therapeutic agents that are aimed at blocking specific steps involved in eosinophil development, migration and activation have recently entered clinical testing and have produced encouraging results and insights into the role of eosinophils. In this Review, we describe recent advances in the development of first-generation eosinophil-targeted therapies and highlight strategies for using personalized medicine to treat eosinophilic disorders.

Insights into the glycosaminoglycan-mediated cytotoxic mechanism of eosinophil cationic protein revealed by NMR

Protein-glycosaminoglycan interactions are essential in many biological processes and human diseases, yet how their recognition occurs is poorly understood. Eosinophil cationic protein (ECP) is a cytotoxic ribonuclease that interacts with glycosaminoglycans at the cell surface; this promotes the destabilization of the cellular membrane and triggers ECP's toxic activity. To understand this membrane destabilization event and the differences in the toxicity of ECP and its homologues, the high resolution solution structure of the complex between full length folded ECP and a heparin-derived trisaccharide (O-iPr-α-D-GlcNS6S-α(1-4)-L-IdoA2S-α(1-4)-D-GlcNS6S) has been solved by NMR methods and molecular dynamics simulations. The bound protein retains the tertiary structure of the free protein. The (2)S(0) conformation of the IdoA ring is preferably recognized by the protein. We have identified the precise location of the heparin binding site, dissected the specific interactions responsible for molecular recognition, and defined the structural requirements for this interaction. The structure reveals the contribution of Arg7, Gln14, and His15 in helix α1, Gln40 in strand β1, His64 in loop 4, and His128 in strand β6 in the recognition event and corroborates the previously reported participation of residues Arg34-Asn39. The participation of the catalytic triad (His15, Lys38, His128) in recognizing the heparin mimetic reveals, at atomic resolution, the mechanism of heparin's inhibition of ECP's ribonucleolytic activity. We have integrated all the available data to propose a molecular model for the membrane interaction process. The solved NMR complex provides the structural model necessary to design inhibitors to block ECP's toxicity implicated in eosinophil pathologies.

Human versus mouse eosinophils: "that which we call an eosinophil, by any other name would stain as red"

The respective life histories of human subjects and mice are well defined and describe a unique story of evolutionary conservation extending from sequence identity within the genome to the underpinnings of biochemical, cellular, and physiologic pathways. As a consequence, the hematopoietic lineages of both species are invariantly maintained, each with identifiable eosinophils. This canonical presence nonetheless does not preclude disparities between human and mouse eosinophils, their effector functions, or both. Indeed, many books and reviews dogmatically highlight differences, providing a rationale to discount the use of mouse models of human eosinophilic diseases. We suggest that this perspective is parochial and ignores the wealth of available studies and the consensus of the literature that overwhelming similarities (and not differences) exist between human and mouse eosinophils. The goal of this review is to summarize this literature and in some cases provide experimental details comparing and contrasting eosinophils and eosinophil effector functions in human subjects versus mice. In particular, our review will provide a summation and an easy-to-use reference guide to important studies demonstrating that although differences exist, more often than not, their consequences are unknown and do not necessarily reflect inherent disparities in eosinophil function but instead species-specific variations. The conclusion from this overview is that despite nominal differences, the vast similarities between human and mouse eosinophils provide important insights as to their roles in health and disease and, in turn, demonstrate the unique utility of mouse-based studies with an expectation of valid extrapolation to the understanding and treatment of patients.