Development Of Innate Lymphoid Cells Research Articles

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.

Epigenetic regulation of innate lymphoid cells.

Innate lymphoid cells (ILCs) lack antigen-specific receptors and are considered the innate arm of the immune system, phenotypically and functionally mirroring CD4+ helper T cells. ILCs are categorized into groups 1, 2, and 3 based on transcription factors and cytokine expression. ILCs predominantly reside in mucosal tissues and play important roles in regional immune responses. The development and function of ILC subsets are controlled by both transcriptional and epigenetic mechanisms, which have been extensively studied in recent years. Epigenetic regulation refers to inheritable changes in gene expression that occur without affecting DNA sequences. This mainly includes chromatin status, histone modifications, and DNA methylation. In this review, we summarize recent discoveries on epigenetic mechanisms regulating ILC development and function, and how these regulations affect disease progression under pathological conditions. Although the ablation of specific epigenetic regulators can cause global changes in corresponding epigenetic modifications to the chromatin, only partial genes with altered epigenetic modifications change their mRNA expression, resulting in specific outcomes in cell differentiation and function. Therefore, elucidating epigenetic mechanisms underlying the regulation of ILCs will provide potential targets for the diagnosis and treatment of inflammatory diseases.

Crosstalk between the gut microbiota and innate lymphoid cells in intestinal mucosal immunity.

The human gastrointestinal mucosa is colonized by thousands of microorganisms, which participate in a variety of physiological functions. Intestinal dysbiosis is closely associated with the pathogenesis of several human diseases. Innate lymphoid cells (ILCs), which include NK cells, ILC1s, ILC2s, ILC3s and LTi cells, are a type of innate immune cells. They are enriched in the mucosal tissues of the body, and have recently received extensive attention. The gut microbiota and its metabolites play important roles in various intestinal mucosal diseases, such as inflammatory bowel disease (IBD), allergic disease, and cancer. Therefore, studies on ILCs and their interaction with the gut microbiota have great clinical significance owing to their potential for identifying pharmacotherapy targets for multiple related diseases. This review expounds on the progress in research on ILCs differentiation and development, the biological functions of the intestinal microbiota, and its interaction with ILCs in disease conditions in order to provide novel ideas for disease treatment in the future.

Deciphering the localization and trajectory of human natural killer cell development.

Innate immune cells represent the first line of cellular immunity, comprised of both circulating and tissue-resident natural killer cells and innate lymphoid cells. These innate lymphocytes arise from a common CD34+ progenitor that differentiates into mature natural killer cells and innate lymphoid cells. The successive stages in natural killer cell maturation are characterized by increased lineage restriction and changes to phenotype and function. Mechanisms of human natural killer cell development have not been fully elucidated, especially the role of signals that drive the spatial localization and maturation of natural killer cells. Cytokines, extracellular matrix components, and chemokines provide maturation signals and influence the trafficking of natural killer cell progenitors to peripheral sites of differentiation. Here we present the latest advances in our understanding of natural killer and innate lymphoid cell development in peripheral sites, including secondary lymphoid tissues (i.e. tonsil). Recent work in the field has provided a model for the spatial distribution of natural killer cell and innate lymphoid cell developmental intermediates in tissue and generated further insights into the developmental niche. In support of this model, future studies using multifaceted approaches seek to fully map the developmental trajectory of human natural killer cells and innate lymphoid cells in secondary lymphoid tissues.

Differential regulation of lineage-determining transcription factor expression in innate lymphoid cell and adaptive T helper cell subsets.

CD4 T helper (Th) cell subsets, including Th1, Th2 and Th17 cells, and their innate counterparts innate lymphoid cell (ILC) subsets consisting of ILC1s, ILC2s and ILC3s, display similar effector cytokine-producing capabilities during pro-inflammatory immune responses. These lymphoid cell subsets utilize the same set of lineage-determining transcription factors (LDTFs) for their differentiation, development and functions. The distinct ontogeny and developmental niches between Th cells and ILCs indicate that they may adopt different external signals for the induction of LDTF during lineage commitment. Increasing evidence demonstrates that many conserved cis-regulatory elements at the gene loci of LDTFs are often preferentially utilized for the induction of LDTF expression during Th cell differentiation and ILC development at different stages. In this review, we discuss the functions of lineage-related cis-regulatory elements in inducing T-bet, GATA3 or RORγt expression based on the genetic evidence provided in recent publications. We also review and compare the upstream signals involved in LDTF induction in Th cells and ILCs both in vitro and in vivo. Finally, we discuss the possible mechanisms and physiological importance of regulating LDTF dynamic expression during ILC development and activation.

Type 3 Innate Lymphoid Cells Protect Leukemic Blasts from Natural Killer Cell Cytotoxicity in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is an aggressive form of leukemia originating in the bone marrow (BM) with poor survival outcomes that has been largely resistant to modern cellular and targeted therapies. To improve therapeutic responses, a better understanding of how AML interacts with or evades immune cells is needed. Innate lymphoid cells (ILCs) are a recently discovered class of immune cells that exert their effector functions in an antigen-independent manner. This sentinel function of ILCs likely makes them among the first immune cell types to interact with leukemic blasts. Under homeostatic conditions, type 3 innate lymphoid cells (ILC3s) play important roles in regulating mucosal immunity through production of GM-CSF and IL-22, among others. In the setting of disease, ILC3s are not confined to mucosal tissues, as recent reports have demonstrated expansion of ILC3 populations in solid tumors (Carrega et al., 2015, Nat. Commun). However, the role of ILC3s in AML is unknown. Therefore, we sought to further study and characterize the role of ILC3s in AML biology. We began by utilizing a previously generated Mll-PTD;Flt3-ITD double knock-in murine model of AML that recapitulates human disease (Zorko et al., 2012, Blood). We conducted scRNA-seq analysis of the BM of leukemic mice compared to non-leukemic controls and observed clustering of a Lin-Eomes-Rorc+Il7r+ ILC3 population unique to the AML cohort that was absent in the control group (Figure 1). Furthermore, gene set enrichment analysis showed strong enrichment of an ILC3 gene signature in this cluster. We then validated this observation via flow cytometry and observed an 18.7-fold increase of ILC3s (Lin-Eomes-RORγt+CD127+) in the BM of leukemic mice relative to controls (1.31% +/- 0.20% AML vs 0.07% +/- 0.02% WT, n=5, p<0.001). Taken together, these data demonstrate ILC3 expansion in the leukemic marrow. We next sought to determine the mechanism(s) leading to expansion of this ILC3 population in AML. We have previously implicated skewed differentiation of a common ILC precursor (ILCP) as a mechanism of NK cell dysregulation in AML (Lordo et al., 2021, J Immunol). To determine whether AML cells are capable of skewing differentiation towards ILC3s, we isolated human ILCPs from healthy donor peripheral blood and cultured them under differentiating conditions with or without the AML cell lines U937 or MV411. We observed a significant increase in ILC3 frequency when co-cultured with AML cells (59.78% +/- 3.06% with U937, 57.84% +/- 2.87% with MV411 vs 28.02% +/- 3.89% alone, n=15, p <0.001). This observation was also recapitulated in the BM of a PDX model (23.91% +/- 3.89% with MV411 vs 3.22% +/- 1.01% without MV411, n=10; p<0.0001) and further validated with single cell clonal assays. Overall, these findings suggest ILC3 expansion in AML is due at least in part to skewing of ILC development. Finally, we wanted to characterize the functional consequences of ILC3s on AML cells. To begin to address this, we co-cultured human ILC3s (Lin-CD94-NKp44+) with the AML cell line U937 in transwells for 48 hours before subjecting the AML cells to a natural killer (NK) cell killing assay. We observed significantly reduced NK cell killing of AML cells when co-cultured with ILC3s compared to controls, suggesting ILC3s protect leukemic cells from NK-mediated killing (24.3% killing +/- 3.81% AML Alone vs 14.57% +/- 1.35% AML with ILC3, n=18, p<0.01). To determine what soluble factor(s) mediate this effect, we performed qRT-PCR on ILC3s following incubation with AML cells and found increases in GM-CSF and IL-22 expression in ILC3s relative to ILC3s cultured alone, which was also validated in our murine AML model. Furthermore, colony forming assays using the murine ILC3-like cell line MNK3 with LSKs (Lin-Sca1+Kit+) isolated from leukemic mice showed increased expression of myeloid markers (CD11b, CD11c, and Gr1) on LSK-derived cells when co-incubated with MNK3 cells relative to LSKs cultured alone. This finding suggests ILC3s may promote myeloid skewing of leukemic precursors. Our data create a novel working model of immune evasion in AML in which ILC3 expansion occurs via AML-mediated skewing of ILC development towards ILC3s which then protect AML blasts from NK cell immune surveillance. Current studies are continuing to study the relationship between ILC3s and AML and how to target these interactions to restore AML susceptibility to immune-mediated therapeutic targeting. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Purification of Bone Marrow Precursors to T Cells and ILCs.

T cells and innate lymphoid cells (ILCs) share expression of many key transcription factors during development and at mature stage, resulting in striking functional similarities between these lineages. Taking into account ILC contribution is thus necessary to appreciate T cell functions during immune responses. Furthermore, understanding ILC development and functions helps to understand T cells. Here we provide methods and protocols to isolate pure populations of multipotent precursors to T cells and innate lymphoid cells (ILCs) from adult mouse bone marrow, using flow cytometric sorting. These include precursors to all lymphocytes (viz., LMPPs and ALPs) and multipotent precursors to ILCs that have been recently refined (viz., specified EILPs, committed EILPs, and ILCPs).

Delta-like 4-Derived Notch Signals Differentially Regulate Thymic Generation of Skin-Homing CCR10+NK1.1+ Innate Lymphoid Cells at Neonatal and Adult Stages.

The thymus is a primary lymphoid organ for T cell development. Increasing evidence found that the thymus is also an important site for development of innate lymphoid cells (ILCs). ILCs generated in thymi acquire unique homing properties that direct their localization into barrier tissues such as the skin and intestine, where they help local homeostasis. Mechanisms underlying the developmental programming of unique tissue-homing properties of ILCs are poorly understood. We report in this article that thymic stroma-derived Notch signaling is differentially involved in thymic generation of a population of NK1.1+ group 1 ILCs (ILC1s) with the CCR10+ skin-homing property in adult and neonatal mice. We found that thymic generation of CCR10+NK1.1+ ILC1s is increased in T cell-deficient mice at adult, but not neonatal, stages, supporting the notion that a large number of developing T cells interfere with signals required for generation of CCR10+NK1.1+ ILC1s. In an in vitro differentiation assay, increasing Notch signals promotes generation of CCR10+NK1.1+ ILC1s from hematopoietic progenitors. Knockout of the Notch ligand Delta-like 4 in thymic stroma impairs generation of CCR10+NK1.1+ ILC1s in adult thymi, but development of CCR10+NK1.1+ ILC1s in neonatal thymi is less dependent on Delta-like 4-derived Notch signals. Mechanistically, the Notch signaling is required for proper expression of the IL-7R CD127 on thymic NK1.1+ ILC1s, and deficiency of CD127 also impairs thymic generation of CCR10+NK1.1+ ILC1s at adult, but not perinatal, stages. Our findings advanced understanding of regulatory mechanisms of thymic innate lymphocyte development.

Multiscale 3D genome organization underlies ILC2 ontogenesis and allergic airway inflammation.

Innate lymphoid cells (ILCs) are well-characterized immune cells that play key roles in host defense and tissue homeostasis. Yet, how the three-dimensional (3D) genome organization underlies the development and functions of ILCs is unknown. Herein, we carried out an integrative analysis of the 3D genome structure, chromatin accessibility and gene expression in mature ILCs. Our results revealed that the local 3D configuration of the genome is rewired specifically at loci associated with ILC biology to promote their development and functional differentiation. Importantly, we demonstrated that the ontogenesis of ILC2s and the progression of allergic airway inflammation are determined by a unique local 3D configuration of the region containing the ILC-lineage-defining factor Id2, which is characterized by multiple interactions between the Id2 promoter and distal regulatory elements bound by the transcription factors GATA-3 and RORα, unveiling the mechanism whereby the Id2 expression is specifically controlled in group 2 ILCs.

Circular RNA circTmem241 drives group III innate lymphoid cell differentiation via initiation of Elk3 transcription

Innate lymphoid cells (ILCs) exert important roles in host defense, tissue repair and inflammatory diseases. However, how ILC lineage specification is regulated remains largely elusive. Here we identify that circular RNA circTmem241 is highly expressed in group III innate lymphoid cells (ILC3s) and their progenitor cells. CircTmem241 deficiency impairs ILC3 commitment and attenuates anti-bacterial immunity. Mechanistically, circTmem241 interacts with Nono protein to recruit histone methyltransferase Ash1l onto Elk3 promoter in ILC progenitor cells (ILCPs). Ash1l-mediated histone modifications on Elk3 promoter enhance chromatin accessibility to initiate Elk3 transcription. Of note, circTmem241−/−, Nono−/− and Ash1l−/− ILCPs display impaired ILC3 differentiation, while Elk3 overexpression rescues ILC3 commitment ability. Finally, circTmem241−/−Elk3−/− mice show lower numbers of ILC3s and are more susceptible to bacterial infection. We reveal that the circTmem241-Nono-Ash1l-Elk3 axis is required for the ILCP differentiation into ILC3P and ILC3 maturation, which is important to manipulate this axis for ILC development on treatment of infectious diseases.

Organoids capture tissue-specific innate lymphoid cell development in mice and humans.

Organoid-based models of murine and human innate lymphoid cell precursor (ILCP) maturation are presented. First, murine intestinal and pulmonary organoids are harnessed to demonstrate that the epithelial niche is sufficient to drive tissue-specific maturation of all innate lymphoid cell (ILC) groups in parallel, without requiring subset-specific cytokine supplementation. Then, more complex human induced pluripotent stem cell (hiPSC)-based gut and lung organoid models are used to demonstrate that human epithelial cells recapitulate maturation of ILC from a stringent systemic human ILCP population, but only when the organoid-associated stromal cells are depleted. These systems offer versatile and reductionist models to dissect the impact of environmental and mucosal niche cues on ILC maturation. In the future, these could provide insight into how ILC activity and development might become dysregulated in chronic inflammatory diseases.

IL-18/IL-18R Signaling Is Dispensable for ILC Development But Constrains the Growth of ILCP/ILCs.

Innate lymphoid cells (ILCs) develop from ILC progenitors in the bone marrow. Various ILC precursors (ILCPs) with different ILC subset lineage potentials have been identified based on the expression of cell surface markers and ILC-associated key transcription factor reporter genes. This study characterized an interleukin (IL)-7Rα+IL-18Rα+ ILC progenitor population in the mouse bone marrow with multi-ILC lineage potential on the clonal level. Single-cell gene expression analysis revealed the heterogeneity of this population and identified several subpopulations with specific ILC subset-biased gene expression profiles. The role of IL-18 signaling in the regulation of IL-18Rα+ ILC progenitors and ILC development was further investigated using Il18- and Il18r1-deficient mice, in vitro differentiation assay, and adoptive transfer model. IL-18/IL-18R-mediated signal was found to not be required for early stages of ILC development. While Il18r1-/- lymphoid progenitors were able to generate all ILC subsets in vitro and in vivo like the wild-type counterpart, increased IL-18 level, as often occurred during infection or under stress, suppressed the growth of ILCP/ILC in an IL-18Ra-dependent manner via inhibiting proliferation and inducing apoptosis.

FOXO1 and FOXO3 Cooperatively Regulate Innate Lymphoid Cell Development.

Natural killer (NK) cells play roles in viral clearance and early surveillance against malignant transformation, yet our knowledge of the underlying mechanisms controlling their development and functions remain incomplete. To reveal cell fate-determining pathways in NK cell progenitors (NKP), we utilized an unbiased approach and generated comprehensive gene expression profiles of NK cell progenitors. We found that the NK cell program was gradually established in the CLP to preNKP and preNKP to rNKP transitions. In line with FOXO1 and FOXO3 being co-expressed through the NK developmental trajectory, the loss of both perturbed the establishment of the NK cell program and caused stalling in both NK cell development and maturation. In addition, we found that the combined loss of FOXO1 and FOXO3 caused specific changes to the composition of the non-cytotoxic innate lymphoid cell (ILC) subsets in bone marrow, spleen, and thymus. By combining transcriptome and chromatin profiling, we revealed that FOXO TFs ensure proper NK cell development at various lineage-commitment stages through orchestrating distinct molecular mechanisms. Combined FOXO1 and FOXO3 deficiency in common and innate lymphoid cell progenitors resulted in reduced expression of genes associated with NK cell development including ETS-1 and their downstream target genes. Lastly, we found that FOXO1 and FOXO3 controlled the survival of committed NK cells via gene regulation of IL-15Rβ (CD122) on rNKPs and bone marrow NK cells. Overall, we revealed that FOXO1 and FOXO3 function in a coordinated manner to regulate essential developmental genes at multiple stages during murine NK cell and ILC lineage commitment.

Development of Human ILCs and Impact of Unconventional Cytotoxic Subsets in the Pathophysiology of Inflammatory Diseases and Cancer.

Innate lymphoid cells (ILCs) were firstly described by different independent laboratories in 2008 as tissue-resident innate lymphocytes mirroring the phenotype and function of T helper cells. ILCs have been subdivided into three distinct subgroups, ILC1, ILC2 and ILC3, according to their cytokine and transcriptional profiles. Subsequently, also Natural Killer (NK) cells, that are considered the innate counterpart of cytotoxic CD8 T cells, were attributed to ILC1 subfamily, while lymphoid tissue inducer (LTi) cells were attributed to ILC3 subgroup. Starting from their discovery, significant advances have been made in our understanding of ILC impact in the maintenance of tissue homeostasis, in the protection against pathogens and in tumor immune-surveillance. However, there is still much to learn about ILC ontogenesis especially in humans. In this regard, NK cell developmental intermediates which have been well studied and characterized prior to the discovery of helper ILCs, have been used to shape a model of ILC ontogenesis. Herein, we will provide an overview of the current knowledge about NK cells and helper ILC ontogenesis in humans. We will also focus on the newly disclosed circulating ILC subsets with killing properties, namely unconventional CD56dim NK cells and cytotoxic helper ILCs, by discussing their possible role in ILC ontogenesis and their contribution in both physiological and pathological conditions.

IL-7 induces type 2 cytokine response in lung ILC2s and regulates GATA3 and CD25 expression.

Interleukin-7 is a cytokine with well-established roles in lymphocyte development and more recently, an expanded role in immune function. IL-7Rα is highly expressed by innate lymphoid cells (ILCs), but how IL-7 directs the development or function of ILCs is not well studied. Using mice with inducible deletion of IL-7Rα, we showed that loss of IL-7 signaling led to impaired production of IL-5, IL-13 and amphiregulin in lung ST2+ group 2 innate lymphoid cells (ILC2s) following influenza/A infection. Conversely, mice treated with IL-7 increased production of IL-5 and IL-13 by lung ILC2s. Moreover, we showed that IL-7 enhanced GATA3 and CD25 expression in ILC2s and loss of IL-7 signaling led to their reduced expression. Altogether, this study demonstrates that IL-7 regulates the function of ILC2s during airway viral infection and induces GATA3 and CD25 expression.

E3 Ubiquitin Ligase Cbl-b Inhibits Type 2 Innate Lymphoid Cell Development by Targeting ST2 for Ubiquitination

Abstract Type 2 innate lymphoid cells (ILC2) play a crucial role in driving allergic airway inflammation, but the regulation of ILC2 development is not fully understood. Previously we have shown that E3 ubiquitin ligase Cbl-b negatively regulates Th2 response, but whether Cbl-b also regulates ILC2-mediated type 2 immunity remains to be defined. In this study, we found that Rag1−/−Cblb−/− mice are hypersensitive to inhalation of A. Fumigatus, a fungus that causes allergic asthma, as revealed by heightened airway hyperresponsiveness (AHR), increased airway inflammation, and mucus production. This hypersensitivity is associated with increased frequencies of ILC2 and eosinophils, but reduced frequency of alveolar macrophages in the lungs. Consistent with this, type 2 cytokines are also increased in the lung homogenates of Rag1−/−Cblb−/− mice. At the molecular level, ST2 undergoes ubiquitination and proteasome-mediated degradation upon IL-33 stimulation, which is abrogated in cells expressing Cbl-b C373A mutant. Therefore, our data indicate that Cbl-b inhibits the development of ILC2 and ILC2-mediated airway inflammation by targeting ST2 for ubiquitination. Supported by NIH R01 AI090901, AI121196, and AI123253

The TOX subfamily: all-round players in the immune system.

The thymocyte selection-related HMG box protein (TOX) subfamily comprises evolutionarily conserved DNA-binding proteins, and is expressed in certain immune cell subsets and plays key roles in the development of CD4+ T cells, innate lymphoid cells (ILCs), T follicular helper (Tfh) cells, and in CD8+ T-cell exhaustion. Although its roles in CD4+ T and natural killer (NK) cells have been extensively studied, recent findings have demonstrated previously unknown roles for TOX in the development of ILCs, Tfh cells, as well as CD8+ T-cell exhaustion; however, the molecular mechanism underlying TOX regulation of these immune cells remains to be elucidated. In this review, we discuss recent studies on the influence of TOX on the development of various immune cells and CD8+ T-cell exhaustion and the roles of specific TOX family members in the immune system. Moreover, this review suggests candidate regulatory targets for cell therapy and immunotherapies.

Intestinal fibroblastic reticular cell niches control innate lymphoid cell homeostasis and function

Innate lymphoid cells (ILCs) govern immune cell homeostasis in the intestine and protect the host against microbial pathogens. Various cell-intrinsic pathways have been identified that determine ILC development and differentiation. However, the cellular components that regulate ILC sustenance and function in the intestinal lamina propria are less known. Using single-cell transcriptomic analysis of lamina propria fibroblasts, we identify fibroblastic reticular cells (FRCs) that underpin cryptopatches (CPs) and isolated lymphoid follicles (ILFs). Genetic ablation of lymphotoxin-β receptor expression in Ccl19-expressing FRCs blocks the maturation of CPs into mature ILFs. Interactome analysis shows the major niche factors and processes underlying FRC-ILC crosstalk. In vivo validation confirms that a sustained lymphotoxin-driven feedforward loop of FRC activation including IL-7 generation is critical for the maintenance of functional ILC populations. In sum, our study indicates critical fibroblastic niches within the intestinal lamina propria that control ILC homeostasis and functionality and thereby secure protective gut immunity.

ILC Differentiation from Progenitors in the Bone Marrow.

Innate lymphoid cells (ILCs) are a family of immune cells that possess similar functions as T cells. We review steps of central ILC development in the bone marrow of adult mice and discuss recent evidence for peripheral ILC development suggesting extramedullary sites of ILC development. We also assess the contribution of development during different phases of life towards shaping the composition of the adult ILC pool. Finally, we briefly review the local cues that lead to heterogeneity of ILCs between tissues. We propose that tissue-resident ILC progenitors may economically allow tissues to elicit rapid expansion of specific ILC types that are needed based on the nature of antigenic assaults in tissues.

Interaction Between Innate Lymphoid Cells and the Nervous System.

The interaction between the immune system and the nervous system remains an intriguing enigma. Recent studies indicate that innate lymphoid cells (ILCs), a unique family of innate effector cells, participate in intense cross talk with the nervous system. In the mucosal barrier sites, ILCs have been found to co-localize with neurons, nerves, glial cell projectors, and neuroendocrine cells. The cross talk between ILCs and peripheral nervous system orchestrates mucosal homeostasis and immunity. In addition, the barrier tissues of the central nervous system (CNS) also provide conductive microenvironment for ILC development and maintenance. Activities of CNS-associated ILCs impact the outcome of various CNS disorders. In this chapter, we review and discuss the intricate and bidirectional interaction between ILCs and nervous system.