Identification of an interleukin (IL)-25-dependent cell population that provides IL-4, IL-5, and IL-13 at the onset of helminth expulsion

Intraperitoneal administration of the anti-IL-23 antibody prevents the establishment of intestinal nematodes in mice

Previous studies have established that an increased Th-9 response creates a hostile environment for nematode parasites. Given that IL-23, a cytokine required for maintenance of the IL-17-secreting phenotype, has inhibitory effects on IL-9 production, we hypothesized that reducing circulating IL-23 by treatment with anti-IL-23 antibodies would reduce the establishment and development of parasitic intestinal nematodes. In this study, we show that animals treated with anti-IL-23 monoclonal antibodies showed a drastic reduction in the number of mouse pinworms (Aspiculuris tetraptera) recovered from the intestine (p < 0.001) at 23 days post-infection compared to the untreated animals. The cytokine levels in Peyer's patches (PP) in treated and infected animals increase the expression of interleukins such as IL-25, IL-21, and IL-9, augmenting mucus production in the crypts, and boosting chemokines, such as OX40 and CCL20 in the mucosa. Our results suggest that the Th17/Th2 regulatory mechanism provoked by the administration of the anti-IL-23 antibody prevents the implantation of the intestinal nematode in mice. The diminished inflammatory IL-17 levels alter the Th9 environment perhaps as a consequence of IL-17 inhibiting IL-9 expression. These Th9 conditions may explain the successful treatment against Inflammatory Bowel Disease (IBD) both with antibodies against IL-23 or through parasitization with nematodes.

Activation of intestinal tuft cell-expressed Sucnr1 triggers type 2 immunity in the mouse small intestine

The hallmark features of type 2 mucosal immunity include intestinal tuft and goblet cell expansion initiated by tuft cell activation. How infectious agents that induce type 2 mucosal immunity are detected by tuft cells is unknown. Published microarray analysis suggested that succinate receptor 1 (Sucnr1) is specifically expressed in tuft cells. Thus, we hypothesized that the succinate-Sucnr1 axis may be utilized by tuft cells to detect certain infectious agents. Here we confirmed that Sucnr1 is specifically expressed in intestinal tuft cells but not in other types of intestinal epithelial cells, and demonstrated that dietary succinate induces tuft and goblet cell hyperplasia via Sucnr1 and the tuft cell-expressed chemosensory signaling elements gustducin and Trpm5. Conventional mice with a genetic Sucnr1 deficiency (Sucnr1^-/-) showed diminished immune responses to treatment with polyethylene glycol and streptomycin, which are known to enhance microbiota-derived succinate, but responded normally to inoculation with the parasitic worm Nippostrongylus brasiliensis that also produces succinate. Thus, Sucnr1 is required for microbiota-induced but not for a generalized worm-induced type 2 immunity.

Seventeen-Year Journey Working With a Master

It had been a great honor for me to work with the late Dr. William E. Paul for 17 years in the Laboratory of Immunology (LI) from 1998 until his passing in 2015. He was such a master in the immunology field. Under his outstanding guidance, my research has been focusing on transcriptional regulation of T helper (Th) cell differentiation, especially, on the role of a master transcription factor GATA3 during Th2 cell differentiation. Just as enormous scientific contributions of Dr. Paul (we all call him Bill) to the immunology community are far beyond his serving as the Chief of the LI, GATA3 also plays important roles in different lymphocytes at various developmental stages besides its critical functions in Th2 cells. In this special review dedicated to the memory of Bill, I will summarize the research that I have carried out in Bill's lab working on GATA3 in the context of related studies by other groups in the field of T cell differentiation and innate lymphoid cell (ILC) development. These include the essential role of GATA3 in regulating Th2/ILC2 differentiation/development and their functions, the critical role of GATA3 during the development of T cells and innate lymphoid cells, and dynamic and quantitative expression of GATA3 in controlling lymphocyte homeostasis and functions.

Fasciola and fasciolosis in ruminants in Europe: Identifying research needs

Fasciola hepatica is a trematode parasite with a global distribution, which is responsible for considerable disease and production losses in a range of food producing species. It is also identified by WHO as a re-emerging neglected tropical disease associated with endemic and epidemic outbreaks of disease in human populations. In Europe, F. hepatica is mostly associated with disease in sheep, cattle and goats. This study reviews the most recent advances in our understanding of the transmission, diagnosis, epidemiology and the economic impact of fasciolosis. We also focus on the impact of the spread of resistance to anthelmintics used to control F. hepatica and consider how vaccines might be developed and applied in the context of the immune-modulation driven by the parasite. Several major research gaps are identified which, when addressed, will contribute to providing focussed and where possible, bespoke, advice for farmers on how to integrate stock management and diagnosis with vaccination and/or targeted treatment to more effectively control the parasite in the face of increasing the prevalence of infection and spread of anthelmintic resistance that are likely to be exacerbated by climate change.

Interactions of the immune and sensory nervous systems in atopy

A striking feature underlying all atopic disorders, such as asthma, atopic dermatitis, and food allergy, is the presence of pathologic sensory responses, reflexes, and behaviors. These symptoms, exemplified by chronic airway irritation and cough, chronic itch and scratching, as well as gastrointestinal discomfort and dysfunction, are often cited as the most debilitating aspects of atopic disorders. Emerging studies have highlighted how the immune system shapes the scope and intensity of sensory responses by directly modulating the sensory nervous system. Additionally, factors produced by neurons have demonstrated novel functions in propagating atopic inflammation at barrier surfaces. In this review, we highlight new studies that have changed our understanding of atopy through advances in characterizing the reciprocal interactions between the immune and sensory nervous systems.

Allergic diseases: From bench to clinic - Contribution of the discovery of interleukin-5

T helper 2 cells produce a number of cytokines including inteleukin (IL)-5, IL-4 and IL-13. Group 2 innate lymphoid cells (ILC2s) also produce IL-5 under sterile conditions. IL-5 is interdigitating homodimeric glycoprotein and a member of the four α helical bundle motifs conserved among hematopoietic cytokines. IL-5 exerts its effects on target cells via IL-5 receptor (IL-5R), composed of an IL-5R α and βc subunit. The membrane proximal proline-rich motif of the cytoplasmic domain of both IL-5R α and βc subunits is essential for IL-5 signal transduction. Although IL-5 was initially identified by its ability to support the growth and terminal differentiation of mouse B cells into antibody-secreting cells, recombinant IL-5 exerts pleiotropic activities on various target cells. For example, IL-5 is now recognized as the major maturation and differentiation factor for eosinophils in mice and humans. Overexpression of IL-5 in mouse significantly increases eosinophil numbers and antibody levels in vivo, while mice lacking a functional gene for IL-5 or IL-5R display developmental and functional impairments in B cell and eosinophil lineages. In mice, the role of the IL-5/IL-5R system in the production and secretion of Immunoglobulin (Ig) M and IgA in mucosal tissues has been reported. Although eosinophils protect against invading pathogens including virus, bacteria and helminthes, they are also involved in the pathogenesis of various diseases, such as food allergy, asthma, and inflammatory bowel diseases. The recent expansion in our understanding in the context of IL-5 and IL-5-producing ILC2s in eosinophil activation and the pathogenesis of eosinophil-dependent inflammatory diseases has led to advances in therapeutic options. A new therapy currently under invetigarion in clinical trials uses humanized monoclonal antibodies against IL-5 or the IL-5R. In this review, we summarize our current understanding of the functions of IL-5 and its receptor, the innate regulation of IL-5-producing cells, and therapeutic potential of anti-IL-5 and anti-eosinophil (IL-5R) antibodies.

Interleukin 17 Family Cytokines: Signaling Mechanisms, Biological Activities, and Therapeutic Implications

The cytokines of the interleukin 17 (IL-17) family play a central role in the control of infections, especially extracellular fungi. Conversely, if unrestrained, these inflammatory cytokines contribute to the pathology of numerous autoimmune and chronic inflammatory conditions. Recent advances have led to the approval of IL-17A-blocking biologics for the treatment of moderate to severe plaque psoriasis, but much remains to be understood about the biological functions, regulation, and signaling pathways downstream of these factors. In this review, we outline the current knowledge of signal transduction and known physiological activities of IL-17 family cytokines. We will highlight in particular the current understanding of these cytokines in the context of skin manifestations of disease.

Group 2 innate lymphocytes at the interface between innate and adaptive immunity

Group 2 innate lymphoid cells (ILC2) are innate immune cells that respond rapidly to their environment through soluble inflammatory mediators and cell-to-cell interactions. As tissue-resident sentinels, ILC2 help orchestrate localized type 2 immune responses. These ILC2-driven type 2 responses are now recognized in diverse immune processes, different anatomical locations, and homeostatic or pathological settings. ILC2-derived cytokines and cell surface signaling molecules function as key regulators of innate and adaptive immunity. Conversely, ILC2 are governed by their environment. As such, ILC2 form an important nexus of the immune system and may present an attractive target for immune modulation in disease.

Population based and animal study on the effects of Schistosoma japonicum infection in the regulation of host glucose homeostasis

Although parasitic infection affects the glucose homeostasis of mice, only few studies have integrated epidemiological and animal data to determine the effect of Schistosoma japonicum infection on mice metabolism. The current study assessed the effects of S. japonicum infection on blood glucose and other metabolic parameters in both patients and animal models of chronic schistomiasis. A total of 2183 patients with chronic schistosomiasis and age- and gender-matched individuals without schistosomiasis (n = 1798) were enrolled in this study. Fasting blood glucose and other metabolic parameters, including body mass index (BMI) and serum triglyceride and total cholesterol, were compared between the two groups. Mice infected with S. japonicum were used to test the effects of the parasite on glucose tolerance. We found that chronic schistosomiasis patients had significantly lower BMI and fasting blood glucose, serum triglyceride, and total cholesterol levels than non-schistosomiasis individuals. In the animal studies, both bisexual and unisexual S. japonicum infection improved glucose tolerance in wild-type mice. Additionally, S. japonicum-infected ob/ob mice, a model that spontaneously develops obesity and diabetes, also had decreased body weight and improved glucose tolerance. We further observed that S. japonicum-infected mice had lower inflammatory gene expression in the visceral white adipose tissue than the control mice. Collectively, our results demonstrated that S. japonicum infection improved glucose tolerance and other metabolic parameters both in human and animals. Downregulated inflammatory gene expression due to S. japonicum infection might be among the mechanisms for the improved glucose tolerance.

ILC2s in infectious diseases and organ-specific fibrosis

Type 2 immune responses evolved to provide host protection against parasitic infections and to support the repair of infection-induced tissue injury. However, persistent chronic organ damage can result in dysregulated production of critical type 2 cytokines supporting tissue remodeling and fibrosis development. Recently, group 2 innate lymphoid cells (ILC2s) were newly described as central innate mediators of type 2 responses. In particular, by secretion of the cytokines IL-5, IL-9, and IL-13 and the growth factor amphiregulin in response to the release of tissue-derived alarmins, ILC2s have been shown to substantially contribute to both the dismissal of metazoan parasites and the repair of infection-dependent or sterile tissue damage. Conversely, cytokine production by ILC2s emerged as a driving force for tissue remodeling and excessive fibrosis in several organ systems including the lung, liver, and skin. In this review, we discuss how ILC2s are specifically implicated in the body's immune response to different pathogenic infections and how dysregulated ILC2s may promote organ-specific fibrosis.

IL-25 in allergic inflammation

IL-25, also known as IL-17E, is a member of the IL-17 cytokine family mostly produced by epithelial cells and innate immune cells. After binding to the IL-17RB/IL-17RA complex, IL-25 induces downstream signaling responses in epithelial cells and type 2 lymphocytes, which initiates, propagates, and sustains type 2 immunity. The function of IL-25 in allergic diseases such as asthma has been well established, and now also is extended to diseases such as inflammatory bowel disease and cancer. This review summarizes the literature on IL-25 and discusses the unsolved questions. Our knowledge on IL-25 will pave the pathway for targeting this cytokine in inflammatory diseases.

Modeling TH 2 responses and airway inflammation to understand fundamental mechanisms regulating the pathogenesis of asthma

In this review, we highlight experiments conducted in our laboratories that have elucidated functional roles for CD4⁺ T-helper type-2 lymphocytes (T_H 2 cells), their associated cytokines, and eosinophils in the regulation of hallmark features of allergic asthma. Notably, we consider the complexity of type-2 responses and studies that have explored integrated signaling among classical T_H 2 cytokines (IL-4, IL-5, and IL-13), which together with CCL11 (eotaxin-1) regulate critical aspects of eosinophil recruitment, allergic inflammation, and airway hyper-responsiveness (AHR). Among our most important findings, we have provided evidence that the initiation of T_H 2 responses is regulated by airway epithelial cell-derived factors, including TRAIL and MID1, which promote T_H 2 cell development via STAT6-dependent pathways. Further, we highlight studies demonstrating that microRNAs are key regulators of allergic inflammation and potential targets for anti-inflammatory therapy. On the background of T_H 2 inflammation, we have demonstrated that innate immune cells (notably, airway macrophages) play essential roles in the generation of steroid-resistant inflammation and AHR secondary to allergen- and pathogen-induced exacerbations. Our work clearly indicates that understanding the diversity and spatiotemporal role of the inflammatory response and its interactions with resident airway cells is critical to advancing knowledge on asthma pathogenesis and the development of new therapeutic approaches.

Interleukin-25 is involved in cutaneous T-cell lymphoma progression by establishing a T helper 2-dominant microenvironment

BACKGROUND

Interleukin (IL)-25 is a member of the IL-17 family, which can promote and augment T-helper (Th) type 2 responses. The expression of IL-25 and its cognate receptor, IL-25 receptor (IL-25R), is upregulated and correlated with disease activity in Th2-associated diseases.

OBJECTIVES

To examine the expression and function of IL-25 in cutaneous T-cell lymphoma (CTCL).

METHODS

Expression and location of IL-25 in lesional skin was investigated with immunohistochemistry. The effect of various cytokines on IL-25 production from normal human epidermal keratinocytes was assessed by quantitative reverse-transcription real-time polymerase chain reaction. Serum IL-25 levels were measured by enzyme-linked immunosorbent assay. The direct effect of IL-25 on tumour cells was also examined using CTCL cell lines and peripheral blood mononuclear cells in patients with Sézary syndrome.

RESULTS

IL-25 expression was increased in epidermal keratinocytes in lesional skin of CTCL. Th2 cytokines, IL-4 and IL-13, and periostin induced IL-25 expression by normal human epidermal keratinocytes. Serum IL-25 levels were increased in patients with advanced CTCL and correlated with serum lactate dehydrogenase levels. MyLa cells expressed IL-25R and its expression was augmented by stimulation with IL-25. IL-25 enhanced IL-13 production from MyLa cells via phosphorylation of signal transducer and activator of transcription 6. Peripheral blood mononuclear cells from one patient with Sézary syndrome expressed IL-25R and showed increase of IL-13 production by IL-25.

CONCLUSIONS

Th2 cytokines highly expressed in CTCL lesional skin induce IL-25 production by epidermal keratinocytes, which may, in turn, lead to formation of a Th2-dominant microenvironment through the direct induction of IL-13 by tumour cells.

Interleukin-25 (IL-25) has a protective role in atherosclerosis development in the aortic arch in mice

Atherosclerosis is a chronic inflammatory disease characterized by the entrapment of apolipoprotein B-containing lipoproteins in the arterial intima, leading to local inflammation. T helper (Th) cell 1-mediated immune responses have been associated with atherosclerosis, and the cytokine interleukin-25 (IL-25 or IL-17E) has been reported to potentially regulate Th1 cell- and Th17 cell-related immune responses. In this study, we evaluated the effects of complete IL-25 deficiency or of a temporal IL-25 blockade on atherosclerosis development in apolipoprotein E-deficient (Apoe^-/-) mice. Mice deficient in both apolipoprotein E and IL-25 (Apoe^-/-/IL-25^-/-) had more Th1 cells in the spleen, along with elevated plasma levels of IL-17 and an increased release of splenic interferon-γ (INF-γ). In support of this observation, a 4-week-long treatment of young Apoe^-/- mice (at 10-14 weeks of age) with an IL-25-blocking antibody increased the release of Th1/Th17-associated cytokines in the spleen. In both mouse models, these findings were associated with increased atherosclerotic plaque formation in the aortic arch. We conclude that complete IL-25 deficiency and a temporal IL-25 blockade during early plaque development aggravate atherosclerosis development in the aortic arch of Apoe^-/- mice, accompanied by an increase in Th1/Th17-mediated immune responses. Our finding that endogenous IL-25 has an atheroprotective role in the murine aortic arch has potential implications for atherosclerosis development and management in humans.

Innate-like CD8+ T-cells and NK cells: converging functions and phenotypes

New data in the worlds of both innate-like CD8+ T-cells and natural killer (NK) cells have, in parallel, clarified some of the phenotypes of these cells and also their associated functions. While these cells are typically viewed entirely separately, the emerging innate functions of T-cells and, similarly, the adaptive functions of NK cells suggest that many behaviours can be considered in parallel. In this review we compare the innate functions of CD8+ T-cells (especially mucosal-associated invariant T-cells) and those of NK cells, and how these relate to expression of phenotypic markers, especially CD161 and CD56.

IL-25 enhances TH17 cell-mediated contact dermatitis by promoting IL-1β production by dermal dendritic cells

BACKGROUND

In addition to thymic stromal lymphopoietin and IL-33, IL-25 is known to induce T_H2 cytokine production by various cell types, including T_H2 cells, T_H9 cells, invariant natural killer T cells, and group 2 innate lymphoid cells, involved in T_H2-type immune responses. Because both T_H2-type and T_H17-type cells/cytokines are crucial for contact hypersensitivity (CHS), IL-25 can contribute to this by enhancing T_H2-type immune responses. However, the precise role of IL-25 in the pathogenesis of fluorescein isothiocyanate-induced CHS is poorly understood.

OBJECTIVE

We investigated the contribution of IL-25 to CHS using Il25^-/- mice.

METHODS

CHS was evaluated by means of measurement of ear skin thickness in mice after fluorescein isothiocyanate painting. Skin dendritic cell (DC) migration, hapten-specific T_H cell differentiation, and detection of IL-1β-producing cells were determined by using flow cytometry, ELISA, and immunohistochemistry, respectively.

RESULTS

In contrast to thymic stromal lymphopoietin, we found that IL-25 was not essential for skin DC migration or hapten-specific T_H cell differentiation in the sensitization phase of CHS. Unexpectedly, mast cell- and non-immune cell-derived IL-25 was important for hapten-specific T_H17 cell-mediated rather than T_H2 cell-mediated inflammation in the elicitation phase of CHS by enhancing T_H17-related, but not T_H2-related, cytokines in the skin. In particular, IL-1β produced by dermal DCs in response to IL-25 was crucial for hapten-specific T_H17 cell activation, contributing to induction of local inflammation in the elicitation phase of CHS.

CONCLUSION

Our results identify a novel IL-25 inflammatory pathway involved in induction of T_H17 cell-mediated, but not T_H2 cell-mediated, CHS. IL-25 neutralization can be a potential approach for treatment of CHS.

Evaluation of the mucosal inflammatory responses to equine cyathostomins in response to anthelmintic treatment

Members of Cyathostominae are pervasive parasites of equids that can cause larval cyathostominosis, a potentially life-threatening disease that occurs when a multitude of encysted larvae synchronously excyst from the wall of the large intestine. Moxidectin and fenbendazole are the two current labeled drugs that target the encysted larval stages; however, there is limited knowledge of the local inflammatory response to the larvae and to the two treatments in clinically healthy horses. This study is the first to evaluate the local inflammatory response to cyathostomin larvae and to larvicidal treatment at 2 and 5 weeks post treatment. Thirty-six ponies with naturally acquired cyathostomin infections were randomly allocated into 3 groups: Group 1, fenbendazole at 10 mg/kg for 5 days, Group 2, a single dose of moxidectin at 0.4 mg/kg, and Group 3, untreated controls. Tissue samples from the cecum and dorsal and ventral colons were used for histopathological and immunohistochemical evaluation. Tissues were stained with routine hematoxylin and eosin (H&E) for light microscopy and immunohistochemically for MAC387, CD20, and CD3 for differentiation of activated macrophages, B cells, and T cells, respectively. Semiquantitative scores were assigned for all inflammatory cell types and fibrous connective tissue. Larvae observed by light microscopy were enumerated and classified by stage. Mucosal ulcerations and submucosal granulomas were also enumerated. Mean macrophage scores were higher in the moxidectin group than the fenbendazole group (p = 0.0185) and the control group had a higher activated macrophage score than both treatment groups (p = 0.0104, p = 0.0004). T lymphocyte scores were higher in the moxidectin group when compared to the control group (p = 0.0069). Goblet cell hyperplasia scores were elevated at 5 weeks post treatment compared to 2 weeks post treatment (p = 0.0047) and were elevated in the ventral colon compared to the dorsal colon (p = 0.0301). Eosinophil scores were elevated surrounding degenerative larvae when compared to intact larvae (p = 0.0001). Mucosal ulcerations were found only in the control group at 2 weeks post treatment. This study found subtle inflammatory differences between treatment groups but provided new information about goblet cells and eosinophils in relation to encysted cyathostomin larvae.

Immunity to gastrointestinal nematode infections

Numerous species of nematodes have evolved to inhabit the gastrointestinal tract of animals and humans, with over a billion of the world's population infected with at least one species. These large multicellular pathogens present a considerable and complex challenge to the host immune system given that individuals are continually exposed to infective stages, as well as the high prevalence in endemic areas. This review summarizes our current understanding of host-parasite interactions, detailing induction of protective immunity, mechanisms of resistance, and resolution of the response. It is clear from studies of well-defined laboratory model systems that these responses are dominated by innate and adaptive type 2 cytokine responses, regulating cellular and soluble effectors that serve to disrupt the niche in which the parasites live by strengthening the physical mucosal barrier and ultimately promoting tissue repair.

Lymphoid tissue inducer-A divergent member of the ILC family

Innate lymphoid cells (ILCs) that are capable of producing effector cytokines reminiscent of CD4⁺ T helper (Th) cells during infections and tissue inflammations have drawn much attention in the immunology field in recent years. Within the ILCs, the lymphoid tissue inducer (LTi) cells that play a critical role in lymphoid organogenesis were identified long before the establishment of the ILC concept. LTi cells, developed and functioning mainly at the fetal stage, and LTi-like cells, presumably generated during the adulthood, are regarded as a subset of type 3 ILCs (ILC3s) because they express the ILC3 lineage-defining transcription factor RORγt, and like other ILC3s, can produce an ILC3 signature cytokine IL-22 and initiate protective immune responses against extracellular bacteria. However, LTi/LTi-like cells have a unique gene expression pattern, and they develop from a progenitor that is distinct from the progenitor of all other ILCs and the progenitor of conventional natural killer (cNK) cells. There are also several other unique features of LTi/LTi-like cells comparing to non-LTi ILC3s. In addition to their classical function in lymphoid organogenesis, LTi/LTi-like cells also have specialized functions in association with the adaptive immune system, which include their effects on T and B cell development, activation and function. In this review, we summarize these specific features of LTi/LTi-like cells and propose that these cells should be considered as a separated innate lymphoid lineage in parallel with other non-LTi ILCs and cNK cells.

Origins and evolution of innate lymphoid cells: Wardens of barrier immunity

The identification, in the late 2000s, of innate lymphoid cells (ILCs) as a new class of non-B, non-T lymphocytes has led to global efforts to understand their functions, plasticity and evolutionary origins and to define their place within the leucocyte family. Although this work has uncovered striking similarities in the developmental cues, lineage-specific transcription factors and functional capacities of innate and adaptive lymphocytes, it has become clear that ILCs play a unique and defining role as stewards of barrier defence and that this sets them apart from their adaptive cousins. This review will explore how the dynamic environment of barrier surfaces has shaped ILC evolution and functionality. We highlight the critical importance of the microbiome and the unique role of ILCs as environmental sensors. We reflect on how these factors may have influenced the development of ILC2s and barrier immunity in the context of exposure to helminth parasites that have been driving forces of our evolution throughout human history. Finally, we argue that the plasticity of ILC function reflects their role as first responders to environmental change.

Group 2 ILCs: A way of enhancing immune protection against human helminths?

Group 2 innate lymphoid cells (ILC2s) play crucial roles in type 2 immune responses associated with allergic and autoimmune diseases, viral and helminth infections and tissue homoeostasis. Experimental models show that in helminth infections ILC2s provide an early source of type 2 cytokines and therefore are essential for the induction of potentially protective type 2 responses. Much of our knowledge of ILC2s in helminth infections has come from experimental mouse models with very few studies analysing ILC2s in natural human infections. In attempts to harness knowledge from paradigms of the development of protective immunity in human helminth infections for vaccine development, the role of ILC2 cells could be pivotal. So far, potential vaccines against human helminth infections have failed to provide effective protection when evaluated in human studies. In addition to appropriate antigen selection, it is apparent that more detailed knowledge on mechanisms of induction and maintenance of protective immune responses is required. Therefore, there is need to understand how ILC2 cells induce type 2 responses and subsequently support the development of a protective immune response in the context of immunizations. Within this review, we summarize the current knowledge of the biology of ILC2s, discuss the importance of ILC2s in human helminth infections and explore how ILC2 responses could be boosted to efficiently induce protective immunity.

Orchestration of epithelial-derived cytokines and innate immune cells in allergic airway inflammation

Allergic asthma, a chronic respiratory disease, is a leading worldwide health problem, which inflames and constricts the airways, leading to breathing difficulty. Many studies have focused on the pathogenesis contributed by the adaptive immune system, including CD4+ T lymphocytes in delayed type hypersensitivity and B cell-produced IgE in anaphylaxis. More recently, a focus on the airway mucosal barrier and the innate immune system has highlighted, in coordination with T and B cells, to initiate and establish disease. This review highlights the impacts of epithelial-derived cytokines and innate immune cells on allergic airway reactions.

Sentinels of the Type 2 Immune Response

Type 2 immune responses have evolved to sense and respond to large, non-replicating infections or non-microbial noxious compounds in tissues. The development of these responses therefore depends upon highly coordinated and tightly regulated tissue-residing cellular sensors and responders. Multiple exposure to type 2 helper T cell (Th2)-inducing stimuli further enhances both the diversity and potency of the response. This review discusses advances in our understanding of the interacting cellular subsets that comprise both primary and secondary type 2 responses. Current knowledge regarding type 2 immune responses in the lung are initially presented and are then contrasted with what is known about the small intestine. The studies described portray an immune response that depends upon well-organized tissue structures, and suggest their modulation as a therapeutic strategy.

Characterization of Group 2 Innate Lymphoid Cells in Allergic Airway Inflammation Models in the Mouse

Allergic asthma is a chronic inflammatory lung disease mediated by type 2 cytokines produced by T helper 2 (Th2) cells as well as the recently discovered group 2 innate lymphoid cells (ILC2). Due to a lack of unique markers, the accurate phenotypic characterization and quantification of ILC2 requires a comprehensive panel of fluorescently labeled antibodies. The markers that are currently used to characterize ILC2 have not been standardized and often vary between research groups, which poses significant challenges when comparing data. Intranasal administration of the pro-inflammatory cytokine IL-33 in mice is associated with strong, Th2 cell-independent ILC2 activation. ILC2 are also activated in mouse models of allergic asthma based on the physiologically relevant house dust mite (HDM) allergen, which parallel eosinophilic airway inflammation observed in asthma patients. Here, we describe the analysis of ILC2 by flow cytometry in these two commonly used allergic airway inflammation models in the mouse.

Interleukin-33 and its Receptor in Pulmonary Inflammatory Diseases

Interleukin-33 (IL-33) is a member of the IL-1 cytokine family. It modulates immune responses and biological functions through binding to its membrane receptor, ST2L. ST2L is a member of the Toll-like/IL-1 (TIR)-receptor superfamily, and its isoform, soluble ST2 (sST2), functions as an inhibitor of the IL-33/ST2L pathway. Levels of IL-33 and sST2 in serum and bronchoalveolar lavage fluid (BAL) are known biomarkers for a variety of disorders such as heart failure, non-small-cell lung cancer, and pulmonary inflammatory diseases. IL-33 also exists in the nuclei, and nuclear IL-33 seems to regulate cytokine gene expression. In this review, we focus on the role of IL-33/ST2 in the pathogenesis of pulmonary inflammatory diseases including asthma, chronic obstructive pulmonary disease (COPD), and lung injury.

The role of innate lymphoid cells in health and disease

Innate lymphoid cells (ILCs) are kind of innate immune cells which can be divided into three main subsets according to their cytokine release profile, transcription factors, and surface markers. ILCs affect the initial stages of immunity in response to microbes and participate in immunity, inflammation, and tissue repair. ILCs modulate immunity through resistance to the pathogens and regulation of autoimmune inflammation and metabolic homeostasis. Therefore dysregulation of ILCs may lead to chronic pathologies such as allergies (i.e., asthma), inflammation (i.e., inflammatory bowel disease), and autoimmunity (i.e., psoriasis, atopic dermatitis, rheumatoid arthritis, multiple sclerosis, and ankylosing spondylitis). Regarding the critical role of ILCs in the regulation of immune system, the elucidation of their function in different conditions makes an interesting target for improvement of novel therapeutic approach to modulate an immune response in different disease context.

Immunological pathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory state of the gastrointestinal tract and can be classified into 2 main clinical phenomena: Crohn's disease (CD) and ulcerative colitis (UC). The pathogenesis of IBD, including CD and UC, involves the presence of pathogenic factors such as abnormal gut microbiota, immune response dysregulation, environmental changes, and gene variants. Although many investigations have tried to identify novel pathogenic factors associated with IBD that are related to environmental, genetic, microbial, and immune response factors, a full understanding of IBD pathogenesis is unclear. Thus, IBD treatment is far from optimal, and patient outcomes can be unsatisfactory. As result of massive studying on IBD, T helper 17 (Th17) cells and innate lymphoid cells (ILCs) are investigated on their effects on IBD. A recent study of the plasticity of Th17 cells focused primarily on colitis. ILCs also emerging as novel cell family, which play a role in the pathogenesis of IBD. IBD immunopathogenesis is key to understanding the causes of IBD and can lead to the development of IBD therapies. The aim of this review is to explain the pathogenesis of IBD, with a focus on immunological factors and therapies.

Type 2 Cysteinyl Leukotriene Receptors Drive IL-33-Dependent Type 2 Immunopathology and Aspirin Sensitivity

Cysteinyl leukotrienes (cysLTs) facilitate mucosal type 2 immunopathology by incompletely understood mechanisms. Aspirin-exacerbated respiratory disease, a severe asthma subtype, is characterized by exaggerated eosinophilic respiratory inflammation and reactions to aspirin, each involving the marked overproduction of cysLTs. Here we demonstrate that the type 2 cysLT receptor (CysLT₂R), which is not targeted by available drugs, is required in two different models to amplify eosinophilic airway inflammation via induced expression of IL-33 by lung epithelial cells. Endogenously generated cysLTs induced eosinophilia and expanded group 2 innate lymphoid cells (ILC2s) in aspirin-exacerbated respiratory disease-like Ptges^-/- mice. These responses were mitigated by deletions of either Cysltr2 or leukotriene C₄ synthase (Ltc4s). Administrations of either LTC₄ (the parent cysLT) or the selective CysLT₂R agonist N-methyl LTC₄ to allergen sensitized wild-type mice markedly boosted ILC2 expansion and IL-5/IL-13 generation in a CysLT₂R-dependent manner. Expansion of ILC2s and IL-5/IL-13 generation reflected CysLT₂R-dependent production of IL-33 by alveolar type 2 cells, which engaged in a bilateral feed-forward loop with ILC2s. Deletion of Cysltr1 blunted LTC₄-induced ILC2 expansion and eosinophilia but did not alter IL-33 induction. Pharmacological blockade of CysLT₂R prior to inhalation challenge of Ptges^-/- mice with aspirin blocked IL-33-dependent mast cell activation, mediator release, and changes in lung function. Thus, CysLT₂R signaling, IL-33-dependent ILC2 expansion, and IL-33-driven mast cell activation are necessary for induction of type 2 immunopathology and aspirin sensitivity. CysLT₂R-targeted drugs may interrupt these processes.

Innate Lymphoid Cells (ILCs) as Mediators of Inflammation, Release of Cytokines and Lytic Molecules

Innate lymphoid cells (ILCs) are an emerging group of immune cells that provide the first line of defense against various pathogens as well as contributing to tissue repair and inflammation. ILCs have been classically divided into three subgroups based on their cytokine secretion and transcription factor profiles. ILC nomenclature is analogous to that of T helper cells. Group 1 ILCs composed of natural killer (NK) cells as well as IFN-γ secreting ILC1s. ILC2s have the capability to produce T_H2 cytokines while ILC3s and lymphoid tissue inducer (LTis) are subsets of cells that are able to secrete IL-17 and/or IL-22. A recent subset of ILC known as ILC4 was discovered, and the cells of this subset were designated as NK17/NK1 due to their release of IL-17 and IFN-γ. In this review, we sought to explain the subclasses of ILCs and their roles as mediators of lytic enzymes and inflammation.

Natural killer cells and anti-tumor immunity

Immune checkpoint inhibitors harness the power of the immune system to fight cancer. The clinical success achieved with antibodies against the inhibitory T cell receptors PD-1 and CTLA4 has focused attention on the possibility of manipulating other immune cells, in particular those involved in innate immunity. Here we review the role of innate lymphoid cells (ILCs) and their contribution to tumor immunity. As the prototypical ILC, the natural killer (NK) cell has an intrinsic ability to detect and kill cancer cells. NK cells are dependent on the cytokine interleukin (IL)-15 for their development and effector activity. We discuss the role of the Suppressor of cytokine (SOCS) proteins in negatively regulating IL-15 and NK cell responses and the potential for targeting these small intracellular regulators as new immune checkpoints.

Combinatorial targeting of TSLP, IL-25, and IL-33 in type 2 cytokine-driven inflammation and fibrosis

Thymic stromal lymphopoietin (TSLP), interleukin-25 (IL-25), and IL-33 are important initiators of type 2-associated mucosal inflammation and immunity. However, their role in the maintenance of progressive type 2 inflammation and fibrosis is much less clear. Using chronic models of helminth infection and allergic lung inflammation, we show that collective disruption of TSLP, IL-25, and IL-33 signaling suppresses chronic and progressive type 2 cytokine-driven inflammation and fibrosis. In a schistosome lung granuloma model or during chronic Schistosoma mansoni infection in the liver, individual ablation of TSLP, IL-25, or IL-33/ST2 had no impact on the development of IL-4/IL-13-dependent inflammation or fibrosis. However, significant reductions in granuloma-associated eosinophils, hepatic fibrosis, and IL-13-producing type 2 innate lymphoid cells (ILC2s) were observed when signaling of all three mediators was simultaneously disrupted. Combined blockade through monoclonal antibody (mAb) treatment also reduced IL-5 and IL-13 expression during primary and secondary granuloma formation in the lungs. In a model of chronic house dust mite-induced allergic lung inflammation, combined mAb treatment did not decrease established inflammation or fibrosis. TSLP/IL-33 double-knockout mice treated with anti-IL-25 mAb during priming, however, displayed decreased inflammation, mucus production, and lung remodeling in the chronic phase. Together, these studies reveal partially redundant roles for TSLP, IL-25, and IL-33 in the maintenance of type 2 pathology and suggest that in some settings, early combined targeting of these mediators is necessary to ameliorate progressive type 2-driven disease.

Interleukin-22 in human inflammatory diseases and viral infections

Interleukin-22 (IL22) is one of the members of IL10 family. Elevated levels of this cytokine can be seen in diseases caused by T lymphocytes, such as Psoriasis, Rheumatoid arthritis, interstitial lung diseases. IL22 is produced by different cells in both innate and acquired immunities. Different types of T cells are able to produce IL22, but the major IL22-producing T-cell is the TCD4. TH22 cell is a new line of TCD4 cells, which differentiated from naive T cells in the presence of TNFα and IL6; 50% of peripheral blood IL22 is produced by these cells. IL22 has important functions in host defense at mucosal surfaces as well as in tissue repair. In this review, we assess the current understanding of this cytokine and focus on the possible roles of IL-22 in autoimmune diseases.

Biomarkers for differentiation of patients with asthma and chronic obstructive pulmonary disease

OBJECTIVE

Asthma and chronic obstructive pulmonary disease (COPD) are airflow limitation diseases with similar clinical manifestations but different pathophysiologic mechanisms. To implement the appropriate treatment, it is important to distinguish between asthma and COPD which sometimes might result difficult in clinical practice. We evaluated biomarkers to distinguish between asthma and COPD.

METHODS

Blood eosinophil counts and fractional exhaled nitric oxide (FeNO) levels were analyzed. Serum periostin, interleukin-25 (IL-25), and immunoglobulin E (IgE) concentrations were compared between patients with asthma (n = 60), including atopic-asthma (n = 30) and non-atopic asthma (n = 30), and patients with COPD (n = 30).

RESULTS

Significantly higher peripheral blood eosinophil counts (p < 0.001), FeNO levels (p < 0.001), and total serum IgE (P = 0.003) concentrations, but not serum periostin (p = 0.584) or serum IL-25 (p = 0.085) concentrations, were detected in patients with asthma compared to patients with COPD. Serum periostin and IgE concentrations were increased in patients with atopic-asthma compared with those with non-atopic asthma and COPD (p < 0.05). The FeNO levels were significantly correlated with the peripheral blood eosinophil counts (r = 0.430, p = 0.001) and serum IL-25 concentrations (r = 0.338, p = 0.009) in patients with asthma. The serum periostin concentrations were also correlated with the serum IgE concentrations (r = 0.375, p = 0.003)and FeNO levels (r = 0.291, p = 0.024) in patients with asthma. Asthma patients were effectively differentiated from COPD patients based on the FeNO levels (p < 0.001) and peripheral blood eosinophil counts (p < 0.001).

CONCLUSIONS

FeNO levels and peripheral blood eosinophil counts were useful biomarkers for distinguishing between patients with asthma and COPD. Serum periostin and IgE concentrations could be biomarkers for atopic asthma.

IL-25 dampens the growth of human germinal center-derived B-cell non Hodgkin Lymphoma by curtailing neoangiogenesis

Interleukin (IL)-25, a member of the IL-17 cytokine superfamily, is produced by immune and non-immune cells and exerts type 2 pro-inflammatory effects in vitro and in vivo. The IL-25 receptor(R) is composed of the IL-17RA/IL-17RB subunits. Previous work showed that germinal centre (GC)-derived B-cell non Hodgkin lymphomas (B-NHL) expressed IL-17AR, formed by IL-17RA and IL-17RC subunits, and IL-17A/IL-17AR axis promoted B-NHL growth by stimulating neoangiogenesis. Here, we have investigated expression and function of IL-25/IL-25R axis in lymph nodes from human GC-derived B-NHL, i.e. Follicular Lymphoma (FL,10 cases), Diffuse Large B Cell Lymphoma (6 cases) and Burkitt Lymphoma (3 cases). Tumor cells expressed IL-25R and IL-25 that was detected also in non-malignant cells by flow cytometry. Immunohistochemical studies confirmed expression of IL-25R and IL-25 in FL cells, and highlighted IL-25 expression in bystander elements of the FL microenvironment. IL-25 i) up-regulated phosphorylation of NFkBp65, STAT-1 and JNK in B-NHL cells; ii) inhibited in vitro proliferation of the latter cells; iii) exerted anti-tumor activity in two in vivo B-NHL models by dampening expression of pro-angiogenic molecules as VEGF-C, CXCL6 and ANGPT3. In conclusion, IL-25, that is intrinsically pro-angiogenic, inhibits B-NHL growth by reprogramming the angiogenic phenotype of B-NHL cells.

Shaping Innate Lymphoid Cell Diversity

Innate lymphoid cells (ILCs) are a key cell type that are enriched at mucosal surfaces and within tissues. Our understanding of these cells is growing rapidly. Paradoxically, these cells play a role in maintaining tissue integrity but they also function as key drivers of allergy and inflammation. We present here the most recent understanding of how genomics has provided significant insight into how ILCs are generated and the enormous heterogeneity present within the canonical subsets. This has allowed the generation of a detailed blueprint for ILCs to become highly sensitive and adaptive sensors of environmental changes and therefore exquisitely equipped to protect immune surfaces.

GATA3 Regulates the Development and Functions of Innate Lymphoid Cell Subsets at Multiple Stages

Innate lymphoid cells (ILCs) are regarded as the innate counterpart of effector CD4 T helper (Th) cells. Just as Th cells, ILCs are classified into distinct subsets based on their functions that are delivered mainly through effector cytokine production. Both ILCs and Th cells play critical roles in various protective immune responses and inflammatory diseases. Similar to Th cell differentiation, the development of ILC subsets depends on several master transcription factors, among which GATA3 is critical for the development and maintenance of type 2 ILCs (ILC2s). However, GATA3 is expressed by all ILC subsets and ILC progenitors, albeit at different levels. In a striking parallel with GATA3 function in T cell development and differentiation, GATA3 also has multiple functions in different ILCs at various stages. In this review, I will discuss how quantitative and dynamic expression of GATA3 regulates the development and functions of ILC subsets.

Intelectin contributes to allergen-induced IL-25, IL-33, and TSLP expression and type 2 response in asthma and atopic dermatitis

The epithelial and epidermal innate cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) have pivotal roles in the initiation of allergic inflammation in asthma and atopic dermatitis (AD). However, the mechanism by which the expression of these innate cytokines is regulated remains unclear. Intelectin (ITLN) is expressed in airway epithelial cells and promotes allergic airway inflammation. We hypothesized that ITLN is required for allergen-induced IL-25, IL-33, and TSLP expression. In two asthma models, Itln knockdown reduced allergen-induced increases in Il-25, Il-33, and Tslp and development of type 2 response, eosinophilic inflammation, mucus overproduction, and airway hyperresponsiveness. Itln knockdown also inhibited house dust mite (HDM)-induced early upregulation of Il-25, Il-33, and Tslp in a model solely inducing airway sensitization. Using human airway epithelial cells, we demonstrated that HDM-induced increases in ITLN led to phosphorylation of epidermal growth factor receptor and extracellular-signal regulated kinase, which were required for induction of IL-25, IL-33, and TSLP expression. In two AD models, Itln knockdown suppressed expression of Il-33, Tslp, and Th2 cytokines and eosinophilic inflammation. In humans, ITLN1 expression was significantly increased in asthmatic airways and in lesional skin of AD. We conclude that ITLN contributes to allergen-induced Il-25, Il-33, and Tslp expression in asthma and AD.

Interactions between Innate Lymphoid Cells and Cells of the Innate and Adaptive Immune System

Type 2 innate lymphoid cells (ILC2s) are a major source of cytokines, which are also produced by Th2 cells and several cell types of the innate immune system. Work over the past few years indicates that ILC2s play a central role in regulating type 2 immune responses against allergens and helminths. ILC2s can interact with a variety of cells types of the innate and adaptive immune system by cell–cell contacts or by communication via soluble factors. In this review, we provide an overview about recent advances in our understanding how ILC2s orchestrate type 2 immune responses with focus on direct interactions between ILC2s and other cells of the immune system.

Monocyte chemotactic protein-induced protein 1 controls allergic airway inflammation by suppressing IL-5-producing TH2 cells through the Notch/Gata3 pathway

BACKGROUND

Asthmatic and allergic inflammation is mediated by T_H2 cytokines (IL-4, IL-5, and IL-13). Although we have learned much about how T_H2 cells are differentiated, the T_H2 checkpoint mechanisms remain elusive.

OBJECTIVES

In this study we investigate how monocyte chemotactic protein-induced protein 1 (MCPIP1; encoded by the Zc3h12a gene) regulates IL-5-producing T_H2 cell differentiation and T_H2-mediated inflammation.

METHODS

The functions of Zc3h12a^-/- CD4 T cells were evaluated by checking the expression of T_H2 cytokines and transcription factors in vivo and in vitro. Allergic airway inflammation of Zc3h12a^-/- mice was examined with murine asthma models. In addition, antigen-specific CD4 T cells deficient in MCPIP1 were transferred to wild-type recipient mice, challenged with ovalbumin (OVA) or house dust mite (HDM), and accessed for T_H2 inflammation.

RESULTS

Zc3h12a^-/- mice have spontaneous severe lung inflammation, with an increase in mainly IL-5- and IL-13-producing but not IL-4-producing T_H2 cells in the lung. Mechanistically, differentiation of IL-5-producing Zc3h12a^-/- T_H2 cells is mediated through Notch signaling and Gata3 independent of IL-4. Gata3 mRNA is stabilized in Zc3h12a^-/- T_H2 cells. MCPIP1 promotes Gata3 mRNA decay through the RNase domain. Furthermore, deletion of MCPIP1 in OVA- or HDM-specific T cells leads to significantly increased T_H2-mediated airway inflammation in OVA or HDM murine models of asthma.

CONCLUSIONS

Our study reveals that MCPIP1 regulates the development and function of IL-5-producing T_H2 cells through the Notch/Gata3 pathway. MCPIP1 represents a new and promising target for the treatment of asthma and other T_H2-mediated diseases.

Novel Therapeutics for Multiple Sclerosis Designed by Parasitic Worms

The evolutionary response to endemic infections with parasitic worms (helminth) was the development of a distinct regulatory immune profile arising from the need to encapsulate the helminths while simultaneously repairing tissue damage. According to the old friend's hypothesis, the diminished exposure to these parasites in the developed world has resulted in a dysregulated immune response that contributes to the increased incidence of immune mediated diseases such as Multiple Sclerosis (MS). Indeed, the global distribution of MS shows an inverse correlation to the prevalence of helminth infection. On this basis, the possibility of treating MS with helminth infection has been explored in animal models and phase 1 and 2 human clinical trials. However, the possibility also exists that the individual immune modulatory molecules secreted by helminth parasites may offer a more defined therapeutic strategy.

Role of interleukin-25 in development of spontaneous arthritis in interleukin-1 receptor antagonist-deficient mice

Interleukin (IL)-25, which is a member of the IL-17 family of cytokines, induces production of such Th2 cytokines as IL-4, IL-5, IL-9 and/or IL-13 by various types of cells, including Th2 cells, Th9 cells and group 2 innate lymphoid cells (ILC2). On the other hand, IL-25 can suppress Th1- and Th17-associated immune responses by enhancing Th2-type immune responses. Supporting this, IL-25 is known to suppress development of experimental autoimmune encephalitis, which is an IL-17-mediated autoimmune disease in mice. However, the role of IL-25 in development of IL-17-mediated arthritis is not fully understood. Therefore, we investigated this using IL-1 receptor antagonist-deficient (IL-1Ra^-/-) mice, which spontaneously develop IL-17-dependent arthritis. However, development of spontaneous arthritis (incidence rate, disease severity, proliferation of synovial cells, infiltration of PMNs, and bone erosion in joints) and differentiation of Th17 cells in draining lymph nodes in IL-25^-/- IL-1Ra^-/- mice were similar to in control IL-25^+/+ IL-1Ra^-/- mice. These observations indicate that IL-25 does not exert any inhibitory and/or pathogenic effect on development of IL-17-mediated spontaneous arthritis in IL-1Ra^-/- mice.

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IL-25 is known to inhibit Th17 cell differentiation.

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IL-25 is known to suppress Th17-mediated autoimmune diseases in mice.

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IL-25 does not play any inhibitory and/or pathogenic role in IL-17-mediated arthritis.

ILC2s activated by IL-25 promote antigen-specific Th2 and Th9 functions that contribute to the control of Trichinella spiralis infection

IL-25, an IL-17 family cytokine, derived from epithelial cells was shown to regulate Th2- and Th9-type immune responses. We previously reported that IL-25 was important in promoting efficient protective immunity against T. spiralis infection; however, the cellular targets of IL-25 to elicit type-2 immunity during infection have not yet been addressed. Here, we investigated IL-25-responding cells and their involvement in mediating type-2 immune response during T. spiralis infection. ILC2 and CD4⁺ Th2 cells residing in the gastrointestinal tract of T. spiralis infected mice were found to express high levels of surface interleukin-17 receptor B (IL-17RB), a component of the IL-25 receptor. Following T. spiralis infection, activated ILC2s upregulated surface MHCII expression and enhanced capacity of effector T helper cell in producing antigen-specific Th2 and Th9 cytokines through MHCII-dependent interactions. Reciprocally, lack of CD4⁺ T helper cells impaired ILC2 function to produce type 2-associated cytokines in responding to IL-25 during T. spiralis infection. Furthermore, mice deficient in IL-17RB showed markedly reduced ILC2 numbers and antigen-specific Th2 and Th9 cytokine production during T. spiralis infection. The Il17rb^-/- mice failed to mount effective antigen specific Th2 and Th9 functions resulting in diminished goblet cell and mast cell responses, leading to delayed worm expulsion in the intestines and muscles. Thus, our data indicated that ILC2s and CD4⁺ Th2 cells are the predominant cellular targets of IL-25 following T. spiralis infection and their collaborative interactions may play a key role in mounting effective antigen-specific Th2 and Th9 cytokine responses against T. spiralis infection.

MicroRNA-mediated regulation of immune responses to intestinal helminth infections

Intestinal helminth infections are highly prevalent in the developing world, often resulting in chronic infection and inflicting high host morbidity. With the emergence of drug-resistant parasites, a limited number of chemotherapeutic drugs available and stalling vaccine efforts, an increased understanding of antihelminth immunity is essential to provide new avenues to therapeutic intervention. MicroRNAs are a class of small, nonprotein coding RNAs which negatively regulate mRNA translation, thus providing finite control over gene expression in a plethora of biological settings. The miRNA-mediated coordinated control of gene expression has been shown to be essential in infection and immunity, in promoting and fine-tuning the appropriate immune response. This review gathers together and discusses observations of miRNA-mediated effects on the immune system and the subsequent impact on our understanding of antihelminth immunity.

Neuronal regulation of type 2 innate lymphoid cells via neuromedin U

Group 2 innate lymphoid cells (ILC2s) regulate inflammation, tissue repair and metabolic homeostasis1. ILC2 activation is driven by host-derived cytokines and alarmins1. While discrete immune cell subsets integrate nervous system cues2–4, it remains unclear whether neuronal-derived signals control ILC2s. Here we show that Neuromedin U (NMU) is a uniquely fast and potent regulator of type 2 innate immunity in the context of a novel neuron-ILC2 unit. We found that ILC2s selectively express Neuromedin U receptor 1 (Nmur1), while mucosal neurons express NMU. ILC2-autonomous activation with NMU resulted in immediate and strong production of innate inflammatory and tissue repair cytokines, in a NMUR1-dependent manner. NMU controlled ILC2s downstream of extracellular signal–regulated kinase (ERK) and calcium (Ca²⁺)-influx-dependent activation of Calcineurin and nuclear factor of activated T cells (NFAT). NMU treatment in vivo resulted in immediate protective type 2 responses. Accordingly, ILC2-autonomous ablation of Nmur1 led to impaired type 2 responses and poor worm infection control. Strikingly, mucosal neurons were found adjacent to ILC2s, directly sensed worm products and alarmins to induce NMU and to control innate type 2 cytokines. Our work reveals that neuron-ILC2 cell units are poised to confer a first-line of immediate tissue protection via coordinated neuro-immune sensory responses.

Interleukin-13/interleukin-4 receptor pathway is crucial for production of Sda-sialomucin in mouse small intestinal mucosa by Nippostrongylus brasiliensis infection

Mucin is a major component of mucus in gastrointestinal mucosa. Increase of specific sialomucins having Sd^a blood group antigen, NeuAcα2-3(GalNAcβ1-4)Galβ1-4GlcNAcβ-, is considered to be associated with expulsion of the parasitic intestinal nematode Nippostrongylus brasiliensis. In this study, we examined the relationship between interleukin (IL)-13 pathway and expression of Sd^a-sialomucins in small intestinal mucosa with N. brasiliensis infection. Nematode infection induced marked increases in small intestinal mucins that reacted with anti-Sd^a antibody in wild type (wt) mice. However, this increase due to infection was supressed in IL-4 receptor α deficient (IL-4Rα^-/-) mice, which lack both IL-4 and IL-13 signaling via IL-4R, and severe combined immunodeficient (SCID) mice, which have defects in B- and T-lymphocytes. Analysis using tandem mass spectroscopy showed that Sd^a-glycans were not expressed in small intestinal mucins in IL-4Rα^-/- and SCID mice after infection despite the appearance of Sd^a-glycans in the infected wt mice. Inoculation of recombinant IL-13 into the infected SCID mice restored expression of Sd^a-glycan. Our results suggest that the IL-13/IL-4R axis is important for the production of Sd^a-sialomucins in the host intestinal mucosa with parasitic nematode infection.