Neuropilin-1 Is Expressed on Lymphoid Tissue Residing LTi-like Group 3 Innate Lymphoid Cells and Associated with Ectopic Lymphoid Aggregates

Innate lymphoid cells in HIV pathogenesis and in the human female genital tract

PURPOSE OF REVIEW

Women are underrepresented in HIV infection and prevention research despite making up half of people living with HIV. The female genital tract (FGT) serves as a primary site of HIV acquisition, but gaps in knowledge remain regarding protective innate immune mechanisms. Innate lymphoid cells are tissue-resident cells involved in mucosal barrier maintenance and protection, and innate lymphoid cells (ILCs) are altered during chronic HIV infection. However, ILCs role in mucosal HIV pathogenesis is unclear and they are poorly characterized in the FGT.

RECENT FINDINGS

Human ILCs differ from their mouse counterparts and plastically adjust to their tissue of residency. Human ILC characterization is difficult due to tissue-specific adaptations and transition between subsets. While evidence for ILC involvement in antiviral activity and barrier maintenance is provided in mouse models, human ILC role in mucosal immunity remain understudied, particularly in the FGT. In chronic HIV/simian immunodeficiency virus (SIV) infection, ILCs are altered in a tissue-specific manner, and SIV models indicate potential for antiviral responses.

SUMMARY

ILCs are tissue-resident plastic cells that provide barrier protection at mucosal surfaces and display antiviral capacity. Considering that HIV is primarily transmitted through mucosal exposure, more research is needed to understand ILC contribution to HIV pathogenesis in human mucosal surfaces relevant for HIV acquisition.

Distinct Tissue-Dependent Composition and Gene Expression of Human Fetal Innate Lymphoid Cells

The human fetal immune system starts to develop in the first trimester and likely plays a crucial role in fetal development and maternal-fetal tolerance. Innate lymphoid cells (ILCs) are the earliest lymphoid cells to arise in the human fetus. ILCs consist of natural killer (NK) cells, ILC1s, ILC2s, and ILC3s that all share a common lymphoid origin. Here, we studied fetal ILC subsets, mainly NK cells and ILC3s and their potential progenitors, across human fetal tissues. Our results show that fetal ILC subsets have distinct distribution, developmental kinetics, and gene expression profiles across human fetal tissues. Furthermore, we identify CD34+RORγt+Eomes- and CD34+RORγt+Eomes+ cells in the fetal intestine, indicating that tissue-specific ILC progenitors exist already during fetal development.

NRP1 antagonism as a novel therapeutic target in nasal polyps of patients with chronic rhinosinusitis

BACKGROUND

Neuropilin-1 (NRP1) is expressed on the surface epithelium of respiratory tract and immune cells, demonstrating its possible function in regulating the immune response in airway disease. However, its role in patient with chronic rhinosinusitis (CRS) remains unknown. This study aimed to elucidate the role of NRP1 in CRS with nasal polyps (CRSwNP).

METHODS

Sinonasal biopsy specimens were immunohistochemically stained to investigate NRP1 expression. Double immunofluorescence, immunoblotting, and real-time polymerase chain reaction were performed to evaluate NRP1 in primary human nasal epithelial cells (hNECs). An NRP1 inhibitor was administered to a murine nasal polyp (NP) model.

RESULTS

NRP1 was highly expressed in the epithelium in patients with CRSwNP compared to nasal tissue from controls and CRS without NP patients. NRP1 and vascular endothelial growth factor were upregulated in hNECs under hypoxia. Treatment with NRP1 inhibitor (EG00229) reduced the secretion of interleukin (IL)-1β, IL-6, IL-8, and IL-33 cytokines, as well as inducible nitric oxide synthase, cyclooxygenase-2, and prostaglandin E2 in hNECs. We found that NRP1 was highly expressed in the airway epithelium in the murine NP model. The group treated with the NRP1 inhibitor had significantly fewer nasal polypoid lesions and reduced accumulations of immune cells.

CONCLUSIONS

These findings reveal that NRP1 is upregulated in CRS and NP epithelium, and the inhibition of NRP1 may lead to a reduction in NP growth and immune cell infiltration. Our results suggest that NRP1 inhibition could be a novel possibility for treating nasal polyposis.

Tissue-specific features of innate lymphoid cells in antiviral defense

Innate lymphocytes (ILCs) rapidly respond to and protect against invading pathogens and cancer. ILCs include natural killer (NK) cells, ILC1s, ILC2s, ILC3s, and lymphoid tissue inducer (LTi) cells and include type I, type II, and type III immune cells. While NK cells have been well recognized for their role in antiviral immunity, other ILC subtypes are emerging as players in antiviral defense. Each ILC subset has specialized functions that uniquely impact the antiviral immunity and health of the host depending on the tissue microenvironment. This review focuses on the specialized functions of each ILC subtype and their roles in antiviral immune responses across tissues. Several viruses within infection-prone tissues will be highlighted to provide an overview of the extent of the ILC immunity within tissues and emphasize common versus virus-specific responses.

Tertiary lymphoid structures in diseases: immune mechanisms and therapeutic advances

Tertiary lymphoid structures (TLSs) are defined as lymphoid aggregates formed in non-hematopoietic organs under pathological conditions. Similar to secondary lymphoid organs (SLOs), the formation of TLSs relies on the interaction between lymphoid tissue inducer (LTi) cells and lymphoid tissue organizer (LTo) cells, involving multiple cytokines. Heterogeneity is a distinguishing feature of TLSs, which may lead to differences in their functions. Growing evidence suggests that TLSs are associated with various diseases, such as cancers, autoimmune diseases, transplant rejection, chronic inflammation, infection, and even ageing. However, the detailed mechanisms behind these clinical associations are not yet fully understood. The mechanisms by which TLS maturation and localization affect immune function are also unclear. Therefore, it is necessary to enhance the understanding of TLS development and function at the cellular and molecular level, which may allow us to utilize them to improve the immune microenvironment. In this review, we delve into the composition, formation mechanism, associations with diseases, and potential therapeutic applications of TLSs. Furthermore, we discuss the therapeutic implications of TLSs, such as their role as markers of therapeutic response and prognosis. Finally, we summarize various methods for detecting and targeting TLSs. Overall, we provide a comprehensive understanding of TLSs and aim to develop more effective therapeutic strategies.

Transcriptomic diversity of innate lymphoid cells in human lymph nodes compared to BM and spleen

Innate lymphoid cells (ILCs) are largely tissue-resident, mostly described within the mucosal tissues. However, their presence and functions in the human draining lymph nodes (LNs) are unknown. Our study unravels the tissue-specific transcriptional profiles of 47,287 CD127+ ILCs within the human abdominal and thoracic LNs. LNs contain a higher frequency of CD127+ ILCs than in BM or spleen. We define independent stages of ILC development, including EILP and pILC in the BM. These progenitors exist in LNs in addition to naïve ILCs (nILCs) that can differentiate into mature ILCs. We define three ILC1 and four ILC3 sub-clusters in the LNs. ILC1 and ILC3 subsets have clusters with high heat shock protein-encoding genes. We identify previously unrecognized regulons, including the BACH2 family for ILC1 and the ATF family for ILC3. Our study is the comprehensive characterization of ILCs in LNs, providing an in-depth understanding of ILC-mediated immunity in humans.

Group 3 innate lymphoid cells in intestinal health and disease

The gastrointestinal tract is an immunologically rich organ, containing complex cell networks and dense lymphoid structures that safeguard this large absorptive barrier from pathogens, contribute to tissue physiology and support mucosal healing. Simultaneously, the immune system must remain tolerant to innocuous dietary antigens and trillions of normally beneficial microorganisms colonizing the intestine. Indeed, a dysfunctional immune response in the intestine underlies the pathogenesis of numerous local and systemic diseases, including inflammatory bowel disease, food allergy, chronic enteric infections or cancers. Here, we discuss group 3 innate lymphoid cells (ILC3s), which have emerged as orchestrators of tissue physiology, immunity, inflammation, tolerance and malignancy in the gastrointestinal tract. ILC3s are abundant in the developing and healthy intestine but their numbers or function are altered during chronic disease and cancer. The latest studies provide new insights into the mechanisms by which ILC3s fundamentally shape intestinal homeostasis or disease pathophysiology, and often this functional dichotomy depends on context and complex interactions with other cell types or microorganisms. Finally, we consider how this knowledge could be harnessed to improve current treatments or provoke new opportunities for therapeutic intervention to promote gut health.

NRP1 downregulation correlates with enhanced ILC2 responses during IL-33 challenge

Group 2 innate lymphoid cells (ILC2s) play critical roles in driving the pathogenesis of allergic airway inflammation. The mechanisms underlying the regulation of ILC2s remain to be fully understood. Here, we identified neuropilin-1 (NRP1) as a surface marker of ILC2s in response to IL-33 stimulation. NRP1 was abundantly expressed in ILC2s from lung under steady state, which was significantly reduced upon IL-33 stimulation. ILC2s with high expression of NRP1 (NRP1high) displayed lower response to IL-33, as compared with NRP1low ILC2s. Transcriptional profiling and flow cytometric analysis showed that downregulation of AKT-mTOR signalling participated in the diminished functionality of NRP1high ILC2s. These observations revealed a potential role of NRP1 in ILC2s responses under allergic inflammatory condition.

The role of gut-lung axis in COPD: Pathogenesis, immune response, and prospective treatment

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and healthcare burden worldwide. The progression of COPD is a combination of genetic predisposition and environmental factors, primarily cigarette smoking, and the underlying mechanisms are still unknown. Intestinal microecology impacts host immunity, metabolism, and resistance to pathogenic infections, which may be involved in pulmonary disease. Moreover, substantial interaction occurs between the intestinal and respiratory immune niches. After reviewing nearly 500 articles, we found the gut-lung axis plays an important role in the development of COPD. COPD patients often have dysbiosis of the intestinal microenvironment, which can affect host immunity through a series of mechanisms, exacerbating or protecting against COPD progression. This paper summarizes how the gut-lung axis influences COPD, including the alterations of intestinal microecology, the pathological mechanisms, and the involved immune responses. Finally, we summarize the latest research advances in COPD treatment from the perspective of regulating the gut-lung axis and intestinal immunity and evaluate the potential value of the gut-lung axis in improving COPD prognosis.

Lung type 3 innate lymphoid cells respond early following Mycobacterium tuberculosis infection

Tuberculosis is the leading cause of death due to an infectious disease worldwide. Innate lymphoid type 3 cells (ILC3s) mediate early protection during Mycobacterium tuberculosis (Mtb) infection. However, the early signaling mechanisms that govern ILC3 activation or recruitment within the lung during Mtb infection are unclear. scRNA-seq analysis of Mtb-infected mouse lung innate lymphoid cells (ILCs) has revealed the presence of different clusters of ILC populations, suggesting heterogeneity. Using mouse models, we show that during Mtb infection, interleukin-1 receptor (IL-1R) signaling on epithelial cells drives ILC3 expansion and regulates ILC3 accumulation in the lung. Furthermore, our data revealed that C-X-C motif chemokine receptor 5 (CXCR5) signaling plays a crucial role in ILC3 recruitment from periphery during Mtb infection. Our study thus establishes the early responses that drive ILC3 accumulation during Mtb infection and points to ILC3s as a potential vaccine target.

IMPORTANCE

Tuberculosis is a leading cause of death due to a single infectious agent accounting for 1.6 million deaths each year. In our study, we determined the role of type 3 innate lymphoid cells in early immune events necessary for achieving protection during Mtb infection. Our study reveals distinct clusters of ILC2, ILC3, and ILC3/ILC1-like cells in Mtb infection. Moreover, our study reveal that IL-1R signaling on lung type 2 epithelial cells plays a key role in lung ILC3 accumulation during Mtb infection. CXCR5 on ILC3s is involved in ILC3 homing from periphery during Mtb infection. Thus, our study provides novel insights into the early immune mechanisms governed by innate lymphoid cells that can be targeted for potential vaccine-induced protection.

The activating receptor NKp65 is selectively expressed by human ILC3 and demarcates ILC3 from mature NK cells

Innate lymphocytes comprise cytotoxic natural killer (NK) cells and tissue-resident innate lymphoid cells (ILC) that are subgrouped according to their cytokine profiles into group 1 ILC (ILC1), ILC2, and ILC3. However, cell surface receptors unambiguously defining or specifically activating such ILC subsets are scarcely known. Here, we report on the physiologic expression of the human activating C-type lectin-like receptor (CTLR) NKp65, a high-affinity receptor for the CTLR keratinocyte-associated C-type lectin (KACL). Tracking rare NKp65 transcripts in human blood, we identify ILC3 to selectively express NKp65. NKp65 expression not only demarcates "bona fide" ILC3 from likewise RORγt-expressing ILC precursors and lymphoid tissue inducer cells but also from mature NK cells which acquire the NKp65-relative NKp80 during a Notch-dependent differentiation from NKp65+ precursor cells. Hence, ILC3 and NK cells mutually exclusively and interdependently express the genetically coupled sibling receptors NKp65 and NKp80. Much alike NKp80, NKp65 promotes cytotoxicity by innate lymphocytes which may become relevant during pathophysiological reprogramming of ILC3. Altogether, we report the selective expression of the activating immunoreceptor NKp65 by ILC3 demarcating ILC3 from mature NK cells and endowing ILC3 with a dedicated immunosensor for the epidermal immune barrier.

Aberrant characteristics of peripheral blood innate lymphoid cells in COPD, independent of smoking history

Background

Distinguishing asthma and COPD can pose challenges in clinical practice. Increased group 1 innate lymphoid cells (ILC1s) have been found in the lungs and peripheral blood of COPD patients, while asthma is associated with elevated levels of ILC2s. However, it is unclear whether the inflammatory characteristics of ILC1s and ILC2s differ between COPD and asthma. This study aims to compare peripheral blood ILC subsets and their expression of inflammatory markers in COPD patients, asthma patients and controls.

Methods

The study utilised multi-colour flow cytometry to analyse peripheral blood ILC populations in clinically stable COPD patients (n=38), asthma patients (n=37), and smoking (n=19) and non-smoking (n=16) controls.

Results

Proportions of peripheral blood inflammatory CD4+ ILC1s were significantly higher in COPD patients than in asthma. Proportions of CD4- ILC1s were increased in COPD patients compared to asthma patients and smoking controls. Frequencies of CD117- ILC2s were significantly reduced in COPD patients compared with asthma patients. In contrast, the fraction of inflammatory CD45RO+ cells within the CD117- ILC2 population was significantly increased. Principal component analyses showed that combined features of the circulating ILC compartment separated COPD patients from asthma patients and both control groups.

Conclusion

Our in-depth characterisation of ILC1 and ILC2 populations in peripheral blood revealed significant differences in their phenotypes between COPD and asthma patients and smoking or non-smoking controls. These findings suggest a role for both ILC subsets in COPD disease pathology, independent of smoking history, and may have implications for patient stratification and therapy development.

Bcl6 is a subset-defining transcription factor of lymphoid tissue inducer-like ILC3

Innate lymphoid cells (ILCs) are tissue-resident effector cells with roles in tissue homeostasis, protective immunity, and inflammatory disease. Group 3 ILCs (ILC3s) are classically defined by the master transcription factor RORγt. However, ILC3 can be further subdivided into subsets that share type 3 effector modules that exhibit significant ontological, transcriptional, phenotypic, and functional heterogeneity. Notably lymphoid tissue inducer (LTi)-like ILC3s mediate effector functions not typically associated with other RORγt-expressing lymphocytes, suggesting that additional transcription factors contribute to dictate ILC3 subset phenotypes. Here, we identify Bcl6 as a subset-defining transcription factor of LTi-like ILC3s in mice and humans. Deletion of Bcl6 results in dysregulation of the LTi-like ILC3 transcriptional program and markedly enhances expression of interleukin-17A (IL-17A) and IL-17F in LTi-like ILC3s in a manner in part dependent upon the commensal microbiota-and associated with worsened inflammation in a model of colitis. Together, these findings redefine our understanding of ILC3 subset biology.

Systematic analysis of various RNA transcripts and construction of biological regulatory networks at the post-transcriptional level for chronic obstructive pulmonary disease

BACKGROUND

Although chronic inflammation, oxidative stress, airway remodeling, and protease-antiprotease imbalance have been implicated in chronic obstructive pulmonary disease (COPD), the exact pathogenesis is still obscure. Gene transcription and post-transcriptional regulation have been taken into account as key regulators of COPD occurrence and development. Identifying the hub genes and constructing biological regulatory networks at the post-transcriptional level will help extend current knowledge on COPD pathogenesis and develop potential drugs.

METHODS

All lung tissues from non-smokers (n = 6), smokers without COPD (smokers, n = 7), and smokers with COPD (COPD, n = 7) were collected to detect messenger RNA (mRNA), microRNA (miRNA), circular RNA (circRNA), and long non-coding RNA (lncRNA) expression and identify the hub genes. Biological regulatory networks were constructed at the post-transcriptional level, including the RNA-binding protein (RBP)-hub gene interaction network and the competitive endogenous RNA (ceRNA) network. In addition, we assessed the composition and abundance of immune cells in COPD lung tissue and predicted potential therapeutic drugs for COPD. Finally, the hub genes were confirmed at both the RNA and protein levels.

RESULTS

Among the 20 participants, a total of 121169 mRNA transcripts, 1871 miRNA transcripts, 4244 circRNA transcripts, and 122130 lncRNA transcripts were detected. There were differences in the expression of 1561 mRNAs, 48 miRNAs, 33 circRNAs, and 545 lncRNAs between smokers and non-smokers, as well as 1289 mRNAs, 69 miRNAs, 32 circRNAs, and 433 lncRNAs between smokers and COPD patients. 18 hub genes were identified in COPD. TGF-β signaling and Wnt/β-catenin signaling may be involved in the development of COPD. Furthermore, the circRNA/lncRNA-miRNA-mRNA ceRNA networks and the RBP-hub gene interaction network were also constructed. Analysis of the immune cell infiltration level revealed that M2 macrophages and activated NK cells were increased in COPD lung tissues. Finally, we identified that the ITK inhibitor and oxybutynin chloride may be effective in treating COPD.

CONCLUSIONS

We identified several novel hub genes involved in COPD pathogenesis. TGF-β signaling and Wnt/β-catenin signaling were the most dysregulated pathways in COPD patients. Our study constructed post-transcriptional biological regulatory networks and predicted small-molecule drugs for the treatment of COPD, which enhanced the existing understanding of COPD pathogenesis and suggested an innovative direction for the therapeutic intervention of the disease.

ILC3: a case of conflicted identity

Innate lymphoid cells type 3 (ILC3s) are the first line sentinels at the mucous tissues, where they contribute to the homeostatic immune response in a major way. Also, they have been increasingly appreciated as important modulators of chronic inflammatory and autoimmune responses, both locally and systemically. The proper identification of ILC3 is of utmost importance for meaningful studies on their role in immunity. Flow cytometry is the method of choice for the detection and characterization of ILC3. However, the analysis of ILC3-related papers shows inconsistency in ILC3 phenotypic definition, as different inclusion and exclusion markers are used for their identification. Here, we present these discrepancies in the phenotypic characterization of human and mouse ILC3s. We discuss the pros and cons of using various markers for ILC3 identification. Furthermore, we consider the possibilities for the efficient isolation and propagation of ILC3 from different organs and tissues for in-vitro and in-vivo studies. This paper calls upon uniformity in ILC3 definition, isolation, and propagation for the increased possibility of confluent interpretation of ILC3's role in immunity.

IL-18 and VEGF-A trigger type 2 innate lymphoid cell accumulation and pro-tumoral function in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a hematologic malignancy associated to an unregulated growth of myeloid cells in bone marrow (BM) and peripheral blood (PB), characterized by the BCR-ABL1 translocation. Given the known cytokine impairment in the leukemic niche of CML, we investigated the impact of this microenvironmental dysregulation on innate lymphoid cells (ILC), whose role in cancer has recently emerged. Three ILC subsets are identified based on transcriptional profiles and cytokine secretion. We observed that interleukin 18 (IL-18) and vascular endothelial growth factor A (VEGF-A) are increased in CML patients' sera and that ILC2 are enriched in CML PB and BM. We found that IL-18 drives ILC2 proliferation and that CML ILC2 highly express CXCR4 and CXCR7 BM-homing receptors, potentially explaining their enrichment in PB and BM, respectively. Next, we showed that ILC2 are hyper-activated through a tumor-derived VEGF-Adependent mechanism, which leads to higher IL-13 secretion. In response to IL-13, leukemic cells increase their clonogenic capacity. Finally, we discovered that the pro-tumoral axis involving VEGF-A, IL-18 and ILC2 was disrupted upon tyrosine kinase inhibitor treatment, normalizing the levels of all these players in CML patients responding to therapy. Overall, our study uncovers the involvement of ILC2 in CML progression, mediated by VEGF-A and IL-18.

Tissue-resident innate lymphoid cells in asthma

Asthma is a chronic airway inflammatory disease whose global incidence increases annually. The role of innate lymphoid cells (ILCs) is a crucial aspect of asthma research with respect to different endotypes of asthma. Based on its pathological and inflammatory features, asthma is divided into type 2 high and type 2 low endotypes. Type-2 high asthma is distinguished by the activation of type 2 immune cells, including T helper 2 (Th2) cells and ILC2s; the production of cytokines interleukin (IL)-4, IL-5 and IL-13; eosinophilic aggregation; and bronchial hyper-responsiveness. Type-2 low asthma represents a variety of endotypes other than type 2 high endotype such as the IL-1β/ILC3/neutrophil endotype and a paucigranulocytic asthma, which may be insensitive to corticosteroid treatment and/or associated with obesity. The complexity of asthma is due to the involvement of multiple cell types, including tissue-resident ILCs and other innate immune cells including bronchial epithelial cells, dendritic cells, macrophages and eosinophils, which provide immediate defence against viruses, pathogens and allergens. On this basis, innate immune cells and adaptive immune cells combine to induce the pathological condition of asthma. In addition, the plasticity of ILCs increases the heterogeneity of asthma. This review focuses on the phenotypes of tissue-resident ILCs and their roles in the different endotypes of asthma, as well as the mechanisms of tissue-resident ILCs and other immune cells. Based on the phenotypes, roles and mechanisms of immune cells, the therapeutic strategies for asthma are reviewed.

Reciprocal costimulatory molecules control the activation of mucosal type 3 innate lymphoid cells during engagement with B cells

Innate lymphoid cells (ILCs) are the counterpart of T helper cells in the innate immune system and share multiple phenotypes with T helper cells. Inducible T-cell costimulator (ICOS) is recognized on T cells and participates in T-cell activation and T and B-cell engagement in lymphoid tissues. However, the role of ICOS in ILC3s and ILC3-involved interactions with the immune microenvironment remains unclear. Here, we found that ICOS expression on human ILC3s was correlated with the activated state of ILC3s. ICOS costimulation enhanced the survival, proliferation, and capacity of ILC3s to produce cytokines (IL-22, IL-17A, IFN-γ, TNF, and GM-CSF). Via synergistic effects of ICOS and CD40 signaling, B cells promoted ILC3 functions, and ILC3-induced T-cell-independent B-cell IgA and IgM secretion primarily required CD40 signaling. Hence, ICOS is essential for the nonredundant role of ILC3s and their interaction with adjacent B cells.

Bronchitis, COPD, and pneumonia after viral endemic of patients with leprosy on Sorok Island in South Korea

Viral respiratory diseases (VRDs) cause lung inflammation and inflammatory cytokine production. We study whether dapsone is responsible for its observed preventive treatment effects of the sustained viral RNA interferon response. Around 2008 and 2012, Korea's Dementia Management Act stipulated drastic changes in the administration of dementia medication by medical staff. Participants were randomized and we compared leprosy patients with VRDs after prescribing dapsone as a standard treatment from 2005 to 2019. Significance was evaluated based on the dapsone-prescribed (+) subgroup and the dapsone-unprescribed (-) subgroup of the VRD diagnosed (+) and VRD undiagnosed (-) subgroup. We analyzed VRD ( +)/(- with dapsone (+)/(-) group and used a T-test, and designed the equation of acetylation with dapsone and acetylcholine (AA) equation. The 6394 VRD participants who received the dapsone intervention compared to the 3255 VRD participants in the control group demonstrated at T2 VRD (+) dapsone (-) (mean (M) = 224.80, SD = 97.50): T3 VRD (-) dapsone (+) (M = 110.87, SD = 103.80), proving that VRD is low when dapsone is taken and high when it is not taken. The t value is 3.10, and the p value is 0.004395 (significant at p < 0.05). After an increase in VRDs peaked in 2009, bronchitis, COPD, and pneumonia surged in 2013. The AA equation was strongly negatively correlated with the prevalence of bronchitis and chronic obstructive pulmonary disease (COPD): with bronchitis, r(15) =  -0.823189, p = 0.005519, and with COPD, r(15) =  -0.8161, p = 0.000207 (significant at p < 0.05). Dapsone treated both bronchitis and COPD. This study provides theoretical clinical data to limit acetylcholine excess during the VRD pandemic for bronchitis, COPD, and pneumonia.

Tertiary lymphoid structures and cytokines interconnections: The implication in cancer immunotherapy

Tertiary lymphoid structures (TLSs) are organized aggregates of lymphocytes and antigen-presenting cells that develop in non-lymphoid tissues during chronic inflammation, resembling the structure and features of secondary lymphoid organs. Numerous studies have shown that TLSs may be an important source of antitumor immunity within solid tumors, facilitating T cell and B cell differentiation and the subsequent production of antitumor antibodies, which are beneficial for cancer prognosis and responses to immunotherapy. The formation of TLS relies on the cytokine signaling network between heterogeneous cell populations, such as stromal cells, lymphocytes and cancer cells. The coordinated action of various cytokines drives the complex process of TLS development. In this review, we will comprehensively describe the mechanisms by which various cytokines regulate TLS formation and function, and the recent advancements and therapeutic potential of exploiting these mechanisms to induce TLS as an emerging immunotherapeutic approach or to enhance existing immunotherapy.

Regulation of tumor angiogenesis by the crosstalk between innate immunity and endothelial cells

Endothelial cells and immune cells are major regulators of cancer progression and prognosis. Endothelial cell proliferation and angiogenesis are required for providing nutrients and oxygen to the nascent tumor and infiltration of immune cells to the tumor is dependent on endothelial cell activation. Myeloid cells and innate lymphocytes have an important role in shaping the tumor microenvironment by crosstalking with cancer cells and structural cells, including endothelial cells. Innate immune cells can modulate the activation and functions of tumor endothelial cells, and, in turn, endothelial cell expression of adhesion molecules can affect immune cell extravasation. However, the mechanisms underlying this bidirectional crosstalk are not fully understood. In this review, we will provide an overview of the current knowledge on the pathways regulating the crosstalk between innate immune cells and endothelial cells during tumor progression and discuss their potential contribution to the development of novel anti-tumor therapeutic approaches.

The roles of tertiary lymphoid structures in chronic diseases

Tertiary lymphoid structures (TLSs) are ectopic lymphoid tissues that drive antigen-specific immune responses at sites of chronic inflammation. Unlike secondary lymphoid organs such as lymph nodes, TLSs lack capsules and have their own unique characteristics and functions. The presumed influence of TLSs on the disease course has led to widespread interest in obtaining a better understanding of their biology and function. Studies using single-cell analyses have suggested heterogeneity in TLS composition and phenotype, and consequently, functional correlates with disease progression are sometimes conflicting. The presence of TLSs correlates with a favourable disease course in cancer and infection. Conversely, in autoimmune diseases and chronic age-related inflammatory diseases including chronic kidney disease, the presence of TLSs is associated with a more severe disease course. However, the detailed mechanisms that underlie these clinical associations are not fully understood. To what extent the mechanisms of TLS development and maturation are shared across organs and diseases is also still obscure. Improved understanding of TLS development and function at the cellular and molecular levels may enable the exploitation of these structures to improve therapies for chronic diseases, including chronic kidney disease.

Contribution of adaptive immunity to human COPD and experimental models of emphysema

The pathophysiology of chronic obstructive pulmonary disease (COPD) and the undisputed role of innate immune cells in this condition have dominated the field in the basic research arena for many years. Recently, however, compelling data suggesting that adaptive immune cells may also contribute to the progressive nature of lung destruction associated with COPD in smokers have gained considerable attention. The histopathological changes in the lungs of smokers can be limited to the large or small airways, but alveolar loss leading to emphysema, which occurs in some individuals, remains its most significant and irreversible outcome. Critically, however, the question of why emphysema progresses in a subset of former smokers remained a mystery for many years. The recognition of activated and organized tertiary T- and B-lymphoid aggregates in emphysematous lungs provided the first clue that adaptive immune cells may play a crucial role in COPD pathophysiology. Based on these findings from human translational studies, experimental animal models of emphysema were used to determine the mechanisms through which smoke exposure initiates and orchestrates adaptive autoreactive inflammation in the lungs. These models have revealed that T helper (Th)1 and Th17 subsets promote a positive feedback loop that activates innate immune cells, confirming their role in emphysema pathogenesis. Results from genetic studies and immune-based discoveries have further provided strong evidence for autoimmunity induction in smokers with emphysema. These new findings offer a novel opportunity to explore the mechanisms underlying the inflammatory landscape in the COPD lung and offer insights for development of precision-based treatment to halt lung destruction.

Function of Innate Lymphoid Cells in Periodontal Tissue Homeostasis: A Narrative Review

Periodontitis is an irreversible inflammatory response that occurs in periodontal tissues. Given the size and diversity of natural flora in the oral mucosa, host immunity must strike a balance between pathogen identification and a complicated system of tolerance. The innate immune system, which includes innate lymphoid cells (ILCs), certainly plays a crucial role in regulating this homeostasis because pathogens are quickly recognized and responded to. ILCs are a recently discovered category of tissue-resident lymphocytes that lack adaptive antigen receptors. ILCs are found in both lymphoid and non-lymphoid organs and are particularly prevalent at mucosal barrier surfaces, where they control inflammatory response and homeostasis. Recent studies have shown that ILCs are important players in periodontitis; however, the mechanisms that govern the innate immune response in periodontitis still require further investigation. This review focuses on the intricate crosstalk between ILCs and the microenvironment in periodontal tissue homeostasis, with the purpose of regulating or improving immune responses in periodontitis prevention and therapy.

Immune subset-committed proliferating cells populate the human foetal intestine throughout the second trimester of gestation

The intestine represents the largest immune compartment in the human body, yet its development and organisation during human foetal development is largely unknown. Here we show the immune subset composition of this organ during development, by longitudinal spectral flow cytometry analysis of human foetal intestinal samples between 14 and 22 weeks of gestation. At 14 weeks, the foetal intestine is mainly populated by myeloid cells and three distinct CD3-CD7+ ILC, followed by rapid appearance of adaptive CD4+, CD8+ T and B cell subsets. Imaging mass cytometry identifies lymphoid follicles from week 16 onwards in a villus-like structure covered by epithelium and confirms the presence of Ki-67+ cells in situ within all CD3-CD7+ ILC, T, B and myeloid cell subsets. Foetal intestinal lymphoid subsets are capable of spontaneous proliferation in vitro. IL-7 mRNA is detected within both the lamina propria and the epithelium and IL-7 enhances proliferation of several subsets in vitro. Overall, these observations demonstrate the presence of immune subset-committed cells capable of local proliferation in the developing human foetal intestine, likely contributing to the development and growth of organized immune structures throughout most of the 2nd trimester, which might influence microbial colonization upon birth.

Innate Lymphoid Cell Plasticity in Mucosal Infections

Mucosal tissue homeostasis is a dynamic process that involves multiple mechanisms including regulation of innate lymphoid cells (ILCs). ILCs are mostly tissue-resident cells which are critical for tissue homeostasis and immune response against pathogens. ILCs can sense environmental changes and rapidly respond by producing effector cytokines to limit pathogen spread and initiate tissue recovery. However, dysregulation of ILCs can also lead to immunopathology. Accumulating evidence suggests that ILCs are dynamic population that can change their phenotype and functions under rapidly changing tissue microenvironment. However, the significance of ILC plasticity in response to pathogens remains poorly understood. Therefore, in this review, we discuss recent advances in understanding the mechanisms regulating ILC plasticity in response to intestinal, respiratory and genital tract pathogens. Key transcription factors and lineage-guiding cytokines regulate this plasticity. Additionally, we discuss the emerging data on the role of tissue microenvironment, gut microbiota, and hypoxia in ILC plasticity in response to mucosal pathogens. The identification of new pathways and molecular mechanisms that control functions and plasticity of ILCs could uncover more specific and effective therapeutic targets for infectious and autoimmune diseases where ILCs become dysregulated.

Embryonic ILC-poiesis across tissues

The family of innate lymphoid cells (ILCs), consisting of Group 1 ILCs (natural killer cells and ILC1), ILC2, and ILC3, are critical effectors of innate immunity, inflammation, and homeostasis post-natally, but also exert essential functions before birth. Recent studies during critical developmental periods in the embryo have hinted at complex waves of tissue colonization, and highlighted the breadth of multipotent and committed ILC progenitors from both classic fetal hematopoietic organs such as the liver, as well as tissue sites such as the lung, thymus, and intestine. Assessment of the mechanisms driving cell fate and function of the ILC family in the embryo will be vital to the understanding ILC biology throughout fetal life and beyond.

The roles of metabolic profiles and intracellular signaling pathways of tumor microenvironment cells in angiogenesis of solid tumors

Innate and adaptive immune cells patrol and survey throughout the human body and sometimes reside in the tumor microenvironment (TME) with a variety of cell types and nutrients that may differ from those in which they developed. The metabolic pathways and metabolites of immune cells are rooted in cell physiology, and not only provide nutrients and energy for cell growth and survival but also influencing cell differentiation and effector functions. Nowadays, there is a growing awareness that metabolic processes occurring in cancer cells can affect immune cell function and lead to tumor immune evasion and angiogenesis. In order to safely treat cancer patients and prevent immune checkpoint blockade-induced toxicities and autoimmunity, we suggest using anti-angiogenic drugs solely or combined with Immune checkpoint blockers (ICBs) to boost the safety and effectiveness of cancer therapy. As a consequence, there is significant and escalating attention to discovering techniques that target metabolism as a new method of cancer therapy. In this review, a summary of immune-metabolic processes and their potential role in the stimulation of intracellular signaling in TME cells that lead to tumor angiogenesis, and therapeutic applications is provided. Video abstract.

Immunologic Role of Innate Lymphoid Cells against Mycobacterial tuberculosis Infection

Tuberculosis (TB), caused by Mycobacterium tuberculosis (M. tb), is one of the leading causes of mortality due to respiratory tract infections worldwide. Infection by M. tb involves activation of a type I immune response characteristic of T helper type 1 (Th1) lymphocytes, natural killer (NK) cells, Interleukin-12 (IL-12), and interferon (IFN)-γ, all of which stimulate the activation of macrophages and robust phagocytosis in order to prevent further infectious manifestations and systemic dissemination. Recent discoveries about innate lymphoid cells (ILCs) have provided further insight about how these cells participate within the protective immune response against M. tb infection and help boost the type I immune response. In order to clearly understand the mechanisms of M. tb infection and advance the efficacy of future treatment and prevention, we must first look at the individual functions each type of immune cell plays within this process, specifically ILCs. By review of the recent literature and current evidence, our group aims to summarize the characterization of the three major groups of ILCs, including NK cells, and analyze the role that each group of ILCs play in the infectious process against M. tb in order to provide a more comprehensive understanding of the host immune response. Equally, previous studies have also highlighted the effects of how administration of the Bacille Calmette–Guérin (BCG) vaccine influences the cells and cytokines of the immune response against M. tb. Our group also aims to highlight the effects that BCG vaccine has on ILCs and how these effects provide added protection against M. tb.

The role of ILC subsets in cancer

The family of innate lymphoid cells (ILCs) are composed of five canonical subsets, NK cells, ILC1, ILC2, ILC3 and Lymphoid tissue inducer cells. ILCs have important functions in early stages of immune response towards infectious agents. ILCs are highly plastic enabling rapid modification of their functions dependent on the type of microbe and tissue environment to optimally counter these microbes. Data that still accumulate in a rapid pace indicate that these cells are also involved in immunity against tumor cells. Paradoxically ILC subsets have been shown to have tumor suppressing and tumor promoting activities. In this brief review we provide a snapshot of our current knowledge of characteristics and functions of tumor infiltrating ILC subsets and speculate on how these cells can be harnessed to mediate anti-tumor immunity.

Disturbed natural killer cell homeostasis in the salivary gland enhances autoimmune pathology via IFN-γ in a mouse model of primary Sjögren's syndrome

OBJECTIVE

Innate lymphoid cells (ILCs), including natural killer (NK) cells, ILC1, ILC2, lymphoid tissue-inducer (LTi) cells, and ILC3 cell, play a key role in various immune responses. Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by chronic inflammation of exocrine glands, such as the lacrimal and salivary glands (SGs). The role of NK cells among ILCs in the pathogenesis of pSS is still unclear. In this study, the characteristics and subsets of NK cells in the salivary gland (SG) tissue were analyzed using a murine model of pSS.

METHODS

Multiple phenotypes and cytotoxic signature of the SG NK cells in control and pSS model mice were evaluated by flow cytometric analysis. Intracellular expression of interferon-γ (IFN-γ) among T cells and NK cells from the SG tissues was compared by in vitro experiments. In addition, pathological analysis was performed using anti-asialo-GM1 (ASGM1) antibody (Ab)-injected pSS model mice.

RESULTS

The number of conventional NK (cNK) cells in the SG of pSS model mice significantly increased compared with that in control mice at 6 weeks of age. The production level of IFN-γ was significantly higher in SG NK cells than in SG T cells. The depletion of NK cells by ASGM1 Ab altered the ratio of tissue resident NK (rNK) cells to cNK cells, which inhibited the injury to SG cells with the recovery of saliva secretion in pSS model mice.

CONCLUSION

The results indicate that SG cNK cells may enhance the autoreactive response in the target organ by upregulating of IFN-γ, whereas SG rNK cells protect target cells against T cell cytotoxicity. Therefore, the activation process and multiple functions of NK cells in the target organ could be helpful to develop potential markers for determining autoimmune disease activity and target molecules for incurable immune disorders.

Innate and Innate-like Effector Lymphocytes in Health and Disease

Lymphocytes can be functionally partitioned into subsets belonging to the innate or adaptive arms of the immune system. Subsets of innate and innate-like lymphocytes may or may not express Ag-specific receptors of the adaptive immune system, yet they are poised to respond with innate-like speed to pathogenic insults but lack the capacity to develop classical immunological memory. These lymphocyte subsets display a number of common properties that permit them to integrate danger and stress signals dispatched by innate sensor cells to facilitate the generation of specialized effector immune responses tailored toward specific pathogens or other insults. In this review, we discuss the functions of distinct subsets of innate and innate-like lymphocytes. A better understanding of the mechanisms by which these cells are activated in different contexts, their interactions with other immune cells, and their role in health and disease may inform the development of new or improved immunotherapies.

Cigarette smoke aggravates asthma by inducing memory-like type 3 innate lymphoid cells

Although cigarette smoking is known to exacerbate asthma, only a few clinical asthma studies have been conducted involving smokers. Here we show, by comparing paired sputum and blood samples from smoking and non-smoking patients with asthma, that smoking associates with significantly higher frequencies of pro-inflammatory, natural-cytotoxicity-receptor-non-expressing type 3 innate lymphoid cells (ILC3) in the sputum and memory-like, CD45RO-expressing ILC3s in the blood. These ILC3 frequencies positively correlate with circulating neutrophil counts and M1 alveolar macrophage frequencies, which are known to increase in uncontrolled severe asthma, yet do not correlate with circulating eosinophil frequencies that characterize allergic asthma. In vitro exposure of ILCs to cigarette smoke extract induces expression of the memory marker CD45RO in ILC3s. Cigarette smoke extract also impairs the barrier function of airway epithelial cells and increases their production of IL-1β, which is a known activating factor for ILC3s. Thus, our study suggests that cigarette smoking increases local and circulating frequencies of activated ILC3 cells, plays a role in their activation, thereby aggravating non-allergic inflammation and the severity of asthma.

Cigarette smoking may exacerbate asthma, but the underlying mechanisms have not been studied extensively in human patients. Here authors show that type 3 innate lymphoid cells with activated phenotypes are found in the sputum and blood of smokers in higher frequencies, which might result in the aggravation of asthma.

Setd2 determines distinct properties of intestinal ILC3 subsets to regulate intestinal immunity

Subsets of group 3 innate lymphoid cells (ILC3s) are heterogeneous in development and function and play differential roles in intestinal immunity. Histone modifications are involved in the fate commitment of immune cells, including ILC3s. Here, we report that deletion of Setd2, histone H3K36 methyltransferase, in ILC3s results in increased generation of NKp46⁺ILC3s with enhanced cytotoxic signatures and tumor-suppressive capacity. Meanwhile, Rag1^-/-Rorc^CreSetd2^flox/flox mice have fewer CCR6⁺ILC3s and less defective solitary intestinal lymphoid tissue formation, accompanied by reduced granulocyte-macrophage colony-stimulating factor (GM-CSF) production by NKp46^-ILC3s and decreased CD11b⁺CD103⁺ dendritic cell accumulation. The deficiency of Setd2^-/-NKp46^-ILC3s may contribute to disturbed RORγt⁺Treg homeostasis and intestinal inflammation in Rag1^-/-Rorc^CreSetd2^flox/flox mice upon T cell reconstitution. Setd2 regulates genome accessibility imprinting gene mRNA expression, with a more profound effect on NKp46⁺ILC3s than NKp46^-ILC3s. Therefore, Setd2 determines distinct chromatin status and transcriptomic programs of ILC3 subsets to affect their function and intestinal immunity.

Innate lymphoid cells in colorectal cancer

Innate lymphoid cells (ILC) can be viewed as the innate counterparts of T cells. In contrast to T cells, ILCs exert their functions in antigen‐independent manners, relying on tissue‐derived signals from other immune cells, stroma and neurons. Natural killer (NK) cells have been known for their antitumour effects for decades. However, the roles of other ILC subtypes in cancer immunity are just now starting to be unravelled. ILCs contribute to both homeostasis and inflammation in the intestinal mucosa. Intestinal inflammation predisposes the intestine for the development of colonic dysplasia and colorectal cancer (CRC). Recent data from mouse models and human studies indicate that ILCs play a role in CRC, exerting both protumoural and antitumoural functions. Studies also suggest that intratumoural ILC frequencies and expression of ILC signature genes can predict disease progression and response to PD‐1 checkpoint therapy in CRC. In this mini‐review, we focus on such recent insights and their implications for understanding the immunobiology of CRC. We also identify knowledge gaps and research areas that require further work.

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

Tissue-resident immune cells reside in distinct niches across organs, where they contribute to tissue homeostasis and rapidly respond to perturbations in the local microenvironment. Innate lymphoid cells (ILCs) are a family of innate immune cells that regulate immune and tissue homeostasis. Across anatomical locations throughout the body, ILCs adopt tissue-specific fates, differing from circulating ILC populations. Adaptations of ILCs to microenvironmental changes have been documented in several inflammatory contexts, including obesity, asthma, and inflammatory bowel disease. While our understanding of ILC functions within tissues have predominantly been based on mouse studies, development of advanced single cell platforms to study tissue-resident ILCs in humans and emerging patient-based data is providing new insights into this lymphocyte family. Within this review, we discuss current concepts of ILC fate and function, exploring tissue-specific functions of ILCs and their contribution to health and disease across organ systems.

Innate Lymphoid Cells in Autoimmune Diseases

Innate lymphoid cells (ILC) are a heterogeneous group of immune cells characterized by lymphoid morphology and cytokine profile similar to T cells but which do not express clonally distributed diverse antigen receptors. These particular cells express transcription factors and cytokines reflecting their similarities to T helper (Th)1, Th2, and Th17 cells and are therefore referred to as ILC1, ILC2, and ILC3. Other members of the ILC subsets include lymphoid tissue inducer (LTi) and regulatory ILC (ILCreg). Natural killer (NK) cells share a common progenitor with ILC and also exhibit a lymphoid phenotype without antigen specificity. ILC are found in low numbers in peripheral blood but are much more abundant at barrier sites such as the skin, liver, airways, lymph nodes, and the gastrointestinal tract. They play an important role in innate immunity due to their capacity to respond rapidly to pathogens through the production of cytokines. Recent evidence has shown that ILC also play a key role in autoimmunity, as alterations in their number or function have been identified in systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Here, we review recent advances in the understanding of the role of ILC in the pathogenesis of autoimmune diseases, with particular emphasis on their role as a potential diagnostic biomarker and as therapeutic targets.

Neuropilin-1 mediates lung tissue-specific control of ILC2 function in type 2 immunity

Group 2 innate lymphoid cells (ILC2s) are highly heterogeneous tissue-resident lymphocytes that regulate inflammation and tissue homeostasis in health and disease. However, how these cells integrate into the tissue microenvironment to perform tissue-specific functions is unclear. Here, we show neuropilin-1 (Nrp1), which is induced postnatally and sustained by lung-derived transforming growth factor beta-1 (TGFβ1), is a tissue-specific marker of lung ILC2s. Genetic ablation or pharmacological inhibition of Nrp1 suppresses IL-5 and IL-13 production by ILC2s and protects mice from the development of pulmonary fibrosis. Mechanistically, TGFβ1-Nrp1 signaling enhances ILC2 function and type 2 immunity by upregulating IL-33 receptor ST2 expression. These findings identify Nrp1 as a tissue-specific regulator of lung-resident ILC2s and highlight Nrp1 as a potential therapeutic target for pulmonary fibrosis.

The Tonsil Lymphocyte Landscape in Pediatric Tonsil Hyperplasia and Obstructive Sleep Apnea

Tonsil hyperplasia is the most common cause of pediatric obstructive sleep apnea (OSA). Despite the growing knowledge in tissue immunology of tonsils, the immunopathology driving tonsil hyperplasia and OSA remains unknown. Here we used multi-parametric flow cytometry to analyze the composition and phenotype of tonsillar innate lymphoid cells (ILCs), T cells, and B cells from pediatric patients with OSA, who had previous polysomnography. Unbiased clustering analysis was used to delineate and compare lymphocyte heterogeneity between two patient groups: children with small tonsils and moderate OSA (n = 6) or large tonsils and very severe OSA (n = 13). We detected disturbed ILC and B cell proportions in patients with large tonsils, characterized by an increase in the frequency of naïve CD27^-CD21^hi B cells and a relative reduction of ILCs. The enrichment of naïve B cells was not commensurate with elevated Ki67 expression, suggesting defective differentiation and/or migration rather than cellular proliferation to be the causative mechanism. Finally, yet importantly, we provide the flow cytometry data to be used as a resource for additional translational studies aimed at investigating the immunological mechanisms of pediatric tonsil hyperplasia and OSA.

Chemokines and Innate Lymphoid Cells in Skin Inflammation

As the outermost barrier, skin plays an important role in protecting our bodies against outside invasion. Under stable conditions or during inflammation, leukocytes migration is essential for restoring homeostasis in the skin. Immune cells trafficking is orchestrated by chemokines; leukocytes express receptors that bind to chemokines and trigger migration. The homeostasis of the immune ecosystem is an extremely complicated dynamic process that requires the cooperation of innate and adaptive immune cells. Emerging studies have been shedding a light on the unique characteristics of skin-resident innate lymphoid cells (ILCs). In this review, we discuss how chemokines orchestrate skin ILCs trafficking and contribute to tissue homeostasis and how abnormal chemokine–chemokine receptor interactions contribute to and augment skin inflammation, as seen in conditions such as contact hypersensitivity, atopic dermatitis, and psoriasis.

Characteristics of tissue-resident ILCs and their potential as therapeutic targets in mucosal and skin inflammatory diseases

Discovery of innate lymphoid cells (ILCs), which are non-T and non-B lymphocytes that have no antigen-specific receptors, changed the classical concept of the mechanism of allergy, which had been explained mainly as antigen-specific acquired immunity based on IgE and Th2 cells. The discovery led to dramatic improvement in our understanding of the mechanism of non-IgE-mediated allergic inflammation. Numerous studies conducted in the past decade have elucidated the characteristics of each ILC subset in various organs and tissues and their ontogeny. We now know that each ILC subset exhibits heterogeneity. Moreover, the functions and activating/suppressing factors of each ILC subset were found to differ among both organs and types of tissue. Therefore, in this review, we summarize our current knowledge of ILCs by focusing on the organ/tissue-specific features of each subset to understand their roles in various organs. We also discuss ILCs' involvement in human inflammatory diseases in various organs and potential therapeutic/preventive strategies that target ILCs.

An in vitro platform supports generation of human innate lymphoid cells from CD34+ hematopoietic progenitors that recapitulate ex vivo identity

Innate lymphoid cells (ILCs) are critical effectors of innate immunity and inflammation, whose development and activation pathways make for attractive therapeutic targets. However, human ILC generation has not been systematically explored, and previous in vitro investigations relied on the analysis of few markers or cytokines, which are suboptimal to assign lineage identity. Here, we developed a platform that reliably generated human ILC lineages from CD34⁺ hematopoietic progenitors derived from cord blood and bone marrow. We showed that one culture condition is insufficient to generate all ILC subsets, and instead, distinct combination of cytokines and Notch signaling are essential. The identity of natural killer (NK)/ILC1s, ILC2s, and ILC3s generated in vitro was validated by protein expression, functional assays, and both global and single-cell transcriptome analysis, recapitulating the signatures and functions of their ex vivo ILC counterparts. These data represent a resource to aid in clarifying ILC biology and differentiation.

The Role of Innate Lymphoid Cells in Chronic Respiratory Diseases

The lung is a vital mucosal organ that is constantly exposed to the external environment, and as such, its defenses are continuously under threat. The pulmonary immune system has evolved to sense and respond to these danger signals while remaining silent to innocuous aeroantigens. The origin of the defense system is the respiratory epithelium, which responds rapidly to insults by the production of an array of mediators that initiate protection by directly killing microbes, activating tissue-resident immune cells and recruiting leukocytes from the blood. At the steady-state, the lung comprises a large collection of leukocytes, amongst which are specialized cells of lymphoid origin known as innate lymphoid cells (ILCs). ILCs are divided into three major helper-like subsets, ILC1, ILC2 and ILC3, which are considered the innate counterparts of type 1, 2 and 17 T helper cells, respectively, in addition to natural killer cells and lymphoid tissue inducer cells. Although ILCs represent a small fraction of the pulmonary immune system, they play an important role in early responses to pathogens and facilitate the acquisition of adaptive immunity. However, it is now also emerging that these cells are active participants in the development of chronic lung diseases. In this mini-review, we provide an update on our current understanding of the role of ILCs and their regulation in the lung. We summarise how these cells and their mediators initiate, sustain and potentially control pulmonary inflammation, and their contribution to the respiratory diseases chronic obstructive pulmonary disease (COPD) and asthma.

CD127+ CD94+ innate lymphoid cells expressing granulysin and perforin are expanded in patients with Crohn's disease

Phenotypic definition of helper ILC1 and NK cells is problematic due to overlapping markers. Recently we showed the identification of cytotoxic ILC3s characterized by expression of CD94. Here we analyse CD127+ ILCs and NK cells in intestinal lamina propria from healthy donors and Crohn's disease patients and identify two populations of CD127+CD94+ ILCs, designated population A and B, that can be distinguished on the expression of CD117, CD18 and cytotoxic molecules. Population B expresses granulysin, a cytotoxic molecule linked to bacterial lysis and/or chemotaxis of monocytes. Granulysin protein is secreted by population B cells upon stimulation with IL-15. Activation of population B in the presence of TGF-β strongly reduces the expression of cytotoxic effector molecules of population B. Strikingly, samples from individuals that suffer from active Crohn's disease display enhanced frequencies of granulysin-expressing effector CD127+CD94+ ILCs in comparison to controls. Thus this study identifies group 1 ILC populations which accumulate in inflamed intestinal tissue of Crohn's disease patients and may play a role in the pathology of the disease.

Delineating spatiotemporal and hierarchical development of human fetal innate lymphoid cells

Whereas the critical roles of innate lymphoid cells (ILCs) in adult are increasingly appreciated, their developmental hierarchy in early human fetus remains largely elusive. In this study, we sorted human hematopoietic stem/progenitor cells, lymphoid progenitors, putative ILC progenitor/precursors and mature ILCs in the fetal hematopoietic, lymphoid and non-lymphoid tissues, from 8 to 12 post-conception weeks, for single-cell RNA-sequencing, followed by computational analysis and functional validation at bulk and single-cell levels. We delineated the early phase of ILC lineage commitment from hematopoietic stem/progenitor cells, which mainly occurred in fetal liver and intestine. We further unveiled interleukin-3 receptor as a surface marker for the lymphoid progenitors in fetal liver with T, B, ILC and myeloid potentials, while IL-3RA- lymphoid progenitors were predominantly B-lineage committed. Notably, we determined the heterogeneity and tissue distribution of each ILC subpopulation, revealing the proliferating characteristics shared by the precursors of each ILC subtype. Additionally, a novel unconventional ILC2 subpopulation (CRTH2- CCR9+ ILC2) was identified in fetal thymus. Taken together, our study illuminates the precise cellular and molecular features underlying the stepwise formation of human fetal ILC hierarchy with remarkable spatiotemporal heterogeneity.

Cells of the human intestinal tract mapped across space and time

The cellular landscape of the human intestinal tract is dynamic throughout life, developing in utero and changing in response to functional requirements and environmental exposures. Here, to comprehensively map cell lineages, we use single-cell RNA sequencing and antigen receptor analysis of almost half a million cells from up to 5 anatomical regions in the developing and up to 11 distinct anatomical regions in the healthy paediatric and adult human gut. This reveals the existence of transcriptionally distinct BEST4 epithelial cells throughout the human intestinal tract. Furthermore, we implicate IgG sensing as a function of intestinal tuft cells. We describe neural cell populations in the developing enteric nervous system, and predict cell-type-specific expression of genes associated with Hirschsprung's disease. Finally, using a systems approach, we identify key cell players that drive the formation of secondary lymphoid tissue in early human development. We show that these programs are adopted in inflammatory bowel disease to recruit and retain immune cells at the site of inflammation. This catalogue of intestinal cells will provide new insights into cellular programs in development, homeostasis and disease.