Praveen Akuthota

Immunoregulatory roles of eosinophils: a new look at a familiar cell

Eosinophils are usually considered as end‐stage degranulating effector cells of innate immunity. However, accumulating evidence has revealed additional roles for eosinophils that are immunoregulatory in nature in both the adaptive and innate arms of immunity. Specifically, eosinophils have key immunoregulatory roles as professional antigen‐presenting cells and as modulators of CD4+ T cell, dendritic cell, B cell, mast cell, neutrophil, and basophil functions. This review addresses the emerging immunoregulatory roles of eosinophils with a focus on recent data that support this new paradigm. Recognizing both the effector and immunoregulatory functions of eosinophils will enable a fuller understanding of the roles of eosinophils in allergic airways inflammation and may be pertinent to therapies that target eosinophils both for their acute and ongoing immunomodulatory functions.

Mepolizumab or Placebo for Eosinophilic Granulomatosis with Polyangiitis.

BACKGROUND Eosinophilic granulomatosis with polyangiitis is an eosinophilic vasculitis. Mepolizumab, an anti–interleukin‐5 monoclonal antibody, reduces blood eosinophil counts and may have value in the treatment of eosinophilic granulomatosis with polyangiitis. METHODS In this multicenter, double‐blind, parallel‐group, phase 3 trial, we randomly assigned participants with relapsing or refractory eosinophilic granulomatosis with polyangiitis who had received treatment for at least 4 weeks and were taking a stable prednisolone or prednisone dose to receive 300 mg of mepolizumab or placebo, administered subcutaneously every 4 weeks, plus standard care, for 52 weeks. The two primary end points were the accrued weeks of remission over a 52‐week period, according to categorical quantification, and the proportion of participants in remission at both week 36 and week 48. Secondary end points included the time to first relapse and the average daily glucocorticoid dose (during weeks 48 through 52). The annualized relapse rate and safety were assessed. RESULTS A total of 136 participants underwent randomization, with 68 participants assigned to receive mepolizumab and 68 to receive placebo. Mepolizumab treatment led to significantly more accrued weeks of remission than placebo (28% vs. 3% of the participants had ≥24 weeks of accrued remission; odds ratio, 5.91; 95% confidence interval [CI], 2.68 to 13.03; P<0.001) and a higher percentage of participants in remission at both week 36 and week 48 (32% vs. 3%; odds ratio, 16.74; 95% CI, 3.61 to 77.56; P<0.001). Remission did not occur in 47% of the participants in the mepolizumab group versus 81% of those in the placebo group. The annualized relapse rate was 1.14 in the mepolizumab group, as compared with 2.27 in the placebo group (rate ratio, 0.50; 95% CI, 0.36 to 0.70; P<0.001). A total of 44% of the participants in the mepolizumab group, as compared with 7% of those in the placebo group, had an average daily dose of prednisolone or prednisone of 4.0 mg or less per day during weeks 48 through 52 (odds ratio, 0.20; 95% CI, 0.09 to 0.41; P<0.001). The safety profile of mepolizumab was similar to that observed in previous studies. CONCLUSIONS In participants with eosinophilic granulomatosis with polyangiitis, mepolizumab resulted in significantly more weeks in remission and a higher proportion of participants in remission than did placebo, thus allowing for reduced glucocorticoid use. Even so, only approximately half the participants treated with mepolizumab had protocol‐defined remission. (Funded by GlaxoSmithKline and the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT02020889.)

Eosinophils as Antigen-Presenting Cells in Allergic Upper Airway Disease

Purpose of reviewThe recognition of eosinophils as complex immunomodulatory cells has been increasing in recent years. One prominent novel immunomodulatory function of eosinophils is their role as antigen-presenting cells (APCs). This review will examine the evidence that has enhanced the understanding of eosinophils as APCs in the context of allergic inflammation, with a focus on data applicable to allergic upper airway disease. Recent findingsRecent studies expand on prior findings that eosinophils can express major histocompatibility complex class II and costimulatory molecules. Eosinophils have also been found to traffic to regional lymph nodes and act as professional APCs in various experimental settings. SummaryAccumulating evidence of the ability of eosinophils to act as APCs suggests that eosinophils may have more complex immunomodulatory roles in allergic upper airway disease than previously appreciated.

Eosinophils and Disease Pathogenesis

Eosinophils are granulocytic innate immune cells whose presence is conspicuous in a variety of disease states, including eosinophilic hyperproliferative and infiltrative processes, as well as conditions associated with maladaptive Th2 inflammation. This review discusses the role of eosinophils in disease pathogenesis, including a consideration of relevant eosinophil biology. Eosinophilic disease patterns of tissue infiltration are also detailed, as are candidate mechanisms by which eosinophils cause fibrosis and hypercoagulability and the importance of eosinophils in allergic inflammation. Eosinophils are unique cells in their spectrum of associated disease, with the promise of future discoveries in delineating the manner in which they contribute to disease pathogenesis.

Lack of independent associations of apolipoprotein E promoter and intron 1 polymorphisms with Alzheimer's disease

Several studies have demonstrated genetic associations between Alzheimers disease (AD) and polymorphisms in the promoter/enhancer regions of the apolipoprotein E (APOE) gene. These studies raise the possibility that APOE transcription control may be involved in altered risks for AD. We evaluated polymorphic sites in the intron-1 enhancer element (IE-1G/C) and in the APOE promoter (-219G/T). For the IE-1 polymorphism, we analyzed 433 individuals (183 AD and 250 controls), and found a strong linkage between the IE-1G allele and APOE-epsilon4. When we controlled for this linkage using log-linear model analysis, we found no independent association between the IE-1 polymorphism and AD. For the -219 polymorphism, we analyzed 475 individuals (168 AD cases, 234 controls, and 73 cases of cerebral amyloid angiopathy (CAA)). We found strong linkages between the -219G allele and APOE-epsilon2 and between the -219 T allele and APOE-epsilon4. Controlling for these linkages, we found no independent association between the -219 polymorphism and AD or CAA. Thus, our studies do not support independent associations between AD and either the IE-1 or the -219 polymorphisms.

Eosinophils: Offenders or General Bystanders in Allergic Airway Disease and Pulmonary Immunity?

Eosinophils have long been noted to be present in asthma and other forms of pulmonary inflammation, but whether they act as true offenders or merely as bystanders has been a point of uncertainty. However, in recent years, there has been increasing evidence suggesting that eosinophils are not passive cells in the respiratory system, acting only as markers of allergic inflammation. This review discusses key evidence from animal models and human clinical trials that support the importance of eosinophils as active and necessary, rather than passive and unnecessary, to the pathogenesis of allergic airway disease. Analyses that are supportive of important immunoregulatory roles of eosinophils in allergic pulmonary inflammation are also reviewed. Data indicating that eosinophils contribute to viral, bacterial, and mycobacterial defense and clearance are detailed. Continually increasing evidence has supported a new conception of eosinophils as being multifaceted immune cells with complex interactions with other immune cells and their local environment.

Coenzyme Q10 levels are low and may be associated with the inflammatory cascade in septic shock

IntroductionMitochondrial dysfunction is associated with increased mortality in septic shock. Coenzyme Q10 (CoQ10) is a key cofactor in the mitochondrial respiratory chain, but whether CoQ10 is depleted in septic shock remains unknown. Moreover, statin therapy may decrease CoQ10 levels, but whether this occurs acutely remains unknown. We measured CoQ10 levels in septic shock patients enrolled in a randomized trial of simvastatin versus placebo.MethodsWe conducted a post hoc analysis of a prospective, randomized trial of simvastatin versus placebo in patients with septic shock (ClinicalTrials.gov ID: NCT00676897). Adult patients with suspected or confirmed infection and the need for vasopressor support were included in the initial trial. For the current analysis, blood specimens were analyzed for plasma CoQ10 and low-density lipoprotein (LDL) levels. The relationship between CoQ10 levels and inflammatory and vascular endothelial biomarkers was assessed using either the Pearson or Spearman correlation coefficient.ResultsWe analyzed 28 samples from 14 patients. CoQ10 levels were low, with a median of 0.49 (interquartile range 0.26 to 0.62) compared to levels in healthy control patients (CoQ10 = 0.95 μmol/L ± 0.29; P < 0.0001). Statin therapy had no effect on plasma CoQ10 levels over time (P = 0.13). There was a statistically significant relationship between plasma CoQ10 levels and levels of vascular cell adhesion molecule (VCAM) (r2 = 0.2; P = 0.008), TNF-α (r2 = 0.28; P = 0.004), IL-8 (r2 = 0.21; P = 0.015), IL-10 (r2 = 0.18; P = 0.025), E-selectin (r2 = 0.17; P = -0.03), IL-1ra (r2 = 0.21; P = 0.014), IL-6 (r2 = 0.17; P = 0.029) and IL-2 (r2 = 0.23; P = 0.009). After adjusting for LDL levels, there was a statistically significant inverse relationship between plasma CoQ10 levels and levels of VCAM (r2 = 0.24; P = 0.01) (Figure 3) and IL-10 (r2 = 0.24; P = 0.02).ConclusionsCoQ10 levels are significantly lower in septic shock patients than in healthy controls. CoQ10 is negatively associated with vascular endothelial markers and inflammatory molecules, though this association diminishes after adjusting for LDL levels.

An Evidence-Based Estimate on the Size of the Potential Patient Pool for Lung Volume Reduction Surgery

BACKGROUND Observational and randomized studies have demonstrated that lung volume reduction surgery (LVRS) improves symptoms, lung function, and survival in selected patients with emphysema. In spite of an approximately 3.8 million patient prevalence of the disease in the US, only 119 LVRS procedures were performed nationwide under Medicare during 2008. In order to obtain evidence-based estimate on the size of the patient pool potentially suitable for LVRS, we analyzed the database from our clinical practice that is representative of a substantial segment of the general emphysema population. METHODS Our pulmonary function test laboratory database between 1996 and 2006 was searched for patients with stage III and IV global initiative for chronic obstructive lung disease (GOLD) who also had lung volumes and carbon monoxide diffusing capacity data. Patients without available chest computed tomographic scans (CT) or with primary diagnoses other than emphysema were excluded. The resultant emphysema cohort was screened using clinical inclusion and exclusion criteria adopted from the National Emphysema Treatment Trial. A suitable clinical profile combined with CT scan evidence of 40% or greater involvement of the lungs and predominantly upper lobe distribution of emphysema were regarded as favorable markers for LVRS. RESULTS Pulmonary function test criteria were met by 959 patients and CT scans were available in 588 patients, but 175 patients were excluded because of primary diagnoses other than emphysema. In the remaining 413 patients, 61 or 15% exhibited favorable clinical profiles and anatomy for LVRS. CONCLUSIONS In a subset of patients that resembles a substantial segment of the general population with advanced emphysema, up to 15% appeared potential candidates for LVRS. Formation of a task force by relevant medical specialty and patient advocate organizations to address the apparent underutilization of LVRS is recommended.

Diurnal Variations of Circulating Extracellular Vesicles Measured by Nano Flow Cytometry

The identification of extracellular vesicles (EVs) as intercellular conveyors of biological information has recently emerged as a novel paradigm in signaling, leading to the exploitation of EVs and their contents as biomarkers of various diseases. However, whether there are diurnal variations in the size, number, and tissue of origin of blood EVs is currently not known, and could have significant implications when using EVs as biomarkers for disease progression. Currently available technologies for the measurement of EV size and number are either time consuming, require specialized equipment, or lack sufficient accuracy across a range of EV sizes. Flow cytometry represents an attractive alternative to these methods; however, traditional flow cytometers are only capable of measuring particles down to 500 nm, which is significantly larger than the average and median sizes of plasma EVs. Utilizing a Beckman Coulter MoFlo XDP flow cytometer with NanoView module, we employed nanoscale flow cytometry (termed nanoFCM) to examine the relative number and scatter distribution of plasma EVs at three different time points during the day in 6 healthy adults. Analysis of liposomes and plasma EVs proved that nanoFCM is capable of detecting biologically-relevant vesicles down to 100 nm in size. With this high resolution configuration, we observed variations in the relative size (FSC/SSC distributions) and concentration (proportions) of EVs in healthy adult plasma across the course of a day, suggesting that there are diurnal variations in the number and size distribution of circulating EV populations. The use of nanoFCM provides a valuable tool for the study of EVs in both health and disease; however, additional refinement of nanoscale flow cytometric methods is needed for use of these instruments for quantitative particle counting and sizing. Furthermore, larger scale studies are necessary to more clearly define the diurnal variations in circulating EVs, and thus further inform their use as biomarkers for disease.

MHC Class II and CD9 in Human Eosinophils Localize to Detergent-Resistant Membrane Microdomains

Eosinophils function in murine allergic airways inflammation as professional antigen-presenting cells (APCs). In murine professional APC cell types, optimal functioning of MHC Class II depends on its lateral association in plasma membranes and colocalization with the tetraspanin CD9 into detergent-resistant membrane microdomains (DRMs). With human eosinophils, we evaluated the localization of MHC Class II (HLA-DR) to DRMs and the functional significance of such localization. In granulocyte-macrophage colony-stimulating factor-stimulated human eosinophils, antibody cross-linked HLA-DR colocalized by immunofluorescence microscopy focally on plasma membranes with CD9 and the DRM marker ganglioside GM1. In addition, HLA-DR coimmunoprecipitates with CD9 after chemical cross-linking of CD9. HLA-DR and CD9 were localized by Western blotting in eosinophil DRM subcellular fractions. DRM disruption with the cholesterol-depleting agent methyl-β-cyclodextrin decreased eosinophil surface expression of HLA-DR and CD9. We show that CD9 is abundant on the surface of eosinophils, presenting the first electron microscopy data of the ultrastructural immunolocalization of CD9 in human eosinophils. Disruption of HLA-DR-containing DRMs decreased the ability of superantigen-loaded human eosinophils to stimulate CD4(+) T-cell activation (CD69 expression), proliferation, and cytokine production. Our results, which demonstrate that eosinophil MHC Class II localizes to DRMs in association with CD9 in a functionally significant manner, represent a novel insight into the organization of the antigen presentation complex of human eosinophils.