Paired immunoglobulin-like receptor A is an intrinsic, self-limiting suppressor of IL-5-induced eosinophil development

Spatial adaptation of eosinophils and their emerging roles in homeostasis, infection and disease

Eosinophils are bone marrow-derived granulocytes that are traditionally associated with type 2 immune responses, such as those that occur during parasite infections and allergy. Emerging evidence demonstrates the remarkable functional plasticity of this elusive cell type and its pleiotropic functions in diverse settings. Eosinophils broadly contribute to tissue homeostasis, host defence and immune regulation, predominantly at mucosal sites. The scope of their activities primarily reflects the breadth of their portfolio of secreted mediators, which range from cytotoxic cationic proteins and reactive oxygen species to multiple cytokines, chemokines and lipid mediators. Here, we comprehensively review basic eosinophil biology that is directly related to their activities in homeostasis, protective immunity, regeneration and cancer. We examine how dysregulation of these functions contributes to the physiopathology of a broad range of inflammatory diseases. Furthermore, we discuss recent findings regarding the tissue compartmentalization and adaptation of eosinophils, shedding light on the factors that likely drive their functional diversification within tissues.

Human leukocyte immunoglobulin-like receptors in health and disease

Human leukocyte immunoglobulin (Ig)-like receptors (LILR) are a family of 11 innate immunomodulatory receptors, primarily expressed on lymphoid and myeloid cells. LILRs are either activating (LILRA) or inhibitory (LILRB) depending on their associated signalling domains (D). With the exception of the soluble LILRA3, LILRAs mediate immune activation, while LILRB1-5 primarily inhibit immune responses and mediate tolerance. Abnormal expression and function of LILRs is associated with a range of pathologies, including immune insufficiency (infection and malignancy) and overt immune responses (autoimmunity and alloresponses), suggesting LILRs may be excellent candidates for targeted immunotherapies. This review will discuss the biology and clinical relevance of this extensive family of immune receptors and will summarise the recent developments in targeting LILRs in disease settings, such as cancer, with an update on the clinical trials investigating the therapeutic targeting of these receptors.

Helminth-derived biomacromolecules as therapeutic agents for treating inflammatory and infectious diseases: What lessons do we get from recent findings?

Despite the tremendous progress in healthcare sectors, a number of life-threatening infectious, inflammatory, and autoimmune diseases are continuously challenging mankind throughout the globe. In this context, recent successes in utilizing helminth parasite-derived bioactive macromolecules viz. glycoproteins, enzymes, polysaccharides, lipids/lipoproteins, nucleic acids/nucleotides, and small organic molecules for treating various disorders primarily resulted from inflammation. Among the several parasites that infect humans, helminths (cestodes, nematodes, and trematodes) are known as efficient immune manipulators owing to their explicit ability to modulate and modify the innate and adaptive immune responses of humans. These molecules selectively bind to immune receptors on innate and adaptive immune cells and trigger multiple signaling pathways to elicit anti-inflammatory cytokines, expansion of alternatively activated macrophages, T-helper 2, and immunoregulatory T regulatory cell types to induce an anti-inflammatory milieu. Reduction of pro-inflammatory responses and repair of tissue damage by these anti-inflammatory mediators have been exploited for treating a number of autoimmune, allergic, and metabolic diseases. Herein, the potential and promises of different helminths/helminth-derived products as therapeutic agents in ameliorating immunopathology of different human diseases and their mechanistic insights of function at cell and molecular level alongside the molecular signaling cross-talks have been reviewed by incorporating up-to-date findings achieved in the field.

Immunoglobulin-like receptors and the generation of innate immune memory

Host immunity is classically divided into "innate" and "adaptive." While the former has always been regarded as the first, rapid, and antigen-nonspecific reaction to invading pathogens, the latter represents the more sophisticated and antigen-specific response that has the potential to persist and generate memory. Recent work however has challenged this dogma, where murine studies have successfully demonstrated the ability of innate immune cells (monocytes and macrophages) to acquire antigen-specific memory to allogeneic major histocompatibility complex (MHC) molecules. The immunoreceptors so far identified that mediate innate immune memory are the paired immunoglobulin-like receptors (PIRs) in mice, which are orthologous to human leukocyte immunoglobulin-like receptors (LILRs). These receptor families are mainly expressed by the myelomonocytic cell lineage, suggesting an important role in the innate immune response. In this review, we will discuss the role of immunoglobulin-like receptors in the development of innate immune memory across species.

Targeting M2 Macrophages Alleviates Airway Inflammation and Remodeling in Asthmatic Mice via miR-378a-3p/GRB2 Pathway

Background: Asthma is a complex respiratory disease characterized by airway inflammation and remodeling. MicroRNAs (miRNAs) mediate various cellular processes including macrophage polarization and play an important role in the pathogenesis of asthma. In present study, we aimed to screen miRNA profiling involved in macrophage polarization and investigate its possible functions and mechanisms.

Methods: An OVA-sensitized mouse model was established and 2-chloroadenosine (2-CA) was used to interfere with macrophages. The airway inflammation and remodeling were assessed. The identification and function of M2 alveolar macrophages were assessed by flow cytometry, RT-qPCR, arginase activity and co-culture experiment. Microarray screening was used to select miRNAs which were related to macrophage polarization and RNA interference (RNAi) technique was performed to confirm the function of the selected miRNA and its target gene.

Results: Alveolar macrophages of asthmatic mice showed significant M2 polarization. 2-CA alleviated airway inflammation and remodeling as well as M2 polarization. In vitro, IL-4-induced M2 macrophages promoted the proliferation of α-SMA-positive cells. And miRNA profiling showed a remarkable increased expression of miR-378a-3p in IL-4 induced M2 macrophages. Dual luciferase reporter assay confirmed growth factor receptor binding protein 2 (GRB2) was a target gene of miR-378a-3p. A miR-378a-3p inhibitor and knockdown of GRB2 repolarized alveolar macrophages from M1 to M2 phenotype.

Conclusion: Our findings suggest that miR-378a-3p/GRB2 pathway regulates the polarization of alveolar macrophages which acts as a potential therapeutic target for airway inflammation and remodeling in asthma.

ATG5 promotes eosinopoiesis but inhibits eosinophil effector functions

Eosinophils are white blood cells that contribute to the regulation of immunity and are involved in the pathogenesis of numerous inflammatory diseases. In contrast to other cells of the immune system, no information is available regarding the role of autophagy in eosinophil differentiation and functions. To study the autophagic pathway in eosinophils, we generated conditional knockout mice in which Atg5 is deleted within the eosinophil lineage only (designated Atg5eoΔ mice). Eosinophilia was provoked by crossbreeding Atg5eoΔ mice with Il5 (IL-5) overexpressing transgenic mice (designated Atg5eoΔIl5tg mice). Deletion of Atg5 in eosinophils resulted in a dramatic reduction in the number of mature eosinophils in blood and an increase of immature eosinophils in the bone marrow. Atg5-knockout eosinophil precursors exhibited reduced proliferation under both in vitro and in vivo conditions but no increased cell death. Moreover, reduced differentiation of eosinophils in the absence of Atg5 was also observed in mouse and human models of chronic eosinophilic leukemia. Atg5-knockout blood eosinophils exhibited augmented levels of degranulation and bacterial killing in vitro. Moreover, in an experimental in vivo model, we observed that Atg5eoΔ mice achieve better clearance of the local and systemic bacterial infection with Citrobacter rodentium. Evidence for increased degranulation of ATG5low-expressing human eosinophils was also obtained in both tissues and blood. Taken together, mouse and human eosinophil hematopoiesis and effector functions are regulated by ATG5, which controls the amplitude of overall antibacterial eosinophil immune responses.

Two cases of refractory eosinophilic granulomatosis with polyangiitis wherein mepolizumab was effective against pulmonary and ear lesions

Recently, mepolizumab, an interleukin (IL)-5 inhibitor, has been indicated for the treatment of eosinophilic granulomatosis with polyangiitis (EGPA) refractory to standard therapies. However, no reports have compared the efficacy of mepolizumab according to symptoms and organ lesions. Herein, we report two cases in which mepolizumab was highly effective in the management of EGPA with lung lesions and otitis media refractory to treatment with multiple immunosuppressive agents. These two cases suggest that mepolizumab is effective in treating pulmonary and ear lesions in EGPA.

Generation of Mouse Eosinophils in Tissue Culture from Unselected Bone Marrow Progenitors

Human eosinophilic leukocytes are found in peripheral blood and tissues at homeostasis and at elevated levels in atopic disorders. As inbred strains of mice (Mus musculus) are currently the models of choice for the study of disease mechanisms in vivo, a full understanding of mouse eosinophils is critical for interpretation of experimental findings. Toward this end, several years ago we presented a protocol for generating mouse eosinophils in tissue culture from unselected bone marrow progenitors (Dyer et al., J Immunol 181: 4004-4009, 2008). This method has been implemented widely and has proven to be effective for generating phenotypically normal eosinophils from numerous mouse strains and genotypes. Here we provide a detailed version of this protocol, along with suggestions and notes for its careful execution. We have also included several protocol variations and suggestions for improvements.

The peptide encoded by a novel putative lncRNA HBVPTPAP inducing the apoptosis of hepatocellular carcinoma cells by modulating JAK/STAT signaling pathways

When the hepatitis B virus (HBV) enters target cells, there are complex trans-regulatory mechanisms involved in the interactions between the virus and the target cells. In the present study, a new gene screened from the hepatoblastoma cell line HepG2 using suppression subtractive hybridization, referred to as lncRNA HBVPTPAP, was used to study the trans-regulation of HBV DNA polymerase. According to the structural characteristics of the full-length sequences, it was classified as long non-coding RNA. However, a unique and complete open reading frame (ORF) was still present. Therefore, to further identify the lncRNA HBVPTPAP gene's encoding potential, this study used several online tools to analyze and verify its encoding polypeptide authenticity. On that basis, the effects of the lncRNA HBVPTPAP gene on the biological behaviors of HepG2 cells and its molecular regulatory mechanism were investigated. It was found that the lncRNA HBVPTPAP subcellular was mainly located in the cytoplasm, and possibly activated the downstream JAK/STAT signaling pathway through the interaction between the encoding polypeptide and PILRA intracellular domain. Then, the mitochondrial apoptosis pathway may have been initiated to induce apoptosis. These results provided a basis for further study of the biological functions of the lncRNA HBVPTPAP gene.

The Emerging Role of Eosinophils as Multifunctional Leukocytes in Health and Disease

Eosinophils are terminally differentiated cytotoxic effector cells that have a role in parasitic infections and allergy by releasing their granule-derived cytotoxic proteins. However, an increasing number of recent observations indicate that eosinophils are not only associated with the pathogenesis of a wide range of diseases, but also contribute to the maintenance of homeostatic responses in previously underappreciated diverse tissues, such as the gastrointestinal (GI) tract and adipose tissue. In this review, we describe biological characteristics of eosinophils, as their developmental properties, permissive proliferation and survival, degranulation activity, and migration properties enable them to distribute to both homeostatic and inflamed tissues. We describe pathologic aspects of eosinophils with a role in asthma and in various GI diseases, including eosinophilic GI disorders, inflammatory bowel disease, and radiation-induced enteropathy. Finally, we discuss the beneficial role of eosinophils, which contribute to the resolution of pathogenic conditions and to the modulation of homeostatic biologic responses.

γδT cells contribute to type 2 inflammatory profiles in eosinophilic chronic rhinosinusitis with nasal polyps

Eosinophilic chronic rhinosinusitis with nasal polyps (ECRS) is a condition linked with type 2 inflammation, poor treatment outcomes, and high recurrence tendency. Although γδT cells have been reported to induce type 2 immune responses and eosinophilic infiltration in several diseases, their role in ECRS has not been fully explored. We aimed to evaluate the association of γδT cells with the type 2 inflammatory profiles in ECRS. Nasal tissue samples obtained from patients with chronic rhinosinusitis with nasal polyps (CRSwNP) (51 eosinophilic and 48 non-eosinophilic), 50 patients with chronic rhinosinusitis without nasal polyps (CRSsNP), and 58 control subjects were examined for γδT cells, inflammatory markers and eosinophils using HE, RT-qPCR, ELISA, immunofluorescence, and flow cytometry. In parallel, studies were also conducted in an ECRS murine model induced by anti-γδT cells neutralizing antibody administration. γδT cells expression was significantly increased in tissues from patients with ECRS compared with non-ECRS, CRSsNP and control subjects. Moreover, inflammatory markers including type 2 proinflammatory cytokines (IL-4, IL-5, IL-13), GATA3, eosinophil cationic protein (ECP), and eotaxin levels were also increased in nasal tissues of patients with ECRS, and Vγ1+ γδT cells mRNA expression was positively correlated with type 2 cytokines, GATA3, and ECP. In the ECRS murine model, anti-Vγ1+ γδT antibody treatment reduced the infiltration of eosinophils and expression of type 2 cytokines, GATA3, and ECP in nasal mucosae. In conclusion, the results of the present study suggest that γδT cells play a crucial role in the type 2 inflammatory profiles and nasal tissue eosinophilic infiltration in patients with ECRS.

Influenza A virus directly modulates mouse eosinophil responses

Allergic asthma and influenza are common respiratory diseases with a high probability of co-occurrence. During the 2009 influenza pandemic, hospitalized patients with influenza experienced lower morbidity if asthma was an underlying condition. We have previously demonstrated that acute allergic asthma protects mice from severe influenza and have implicated eosinophils in the airways of mice with allergic asthma as participants in the antiviral response. However, very little is known about how eosinophils respond to direct exposure to influenza A virus (IAV) or the microenvironment in which the viral burden is high. We hypothesized that eosinophils would dynamically respond to the presence of IAV through phenotypic, transcriptomic, and physiologic changes. Using our mouse model of acute fungal asthma and influenza, we showed that eosinophils in lymphoid tissues were responsive to IAV infection in the lungs and altered surface expression of various markers necessary for cell activation in a niche-specific manner. Siglec-F expression was altered in a subset of eosinophils after virus exposure, and those expressing high Siglec-F were more active (IL-5Rα^hi CD62L^lo ). While eosinophils exposed to IAV decreased their overall transcriptional activity and mitochondrial oxygen consumption, transcription of genes encoding viral recognition proteins, Ddx58 (RIG-I), Tlr3, and Ifih1 (MDA5), were up-regulated. CD8⁺ T cells from IAV-infected mice expanded in response to IAV PB1 peptide-pulsed eosinophils, and CpG methylation in the Tbx21 promoter was reduced in these T cells. These data offer insight into how eosinophils respond to IAV and help elucidate alternative mechanisms by which they regulate antiviral immune responses during IAV infection.

Recent advances in potential targets for eosinophilic esophagitis treatments

Introduction: Diagnostic and therapeutic strategies in eosinophilic esophagitis (EoE) are constantly evolving. Recently, the improved understanding of EoE pathogenesis has led to identification of a variety of other potential targets that have never been considered before.Areas covered: In September 2019, we performed structured literature searches in Medline and PubMed, Cochrane meta-analyses, and abstracts of international congresses to review new potential therapeutic approaches for EoE.Expert opinion: The advent of omics disciplines has been helping in finding new molecular targets in EoE pathogenesis and may provide future guidance for deep phenotyping of the disease and therefore facilitate the possibility of personalized medicine. Interestingly, these new treatments should be focused on the restoration of epithelial barrier dysfunction, downregulation of specific molecular pathways of eosinophilic inflammation, and finally, prevention of esophageal remodeling. In this review, we highlight the most recent insights in EoE pathogenesis, which open new pathways for developing new therapeutic targets for clinical practice.

The Orphan Cytokine Receptor CRLF3 Emerged With the Origin of the Nervous System and Is a Neuroprotective Erythropoietin Receptor in Locusts

The orphan cytokine receptor-like factor 3 (CRLF3) was identified as a neuroprotective erythropoietin receptor in locust neurons and emerged with the evolution of the eumetazoan nervous system. Human CRLF3 belongs to class I helical cytokine receptors that mediate pleiotropic cellular reactions to injury and diverse physiological challenges. It is expressed in various tissues including the central nervous system but its ligand remains unidentified. A CRLF3 ortholog in the holometabolous beetle Tribolium castaneum was recently shown to induce anti-apoptotic mechanisms upon stimulation with human recombinant erythropoietin. To test the hypothesis that CRLF3 represents an ancient cell-protective receptor for erythropoietin-like cytokines, we investigated its presence across metazoan species. Furthermore, we examined CRLF3 expression and function in the hemimetabolous insect Locusta migratoria. Phylogenetic analysis of CRLF3 sequences indicated that CRLF3 is absent in Porifera, Placozoa and Ctenophora, all lacking the traditional nervous system. However, it is present in all major eumetazoan groups ranging from cnidarians over protostomians to mammals. The CRLF3 sequence is highly conserved and abundant amongst vertebrates. In contrast, relatively few invertebrates express CRLF3 and these sequences show greater variability, suggesting frequent loss due to low functional importance. In L. migratoria, we identified the transcript Lm-crlf3 by RACE-PCR and detected its expression in locust brain, skeletal muscle and hemocytes. These findings correspond to the ubiquitous expression of crlf3 in mammalian tissues. We demonstrate that the sole addition of double-stranded RNA to the culture medium (called soaking RNA interference) specifically interferes with protein expression in locust primary brain cell cultures. This technique was used to knock down Lm-crlf3 expression and to abolish its physiological function. We confirmed that recombinant human erythropoietin rescues locust brain neurons from hypoxia-induced apoptosis and showed that this neuroprotective effect is absent after knocking down Lm-crlf3. Our results affirm the erythropoietin-induced neuroprotective function of CRLF3 in a second insect species from a different taxonomic group. They suggest that the phylogenetically conserved CRLF3 receptor may function as a cell protective receptor for erythropoietin or a structurally related cytokine also in other animals including vertebrate and mammalian species.

Safety and Efficacy of Mepolizumab in Patients with Eosinophilic Granulomatosis with Polyangiitis

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare form of vasculitis disorder which involves multiple organ systems and is characterized by asthma, pulmonary infiltrates, sinusitis, neuropathy, and peripheral eosinophilia. It also has an effect on the heart, skin, kidneys, and gastrointestinal tract. Interlukin-5 (IL-5) is involved in maturation and activation of eosinophil, the production of which is increased in the EGPA. Treatments of EGPA are limited to systemic corticosteroids and immunomodulators. These drugs are associated with significant side effects. Besides this, the response of patients to these drugs may be disappointing. Frequent relapses, the need for long-term medium-to-high-dose glucocorticoid therapy, and failure to achieve remission are not uncommon findings. There is a need for noble agents that could reduce frequent relapses and the dose of systemic glucocorticoids and maintain a sustained remission without significant side effects. Mepolizumab is IL-5 antagonist and may have value in treating patients with EGPA. Therefore, we did a systematic review to evaluate the efficacy and safety of mepolizumab in patients with EGPA.

TCF-1 and HEB cooperate to establish the epigenetic and transcription profiles of CD4+CD8+ thymocytes

Thymocyte development requires a complex orchestration of multiple transcription factors. Ablating either TCF-1 or HEB in CD4+CD8+ thymocytes elicits similar developmental outcomes including increased proliferation, decreased survival, and fewer late Tcra rearrangements. Here, we provide a mechanistic explanation for these similarities by showing that TCF-1 and HEB share ~7,000 DNA-binding sites genome wide and promote chromatin accessibility. The binding of both TCF-1 and HEB was required at these shared sites for epigenetic and transcriptional gene regulation. Binding of TCF-1 and HEB to their conserved motifs in the enhancer regions of genes associated with T cell differentiation promoted their expression. Binding to sites lacking conserved motifs in the promoter regions of cell-cycle-associated genes limited proliferation. TCF-1 displaced nucleosomes, allowing for chromatin accessibility. Importantly, TCF-1 inhibited Notch signaling and consequently protected HEB from Notch-mediated proteasomal degradation. Thus, TCF-1 shifts nucleosomes and safeguards HEB, thereby enabling their cooperation in establishing the epigenetic and transcription profiles of CD4+CD8+ thymocytes.

Necroinflammation emerges as a key regulator of hematopoiesis in health and disease

The hematopoietic system represents an organ system with an exceptional capacity for the production of mature blood cells from a small and mostly quiescent pool of hematopoietic stem cells (HSCs). This extraordinary capacity includes self-renewal but also the propensity to rapidly respond to extrinsic needs, such as acute infections, severe inflammation, and wound healing. In recent years, it became clear that inflammatory signals such as cytokines, chemokine and danger signals from pathogens (PAMPs) or dying cells (DAMPs) impact on HSCs, shaping their proliferation status, lineage bias, and repopulating ability and subsequently increasing the output of mature effector cells. However, inflammatory danger signals negatively impact on the capacity of HSCs to self-renew and to maintain their stem cell capabilities. This is evidenced in conditions of chronic inflammation where bone marrow failure may originate from HSC exhaustion. Even in hematopoietic cancers, inflammatory signals shape the phenotype of the malignant clone as exemplified by necrosome-dependent inflammation elicited during malignant transformation in acute myeloid leukemia. Accordingly, understanding the contribution of inflammatory signals, and specifically necroinflammation, to HSC integrity, HSC long-term functionality, and malignant transformation has attracted substantial research and clinical interest. In this review, we highlight recent developments and open questions at the interplay between inflammation, regulated necrosis, and HSC biology in the context of blood cell development, acute and chronic inflammation, and hematopoietic cancer.

mTOR complexes differentially orchestrates eosinophil development in allergy

Eosinophil infiltration is considered a hallmark in allergic airway inflammation, and the blockade of eosinophil differentiation may be an effective approach for treating eosinophil-related disorders. Mammalian target of rapamycin (mTOR) is a vital modulator in cell growth control and related diseases, and we have recently demonstrated that rapamycin can suppress eosinophil differentiation in allergic airway inflammation. Considering its critical role in haematopoiesis, we further investigated the role of mTOR in eosinophil differentiation in the context of asthmatic pathogenesis. Intriguingly, the inhibition of mTOR, either by genetic deletion or by another pharmacological inhibitor torin-1, accelerated the eosinophil development in the presence of IL-5. However, this was not observed to have any considerable effect on eosinophil apoptosis. The effect of mTOR in eosinophil differentiation was mediated by Erk signalling. Moreover, myeloid specific knockout of mTOR or Rheb further augmented allergic airway inflammation in mice after allergen exposure. Ablation of mTOR in myeloid cells also resulted in an increased number of eosinophil lineage-committed progenitors (Eops) in allergic mice. Collectively, our data uncovered the differential effects of mTOR in the regulation of eosinophil development, likely due to the distinct functions of mTOR complex 1 or 2, which thus exerts a pivotal implication in eosinophil-associated diseases.

CD300 family receptors regulate eosinophil survival, chemotaxis, and effector functions

The CD300 family of receptors is an evolutionary conserved receptor family that belongs to the Ig superfamily and is expressed predominantly by the myeloid lineage. Over the past couple of years, accumulating data have shown that eosinophils express various Ig superfamily receptors that regulate key checkpoints in their biology including their maturation, transition from the bone marrow to the peripheral blood, migration, adhesion, survival, and effector functions in response to numerous activating signals such as IL-4, IL-33, and bacteria. In this review, we will present the emerging roles of CD300 family receptors and specifically CD300a and CD300f in the regulation of these eosinophil activities. The structure and expression pattern of these molecules will be discussed and their involvement in suppressing or co-activating eosinophil functions in health and disease will be illustrated.

Functions of tissue-resident eosinophils

Eosinophils are a prominent cell type in particular host responses such as the response to helminth infection and allergic disease. Their effector functions have been attributed to their capacity to release cationic proteins stored in cytoplasmic granules by degranulation. However, eosinophils are now being recognized for more varied functions in previously underappreciated diverse tissue sites, based on the ability of eosinophils to release cytokines (often preformed) that mediate a broad range of activities into the local environment. In this Review, we consider evolving insights into the tissue distribution of eosinophils and their functional immunobiology, which enable eosinophils to secrete in a selective manner cytokines and other mediators that have diverse, 'non-effector' functions in health and disease.

Parasite-Derived Proteins for the Treatment of Allergies and Autoimmune Diseases

The morbidity associated with atopic diseases and immune dysregulation disorders such as asthma, food allergies, multiple sclerosis, atopic dermatitis, type 1 diabetes mellitus, and inflammatory bowel disease has been increasing all around the world over the past few decades. Although the roles of non-biological environmental factors and genetic factors in the etiopathology have been particularly emphasized, they do not fully explain the increase; for example, genetic factors in a population change very gradually. Epidemiological investigation has revealed that the increase also parallels a decrease in infectious diseases, especially parasitic infections. Thus, the reduced prevalence of parasitic infections may be another important reason for immune dysregulation. Parasites have co-evolved with the human immune system for a long time. Some parasite-derived immune-evasion molecules have been verified to reduce the incidence and harmfulness of atopic diseases in humans by modulating the immune response. More importantly, some parasite-derived products have been shown to inhibit the progression of inflammatory diseases and consequently alleviate their symptoms. Thus, parasites, and especially their products, may have potential applications in the treatment of autoimmune diseases. In this review, the potential of parasite-derived products and their analogs for use in the treatment of atopic diseases and immune dysregulation is summarized.

Mouse Eosinophils: Identification, Isolation, and Functional Analysis

Eosinophils are bone marrow-derived cells that differentiate in the bone marrow and migrate into the peripheral blood primarily under the regulation of interleukin (IL)-5. Eosinophil levels in the blood are relatively low. However, under steady-state conditions and in settings of allergic inflammation, parasite infections, or even cancer, they migrate and mainly reside in mucosal tissues where they have key effector and immune-modulating functions. Functional studies using eosinophils are not simple, since these cells are terminally differentiated and rapidly die in vitro. Thus, establishing simple methods to characterize, obtain, and functionally assess eosinophil activities is important. In this unit, we describe methodology for identifying tissue eosinophils by flow cytometry. In addition, we provide detailed methods for isolating eosinophils and for differentiating them from bone marrow cells for further functional studies. © 2017 by John Wiley & Sons, Inc.

Regulation of eosinophil development and survival

PURPOSE OF REVIEW

Eosinophils are a subset of granulocytes generally associated with type 2 immune responses. They can contribute to protection against helminths but also mediate pro-inflammatory functions during allergic immune responses. Only recently, eosinophils were also found to exert many other functions such as regulation of glucose and fat metabolism, thermogenesis, survival of plasma cells, and antitumor activity. The mechanisms that control eosinophil development and survival are only partially understood.

RECENT FINDINGS

Here we review new findings regarding the role of cell-extrinsic and cell-intrinsic factors for eosinophilopoiesis and eosinophil homeostasis. Several reports provide new insights in the regulation of eosinophil development by transcription factors, miRNAs and epigenetic modifications. Danger signals like lipopolysaccharide or alarmins can activate eosinophils but also prolong their lifespan. We further reflect on the observations that eosinophil development is tightly controlled by the unfolded protein stress response and formation of cytoplasmic granules.

SUMMARY

Eosinophils emerge as important regulators of diverse biological processes. Their differentiation and survival is tightly regulated by factors that are still poorly understood. Newly identified pathways involved in eosinophilopoiesis and eosinophil homeostasis may lead to development of new therapeutic options for treatment of eosinophil-associated diseases.

Regulation of immune and neural function via leukocyte Ig-like receptors

Leukocyte Ig-like receptors (LILRs)/Ig-like transcripts (ILTs) are expressed on innate and adaptive immune cells and maintain immune homeostasis. LILRs consist of activating and inhibitory-type receptors that regulate adequate cellular functions. LILRs were firstly identified as MHC class I receptors, therefore expression and/or polymorphisms of LILRs are reported to associate with autoimmune disorders and transplant rejection; however, recent accumulating evidences have revealed that LILRs recognize with diverse ligands including bacteria and virus. In addition, inhibitory LILRB2 (ILT4) and murine relative paired Ig-like receptor (PIR)-B are expressed on neuron and is involved in the dysregulation of central nervous system via interaction with neuronal ligands including amyloid β-protein. In this review, we summarize recent discoveries on the functions of inhibitory MHC class I receptors, and discuss their regulatory roles in immune responses and neural functions.

Eosinophilic gastroenteritis presenting as upper gastrointestinal hematoma and ulcers after endoscopic biopsy: A case report and literature review

RATIONALE

Eosinphilic gastroenteritis (EG) is a gastrointestinal disorder characterized by eosinophilic infiltration with various manifestations. The diagnosis is usually confirmed by an endoscopic biopsy, which is considered a safe and routine procedure for the majority.

PATIENT CONCERNS

We report a 54-year-old male who was presented with intermittent periumbilical pain and melena, and only revealed verrucous gastritis by endoscopy.

DIAGNOSES

The patient's condition worsened two days after the endoscopic biopsy, and another endoscopy found hematoma and ulcers in upper gastrointestinal tract. He was diagnosed with EG by the pathological analysis of biopsy specimen.

INTERVENTIONS

Oral methylprednisolone and Montelukast were prescribed.

OUTCOMES

The patient got remission after initiation of the treatment.

LESSONS

This case highlights an extremely rare but potentially severe complication of endoscopic biopsies in patients with EG. Physicians should be cautious with hematoma or ulceration, and consider it in such patients who undergo this procedure.

Transcriptome profiling of mouse colonic eosinophils reveals a key role for eosinophils in the induction of s100a8 and s100a9 in mucosal healing

Eosinophils are bone marrow-derived cells that have been largely implicated in Th2-associated diseases. Recent data highlights a key role for eosinophils in mucosal innate immune responses especially in the gastrointestinal (GI) tract, which is one of the largest eosinophil reservoirs in the body. Although eosinophils express and synthesize a plethora of proteins that can mediate their effector activities, the transcriptome signature of eosinophils in mucosal inflammation and subsequent repair has been considerably overlooked. We demonstrate that eosinophils are recruited to the colon in acute inflammatory stages where they promote intestinal inflammation and remain in substantial numbers throughout the mucosal healing process. Microarray analysis of primary colonic eosinophils that were sorted at distinct stages of mucosal inflammation and repair revealed dynamic regulation of colonic eosinophil mRNA expression. The clinically relevant genes s100a8 and s100a9 were strikingly increased in colonic eosinophils (up to 550-fold and 80-fold, respectively). Furthermore, local and systemic expression of s100a8 and s100a9 were nearly diminished in eosinophil-deficient ΔdblGATA mice, and were re-constituted upon adoptive transfer of eosinophils. Taken together, these data may provide new insight into the involvement of eosinophils in colonic inflammation and repair, which may have diagnostic and therapeutic implications.

Autoimmune arthritis induces paired immunoglobulin-like receptor B expression on CD4+ T cells from SKG mice

The chronic, destructive autoimmune arthritis in SKG mice, which closely resembles human rheumatoid arthritis, is the result of self-reactive T cells escaping thymic deletion. Since the inhibitory receptor LIR-1 is up-regulated on auto-reactive T cells in human rheumatoid arthritis, the role of its murine ortholog PIR-B was investigated. Peripheral CD4⁺ T cells from SKG mice were found to frequently express PIR-B, and this population produces more frequently IL-17 upon in vitro stimulation compared to PIR-B^- cells. A much larger fraction of PIR-B⁺ T cells, however, was found to secret no IL-17, but IFN-γ. With regards to the clinical course of the disease, high frequencies of PIR-B⁺ CD4⁺ T cells were found to be associated with a milder course of arthritis, suggesting that the net effect of PIR-B expression is suppression of autoreactive T cells. Our results indicate that overexpression of PIR-B on IL-17-producing SKG CD4⁺ T cells might represent an effective counter-regulatory mechanism against the destructive potential of those cells. More importantly, a major population of PIR-B⁺ T cells in SKG mice appears to play an inhibitory role by way of their IFN-γ production, since high frequencies of those cells ameliorate the disease.

CD300f:IL-5 cross-talk inhibits adipose tissue eosinophil homing and subsequent IL-4 production

Eosinophils and their associated cytokines IL-4 and IL-5 are emerging as central orchestrators of the immune-metabolic axis. Herein, we demonstrate that cross-talk between the Ig-superfamily receptor CD300f and IL-5 is a key checkpoint that modifies the ability of eosinophils to regulate metabolic outcomes. Generation of Il5 ^Tg /Cd300f ^-/- mice revealed marked and distinct increases in eosinophil levels and their production of IL-4 in the white and brown adipose tissues. Consequently, Il5 ^Tg /Cd300f ^-/- mice had increased alternatively activated macrophage accumulation in the adipose tissue. Cd300f ^-/- mice displayed age-related accumulation of eosinophils and macrophages in the adipose tissue and decreased adipose tissue weight, which was associated with decreased diet-induced weight gain and insulin resistance. Notably, Il5 ^Tg /CD300f ^-/- were protected from diet-induced weight gain and glucose intolerance. These findings highlight the cross-talk between IL-5 receptor and CD300f as a novel pathway regulating adipose tissue eosinophils and offer new entry points for therapeutic intervention for obesity and its complications.

Recent advances in understanding eosinophil biology

With the advent of novel therapies targeting eosinophils, there has been renewed interest in understanding the basic biology of this unique cell. In this context, murine models and human studies have continued to highlight the role of the eosinophil in homeostatic functions and immunoregulation. This review will focus on recent advances in our understanding of eosinophil biology that are likely to have important consequences on the development and consequences of eosinophil-targeted therapies. Given the breadth of the topic, the discussion will be limited to three areas of interest: the eosinophil life cycle, eosinophil heterogeneity, and mechanisms of cell-cell communication.

Non-apoptotic functions of caspases in myeloid cell differentiation

Subtle caspase activation is associated with the differentiation of several myeloid lineages. A tightly orchestrated dance between caspase-3 activation and the chaperone HSP70 that migrates to the nucleus to protect the master regulator GATA-1 from cleavage transiently occurs in basophilic erythroblasts and may prepare nucleus and organelle expel that occurs at the terminal phase of erythroid differentiation. A spatially restricted activation of caspase-3 occurs in maturing megakaryocytes to promote proplatelet maturation and platelet shedding in the bloodstream. In a situation of acute platelet need, caspase-3 could be activated in response to IL-1α and promote megakaryocyte rupture. In peripheral blood monocytes, colony-stimulating factor-1 provokes the formation of a molecular platform in which caspase-8 is activated, which downregulates nuclear factor-kappa B (NF-κB) activity and activates downstream caspases whose target fragments such as those generated by nucleophosmin (NPM1) cleavage contribute to the generation of resting macrophages. Human monocytes secrete mature IL-1β in response to lipopolysaccharide through an alternative inflammasome activation that involves caspase-8, a pathway that does not lead to cell death. Finally, active caspase-3 is part of the proteases contained in secretory granules of mast cells. Many questions remain on how these proteases are activated in myeloid cell lineages, which target proteins are cleaved, whereas other are protected from proteolysis, the precise role of cleaved proteins in cell differentiation and functions, and the link between these non-apoptotic functions of caspases and the death of these diverse cell types. Better understanding of these functions may generate therapeutic strategies to control cytopenias or modulate myeloid cell functions in various pathological situations.

A key requirement for CD300f in innate immune responses of eosinophils in colitis

Eosinophils are traditionally studied in the context of type 2 immune responses. However, recent studies highlight key innate immune functions for eosinophils especially in colonic inflammation. Surprisingly, molecular pathways regulating innate immune activities of eosinophil are largely unknown. We have recently shown that the CD300f is highly expressed by colonic eosinophils. Nonetheless, the role of CD300f in governing innate immune eosinophil activities is ill-defined. RNA sequencing of 162 pediatric Crohn's disease patients revealed upregulation of multiple Cd300 family members, which correlated with the presence of severe ulcerations and inflammation. Increased expression of CD300 family receptors was also observed in active ulcerative colitis (UC) and in mice following induction of experimental colitis. Specifically, the expression of CD300f was dynamically regulated in monocytes and eosinophils. Dextran sodium sulfate (DSS)-treated Cd300f^-/- mice exhibit attenuated disease activity and histopathology in comparison with DSS-treated wild type (WT). Decreased disease activity in Cd300f^-/- mice was accompanied with reduced inflammatory cell infiltration and nearly abolished production of pro-inflammatory cytokines. Monocyte depletion and chimeric bone marrow transfer experiments revealed a cell-specific requirement for CD300f in innate immune activation of eosinophils. Collectively, we uncover a new pathway regulating innate immune activities of eosinophils, a finding with significant implications in eosinophil-associated gastrointestinal diseases.

Eosinophilic Gastroenteritis and Colitis: a Comprehensive Review

Eosinophilic gastrointestinal disorders, including eosinophilic esophagitis, gastroenteritis, and colitis, refer to a spectrum of clinical diseases that present with variable degrees of infiltration of the gastrointestinal tract by eosinophils in the absence of other known causes of tissue eosinophilia. Clinical symptoms and laboratory findings are usually non-specific and may or may not be accompanied by peripheral blood eosinophilia. The extent of eosinophilic infiltration of the gastrointestinal wall varies from mucosal to transmural and serosal involvement. Diagnosis requires presence of gastrointestinal symptoms, demonstration of gastrointestinal eosinophilia by biopsy, and exclusion of other known causes of tissue eosinophilia. Many studies have pointed toward the eosinophil as the major offender; however, the exact functional role of the eosinophil in the pathogenesis of eosinophilic gastrointestinal disorders remains unclear. The roles of T-helper-2 cytokines and other mediators, such as eotaxin-1 and interleukin-5, have gained significant importance in the pathobiology of eosinophilic gastrointestinal disorders. Current understanding of treatment is based on case reports and a few case series, as there is a lack of large prospective studies. Steroids are currently the mainstay of therapy, but the roles of other drugs such as leukotriene inhibitors, mast cell stabilizers, interleukin-5 inhibitors, and anti-immunoglobulin E, along with other targets in the immune pathway, are currently being explored.

Emerging Roles for Eosinophils in the Tumor Microenvironment

Eosinophils are evolutionary conserved cells largely studied in the context of allergy. Although eosinophils were first described in tumors more than 120 years ago, their roles in cancer are often overlooked. This is puzzling given their potent immune modulatory, cytotoxic, and/or tissue repair capabilities, and recent studies demonstrating key roles for eosinophils in contexts far beyond their 'classical' field (e.g., metabolism, thermogenesis, and tissue regeneration). Recent data suggest that this frequently ignored cell is emerging as a potent immune effector and immune modulator in the tumor microenvironment. This review discusses the relevance of eosinophils to tumorigenesis and the potential to harness their function in cancer therapies.

RhoH is a negative regulator of eosinophilopoiesis

Eosinophils are frequently elevated in pathological conditions and can cause tissue damage and disease exacerbation. The number of eosinophils in the blood is largely regulated by factors controlling their production in the bone marrow. While several exogenous factors, such as interleukin-5, have been described to promote eosinophil differentiation, comparatively little is known about eosinophil-intrinsic factors that control their de novo generation. Here, we report that the small atypical GTPase RhoH is induced during human eosinophil differentiation, highly expressed in mature blood eosinophils and further upregulated in patients suffering from a hypereosinophilic syndrome. Overexpression of RhoH increases, in a Rho-associated protein kinase-dependent manner, the expression of GATA-2, a transcription factor involved in regulating eosinophil differentiation. In RhoH^-/- mice, we observed reduced GATA-2 expression as well as accelerated eosinophil differentiation both in vitro and in vivo. Conversely, RhoH overexpression in bone marrow progenitors reduces eosinophil development in mixed bone marrow chimeras. These results highlight a novel negative regulatory role for RhoH in eosinophil differentiation, most likely in consequence of altered GATA-2 levels.

Paired Ig-like Receptor B Inhibits IL-13-Driven Eosinophil Accumulation and Activation in the Esophagus

Eosinophilic esophagitis (EoE) is a Th2 cytokine-associated disease characterized by eosinophil infiltration, epithelial cell hyperplasia, and tissue remodeling. Recent studies highlighted a major contribution for IL-13 in EoE pathogenesis. Paired Ig-like receptor B is a cell surface immune-inhibitory receptor that is expressed by eosinophils and postulated to regulate eosinophil development and migration. We report that Pirb is upregulated in the esophagus after inducible overexpression of IL-13 (CC10-Il13(Tg) mice) and is overexpressed by esophageal eosinophils. CC10-Il13(Tg)/Pirb(-/-) mice displayed increased esophageal eosinophilia and EoE pathology, including epithelial cell thickening, fibrosis, and angiogenesis, compared with CC10-Il13(Tg)/Pirb(+/+) mice. Transcriptome analysis of primary Pirb(+/+) and Pirb(-/-) esophageal eosinophils revealed increased expression of transcripts associated with promoting tissue remodeling in Pirb(-/-) eosinophils, including profibrotic genes, genes promoting epithelial-to-mesenchymal transition, and genes associated with epithelial growth. These data identify paired Ig-like receptor B as a molecular checkpoint in IL-13-induced eosinophil accumulation and activation, which may serve as a novel target for future therapy in EoE.

The Expanding Spectrum of Ligands for Leukocyte Ig-like Receptors

The human leukocyte Ig-like receptor family is part of the paired receptor system. The receptors are widely expressed by various immune cells, and new functions continue to emerge. Understanding the range of functions of the receptors is of general interest because several types of pathogens exploit the receptors and genetic diversity of the receptors has been linked to various autoimmune diseases. Class I major histocompatibility molecules were the first ligands appreciated for these receptors, but the types of ligands identified over the last several years are quite diverse, including intact pathogens, immune-modulatory proteins, and molecules normally found within the CNS. This review focuses on the types of ligands described to date, how the individual receptors bind to several distinct types of ligands, and the known functional consequences of those interactions.

Fight or flight: regulation of emergency hematopoiesis by pyroptosis and necroptosis

PURPOSE OF REVIEW

A feature of the innate immune response that is conserved across kingdoms is the induction of cell death. In this review, we discuss the direct and indirect effects of increased inflammatory cell death, including pyroptosis - a caspase-1-dependent cell death - and necroptosis - a receptor-interacting protein kinase 3/mixed lineage kinase domain-like protein-dependent, caspase-independent cell death - on emergency hematopoiesis.

RECENT FINDINGS

Activation of nonapoptotic cell death pathways during infection can trigger release of cytokines and/or damage-associated molecular patterns such as interleukin (IL)-1α, IL-1β, IL-18, IL-33, high-mobility group protein B1, and mitochondrial DNA to promote emergency hematopoiesis. During systemic infection, pyroptosis and necroptosis can directly kill hematopoietic stem and progenitor cells, which results in impaired hematopoiesis, cytopenia, and immunosuppression. Although originally described as discrete entities, there now appear to be more intimate connections between the nonapoptotic and death receptor signaling pathways.

SUMMARY

The choice to undergo pyroptotic and necroptotic cell death constitutes a rapid response system serving to eliminate infected cells, including hematopoietic stem and progenitor cells. This system has the potential to be detrimental to emergency hematopoiesis during severe infection. We discuss the potential of pharmacological intervention for the pyroptosis and necroptosis pathways that may be beneficial during periods of infection and emergency hematopoiesis.

A protective role for IL-13 receptor α 1 in bleomycin-induced pulmonary injury and repair

Molecular mechanisms that regulate lung repair vs. progressive scarring in pulmonary fibrosis remain elusive. Interleukin (IL)-4 and IL-13 are pro-fibrotic cytokines that share common receptor chains including IL-13 receptor (R) α1 and are key pharmacological targets in fibrotic diseases. However, the roles of IL-13Rα1 in mediating lung injury/repair are unclear. We report dysregulated levels of IL-13 receptors in the lungs of bleomycin-treated mice and to some extent in idiopathic pulmonary fibrosis patients. Transcriptional profiling demonstrated an epithelial cell-associated gene signature that was homeostatically dependent on IL-13Rα1 expression. IL-13Rα1 regulated a striking array of genes in the lung following bleomycin administration and Il13ra1 deficiency resulted in exacerbated bleomycin-induced disease. Increased pathology in bleomycin-treated Il13ra1(-/-) mice was due to IL-13Rα1 expression in structural and hematopoietic cells but not due to increased responsiveness to IL-17, IL-4, IL-13, increased IL-13Rα2 or type 1 IL-4R signaling. These data highlight underappreciated protective roles for IL-13Rα1 in lung injury and homeostasis.

Eosinophilia: a pragmatic approach to diagnosis and treatment

Eosinophilia is associated with a wide variety of allergic, rheumatologic, infectious, neoplastic, and rare idiopathic disorders. Clinical manifestations range from benign asymptomatic presentations to life-threatening complications, including endomyocardial fibrosis and thromboembolism. The prognosis and choice of treatment depend not only on the degree of eosinophilia and severity of organ involvement, but also on the etiology of the eosinophilia. Unfortunately, despite recent advances in molecular and immunologic techniques, the etiology remains unproven in the overwhelming majority of cases. This review presents a practical approach to the diagnosis and treatment of patients presenting with unexplained marked eosinophilia. A brief overview of the mechanisms of eosinophilia and eosinophil pathogenesis is also provided.

CD300f associates with IL-4 receptor α and amplifies IL-4-induced immune cell responses

IL-4 receptor (R) α, the common receptor chain for IL-4 and IL-13, is a critical component in IL-4- and IL-13-mediated signaling and subsequent effector functions such as those observed in type 2 inflammatory responses. Nonetheless, the existence of intrinsic pathways capable of amplifying IL-4Rα-induced responses remains unknown. In this study, we identified the myeloid-associated Ig receptor CD300f as an IL-4-induced molecule in macrophages. Subsequent analyses demonstrated that CD300f was colocalized and physically associated with IL-4Rα. Using Cd300f(-/-) cells and receptor cross-linking experiments, we established that CD300f amplified IL-4Rα-induced responses by augmenting IL-4/IL-13-induced signaling, mediator release, and priming. Consistently, IL-4- and aeroallergen-treated Cd300f(-/-) mice displayed decreased IgE production, chemokine expression, and inflammatory cell recruitment. Impaired responses in Cd300f(-/-) mice were not due to the inability to generate a proper Th2 response, because IL-4/IL-13 levels were markedly increased in allergen-challenged Cd300f(-/-) mice, a finding that is consistent with decreased cytokine consumption. Finally, CD300f expression was increased in monocytes and eosinophils obtained from allergic rhinitis patients. Collectively, our data highlight a previously unidentified role for CD300f in IL-4Rα-induced immune cell responses. These data provide new insights into the molecular mechanisms governing IL-4Rα-induced responses, and may provide new therapeutic tools to target IL-4 in allergy and asthma.

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.

Eosinophils in mucosal immune responses

Eosinophils, multifunctional cells that contribute to both innate and adaptive immunity, are involved in the initiation, propagation, and resolution of immune responses, including tissue repair. They achieve this multifunctionality by expression of a diverse set of activation receptors, including those that directly recognize pathogens and opsonized targets, and by their ability to store and release preformed cytotoxic mediators that participate in host defense, to produce a variety of de novo pleotropic mediators and cytokines, and to interact directly and indirectly with diverse cell types, including adaptive and innate immunocytes and structural cells. Herein, we review the basic biology of eosinophils and then focus on new emerging concepts about their role in mucosal immune homeostasis, particularly maintenance of intestinal IgA. We review emerging data about their development and regulation and describe new concepts concerning mucosal eosinophilic diseases. We describe recently developed therapeutic strategies to modify eosinophil levels and function and provide collective insight about the beneficial and detrimental functions of these enigmatic cells.

Generation of eosinophils from cryopreserved murine bone marrow cells

Eosinophils are produced in the bone marrow from CD34⁺ eosinophil lineage–committed progenitors, whose levels in the bone marrow are elevated in a variety of human diseases. These findings suggest that increased eosinophil lineage–committed progenitor production is an important process in disease-associated eosinophilia. The pathways central to the biology of the eosinophil lineage–committed progenitor remain largely unknown. Thus, developing new methods to investigate the regulators of eosinophil lineage–committed progenitor differentiation is needed to identify potential therapeutic targets to specifically inhibit eosinophil production. We tested cytokine regimens to optimize liquid cultures for the study of eosinophil lineage–committed progenitor and eosinophil precursor differentiation into mature eosinophils. Stem cell factor (but not fms-related tyrosine kinase 3 ligand) was required for optimal yield of eosinophils. Furthermore, we evaluated the effects of cell preservation and scale on the culture, successfully culturing functional eosinophils from fresh and frozen murine bone marrow cells and in a standard-sized and 96-well culture format. In summary, we have developed an adaptable culture system that yields functionally competent eosinophils from murine low-density bone marrow cells and whose cytokine regime includes expansion of progenitors with stem cell factor alone with subsequent differentiation with interleukin 5.

Roles and regulation of gastrointestinal eosinophils in immunity and disease

Eosinophils have historically been considered to be destructive end-stage effector cells that have a role in parasitic infections and allergic reactions by the release of their granule-derived cytotoxic proteins. However, an increasing number of experimental observations indicate that eosinophils also are multifunctional leukocytes involved in diverse inflammatory and physiologic immune responses. Under homeostatic conditions, eosinophils are particularly abundant in the lamina propria of the gastrointestinal tract, where their involvement in various biological processes within the gastrointestinal tract has been posited. In this review, we summarize the molecular steps involved in eosinophil development and describe eosinophil trafficking to the gastrointestinal tract. We synthesize the current findings on the phenotypic and functional properties of gastrointestinal eosinophils and the accumulating evidence that they have a contributory role in gastrointestinal disorders, with a focus on primary eosinophilic gastrointestinal disorders. Finally, we discuss the potential role of eosinophils as modulators of the intestinal immune system.

From innate to adaptive immune response in muscular dystrophies and skeletal muscle regeneration: the role of lymphocytes

Skeletal muscle is able to restore contractile functionality after injury thanks to its ability to regenerate. Following muscle necrosis, debris is removed by macrophages, and muscle satellite cells (MuSCs), the muscle stem cells, are activated and subsequently proliferate, migrate, and form muscle fibers restoring muscle functionality. In most muscle dystrophies (MDs), MuSCs fail to properly proliferate, differentiate, or replenish the stem cell compartment, leading to fibrotic deposition. However, besides MuSCs, interstitial nonmyogenic cells and inflammatory cells also play a key role in orchestrating muscle repair. A complete understanding of the complexity of these mechanisms should allow the design of interventions to attenuate MDs pathology without disrupting regenerative processes. In this review we will focus on the contribution of immune cells in the onset and progression of MDs, with particular emphasis on Duchenne muscular dystrophy (DMD). We will briefly summarize the current knowledge and recent advances made in our understanding of the involvement of different innate immune cells in MDs and will move on to critically evaluate the possible role of cell populations within the acquired immune response. Revisiting previous observations in the light of recent evidence will likely change our current view of the onset and progression of the disease.

Interleukin-33 requires CMRF35-like molecule-1 expression for induction of myeloid cell activation

BACKGROUND

IL-33 is a potent activator of various cells involved in allergic inflammation, including eosinophils and mast cells. Despite its critical role in Th2 disease settings, endogenous molecular mechanisms that may regulate IL-33-induced responses remain to be defined. We have recently shown that eosinophils express CMRF35-like molecule (CLM)-1. Yet, the role of CLM-1 in regulating eosinophil functions is still elusive.

METHODS

CLM-1 and CLM-8 expression and cellular localization were assessed in murine bone marrow-derived and/or peritoneal cells at baseline and following IL-33 stimulation (flow cytometry, western blot). IL-33-induced mediator release and signaling were assessed in wild-type (wt) and Clm1(-/-) cells and mice.

RESULTS

BM-derived eosinophils express high levels of glycosylated CLM-1. IL-33 induced a rapid, specific, concentration- and time-dependent upregulation of CLM-1 in eosinophils (in vitro and in vivo). Clm1(-/-) eosinophils secreted less IL-33-induced mediators than wt eosinophils. CLM-1 co-localized to ST2 following IL-33 stimulation and was required for IL-33-induced NFκB and p38 phosphorylation. Th2 cytokine (e.g., IL-5, IL-13) and chemokine (e.g., eotaxins, CCL2) secretion was markedly attenuated in IL-33-treated Clm1(-/-) mice. Subsequently, IL-33-challenged mice displayed reduced infiltration of mast cells, macrophages, neutrophils, and B cells. Despite the markedly impaired IL-33-induced eotaxin expression in Clm1(-/-) mice, eosinophil accumulation was similar in wt and Clm1(-/-) mice, due to hyperchemotactic responses of Clm1(-/-) eosinophils.

CONCLUSIONS

CLM-1 is a novel regulator of IL-33-induced eosinophil activation. These data contribute to the understanding of endogenous molecular mechanisms regulating IL-33-induced responses and may ultimately lead to receptor-based tools for future therapeutic intervention in IL-33-associated diseases.

Mitochondria in the center of human eosinophil apoptosis and survival

Eosinophils are abundantly present in most phenotypes of asthma and they contribute to the maintenance and exacerbations of the disease. Regulators of eosinophil longevity play critical roles in determining whether eosinophils accumulate into the airways of asthmatics. Several cytokines enhance eosinophil survival promoting eosinophilic airway inflammation while for example glucocorticoids, the most important anti-inflammatory drugs used to treat asthma, promote the intrinsic pathway of eosinophil apoptosis and by this mechanism contribute to the resolution of eosinophilic airway inflammation. Mitochondria seem to play central roles in both intrinsic mitochondrion-centered and extrinsic receptor-mediated pathways of apoptosis in eosinophils. Mitochondria may also be important for survival signalling. In addition to glucocorticoids, another important agent that regulates human eosinophil longevity via mitochondrial route is nitric oxide, which is present in increased amounts in the airways of asthmatics. Nitric oxide seems to be able to trigger both survival and apoptosis in eosinophils. This review discusses the current evidence of the mechanisms of induced eosinophil apoptosis and survival focusing on the role of mitochondria and clinically relevant stimulants, such as glucocorticoids and nitric oxide.