Eosinophils in the pathogenesis of allergic airways disease

Regulation of spontaneous eosinophil apoptosis-a neglected area of importance

Asthma is characterized by the accumulation of eosinophils in the airways in most phenotypes. Eosinophils are inflammatory cells that require an external survival-prolonging stimulus such as granulocyte macrophage-colony-stimulating factor (GM-CSF), interleukin (IL)-5, or IL-3 for survival. In their absence, eosinophils are programmed to die by spontaneous apoptosis in a few days. Eosinophil apoptosis can be accelerated by Fas ligation or by pharmacological agents such as glucocorticoids. Evidence exists for the relevance of these survival-prolonging and pro-apoptotic agents in the regulation of eosinophilic inflammation in inflamed airways. Much less is known about the physiological significance and mechanisms of spontaneous eosinophil apoptosis even though it forms the basis of regulation of eosinophil longevity by pathophysiological factors and pharmacological agents. This review concentrates on discussing the mechanisms of spontaneous eosinophil apoptosis compared to those of glucocorticoid- and Fas-induced apoptosis. We aim to answer the question whether the external apoptotic stimuli only augment the ongoing pathway of spontaneous apoptosis or truly activate a specific pathway.

Architecture and inflammatory cell composition of the feline lung with special consideration of eosinophil counts

An increase in the number of eosinophils in bronchoalveolar lavage fluid (BALF) is a hallmark of feline asthma; however, a wide range in the percentage of eosinophils in BALF has been documented in healthy cats. In this study, BALF and lung tissue were collected from 15 cats without respiratory disease, BALF was taken from 15 cats with asthma and lung tissue was collected from six different asthmatic cats. Total nucleated cell count (TNCC) and inflammatory cell percentages were measured in BALF and lung tissue was evaluated microscopically. Asthmatic cats had a significantly higher eosinophil count in lung tissue, but BALF TNCC did not differ significantly between groups. Cats without respiratory signs had significantly more numerous macrophages and lymphocytes in BALF than asthmatics, but significantly lower percentages of eosinophils (4.2 ± 7.8% versus 49.4 ± 20.6%, P <0.001). In healthy feline airways a BALF eosinophil percentage of <5% can be expected. Dominant microscopical findings in feline asthma include high eosinophil counts, airway remodelling and inflammation. There is good correlation between the findings in BALF and tissue in feline asthma.

Inhibitory action of quercetin on eosinophil activation in vitro

The influence of quercetin on eosinophil functions was examined in vitro and in vivo. The first set of experiments was undertaken to examine whether quercetin could suppress eosinophilia and IgE hyperproduction induced by Mesocestoides corti infection in BALB/c mice. The number of peripheral blood eosinophils and IgE levels were examined 21 days after infection. Oral administration of quercetin for 21 days could not suppress both peripheral blood eosinophilia and IgE hyperproduction, even when 20.0 mg/kg quercetin was used for treatment. The second part of the experiment was designed to examine the influence of quercetin on eosinophil activation induced by SCF stimulation in vitro. Eosinophils were obtained from M. corti-infected mice and stimulated with SCF in the presence of various concentrations of quercetin for 24 h. The addition of quercetin into cell cultures could suppress eosinophil activation induced by SCF stimulation as assessed by measuring the contents of RANTES, MIP-1β, ECP, and MBP in culture supernatants. The minimum concentration of quercetin which caused significant suppression of factor secretion was 5.0 μM. These results may suggest that quercetin will be a good candidate for the supplement on the management of eosinophil-mediated diseases, such as allergic rhinitis and asthma.

Human eosinophils express functional CCR7

Human eosinophils display directed chemotactic activity toward an array of soluble chemokines. Eosinophils have been observed to migrate to draining lymph nodes in experimental models of allergic inflammation, yet it is unknown whether eosinophils express CCR7, a key chemokine receptor in coordinating leukocyte trafficking to lymph nodes. The purpose of this study is to demonstrate expression of CCR7 by human eosinophils and functional responses to CCL19 and CCL21, the known ligands of CCR7. Human eosinophils were purified by negative selection from healthy donors. CCR7 expression of freshly purified, unstimulated eosinophils and of IL-5-primed eosinophils was determined by flow cytometry and Western blot. Chemotaxis to CCL19 and CCL21 was measured in transwell assays. Shape changes to CCL19 and CCL21 were analyzed by flow cytometry and microscopy. Calcium fluxes of fluo-4 AM-loaded eosinophils were recorded by flow cytometry after chemokine stimulation. ERK phosphorylation of CCL19- and CCL21-stimulated eosinophils was measured by Western blot and Luminex assay. Human eosinophils expressed CCR7 as demonstrated by flow cytometry and Western blots. Eosinophils exhibited detectable cell surface expression of CCR7. IL-5-primed eosinophils exhibited chemotaxis toward CCL19 and CCL21 in a dose-dependent fashion. Upon stimulation with CCL19 or CCL21, IL-5-primed eosinophils demonstrated dose-dependent shape changes with polarization of F-actin and exhibited calcium influxes. Finally, primed eosinophils stimulated with CCL19 or CCL21 exhibited increased phosphorylation of ERK in response to both CCR7 ligands. We demonstrate that human eosinophils express CCR7 and have multipotent responses to the known ligands of CCR7.

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.

RAGE regulation and signaling in inflammation and beyond

RAGE is a key molecule in the onset and sustainment of the inflammatory response. New studies indicate that RAGE might represent a new link between the innate and adaptive immune system. RAGE belongs to the superfamily of Ig cell-surface receptors and is expressed on all types of leukocytes promoting activation, migration, or maturation of the different cells. RAGE expression is prominent on the activated endothelium, where it mediates leukocyte adhesion and transmigration. Moreover, proinflammatory molecules released from the inflamed or injured vascular system induce migration and proliferation of SMCs. RAGE binds a large number of different ligands and is therefore considered as a PRR, recognizing a structural motif rather than a specific ligand. In this review, we summarize the current knowledge about the signaling pathways activated in the different cell types and discuss a potential activation mechanism of RAGE, as well as putative options for therapeutic intervention.

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

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

Symptom score for allergic rhinitis

OBJECTIVES

To determine the prevalence of allergic rhinitis in our study population and the correlation between the Score for Allergic Rhinitis (SFAR) and nasal smear eosinophil count.

STUDY DESIGN

Cross-sectional study.

SETTING

Ear, nose, and throat clinic, University of Ilorin Teaching Hospital, Nigeria; a 450-bed tertiary health facility.

SUBJECTS

Two hundred seventy-five consecutive, consenting patients who presented with nasal symptoms.

METHODS

Information on the 8-parameter symptom score was collected using a semistructured questionnaire by interview. Nasal smear slides were air dried, fixed with 95% alcohol, stained using May-Grünwald-Giemsa stain, and examined under a light microscope.

RESULTS

Of the 275 participants seen during the 1-year study, 116 (42.2%) were males. The mean ± SD age was 38.5 ± 16.3 (range, 14-75) years. Eighty-one (29.5%) were diagnosed with allergic rhinitis using a nasal smear eosinophil count. The most common symptom was excessive sneezing, involving 93% of patients with allergic rhinitis (P < .001). The prevalence of allergic rhinitis using SFAR was 31.6%. The SFAR cutoff was set at >8 (P < .001). The sensitivity and specificity for SFAR were 94.8% (confidence interval [CI], 90.5%-97.4%) and 95.1% (CI, 87.2%-98.4%), respectively. A high Spearman's correlation (0.88) was obtained for SFAR when correlated with nasal smear eosinophil count.

CONCLUSION

The prevalence of allergic rhinitis using SFAR was 31.6%. The study shows that SFAR can be used as a simple, valid diagnostic tool in allergic rhinitis. This is important in rural settings where access to laboratory investigations might not be readily available.

Eosinophils in fungus-associated allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to fungal allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma with fungal sensitization is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen that is worsened by environmental exposure to airborne fungi and which leads to a disease course that is often very difficult to treat with standard asthma therapies. As a result of complex interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to fungal allergens may experience a greater degree of airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. From their development in the bone marrow to their recruitment to the lung via chemokine and cytokine networks, eosinophils form an important component of the inflammatory milieu that is associated with this syndrome. Eosinophils are recognized as complex multi-factorial leukocytes with diverse functions in the context of allergic fungal asthma. In this review, we will consider recent advances in our understanding of the molecular mechanisms that are associated with eosinophil development and migration to the allergic lung in response to fungal inhalation, along with the eosinophil’s function in the immune response to and the immunopathology attributed to fungus-associated allergic pulmonary disease.

Evidence for ligand-specific conformations of the histamine H(2)-receptor in human eosinophils and neutrophils

The histamine H(2)-receptor (H(2)R) couples to G(S)-proteins and induces adenylyl cyclase-mediated cAMP accumulation. In human neutrophils and eosinophils, the H(2)R reduces chemotactic peptide-stimulated superoxide anion (O(2)(-)) formation. However, pharmacological characterization of the H(2)R in these cells is far from being complete. The aim of this study was to provide a comprehensive profiling of the H(2)R in neutrophils and eosinophils. Histamine inhibited O(2)(-) formation in human neutrophils more effectively than in eosinophils. H(2)R agonists mimicked the effects of histamine and H(2)R antagonists blocked the effects of histamine. We noticed multiple discrepancies in the potencies and efficacies of H(2)R agonists with respect to cAMP accumulation and inhibition of O(2)(-) formation in both cell types. There were also differences in the antagonist profiles between cAMP accumulation and inhibition of O(2)(-) formation in neutrophils. Moreover, the pharmacological profile of the recombinant H(2)R did not match the H(2)R profile in native cells. The H(2)R sequence identified in human neutrophils corresponds to the published H(2)R sequence, excluding the exclusive expression of a new H(2)R isoform as explanation for the differences. Very likely, the differences between ligands are explained by the existence of ligand-specific receptor conformations with unique affinities, potencies and efficacies. Thus, our data provide evidence for the notion that the concept of ligand-specific receptor conformations can be extended from recombinant systems to native cells.

Inflammatory mediators in induced sputum and airway hyperresponsiveness in cough variant asthma during long-term inhaled corticosteroid treatment

Objective. This study aimed to investigate improvements in inflammatory mediator levels in induced sputum and airway hyperresponsiveness (AHR) in cough variant asthma (CVA) during long-term inhaled corticosteroid (ICS) treatment. Patients and Methods. Patients with CVA (N = 35) and classic asthma (N = 26) and healthy subjects (N = 24) were recruited into this study. All patients were treated with budesonide (400 μg/day). Measurement of inflammatory mediators in induced sputum and PD20-FEV₁ (the accumulated provocative dose resulting in a 20% decrease in FEV₁) in histamine-challenged subjects was performed every three months after the start of medication. Interleukin- (IL-) 5 and IL-10 were assayed by ELISA, and the percentage of eosinophils was detected with Giemsa stain. Trends during the follow-up period were analyzed using a general linear model. Results. Inflammatory mediator levels in induced sputum and PD20-FEV₁ in patients with CVA and classic asthma differed from those in the control group, although no differences were found in the two asthmatic groups. PD20-FEV₁ significantly increased in CVA patients after ICS treatment for 3 months, while classic asthma patients exhibited a delayed change in AHR. After ICS treatment, levels of IL-5 and IL-10 as well as the percentage of eosinophils in the CVA group were altered at 3 months and 6 months, respectively. Accordingly, the level of inflammatory mediators in classic asthma changed more slowly. Conclusion. CVA has a greater improvement in airway inflammation and airway hyperresponsiveness (AHR) than classic asthma with respect to inhaled corticosteroid (ICS). Short-term ICS considerably reduces AHR although longer treatment is required for complete control of airway inflammation.

IL-4 engagement of the type I IL-4 receptor complex enhances mouse eosinophil migration to eotaxin-1 in vitro

Background

Previous work from our laboratory demonstrated that IL-4Rα expression on a myeloid cell type was responsible for enhancement of Th2-driven eosinophilic inflammation in a mouse model of allergic lung inflammation. Subsequently, we have shown that IL-4 signaling through type I IL-4 receptors on monocytes/macrophages strongly induced activation of the IRS-2 pathway and a subset of genes characteristic of alternatively activated macrophages. The direct effect(s) of IL-4 and IL-13 on mouse eosinophils are not clear. The goal of this study was determine the effect of IL-4 and IL-13 on mouse eosinophil function.

Methods

Standard Transwell chemotaxis assay was used to assay migration of mouse eosinophils and signal transduction was assessed by Western blotting.

Results

Here we determined that (i) mouse eosinophils express both type I and type II IL-4 receptors, (ii) in contrast to human eosinophils, mouse eosinophils do not chemotax to IL-4 or IL-13 although (iii) pre-treatment with IL-4 but not IL-13 enhanced migration to eotaxin-1. This IL-4-mediated enhancement was dependent on type I IL-4 receptor expression: γC-deficient eosinophils did not show enhancement of migratory capacity when pre-treated with IL-4. In addition, mouse eosinophils responded to IL-4 with the robust tyrosine phosphorylation of STAT6 and IRS-2, while IL-13-induced responses were considerably weaker.

Conclusions

The presence of IL-4 in combination with eotaxin-1 in the allergic inflammatory milieu could potentiate infiltration of eosinophils into the lungs. Therapies that block IL-4 and chemokine receptors on eosinophils might be more effective clinically in reducing eosinophilic lung inflammation.

Pattern-recognition receptors in human eosinophils

The pattern-recognition receptor (PRR) family includes Toll-like receptors (TLRs), nucleotide-binding oligomerization domain (NOD) -like receptors (NLRs), RIG-I-like receptors (RLRs), C-type lectin receptors (CLRs) and the receptor for advanced glycation end products (RAGE). They recognize various microbial signatures or host-derived danger signals and trigger an immune response. Eosinophils are multifunctional leucocytes involved in the pathogenesis of several inflammatory processes, including parasitic helminth infection, allergic diseases, tissue injury and tumour immunity. Human eosinophils express several PRRs, including TLR1-5, TLR7, TLR9, NOD1, NOD2, Dectin-1 and RAGE. Receptor stimulation induces survival, oxidative burst, activation of the adhesion system and release of cytokines (interleukin-1β, interleukin-6, tumour necrosis factor-α and granulocyte-macrophage colony-stimulating factor), chemokines (interleukin-8 and growth-related oncogene-α) and cytotoxic granule proteins (eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase and major basic protein). It is also evident that eosinophils play an immunomodulatory role by interacting with surrounding cells. The presence of a broad range of PRRs in eosinophils indicates that they are not only involved in defence against parasitic helminths, but also against bacteria, viruses and fungi. From a clinical perspective, eosinophilic PRRs seem to be involved in both allergic and malignant diseases by causing exacerbations and affecting tumour growth, respectively.

Eosinophils in glioblastoma biology

Glioblastoma multiforme (GBM) is the most common primary brain tumor in adults. The development of this malignant glial lesion involves a multi-faceted process that results in a loss of genetic or epigenetic gene control, un-regulated cell growth, and immune tolerance. Of interest, atopic diseases are characterized by a lack of immune tolerance and are inversely associated with glioma risk. One cell type that is an established effector cell in the pathobiology of atopic disease is the eosinophil. In response to various stimuli, the eosinophil is able to produce cytotoxic granules, neuromediators, and pro-inflammatory cytokines as well as pro-fibrotic and angiogenic factors involved in pathogen clearance and tissue remodeling and repair. These various biological properties reveal that the eosinophil is a key immunoregulatory cell capable of influencing the activity of both innate and adaptive immune responses. Of central importance to this report is the observation that eosinophil migration to the brain occurs in response to traumatic brain injury and following certain immunotherapeutic treatments for GBM. Although eosinophils have been identified in various central nervous system pathologies, and are known to operate in wound/repair and tumorstatic models, the potential roles of eosinophils in GBM development and the tumor immunological response are only beginning to be recognized and are therefore the subject of the present review.

IL-8, IL-10, TGF-β, and GCSF levels were increased in severe persistent allergic asthma patients with the anti-IgE treatment

BACKGROUND

Allergic asthma is showed an increase in Th2-cytokine and IgE levels and an accumulation activation of Th2 cells, eosinophils and mast cells. However, recent studies focused on cell-based mechanisms for the pathogenesis of allergic asthma. Objectives. In this study, we compare the anti-IgE treatment modality in the dynamics of immune system cytokine levels in severe persistent asthma (SPA) patients who had no other any allergic disease, newly diagnosed allergic asthma patients and healthy volunteers.

STUDY DESIGN

The study population consisted of 14 SPA patients, 14 newly diagnosed allergic asthma patients and 14 healthy volunteers included as controls. Cytokine levels were measured. Total and specific IgE levels of anti-IgE monoclonal antibody treated patients, serum high-sensitivity C-reactive protein (hsCRP) levels, FEV1/FVC rates and asthma control test (ACT) were measured for the clinical follow-up.

RESULTS

We observed that SPA patients presented increasing levels of IL-8, IL-10, TGF-β and GCSF during the anti-IgE treatment in period of sampling times at 4 months and 18 months. However this increase was not correlated neither with serum hsCRP levels nor FEV1/FVC rates.

CONCLUSIONS

Our study gives a different perspective for the SPA and anti-IgE immunotherapy efficacy at the cell cytokine-linked step.

NOD-like receptors and RIG-I-like receptors in human eosinophils: activation by NOD1 and NOD2 agonists

NOD-like receptors (NLRs) and RIG-I-like receptors (RLRs) are newly discovered pattern-recognition receptors. They detect substructures of bacterial peptidoglycan and viral RNA, respectively, thereby initiating an immune response. However, their role in eosinophil activation remains to be explored. The aim of this study was to characterize the expression of a range of NLRs and RLRs in purified human eosinophils and assess their functional importance. Expression of NOD1, NOD2, NLRP3, RIG-I and MDA-5 was investigated using real-time reverse transcription PCR, flow cytometry and immunohistochemistry. The effects of the corresponding agonists iE-DAP (NOD1), MDP (NOD2), alum (NLRP3) and poly(I:C)/LyoVec (RIG-I/MDA-5) were studied in terms of cytokine secretion, degranulation, survival, expression of adhesion molecules and activation markers, and chemotactic migration. Eosinophils expressed NOD1 and NOD2 mRNA and protein. Low levels of RIG-I and MDA-5 were found, whereas expression of NLRP3 was completely absent. In accordance, stimulation with iE-DAP and MDP was found to induce secretion of interleukin-8, up-regulate expression of CD11b, conversely down-regulate CD62 ligand, increase expression of CD69 and induce migration. The MDP also promoted release of eosinophil-derived neurotoxin, whereas iE-DAP failed to do so. No effects were seen upon stimulation with alum or poly(I:C)/LyoVec. Moreover, the NOD1-induced and NOD2-induced activation was mediated via the nuclear factor-κB signalling pathway and augmented by interleukin-5 and granulocyte-macrophage colony-stimulating factor, but not interferon-γ. Taken together, the NLR system represents a novel pathway for eosinophil activation. The responses are enhanced in the presence of cytokines that regulate T helper type 2 immunity, suggesting that the NLRs constitute a link between respiratory infections and exacerbations of allergic disease.

Human eosinophils express RAGE, produce RAGE ligands, exhibit PKC-delta phosphorylation and enhanced viability in response to the RAGE ligand, S100B

This study tested the hypothesis that human eosinophils produce ligands for the receptor for advanced glycation end-products (RAGE), express RAGE and exhibit RAGE-mediated responses. In examining our microarray data, we identified the presence of RAGE and RAGE ligand (S100A4, S100A6, S100A8, S100A9, S100A11, S100P, HMGB1) transcripts. Expression of eosinophil RAGE mRNA was also compared with a known positive control and further assessed via bioinformatics and sequence analysis of RAGE cDNA. Positive and negative controls were used to identify RAGE, S100A8 and S100A9 protein in human primary eosinophils. Immunoblot assessment of eosinophils treated with cytokines (IL-5 or granulocyte macrophage colony-stimulating factor) indicated an up-regulation of S100A8 and S100A9 production, whereas co-treatment of eosinophils with a RAGE ligand and cytokines displayed a down-regulation in the levels of RAGE. Analysis of eosinophil-conditioned media revealed that eosinophils are capable of releasing RAGE, S100A8 and S100A9. To test the eosinophil response to RAGE activation, the most well-characterized RAGE ligand, S100B, was examined. Treatment of eosinophils with S100B resulted in RAGE-mediated PKC-delta phosphorylation, a 3-fold dose-dependent increase in cell survival and an increase in the level of cellular RAGE. Combined, these studies reveal eosinophil expression of RAGE, RAGE ligands and RAGE-mediated responses. The expression of eosinophil RAGE, soluble RAGE and RAGE ligands may be pivotal to the functions of eosinophils in various human diseases involving RAGE and S100 ligands.

Can anti-IgE therapy prevent airway remodeling in allergic asthma?

Airway remodeling is a central feature of asthma. It is exemplified by thickening of the lamina reticularis and structural changes to the epithelium, submucosa, smooth muscle, and vasculature of the airway wall. Airway remodeling may result from persistent airway inflammation. Immunoglobulin E (IgE) is an important mediator of allergic reactions and has a central role in airway inflammation and asthma-related symptoms. Anti-IgE therapies (such as omalizumab) have the potential to block an early step in the allergic cascade and therefore have the potential to reduce airway remodeling. The reduction in free IgE levels following anti-IgE therapy leads to reductions in high-affinity IgE receptor (FcεRI) expression on mast cells, basophils, and dendritic cells. This combined effect results in attenuation of several markers of inflammation, including peripheral and bronchial tissue eosinophilia and levels of granulocyte macrophage colony-stimulating factor, interleukin (IL)-2, IL-4, IL-5, and IL-13. Considering the previously demonstrated anti-inflammatory effects of anti-IgE therapy, along with results from a small study showing continued benefit after discontinuation of long-term treatment, a larger study to assess its effect on markers of airway remodeling is underway.

GM-CSF production by glioblastoma cells has a functional role in eosinophil survival, activation, and growth factor production for enhanced tumor cell proliferation

Medicinal interventions of limited efficacy are currently available for the treatment of glioblastoma multiforme (GBM), the most common and lethal primary brain tumor in adults. The eosinophil is a pivotal immune cell in the pathobiology of atopic disease that is also found to accumulate in certain tumor tissues. Inverse associations between atopy and GBM risk suggest that the eosinophil may play a functional role in certain tumor immune responses. To assess the potential interactions between eosinophils and GBM, we cultured human primary blood eosinophils with two separate human GBM-derived cell lines (A172, U87-MG) or conditioned media generated in the presence or absence of TNF-α. Results demonstrated differential eosinophil adhesion and increased survival in response to coculture with GBM cell lines. Eosinophil responses to GBM cell line-conditioned media included increased survival, activation, CD11b expression, and S100A9 release. Addition of GM-CSF neutralizing Abs to GBM cell cultures or conditioned media reduced eosinophil adhesion, survival, and activation, linking tumor cell-derived GM-CSF to the functions of eosinophils in the tumor microenvironment. Dexamethasone, which has been reported to inhibit eosinophil recruitment and shrink GBM lesions on contrast-enhanced scans, reduced the production of tumor cell-derived GM-CSF. Furthermore, culture of GBM cells in eosinophil-conditioned media increased tumor cell viability, and generation of eosinophil-conditioned media in the presence of GM-CSF enhanced the effect. These data support the idea of a paracrine loop between GM-CSF-producing tumors and eosinophil-derived growth factors in tumor promotion/progression.

Targeting chemokine receptors in allergic disease

The directed migration of cells in response to chemical cues is known as chemoattraction, and plays a key role in the temporal and spatial positioning of cells in lower- and higher-order life forms. Key molecules in this process are the chemotactic cytokines, or chemokines, which, in humans, constitute a family of approx. 40 molecules. Chemokines exert their effects by binding to specific GPCRs (G-protein-coupled receptors) which are present on a wide variety of mature cells and their progenitors, notably leucocytes. The inappropriate or excessive generation of chemokines is a key component of the inflammatory response observed in several clinically important diseases, notably allergic diseases such as asthma. Consequently, much time and effort has been directed towards understanding which chemokine receptors and ligands are important in the allergic response with a view to therapeutic intervention. Such strategies can take several forms, although, as the superfamily of GPCRs has historically proved amenable to blockade by small molecules, the development of specific antagonists has been has been a major focus of several groups. In the present review, I detail the roles of chemokines and their receptors in allergic disease and also highlight current progress in the development of relevant chemokine receptor antagonists.

Piecemeal degranulation in human eosinophils: a distinct secretion mechanism underlying inflammatory responses

Secretion is a fundamental cell process underlying different physiological and pathological events. In cells from the human immune system such as eosinophils, secretion of mediators generally occurs by means of piecemeal degranulation, an unconventional secretory pathway characterized by vesicular transport of small packets of materials from the cytoplasmic secretory granules to the cell surface. During piecemeal degranulation in eosinophils, a distinct transport vesicle system, which includes large, pleiomorphic vesiculo-tubular carriers is mobilized and enables regulated release of granule-stored proteins such as cytokines and major basic protein. Piecemeal degranulation underlies distinct functions of eosinophils as effector and immunoregulatory cells. This review focuses on the structural and functional advances that have been made over the last years concerning the intracellular trafficking and secretion of eosinophil proteins by piecemeal degranulation during inflammatory responses.

An ovine tracheal explant culture model for allergic airway inflammation

Background

The airway epithelium is thought to play an important role in the pathogenesis of asthmatic disease. However, much of our understanding of airway epithelial cell function in asthma has been derived from in vitro studies that may not accurately reflect the interactive cellular and molecular pathways active between different tissue constituents in vivo.

Methods

Using a sheep model of allergic asthma, tracheal explants from normal sheep and allergic sheep exposed to house dust mite (HDM) allergen were established to investigate airway mucosal responses ex vivo. Explants were cultured for up to 48 h and tissues were stained to identify apoptotic cells, goblet cells, mast cells and eosinophils. The release of cytokines (IL-1α, IL-6 and TNF-α) by cultured tracheal explants, was assessed by ELISA.

Results

The general morphology and epithelial structure of the tracheal explants was well maintained in culture although evidence of advanced apoptosis within the mucosal layer was noted after culture for 48 h. The number of alcian blue/PAS positive mucus-secreting cells within the epithelial layer was reduced in all cultured explants compared with pre-cultured (0 h) explants, but the loss of staining was most evident in allergic tissues. Mast cell and eosinophil numbers were elevated in the allergic tracheal tissues compared to naïve controls, and in the allergic tissues there was a significant decline in mast cells after 24 h culture in the presence or absence of HDM allergen. IL-6 was released by allergic tracheal explants in culture but was undetected in cultured control explants.

Conclusions

Sheep tracheal explants maintain characteristics of the airway mucosa that may not be replicated when studying isolated cell populations in vitro. There were key differences identified in explants from allergic compared to control airways and in their responses in culture for 24 h. Importantly, this study establishes the potential for the application of tracheal explant cultures in relevant ex vivo investigations on the therapeutic and mechanistic modalities of asthmatic disease.

IL-33 exacerbates eosinophil-mediated airway inflammation

IL-33 has emerged as an important mediator in the immunopathogenesis of allergy and asthma. However, the role of IL-33 in eosinophil-mediated inflammation has not been fully explored. In this article, we report that IL-33 directly stimulates eosinophil differentiation from CD117(+) progenitors in an IL-5-dependent manner. Although resting eosinophils expressed moderate levels of the IL-33R alpha-chain (ST2L), eosinophils that accumulated in the airways of mice with OVA-induced asthma expressed increased amounts of ST2L. In vitro, IL-33 and GM-CSF are potent inducers of ST2L expression on eosinophils, and IL-33 induced the production of IL-13, CCL17, and TGF-beta by eosinophils. In adoptive-transfer experiments, IL-33 exacerbated eosinophil-mediated airway inflammation by increasing the levels of eosinophils, macrophages, lymphocytes, IL-13, TGF-beta, CCL3, CCL17, and CCL24 in the lungs. IL-33 also enhanced the eosinophil-mediated differentiation of airway macrophages toward the alternatively activated macrophage phenotype in an IL-13-dependent manner. Taken together, this study demonstrates that the IL-33/ST2 signaling pathway activates airway eosinophils that exacerbate airway inflammation in an autocrine and paracrine manner.

Optimal management of preschool asthma

Asthma is common in most parts of the world and remains the most common single reason preschool aged children are admitted to hospital in developed countries. In determining what the optimal management of preschool asthma is, several factors must be considered, including: the aims of treating preschool asthma; which children require treatment; and what treatment is effective. The most controversial aspects of treating preschool asthma relate to maintenance treatment. Guidelines for managing asthma in children have been developed; however, the relative lack of appropriate clinical trials in preschool children is a problem. Prolonged treatment with inhaled corticosteroids controls asthma during treatment but has no disease-modifying effects. Intermittent treatment with inhaled corticosteroids initiated at the onset of asthma-like symptoms and continued for short periods is ineffective. Short-term treatment with leukotriene receptor antagonists provides symptomatic relief but evidence for long-term efficacy is lacking. Further data are needed to determine optimal asthma management in preschool children.

Up-regulation of Orai1 in murine allergic rhinitis

Orai1 is an essential pore-forming subunit of the Ca(2+) release-activated Ca(2+) channels and plays a key role in the store-operated Ca(2+) entry. However, little is known about the function of this pathway in allergic airway diseases. In this study, we evaluated Orai1 expression in normal and allergic rhinitis (AR) mice airway and spleen. AR models were established by repetitive intraperitoneal sensitization followed by intranasal challenge with ovalbumin. Sneezing was counted, and eosinophils infiltration was analyzed through Luna stain. We performed the analysis of Orai1 protein in airway and spleen by immunohistochemical staining, Western blotting and enzyme-linked immunosorbent assay, and quantitatively examined Orai1 mRNA in the above tissues by real-time reverse transcription-polymerase chain reaction. Sneezes and eosinophil counts in the AR group were increased in comparison to those in the normal group. Orai1 protein was expressed in mucosal epithelium and submucosal glands epithelium of airway, and in immune cells of spleen. The immunostaining appeared stronger in AR mice than that in normal ones. Both the Orai1 protein and mRNA levels showed up-regulation in the AR group compared with those in the normal one. Our results indicate that Orai1 is up-regulated in the airway and spleen in allergic inflammation and may participate in the pathogenesis of allergic rhinitis.

Allergies and diabetes as risk factors for dengue hemorrhagic fever: results of a case control study

Background

The physiopathology of dengue hemorrhagic fever (DHF), a severe form of Dengue Fever, is poorly understood. We are unable to identify patients likely to progress to DHF for closer monitoring and early intervention during epidemics, so most cases are sent home. This study explored whether patients with selected co-morbidities are at higher risk of developing DHF.

Methods

A matched case-control study was conducted in a dengue sero-positive population in two Brazilian cities. For each case of DHF, 7 sero-positive controls were selected. Cases and controls were interviewed and information collected on demographic and socio-economic status, reported co-morbidities (diabetes, hypertension, allergy) and use of medication. Conditional logistic regression was used to calculate the strength of the association between the co-morbidities and occurrence of DHF.

Results

170 cases of DHF and 1,175 controls were included. Significant associations were found between DHF and white ethnicity (OR = 4.70; 2.17–10.20), high income (OR = 6.84; 4.09–11.43), high education (OR = 4.67; 2.35–9.27), reported diabetes (OR = 2.75; 1.12–6.73) and reported allergy treated with steroids (OR = 2.94; 1.01–8.54). Black individuals who reported being treated for hypertension had 13 times higher risk of DHF then black individuals reporting no hypertension.

Conclusions

This is the first study to find an association between DHF and diabetes, allergy and hypertension. Given the high case fatality rate of DHF (1–5%), we believe that the evidence produced in this study, when confirmed in other studies, suggests that screening criteria might be used to identify adult patients at a greater risk of developing DHF with a recommendation that they remain under observation and monitoring in hospital.

Dengue is an arboviral disease that affects large areas of countries in tropical and subtropical regions of the world. Around 500,000 cases and 22,000 deaths of dengue hemorrhagic fever (DHF)/Dengue Shock Syndrome (DSS), the most severe presentations of this disease, occur annually. It is unclear why some cases of dengue fever (0.5% to 4%) progress to DHF/DSS. There is weak evidence that some diseases could have a role in this process, such as diabetes, hypertension, and allergies. In epidemics most dengue fever cases are sent home as there are too many to be kept in observation, but if it were possible to identify those with a higher risk of progression to DHF, they could be kept for observation, for early detection of signs, symptoms and alterations in laboratory tests suggestive of DHF, to enable timely and effective clinical management and early intervention. We study this issue and we believe that the evidence produced in this study, when confirmed in other studies, suggests that screening criteria might be used to identify adult patients at a greater risk of developing DHF with a recommendation that they remain under observation and monitoring in a hospital.

Increased plasma reactive oxidant levels and their relationship to blood cells, total IgE, and allergen-specific IgE levels in asthmatic children

Asthma is a disorder characterized by inflammation of the airways. Oxidative stress may play a role in the pathophysiology of several diseases including asthma. Characterizing biomarkers of oxidative stress in the context of other systemic measures of immune function or inflammation could provide insight regarding underlying mechanisms inducing asthma. We evaluated whether oxidative stress in the form of plasma reactive oxidants differs between asthmatic and non-asthmatic children and elucidate relationships between plasma reactive oxidants and other asthma-related immunological markers. Plasma reactive oxidants, white blood cell counts, total serum immunoglobulin E(IgE), and a multi-allergen-specific IgE screen were measured in 74 asthmatic and 74 non-asthmatic children(9 to 13 years of age) from the Detroit, Michigan area. Plasma reactive oxidants were measured using a lucigenin-based chemiluminescence assay. Plasma reactive oxidants, eosinophils, and neutrophils(absolute counts and percent of total white blood cell counts), total IgE, and allergen-specific IgE levels were elevated in asthmatics after adjusting for age, gender, and ethnicity. IgE(total or allergen-specific), eosinophils and neutrophils were not significantly associated with plasma reactive oxidant levels. The association between plasma reactive oxidants and asthma status was similar when eosinophils, neutrophils, total IgE, or allergen-specific IgE were included as possible confounders in multivariate logistic regression models. In conclusion, plasma reactive oxidants are elevated in asthmatics and appear to be an independent predictor of asthma status. Measurement of plasma reactive oxidants may be a useful adjunct diagnostic tool and potential mechanistic indicator relevant to the study of asthma and asthma exacerbation.

Phosphatidylinositol 3-kinase isoforms as targets in respiratory disease

Respiratory diseases such as chronic obstructive pulmonary disease [COPD], severe asthma, cystic fibrosis [CF] and idiopathic pulmonary fibrosis [IPF] are inadequately controlled by current therapies. The underlying molecular mechanisms and pathogenesis of these diseases remain unclear, making identification and validation of potential new therapeutic targets difficult. However, recent studies have identified the central signalling mediator PI3K as playing an integral role in the immune system including initiation and maintenance of inflammatory responses. Specifically, the relatively leukocyte-specific PI3Kgamma and PI3Kdelta isoforms are central to leukocyte function and can be targeted pharmacologically. Early to man studies using selective PI3K isoform inhibitors are required to determine whether they have a future in treating respiratory disease, particularly in controlling both innate and adaptive inflammatory responses as well as restoring glucocorticoid function and reducing tumorigenesis.

Eosinophilic airway inflammation in a cynomolgus monkey

The present article describes an occurrence of eosinophilic airway inflammation of a 4-year-old female cynomolgus monkey in a vehicle control group of a routine toxicology study. Histologically, the airway lesion was characterized by prominent eosinophilic infiltrates, accompanied by mast cells, lymphocytes, and plasmacytes. The eosinophilic infiltrates were distributed throughout the airway: from trachea through respiratory bronchioles in the lung. The morphological feature of the lesion was indicative of an allergic airway disorder that can occur in humans with asthma. The present case is remarkable in that there is a paucity of reports on naturally occurring allergic airway disorders in nonhuman primates.

Increased plasma reactive oxidant levels and their relationship to blood cells, total IgE, and allergen-specific IgE levels in asthmatic children

Asthma is a disorder characterized by inflammation of the airways. Oxidative stress may play a role in the pathophysiology of several diseases including asthma. Characterizing biomarkers of oxidative stress in the context of other systemic measures of immune function or inflammation could provide insight regarding underlying mechanisms inducing asthma. We evaluated whether oxidative stress in the form of plasma reactive oxidants differs between asthmatic and non-asthmatic children and elucidate relationships between plasma reactive oxidants and other asthma-related immunological markers. Plasma reactive oxidants, white blood cell counts, total serum immunoglobulin E (IgE), and a multi-allergen-specific IgE screen were measured in 74 asthmatic and 74 non-asthmatic children (9 to 13 years of age) from the Detroit, Michigan area. Plasma reactive oxidants were measured using a lucigenin-based chemiluminescence assay. Plasma reactive oxidants, eosinophils, and neutrophils (absolute counts and percent of total white blood cell counts), total IgE, and allergen-specific IgE levels were elevated in asthmatics after adjusting for age, gender, and ethnicity. IgE (total or allergen-specific), eosinophils and neutrophils were not significantly associated with plasma reactive oxidant levels. The association between plasma reactive oxidants and asthma status was similar when eosinophils, neutrophils, total IgE, or allergen-specific IgE were included as possible confounders in multivariate logistic regression models. In conclusion, plasma reactive oxidants are elevated in asthmatics and appear to be an independent predictor of asthma status. Measurement of plasma reactive oxidants may be a useful adjunct diagnostic tool and potential mechanistic indicator relevant to the study of asthma and asthma exacerbation.

Chronic inflammation and asthma

Allergic asthma is a complex and chronic inflammatory disorder which is associated with airway hyper-responsiveness and tissue remodelling of the airway structure. Although originally thought to be a Th2-driven inflammatory response to inhaled innocuous allergen, the immune response in asthma is now considered highly heterogeneous. There are now various in vivo systems which have been designed to examine the pathways leading to the development of this chronic immune response and reflect, in part this heterogeneity. Furthermore, the emergence of endogenous immunoregulatory pathways and active pro-resolving mediators hold great potential for future therapeutic intervention. In this review, the key cellular and molecular mediators relating to chronic allergic airway disease are discussed, as well as emerging players in the regulation of chronic allergic inflammation.

Pulmonary eosinophilia is attenuated by early responding CD8(+) memory T cells in a murine model of RSV vaccine-enhanced disease

Vaccination with formalin-inactivated respiratory syncytial virus (RSV) vaccine results in enhanced respiratory tract inflammation and injury following subsequent RSV infection. RSV vaccine-enhanced disease can also be produced in mice by prior vaccination with a vaccinia virus vector containing the RSV G protein, followed by intranasal infectious RSV challenge, a process characterized by induction of a potent memory CD4(+) T-cell response to challenge infection with some features characteristic of Th-2 CD4(+) T-cell responses, including increased eosinophil accumulation in pulmonary inflammatory infiltrates. The adaptive immune response to the RSV G protein in immunized BALB/c mice is characterized by a weak or absent primary and secondary recall CD8(+) T-cell response. These and related results have led to the hypothesis that the failure of the infected animals to mount an effective CD8(+) memory T-cell (CD8(+) Tm) response in this model could account for the pulmonary eosinophilia associated with the development of enhanced disease, and that CD8(+) T cells may control the development of eosinophilia. In this study, we investigated how and when the generation of a CD8(+) Tm response to RSV infection might affect the development of pulmonary eosinophilia in this model of vaccine-enhanced disease. By defining the CD8(+) T-cell response kinetics and monitoring lung parenchymal eosinophil accumulation, we show that the establishment of an RSV-specific CD8(+) Tm response in the infected lungs early after challenge infection (i.e., within the first 3 d of RSV infection) is necessary and sufficient to control pulmonary eosinophilia development. Additionally, our work suggests that the mechanism by which CD8(+) T cells regulate this process is not by modulating the differentiation or development of the CD4(+) Tm response. Rather, we demonstrate that IL-10 produced by early responding CD8(+) Tm cells may regulate the pulmonary eosinophilia development observed in RSV vaccine-enhanced disease.

Vesicle-mediated secretion of human eosinophil granule-derived major basic protein

Major basic protein (MBP), the predominant cationic protein of human eosinophil specific granules, is stored within crystalloid cores of these granules. Secretion of MBP contributes to the immunopathogenesis of varied diseases. Prior electron microscopy (EM) of eosinophils in sites of inflammation noted losses of granule cores in the absence of granule exocytosis and suggested that eosinophil granule proteins might be released through piecemeal degranulation (PMD), a secretory process mediated by transport vesicles. Because release of eosinophil granule-derived MBP through PMD has not been studied, we evaluated secretion of this cationic protein by human eosinophils. Intracellular localizations of MBP were studied within nonstimulated and eotaxin-stimulated human eosinophils by both immunofluorescence and a pre-embedding immunonanogold EM method that enables optimal epitope preservation and antigen access to membrane microdomains. In parallel, quantification of transport vesicles was assessed in eosinophils from a patient with hypereosinophilic syndrome (HES). Our data demonstrate vesicular trafficking of MBP within eotaxin-stimulated eosinophils. Vesicular compartments, previously implicated in transport from granules to the plasma membrane, including large vesiculotubular carriers termed eosinophil sombrero vesicles (EoSVs), were found to contain MBP. These secretory compartments were significantly increased in numbers within HES eosinophils. Moreover, in addition to granule-stored MBP, even unstimulated eosinophils contained appreciable amounts of MBP within secretory vesicles, as evidenced by immunonanogold EM and immunofluorescent colocalizations of MBP and CD63. These data suggest that eosinophil MBP, with its multiple extracellular activities, can be mobilized from granules by PMD into secretory vesicles and both granule- and secretory vesicle-stored pools of MBP are available for agonist-elicited secretion of MBP from human eosinophils. The recognition of PMD as a secretory process to release MBP is important to understand the pathological basis of allergic and other eosinophil-associated inflammatory diseases.

Gastrointestinal nematode infection interferes with experimental allergic airway inflammation but not atopic dermatitis

BACKGROUND

Some helminth infections are negatively associated with the prevalence of allergic disorders, arguing for a modulation of allergic reactions by the parasites, depending on the worm species, intensity and phase of infection and the type of disease.

OBJECTIVE

The aim of this study was to analyse the influence of a chronic infection with the gastrointestinal nematode Heligmosomoides polygyrus, in a murine model of allergic airway disease and of atopic dermatitis (AD), respectively.

METHODS

Mice were infected with H. polygyrus and systemically sensitized with the model allergen ovalbumin. Subsequently, the animals were challenged with the allergen either via the airways for induction of airway disease, or via skin patches for induction of dermatitis.

RESULTS

Mice concomitantly infected with H. polygyrus showed diminished eosinophil and lymphocyte recruitment into the lungs and decreased allergen-specific IgE levels when compared with sensitized and airway challenged controls. In addition, animals showed a trend towards reduced airway hyper-reactivity. In contrast, no significant differences in the severity of eczematous skin lesions were observed between infected and control animals in the AD model. Although H. polygyrus infection reduced CD8+ and CD4+ T-cell infiltration into the skin and production of allergen-specific IgE, mast cell recruitment was significantly increased in worm-infected mice in the dermatitis model. The worm infection was associated with significantly elevated numbers of Foxp3+ regulatory T cells (Treg) in peribronchial lymph nodes in H. polygyrus-infected sensitized and airway challenged mice. In contrast, Treg cells were basically absent in eczematous skin and their number was not increased in skin-draining lymph nodes of mice with experimental dermatitis.

CONCLUSION

Infection with the gastrointestinal nematode used in our study leads to significant inhibition of mucosa-associated but not cutaneous allergic reactions, pointing to a site specificity of the immunomodulation exerted by helminths. This finding might be an important aspect for future considerations of helminths for treatment of allergic diseases.

Recruitment of CD34+ progenitor cells into peripheral blood and asthma severity

BACKGROUND

Previous studies have suggested that the number of progenitor cells is elevated in the peripheral blood of asthmatic patients and that the number of progenitors correlate with the severity of the disease.

OBJECTIVE

To evaluate the number of leukocyte progenitor and eosinophil progenitor cells in the peripheral blood of patients with bronchial asthma in relation to disease severity.

METHODS

The study involved 51 patients with asthma (25 patients with a mild form and 26 with a severe form of the disease) and a group of 12 healthy controls. Using the flow cytometric method, leukocyte (CD34+ leukocytes) and eosinophil progenitors (CD34+CD125+) were detected in the peripheral blood of both asthmatic patients and healthy controls.

RESULTS

Patients with asthma had significantly more leukocyte progenitor cells (median, 0.06% vs 0.016%) and eosinophil progenitor cells (median, 0.046% vs 0.004%) compared with the controls. Patients with severe asthma had more leukocyte progenitor cells (0.12% vs 0.035%) and more eosinophil progenitor cells (0.102% vs 0.019%) than patients with mild asthma. The number of circulating leukocyte and eosinophil progenitor cells inversely correlated with the forced expiratory volume in 1 second percentage of predicted value (r = -0.4 and r = -0.35, respectively) and positively correlated (r = 0.63 and r = 0.65, respectively) with the dose of inhaled steroids used to control asthma.

CONCLUSION

These data suggest that the presence of leukocyte precursors and eosinophil progenitor cells in the peripheral blood of asthmatic patients may reflect ongoing airway inflammation.

Targeting eosinophils in asthma

Recruitment of eosinophils has long been recognized as a hallmark of the inflammatory response in asthma. However, the functions of this population of cells in host defense remain poorly understood. Eosinophils play an important part in the inflammatory response and have key regulatory roles in the afferent arm of the immune response. More recently, eosinophils have been demonstrated to participate in host defense against respiratory viruses. The specific contributions of eosinophils to the pathophysiology of asthma remain controversial. However, the balance of evidence indicates that they have a significant role in the disease, suggesting that they may be appropriate targets for therapy. Towards this end, a novel intervention of considerable potential interest is the use of an antibody directed against the beta common chain of the receptor for interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor. However, eliminating eosinophils may not be a risk-free therapeutic strategy, as there is potentially an increased likelihood of respiratory viral infections. This may predispose to the development of acute exacerbations of asthma, an outcome that would have significant clinical implications.

Innate immunity and aging

Advanced age is associated with defects in all of the cells of the innate immune system, including numbers, function, and early stages of activation. This review, presents the current state of the field on the impact of age on the innate immune system. The analysis of the literature suggests that a dysfunctional innate immune system is a contributing factor to aberrant outcomes after injury or infection and to the development of many of the diseases observed in the elderly. Gaining an understanding of the nature of the defects in innate immune cells may allow the development of therapeutic strategies aimed to restore innate immune function in aged individuals.

Innate immunity and aging

Advanced age is associated with defects in all of the cells of the innate immune system, including numbers, function, and early stages of activation. This review, presents the current state of the field on the impact of age on the innate immune system. The analysis of the literature suggests that a dysfunctional innate immune system is a contributing factor to aberrant outcomes after injury or infection and to the development of many of the diseases observed in the elderly. Gaining an understanding of the nature of the defects in innate immune cells may allow the development of therapeutic strategies aimed to restore innate immune function in aged individuals.

A helminth immunomodulator reduces allergic and inflammatory responses by induction of IL-10-producing macrophages

The coincidence between infections with parasitic worms and the reduced prevalence of allergic disease in humans and in animal models has prompted the search for helminth molecules with antiallergic and antiinflammatory potential. We report herein that filarial cystatin, a secreted protease inhibitor of filarial nematodes, suppresses Th2-related inflammation and the ensuing asthmatic disease in a murine model of OVA-induced allergic airway responsiveness. Treatment with recombinant filarial cystatin inhibited eosinophil recruitment, reduced levels of OVA-specific and total IgE, down-regulated IL-4 production, and suppressed allergic airway hyperreactivity when applied during or after sensitization and before challenge with the allergen. Depletion of macrophages by clodronate-containing liposomes prevented the curative effects and restored the levels of infiltrating cells, IgE, and allergic airway reactivity. Blocking of IL-10 by application of anti-IL-10 receptor Abs restored the reduced number of infiltrating cells and the levels of OVA-specific IgE. In contrast, depletion of regulatory T cells by anti-CD25 Abs had only limited effects. Cystatin also modulated macrophage-mediated inflammation in a murine model of dextran sulfate sodium-induced colitis, leading to reduction of inflammatory infiltrations and epithelial damage. Our data demonstrate that treatment with a single helminth protein can exert the antiallergic effects of helminth infections.

Eosinophilia during intestinal infection

Eosinophilia is a common finding in tropical developing countries, and is mainly caused by chronic helminth infections, predominantly of the gut. Although only a minority of infections is symptomatic, development during childhood can be impaired, and in some patients serious complications and sequelae may occur. Eosinophilia in helminth infection is typically associated with a strong Th2 immune response, and eosinophils can effectively kill or damage larvae and adult worms in vitro. However, in vivo, eosinophils are only partly effective in the control of helminth infection, and recent research has shown that eosinophils are involved in a range of immunomodulatory effects, such as increased production of the down-modulatory cytokines interleukin 10 and tumour growth factor beta, as well as stimulation of regulatory T cells and alternatively activated macrophages. Increasing evidence suggests that immunomodulation favours parasite survival and reduces immune pathology. On the other hand, immunomodulation induced by helminth infections may contribute to protection from allergic and autoimmune responses, as proposed by the 'hygiene hypothesis' to explain the increase in allergic diseases in the industrialised world. The predictive value of eosinophilia for the presence of helminth infections is limited and depends on the epidemiological background and the extent of the eosinophilia. It increases considerably in populations with a high prevalence of parasitic infections, as in developing tropical countries or in travellers to those areas.

Electron tomography and immunonanogold electron microscopy for investigating intracellular trafficking and secretion in human eosinophils

Electron tomography (ET) has increasingly been used to understand the complexity of membrane systems and protein-trafficking events. By ET and immunonanogold electron microscopy, we recently defined a route for vesicular transport and release of granule-stored products from within activated human eosinophils, cells specialized in the secretion of numerous cytokines and other proteins during inflammatory responses. Here, we highlight these techniques as important tools to unveil a distinct eosinophil vesicular system and secretory pathway.

Vitamin A deficiency decreases and high dietary vitamin A increases disease severity in the mouse model of asthma

The Th1/Th2 paradigm has become an important issue in the pathogenesis of asthma, characterized by normal Th1 and elevated Th2 cytokine expression. Vitamin A deficiency (VAD) can produce a Th1 bias, whereas high-level dietary vitamin A can promote a Th2 bias. We used the OVA exposure mouse model to determine the contributions of vitamin A-deficient, control (4IU/g), and high-level vitamin A (250-IU/g) diets to the development of allergic airway inflammation and hyperresponsiveness. VAD reduced serum IgE and IgG1 responses, pulmonary eosinophilia, and the levels of IL-4 and IL-5 in bronchoalveolar lavage specimens, whereas the 250-IU/g diet increased serum IgE. Also, VAD blocked pulmonary hyperresponsiveness following methacholine challenge while the 250-IU/g diet exacerbated pulmonary hyperresponsiveness. In conclusion, VAD diminished and high-level dietary vitamin A enhanced the development of experimental asthma in this model system. These data suggest that excessive intake of vitamin A may increase the risk or severity of asthma in industrialized countries whereas vitamin A deficiency continues to increase mortality from infectious diseases in developing countries.

Allergic pulmonary inflammation in mice is dependent on eosinophil-induced recruitment of effector T cells

The current paradigm surrounding allergen-mediated T helper type 2 (Th2) immune responses in the lung suggests an almost hegemonic role for T cells. Our studies propose an alternative hypothesis implicating eosinophils in the regulation of pulmonary T cell responses. In particular, ovalbumin (OVA)-sensitized/challenged mice devoid of eosinophils (the transgenic line PHIL) have reduced airway levels of Th2 cytokines relative to the OVA-treated wild type that correlated with a reduced ability to recruit effector T cells to the lung. Adoptive transfer of Th2-polarized OVA-specific transgenic T cells (OT-II) alone into OVA-challenged PHIL recipient mice failed to restore Th2 cytokines, airway histopathologies, and, most importantly, the recruitment of pulmonary effector T cells. In contrast, the combined transfer of OT-II cells and eosinophils into PHIL mice resulted in the accumulation of effector T cells and a concomitant increase in both airway Th2 immune responses and histopathologies. Moreover, we show that eosinophils elicit the expression of the Th2 chemokines thymus- and activation-regulated chemokine/CCL17 and macrophage-derived chemokine/CCL22 in the lung after allergen challenge, and blockade of these chemokines inhibited the recruitment of effector T cells. In summary, the data suggest that pulmonary eosinophils are required for the localized recruitment of effector T cells.

Mechanisms of eosinophil secretion: large vesiculotubular carriers mediate transport and release of granule-derived cytokines and other proteins

Eosinophils generate and store a battery of proteins, including classical cationic proteins, cytokines, chemokines, and growth factors. Rapid secretion of these active mediators by eosinophils is central to a range of inflammatory and immunoregulatory responses. Eosinophil products are packaged within a dominant population of cytoplasmic specific granules and generally secreted by piecemeal degranulation, a process mediated by transport vesicles. Large, pleiomorphic vesiculotubular carriers were identified recently as key players for moving eosinophil proteins from granules to the plasma membrane for extracellular release. During secretion, these specialized, morphologically distinct carriers, termed eosinophil sombrero vesicles, are actively formed and direct differential and rapid release of eosinophil proteins. This review highlights recent discoveries concerning the organization of the human eosinophil secretory pathway. These discoveries are defining a broader role for large vesiculotubular carriers in the intracellular trafficking and secretion of proteins, including selective receptor-mediated mobilization and transport of cytokines.