The biology of innate lymphoid cells

The interplay between innate lymphoid cells and microbiota

Innate lymphoid cells (ILCs) are mainly resident in mucosal tissues such as gastrointestinal tract and respiratory tract, so they are closely linked to the microbiota. ILCs can protect commensals to maintain homeostasis and increase resistance to pathogens. Moreover, ILCs also play an early role in defense against a variety of pathogenic microorganisms including pathogenic bacteria, viruses, fungi and parasites, before the intervention of adaptive immune system. Due to the lack of adaptive antigen receptors expressed on T cells and B cells, ILCs need to use other means to sense the signals of microbiota and play a role in corresponding regulation. In this review, we focus on and summarize three major mechanisms used in the interaction between ILCs and microbiota: the mediation of accessory cells represented by dendritic cells; the metabolic pathways of microbiota or diet; the participation of adaptive immune cells.

Prediction of distinct populations of innate lymphoid cells by transcriptional profiles

Innate lymphoid cells (ILCs) are a unique type of lymphocyte that differ from adaptive lymphocytes in that they lack antigen receptors, which primarily reside in tissues and are closely associated with fibers. Despite their plasticity and heterogeneity, identifying ILCs in peripheral blood can be difficult due to their small numbers. Accurately and rapidly identifying ILCs is critical for studying homeostasis and inflammation. To address this challenge, we collect single-cell RNA-seq data from 647 patients, including 26,087 transcripts. Background screening, Lasso analysis, and principal component analysis (PCA) are used to select features. Finally, we employ a deep neural network to classify lymphocytes. Our method achieved the highest accuracy compared to other approaches. Furthermore, we identified four genes that play a vital role in lymphocyte development. Adding these gene transcripts into model, we were able to increase the model's AUC. In summary, our study demonstrates the effectiveness of using single-cell transcriptomic analysis combined with machine learning techniques to accurately identify congenital lymphoid cells and advance our understanding of their development and function in the body.

Transcription factor TCF-1 regulates the functions, but not the development, of lymphoid tissue inducer subsets in different tissues

Lymphoid tissue inducer (LTi) cells, a subset of innate lymphoid cells (ILCs), play an essential role in the formation of secondary lymphoid tissues. However, the regulation of the development and functions of this ILC subset is still elusive. In this study, we report that the transcription factor T cell factor 1 (TCF-1), just as GATA3, is indispensable for the development of non-LTi ILC subsets. While LTi cells are still present in TCF-1-deficient mice, the organogenesis of Peyer's patches (PPs), but not of lymph nodes, is impaired in these mice. LTi cells from different tissues have distinct gene expression patterns, and TCF-1 regulates the expression of lymphotoxin specifically in PP LTi cells. Mechanistically, TCF-1 may directly and/or indirectly regulate Lta, including through promoting the expression of GATA3. Thus, the TCF-1-GATA3 axis, which plays an important role during T cell development, also critically regulates the development of non-LTi cells and tissue-specific functions of LTi cells.

Beyond αβ T cells: NK, iNKT, and γδT cell biology in leukemic patients and potential for off-the-shelf adoptive cell therapies for AML

Acute myeloid leukemia (AML) remains an elusive disease to treat, let alone cure, even after highly intensive therapies such as stem cell transplants. Adoptive cell therapeutic strategies based on conventional alpha beta (αβ)T cells are an active area of research in myeloid neoplasms given their remarkable success in other hematologic malignancies, particularly B-cell-derived acute lymphoid leukemia, myeloma, and lymphomas. Several limitations have hindered clinical application of adoptive cell therapies in AML including lack of leukemia-specific antigens, on-target-off-leukemic toxicity, immunosuppressive microenvironments, and leukemic stem cell populations elusive to immune recognition and destruction. While there are promising T cell-based therapies including chimeric antigen receptor (CAR)-T designs under development, other cytotoxic lymphocyte cell subsets have unique phenotypes and capabilities that might be of additional benefit in AML treatment. Of particular interest are the natural killer (NK) and unconventional T cells known as invariant natural killer T (iNKT) and gamma delta (γδ) T cells. NK, iNKT, and γδT cells exhibit intrinsic anti-malignant properties, potential for alloreactivity, and human leukocyte-antigen (HLA)-independent function. Here we review the biology of each of these unconventional cytotoxic lymphocyte cell types and compare and contrast their strengths and limitations as the basis for adoptive cell therapies for AML.

Transcriptional and chromatin profiling of human blood innate lymphoid cell subsets sheds light on HIV-1 pathogenesis

Innate lymphoid cells (ILCs) are a diverse population of cells that include NK cells and contribute to tissue homeostasis and repair, inflammation, and provide protection from infection. The interplay between human blood ILCs, as well as their responses to HIV-1 infection, remains poorly understood. This study used transcriptional and chromatin profiling to explore these questions. Transcriptional profiling and flow cytometry analysis support that there are four main ILC subsets found in human blood. Unlike in mice, human NK cells expressed the tissue repair protein amphiregulin (AREG). AREG production was induced by TCF7/WNT, IL-2, and IL-15, and inhibited by TGFB1, a cytokine increased in people living with HIV-1. In HIV-1 infection, the percentage of AREG+ NK cells correlated positively with the numbers of ILCs and CD4+ T cells but negatively with the concentration of inflammatory cytokine IL-6. NK-cell knockout of the TGFB1-stimulated WNT antagonist RUNX3 increased AREG production. Antiviral gene expression was increased in all ILC subsets from HIV-1 viremic people, and anti-inflammatory gene MYDGF was increased in an NK-cell subset from HIV-1-infected people whose viral load was undetectable in the absence of antiretroviral therapy. The percentage of defective NK cells in people living with HIV-1 correlated inversely with ILC percentage and CD4+ T-cell counts. CD4+ T cells and their production of IL-2 prevented the loss of NK-cell function by activating mTOR. These studies clarify how ILC subsets are interrelated and provide insight into how HIV-1 infection disrupts NK cells, including an uncharacterized homeostatic function in NK cells.

IL-17: Balancing Protective Immunity and Pathogenesis

The biological role of interleukin 17 (IL-17) has been explored during recent decades and identified as a pivotal player in coordinating innate and adaptive immune responses. Notably, IL-17 functions as a double-edged sword with both destructive and protective immunological roles. While substantial progress has implicated unrestrained IL-17 in a variety of infectious diseases or autoimmune conditions, IL-17 plays an important role in protecting the host against pathogens and maintaining physiological homeostasis. In this review, we describe canonical IL-17 signaling mechanisms promoting neutrophils recruitment, antimicrobial peptide production, and maintaining the epithelium barrier integrity, as well as some noncanonical mechanisms involving IL-17 that elicit protective immunity.

Immunomodulatory effects of inulin and its intestinal metabolites

"Dietary fiber" (DF) refers to a type of carbohydrate that cannot be digested fully. DF is not an essential nutrient, but it plays an important part in enhancing digestive capacity and maintaining intestinal health. Therefore, DF supplementation in the daily diet is highly recommended. Inulin is a soluble DF, and commonly added to foods. Recently, several studies have found that dietary supplementation of inulin can improve metabolic function and regulate intestinal immunity. Inulin is fermented in the colon by the gut microbiota and a series of metabolites is generated. Among these metabolites, short-chain fatty acids provide energy to intestinal epithelial cells and participate in regulating the differentiation of immune cells. Inulin and its intestinal metabolites contribute to host immunity. This review summarizes the effect of inulin and its metabolites on intestinal immunity, and the underlying mechanisms of inulin in preventing diseases such as type 2 diabetes mellitus, inflammatory bowel disease, chronic kidney disease, and certain cancer types.

Diet-mediated constitutive induction of novel IL-4+ ILC2 cells maintains intestinal homeostasis in mice

Group 2 innate lymphoid cells (ILC2s) expressing IL-5 and IL-13 are localized at various mucosal tissues and play critical roles in the induction of type 2 inflammation, response to helminth infection, and tissue repair. Here, we reveal a unique ILC2 subset in the mouse intestine that constitutively expresses IL-4 together with GATA3, ST2, KLRG1, IL-17RB, and IL-5. In this subset, IL-4 expression is regulated by mechanisms similar to but distinct from those observed in T cells and is partly affected by IL-25 signaling. Although the absence of the microbiota had marginal effects, feeding mice with a vitamin B1-deficient diet compromised the number of intestinal IL-4+ ILC2s. The decrease in the number of IL-4+ ILC2s caused by the vitamin B1 deficiency was accompanied by a reduction in IL-25-producing tuft cells. Our findings reveal that dietary vitamin B1 plays a critical role in maintaining interaction between tuft cells and IL-4+ ILC2s, a previously uncharacterized immune cell population that may contribute to maintaining intestinal homeostasis.

Cxxc finger protein 1 maintains homeostasis and function of intestinal group 3 innate lymphoid cells with aging

Aging is accompanied by homeostatic and functional dysregulation of multiple immune cell subsets. Group 3 innate lymphoid cells (ILC3s) constitute a heterogeneous cell population that plays pivotal roles in intestinal immunity. In this study, we found that ILC3s in aged mice exhibited dysregulated homeostasis and function, leading to bacterial and fungal infection susceptibility. Moreover, our data revealed that the enrichment of the H3K4me3 modification in effector genes of aged gut CCR6+ ILC3s was specifically decreased compared to young mice counterparts. Disruption of Cxxc finger protein 1 (Cxxc1) activity, a key subunit of H3K4 methyltransferase, in ILC3s led to similar aging-related phenotypes. An integrated analysis revealed Kruppel-like factor 4 (Klf4) as a potential Cxxc1 target. Klf4 overexpression partially restored the differentiation and functional defects seen in both aged and Cxxc1-deficient intestinal CCR6+ ILC3s. Therefore, these data suggest that targeting intestinal ILC3s may provide strategies to protect against age-related infections.

The enrichment of Arg1+ILC2s and ILCregs facilitates the progression of endometriosis: A preliminary study

Innate lymphoid cells (ILCs) are a kind of lymphocytes that reside in the tissue and have an essential function in the immune microenvironment. However, the relationship between endometriosis (EMS) and ILCs is complex and not fully understood. This study examines several groups of ILCs in the peripheral blood (PB), peritoneal fluid (PF) and endometrium of patients with EMS via flow cytometry. The study observed an increase in PB ILCs, particularly ILC2s and ILCregs subsets and Arg1+ILC2s in the EMS patients were highly activated. EMS patients had significantly higher levels of serum interleukin (IL)-10/33/25 compared to controls. We also found an elevation of Arg1+ILC2s in the PF and higher levels of ILC2s and ILCregs in ectopic endometrium compared with eutopic. Importantly, a positive correlation was observed between the enrichment of Arg1+ILC2s and ILCregs in the PB of EMS patients. The findings indicate that the involvement of Arg1+ILC2s and ILCregs fosters potentially endometriosis progression.

Intestinal Immune Imbalance is an Alarm in the Development of IBD

Immune regulation plays a crucial role in human health and disease. Inflammatory bowel disease (IBD) is a chronic relapse bowel disease with an increasing incidence worldwide. Clinical treatments for IBD are limited and inefficient. However, the pathogenesis of immune-mediated IBD remains unclear. This review describes the activation of innate and adaptive immune functions by intestinal immune cells to regulate intestinal immune balance and maintain intestinal mucosal integrity. Changes in susceptible genes, autophagy, energy metabolism, and other factors interact in a complex manner with the immune system, eventually leading to intestinal immune imbalance and the onset of IBD. These events indicate that intestinal immune imbalance is an alarm for IBD development, further opening new possibilities for the unprecedented development of immunotherapy for IBD.

Prognosis and therapeutic benefits prediction based on NK cell marker genes through single-cell RNA-seq with integrated bulk RNA-seq analysis for hepatocellular carcinoma

Tumor-infiltrating immune cells greatly participate in regulating tumorigenesis and metastasis of hepatocellular carcinoma (HCC). Natural killer cell, as an important role of innate immunity, plays an indispensable role in antitumor immunity and regulate tumor development. In this study, we firstly identified 251 NK cell marker genes of HCC based on single-cell RNA sequencing data. Subsequently, an NK cell marker genes-related prognostic signature (NKPS) was developed in the cancer genome atlas (TCGA) cohort for risk stratification and prognosis prediction. The predictive value of the NKPS in prognosis was well validated in different clinical subgroups and three external datasets (ICGC-LIHC cohort, GSE14520 cohort and Guilin cohort). Moreover, multivariate analysis revealed the independent prognostic value of NKPS for OS in HCC. Further functional analysis indicated the NKPS was associated with basic cellular processes, that may contribute to the development and progression of HCC. Thereafter, immune characteristics as well as the therapeutic benefits in NKPS risk score-defined subgroups were analyzed. Patients with low-risk score exhibited immune-active status, manifested as higher immune scores, more infiltration of CD8+ T cells and macrophage M1, and higher T-cell receptor (TCR) richness and diversity. Remarkably, the NKPS was negatively correlated with immunotherapy response-related signatures. In addition, the low-risk group exhibited significantly improved therapeutic benefits, either from immunotherapy or traditional chemotherapy and target therapy. Overall, the NKPS showed an excellent predictive value for prognosis and therapeutic responses for HCC, which might also provide novel insights into better HCC management strategies.

The Emerging Role of Innate Lymphoid Cells (ILCs) and Alarmins in Celiac Disease: An Update on Pathophysiological Insights, Potential Use as Disease Biomarkers, and Therapeutic Implications

Celiac disease (CD) is an intestinal disease that develops in genetically predisposed individuals and is triggered by the ingestion of gluten. CD was considered a Th1-disease. Today, the role of Th17, IL-21, and IL-17A lymphocytes is well known. Inflammation is regulated by the activity of gluten-specific CD4+ T lymphocytes that produce pro-inflammatory cytokines, including IFN-γ, TNF-α, and IL-21, perpetuating the Th1 response. These cytokines determine an inflammatory state of the small intestine, with consequent epithelial infiltration of lymphocytes and an alteration of the architecture of the duodenal mucosa. B cells produce antibodies against tissue transglutaminase and against deamidated gliadin. Although the role of the adaptive immune response is currently known, the evidence about the role of innate immunity cells is still poorly understood. Epithelial damage determines the release of damage-associated molecular patterns (DAMPs), also known as alarmins. Together with the intestinal epithelial cells and the type 1 innate lymphoid cells (ILC1s), alarmins like TSLP, IL-33, and HMGB1 could have a fundamental role in the genesis and maintenance of inflammation. Our study aims to evaluate the evidence in the literature about the role of ILCs and alarmins in celiac disease, evaluating the possible future diagnostic and therapeutic implications.

Monitoring Group 2 Innate Lymphoid Cell Biology in Models of Lung Inflammation

Innate lymphoid cells (ILCs) are a rare cell population subdivided into ILC1s, ILC2s, and ILC3s, based on transcription factor expression and cytokine production. In models of lung inflammation, the release of alarmins from the epithelium activates ILC2s and promotes the production of Th2-cytokines and the proliferation and migration of ILC2s within the lung. ILC2s are the innate counterpart to CD4⁺ Th2s and, as such, express Gata-3 and produce IL-4, IL-5, and IL-13. Due to the low number of ILCs and the lack of specific surface markers, flow cytometry is the most reliable technique for the identification and characterization of ILCs. In this protocol, multicolor flow cytometry is utilized to identify Lineage- Thy1.2+ ILCs. Intracellular cytokine staining further identifies ILC2s within the lung. This protocol presents a reliable method for promoting ILC2-mediated lung inflammation and for monitoring ILC2 biology. Key features In this protocol, ILC2s are expanded via intranasal challenges withAlternaria alternata, a fungal allergen, or recombinant IL-33. Bronchoalveolar lavage (BAL) and lung are collected and processed into single-cell suspension for multicolor flow cytometric analysis, including intracellular staining of transcription factors and cytokines. During lung inflammation, the percentage of ILC2s and eosinophils increases. ILC2s express greater levels ofGata-3andKi-67and produce greater amounts of IL-5 and IL-13. Graphical overview.

Enteric glia at center stage of inflammatory bowel disease

Although our understanding of the pathophysiology of inflammatory bowel disease (IBD) is increasing, the expanding body of knowledge does not simplify the equation but rather reveals diverse, interconnected, and complex mechanisms in IBD. In addition to immune overactivation, defects in intestinal epithelial barrier (IEB) functioning, dysbiosis, and structural and functional abnormalities of the enteric nervous system are emerging as new elements contributing to the development of IBD. In addition to molecular changes in IBD, enteric glia from patients with Crohn's disease (CD) exhibits the inability to strengthen the IEB; these defects are not observed in patients with ulcerative colitis. In addition, there is a growing body of work describing that enteric glia interacts with not only enterocytes and enteric neurons but also other local cellular neighbours. Thus, because of their functions as connectors and regulators of immune cells, IEB, and microbiota, enteric glia could be the keystone of digestive homeostasis that is lacking in patients with CD.

Valero's host index is useful in predicting radiation-induced trismus and osteoradionecrosis of the jaw risks in locally advanced nasopharyngeal carcinoma patients

BACKGROUND

In the absence of previous research, we sought to assess the H-Index's predictive significance for radiation-induced trismus (RIT) and osteoradionecrosis of the jaw (ORNJ) in patients with locally advanced nasopharyngeal carcinoma (LA-NPC) receiving concurrent chemoradiotherapy (C-CRT).

PATIENTS AND METHODS

The research comprised 295 LA-NPC patients who had C-CRT and pre- and post-C-CRT oral exams between June 2010 and December 2021. The H-Index was calculated using neutrophils, monocytes, lymphocytes, hemoglobin, and albumin measurements obtained on the first day of C-CRT. Patients were divided into three and two H-index groups, respectively, based on previously established cutoff values (1.5 and 3.5) and the cutoff value determined by our receiver operating characteristic (ROC) curve analysis. The primary objective was the presence of any significant connections between pretreatment H-Index groups and post-C-CRT RIT and ORNJ rates.

RESULTS

RIT and ORNJ was diagnosed in 46 (15.6%) and 13 (7.8%) patients, respectively. The original H-Index grouping could only categorize RIT and ORNJ risks at a cutoff value of 3.5, with no significant differences in RIT and ORNJ rates between groups with H-Index 1.5 and 1.5 to 3.5 (P < 0.05 for each). The ideal H-Index cutoff for both RIT and ORNJ rates was found to be 5.5 in ROC curve analysis, which divided the entire research population into two groups: H-Index ≤ 5.5 (N = 195) and H-Index > 5.5 (N = 110). Intergroup comparisons revealed that patients in the H-Index > 5.5 group had significantly higher rates of either RIT (31.8% vs. 5.9%; P < 0.001) or ORNJ (17.3% vs. 2.2%; P < 0.001) than their H-Index ≤ 5.5 counterparts. The results of the multivariate analysis showed that H-Index > 5.5 was independently linked to significantly higher RIT (P < 0.001) and ORNJ (P < 0.001) rates.

CONCLUSION

Pre-C-CRT H-Index > 5.5 is associated with significantly increased RIT and ORNJ rates in LA-NPC patients receiving definitive C-CRT.

Parallel origins and functions of T cells and ILCs

Innate lymphoid cells (ILCs) are tissue resident cells that are triggered through a relatively broad spectrum of alarmins, inflammatory cues, neuropeptides, and hormones. Functionally, ILCs are akin to subsets of helper T cells and are characterized by a similar effector cytokine profile. They also share a dependency on many of the same essential transcription factors identified for the maintenance and survival of T cells. The key distinguishing factor between the ILC family and T cells is the lack of antigen-specific T cell receptor (TCR) on ILCs and, thus, they can be considered the "ultimate invariant T cells". ILCs, like T cells, orchestrate downstream effector inflammatory responses by adjusting the cytokine microenvironment in a fashion that promotes protection, health, and homeostasis at mucosal barrier sites. But also, like T cells, ILCs have recently been implicated in several pathological inflammatory disease states. This review focuses on the selective role of ILCs in the development of allergic airway inflammation (AAI) and fibrosis in the gut where a complex ILC interplay has been shown to either attenuate or worsen disease. Finally, we discuss new data on TCR gene rearrangements in subsets of ILCs that challenge the current dogma linking their origin to committed bone marrow progenitors and instead propose a thymic origin for at least some ILCs. In addition, we highlight how naturally occurring TCR rearrangements and the expression of major histocompatibility (MHC) molecules in ILCs provide a useful natural barcode for these cells and may prove instrumental in studying their origins and plasticity.

Inflammatory Cues Direct Skin-Resident Type 1 Innate Lymphoid Cells to Adopt a Psoriasis-Promoting Identity

Innate lymphoid cells (ILCs) are gatekeepers in barrier organs, where they maintain tissue integrity and contribute to host defense as well as tissue repair. Inappropriate activation of ILCs, however, can lead to immunopathology with detrimental results. In this study, we focused on type 1 ILCs (ILC1s), which under inflammatory conditions constitute a poorly defined population with ambiguous functions. To delineate the properties of ILC1s in skin pathology, we used the well-established mouse model of imiquimod-induced psoriasis. Although ILC1s represented a minority among cutaneous lymphocytes in vehicle-treated controls, they rapidly expanded during early psoriasis and ultimately increased by >20-fold. This rapid increase was verified using two additional psoriasis models. Inflammatory ILC1s from imiquimod-treated skin were defined as CD44+, CXCR6+, and CD11b+ and substantially contributed to TNF-α and GM-CSF production, rendering them a potential candidate to shape the inflammatory infiltrate. In accordance with the psoriasis-specific microenvironment, skin ILC1s upregulated the IL-23 receptor whereas expression of the IL-12Rβ2 subunit was diminished. As a consequence, neutralization of IL-12 only had a minor impact, whereas blocking IL-23 reduced both ILC1 abundance and disease severity. Together, our findings identify skin ILC1s as a likely player in early psoriasis and a prospective target for therapeutic approaches.

Alcohol-mediated susceptibility to lung fibrosis is associated with group 2 innate lymphoid cells in mice

Chronic alcohol ingestion promotes acute lung injury and impairs immune function. However, the mechanisms involved are incompletely understood. Here, we show that alcohol feeding enhances bleomycin-induced lung fibrosis and inflammation via the regulation of type 2 innate immune responses, especially by group 2 innate lymphoid cells (ILC2s). Neuroimmune interactions have emerged as critical modulators of lung inflammation. We found alcohol consumption induced the accumulation of ILC2 and reduced the production of the neuropeptide calcitonin gene-related peptide (CGRP), primarily released from sensory nerves and pulmonary neuroendocrine cells (PNECs). CGRP potently suppressed alcohol-driven type 2 cytokine signals in vivo. Vagal ganglia TRPV1+ afferents mediated immunosuppression occurs through the release of CGRP. Inactivation of the TRPV1 receptor enhanced bleomycin-induced fibrosis. In addition, mice lacking the CGRP receptor had the increased lung inflammation and fibrosis and type 2 cytokine production as well as exaggerated responses to alcohol feeding. Together, these data indicate that alcohol consumption regulates the interaction of CGRP and ILC2, which is a critical contributor of lung inflammation and fibrosis.

In vitro models to study natural killer cell dynamics in the tumor microenvironment

Immunotherapy is revolutionizing cancer therapy. The rapid development of new immunotherapeutic strategies to treat solid tumors is posing new challenges for preclinical research, demanding novel in vitro methods to test treatments. Such methods should meet specific requirements, such as enabling the evaluation of immune cell responses like cytotoxicity or cytokine release, and infiltration into the tumor microenvironment using cancer models representative of the original disease. They should allow high-throughput and high-content analysis, to evaluate the efficacy of treatments and understand immune-evasion processes to facilitate development of new therapeutic targets. Ideally, they should be suitable for personalized immunotherapy testing, providing information for patient stratification. Consequently, the application of in vitro 3-dimensional (3D) cell culture models, such as tumor spheroids and organoids, is rapidly expanding in the immunotherapeutic field, coupled with the development of novel imaging-based techniques and -omic analysis. In this paper, we review the recent advances in the development of in vitro 3D platforms applied to natural killer (NK) cell-based cancer immunotherapy studies, highlighting the benefits and limitations of the current methods, and discuss new concepts and future directions of the field.

GATA3 induces the pathogenicity of Th17 cells via regulating GM-CSF expression

T-bet-expressing Th17 (T-bet+RORγt+) cells are associated with the induction of pathology during experimental autoimmune encephalomyelitis (EAE) and the encephalitic nature of these Th17 cells can be explained by their ability to produce GM-CSF. However, the upstream regulatory mechanisms that control Csf2 (gene encoding GM-CSF) expression are still unclear. In this study, we found that Th17 cells dynamically expressed GATA3, the master transcription factor for Th2 cell differentiation, during their differentiation both in vitro and in vivo. Early deletion of Gata3 in three complimentary conditional knockout models by Cre-ERT2, hCd2 Cre and Tbx21 Cre, respectively, limited the pathogenicity of Th17 cells during EAE, which was correlated with a defect in generating pathogenic T-bet-expressing Th17 cells. These results indicate that early GATA3-dependent gene regulation is critically required to generate a de novo encephalitogenic Th17 response. Furthermore, a late deletion of Gata3 via Cre-ERT2 in the adoptive transfer EAE model resulted in a cell intrinsic failure to induce EAE symptoms which was correlated with a substantial reduction in GM-CSF production without affecting the generation and/or maintenance of T-bet-expressing Th17 cells. RNA-Seq analysis of Gata3-sufficient and Gata3-deficient CNS-infiltrating CD4+ effector T cells from mixed congenic co-transfer recipient mice revealed an important, cell-intrinsic, function of GATA3 in regulating the expression of Egr2, Bhlhe40, and Csf2. Thus, our data highlights a novel role for GATA3 in promoting and maintaining the pathogenicity of T-bet-expressing Th17 cells in EAE, via putative regulation of Egr2, Bhlhe40, and GM-CSF expression.

Attenuation of immune activation in patients with multiple sclerosis on a wheat-reduced diet: a pilot crossover trial

Background

Western lifestyle has been associated with an increase in relapsing-remitting multiple sclerosis (RRMS). In mice, dietary wheat amylase-trypsin inhibitors (ATIs) activate intestinal myeloid cells and augment T cell-mediated systemic inflammation.

Objective

The aim of this study was to assess whether a wheat- and thus ATI-reduced diet might exert beneficial effects in RRMS patients with modest disease activity.

Methods

In this 6-month, crossover, open-label, bicentric proof-of-concept trial, 16 RRMS patients with stable disease course were randomized to either 3 months of a standard wheat-containing diet with consecutive switch to a > 90% wheat-reduced diet, or vice versa.

Results

The primary endpoint was negative, as the frequency of circulating pro-inflammatory T cells did not decrease during the ATI-reduced diet. We did, however, observe decreased frequencies of CD14+ CD16++ monocytes and a concomitant increase in CD14++ CD16- monocytes during the wheat-reduced diet interval. This was accompanied by an improvement in pain-related quality of life in health-related quality of life assessed (SF-36).

Conclusion

Our results suggest that the wheat- and thus ATI-reduced diet was associated with changes in monocyte subsets and improved pain-related quality of life in RRMS patients. Thus, a wheat (ATI)-reduced diet might be a complementary approach accompanying immunotherapy for some patients.

Registration

German Clinical Trial Register (No. DRKS00027967).

Role of epigenetics in innate lymphoid cells

Epigenetics plays a crucial role in gene regulation and cell function without changing the DNA sequence. The process of differentiation in eukaryotes during cellular morphogenesis is a paradigm of epigenetic change; stem cells develop into pluripotent cell lines in the embryo, eventually becoming terminally developed cells. Recently, epigenetic changes were shown to play an important role in immune cell development, activation and differentiation, which impacts chromatin remodeling, DNA methylation, post-translational histone modifications and small or lncRNA engagement. Innate lymphoid cells (ILCs) are newly identified immune cells that lack antigen receptors. ILCs differentiate from hematopoietic stem cells via multipotent progenitor stages. In this editorial, the authors discuss the epigenetic regulation of ILC differentiation and function.

The Functional Role of Group 2 Innate Lymphoid Cells in Asthma

Asthma is a heterogeneous disease characterized by chronic airway inflammation. Group 2 innate lymphoid cells (ILC2) play an important role in the pathogenesis of asthma. ILC2s lack antigen-specific receptors and respond to epithelial-derived cytokines, leading to the induction of airway eosinophilic inflammation in an antigen-independent manner. Additionally, ILC2s might be involved in the mechanism of steroid resistance. Numerous studies in both mice and humans have shown that ILC2s induce airway inflammation through inflammatory signals, including cytokines and other mediators derived from immune or non-immune cells. ILC2s and T helper type 2 (Th2) cells collaborate through direct and indirect interactions to organize type 2 immune responses. Interestingly, the frequencies or numbers of ILC2 are increased in the blood and bronchoalveolar lavage fluid of asthma patients, and the numbers of ILC2s in the blood and sputum of severe asthmatics are significantly larger than those of mild asthmatics. These findings may contribute to the regulation of the immune response in asthma. This review article highlights our current understanding of the functional role of ILC2s in asthma.

ILC2s control obesity by regulating energy homeostasis and browning of white fat

Innate lymphoid cells (ILCs) have been a hot topic in recent research, they are widely distributed in vivo and play an important role in different tissues. The important role of group 2 innate lymphoid cells (ILC2s) in the conversion of white fat into beige fat has attracted widespread attention. Studies have shown that ILC2s regulate adipocyte differentiation and lipid metabolism. This article reviews the types and functions of ILCs, focusing on the relationship between differentiation, development and function of ILC2s, and elaborates on the relationship between peripheral ILC2s and browning of white fat and body energy homeostasis. This has important implications for the future treatment of obesity and related metabolic diseases.

Deciphering immune microenvironment and cell evasion mechanisms in human gliomas

Gliomas are considered one of the most malignant cancers in the body. Despite current therapies, including surgery, chemotherapy, and radiotherapy, these tumors usually recur with more aggressive and resistant phenotypes. Indeed, the survival following these conventional therapies is very poor, which makes immunotherapy the subject of active research at present. The anti-tumor immune response could also be considered a prognostic factor since each stage of cancer development is regulated by immune cells. However, glioma microenvironment contains malignant cells that secrete numerous chemokines, cytokines and growth factors, promoting the infiltration of immunosuppressive cells into the tumor, which limit the functioning of the immune system against glioma cells. Recently, researchers have been able to reverse the immune resistance of cancer cells and thus activate the anti-tumor immune response through different immunotherapy strategies. Here, we review the general concept of glioma's immune microenvironment and report the impact of its distinct components on the anti-tumor immune response. We also discuss the mechanisms of glioma cell evasion from the immune response and pinpoint some potential therapeutic pathways, which could alleviate such resistance.

Natural killer cells- from innate cells to the discovery of adaptability

Natural Killer (NK) cells have come a long way since their first description in the 1970's. The most recent reports of their adaptive-like behavior changed the way the immune system dichotomy is described. Adaptive NK cells present characteristics of both the innate and adaptive immune system. This NK cell subpopulation undergoes a clonal-like expansion in response to an antigen and secondary encounters with the same antigen result in an increased cytotoxic response. These characteristics can be of extreme importance in the clinical setting, especially as adoptive immunotherapies, since NK cells present several advantages compared other cell types. This review will focus on the discovery and the path to the current knowledge of the adaptive NK cell population.

The Notch signaling pathway: a potential target for cancer immunotherapy

Dysregulation of the Notch signaling pathway, which is highly conserved across species, can drive aberrant epigenetic modification, transcription, and translation. Defective gene regulation caused by dysregulated Notch signaling often affects networks controlling oncogenesis and tumor progression. Meanwhile, Notch signaling can modulate immune cells involved in anti- or pro-tumor responses and tumor immunogenicity. A comprehensive understanding of these processes can help with designing new drugs that target Notch signaling, thereby enhancing the effects of cancer immunotherapy. Here, we provide an up-to-date and comprehensive overview of how Notch signaling intrinsically regulates immune cells and how alterations in Notch signaling in tumor cells or stromal cells extrinsically regulate immune responses in the tumor microenvironment (TME). We also discuss the potential role of Notch signaling in tumor immunity mediated by gut microbiota. Finally, we propose strategies for targeting Notch signaling in cancer immunotherapy. These include oncolytic virotherapy combined with inhibition of Notch signaling, nanoparticles (NPs) loaded with Notch signaling regulators to specifically target tumor-associated macrophages (TAMs) to repolarize their functions and remodel the TME, combining specific and efficient inhibitors or activators of Notch signaling with immune checkpoint blockers (ICBs) for synergistic anti-tumor therapy, and implementing a customized and effective synNotch circuit system to enhance safety of chimeric antigen receptor (CAR) immune cells. Collectively, this review aims to summarize how Notch signaling intrinsically and extrinsically shapes immune responses to improve immunotherapy.

Immune cells and associated molecular markers in dermal fibrosis with focus on raised cutaneous scars

Raised dermal scars including hypertrophic, and keloid scars as well as scalp-associated fibrosing Folliculitis Keloidalis Nuchae (FKN) are a group of fibrotic raised dermal lesions that mostly occur following cutaneous injury. They are characterized by increased extracellular matrix (ECM) deposition, primarily excessive collagen type 1 production by hyperproliferative fibroblasts. The extent of ECM deposition is thought to be proportional to the severity of local skin inflammation leading to excessive fibrosis of the dermis. Due to a lack of suitable study models, therapy for raised dermal scars remains ill-defined. Immune cells and their associated markers have been strongly associated with dermal fibrosis. Therefore, modulation of the immune system and use of anti-inflammatory cytokines are of potential interest in the management of dermal fibrosis. In this review, we will discuss the importance of immune factors in the pathogenesis of raised dermal scarring. The aim here is to provide an up-to-date comprehensive review of the literature, from PubMed, Scopus, and other relevant search engines in order to describe the known immunological factors associated with raised dermal scarring. The importance of immune cells including mast cells, macrophages, lymphocytes, and relevant molecules such as cytokines, chemokines, and growth factors, antibodies, transcription factors, and other immune-associated molecules as well as tissue lymphoid aggregates identified within raised dermal scars will be presented. A growing body of evidence points to a shift from proinflammatory Th1 response to regulatory/anti-inflammatory Th2 response being associated with the development of fibrogenesis in raised dermal scarring. In summary, a better understanding of immune cells and associated molecular markers in dermal fibrosis will likely enable future development of potential immune-modulated therapeutic, diagnostic, and theranostic targets in raised dermal scarring.

Lymphoid cell development from fetal hematopoietic progenitors and human pluripotent stem cells

Lymphoid cells encompass the adaptive immune system, including T and B cells and Natural killer T cells (NKT), and innate immune cells (ILCs), including Natural Killer (NK) cells. During adult life, these lineages are thought to derive from the differentiation of long-term hematopoietic stem cells (HSCs) residing in the bone marrow. However, during embryogenesis and fetal development, the ontogeny of lymphoid cells is both complex and multifaceted, with a large body of evidence suggesting that lymphoid lineages arise from progenitor cell populations antedating the emergence of HSCs. Recently, the application of single cell RNA-sequencing technologies and pluripotent stem cell-based developmental models has provided new insights into lymphoid ontogeny during embryogenesis. Indeed, PSC differentiation platforms have enabled de novo generation of lymphoid immune cells independently of HSCs, supporting conclusions drawn from the study of hematopoiesis in vivo. Here, we examine lymphoid development from non-HSC progenitor cells and technological advances in the differentiation of human lymphoid cells from pluripotent stem cells for clinical translation.

Potential Role of Innate Lymphoid Cells in the Pathogenesis and Treatment of Skin Diseases

Group 2 innate lymphoid cells (ILC2s) are lymphoid cells that are resident in mucosal tissues, especially the skin, which, once stimulated by epithelial cell-derived cytokines, release IL-5, IL-13, and IL-4, as the effectors of type 2 immune responses. This research aims to evaluate the role of ILC2s in the pathogenesis of skin diseases, with a particular focus on inflammatory cutaneous disorders, in order to also elucidate potential therapeutic perspectives. The research has been conducted in articles, excluding reviews and meta-analyses, on both animals and humans. The results showed that ILC2s play a crucial role in the pathogenesis of systemic skin manifestations, prognosis, and severity, while a potential antimelanoma role is emerging from the new research. Future perspectives could include the development of new antibodies targeting or stimulating ILC2 release. This evidence could add a new therapeutic approach to inflammatory cutaneous conditions, including allergic ones.

Innate lymphoid cells and innate-like T cells in cancer - at the crossroads of innate and adaptive immunity

Immunotherapies targeting conventional T cells have revolutionized systemic treatment for many cancers, yet only a subset of patients benefit from these approaches. A better understanding of the complex immune microenvironment of tumours is needed to design the next generation of immunotherapeutics. Innate lymphoid cells (ILCs) and innate-like T cells (ILTCs) are abundant, tissue-resident lymphocytes that have recently been shown to have critical roles in many types of cancers. ILCs and ILTCs rapidly respond to changes in their surrounding environment and act as the first responders to bridge innate and adaptive immunity. This places ILCs and ILTCs as pivotal orchestrators of the final antitumour immune response. In this Review, we outline hallmarks of ILCs and ILTCs and discuss their emerging role in antitumour immunity, as well as the pathophysiological adaptations leading to their pro-tumorigenic function. We explore the pleiotropic, in parts redundant and sometimes opposing, mechanisms that underlie the delicate interplay between the different subsets of ILCs and ILTCs. Finally, we highlight their role in amplifying and complementing conventional T cell functions and summarize immunotherapeutic strategies for targeting ILCs and ILTCs in cancer.

Development of Type 1 Diabetes in Mice Is Associated with a Decrease in IL-2-Producing ILC3 and FoxP3+ Treg in the Small Intestine

Recent data indicate the link between the number and function of T regulatory cells (Treg) in the gut immune tissue and initiation and development of autoimmunity associated with type 1 diabetes (T1D). Since type 3 innate lymphoid cells (ILC3) in the small intestine are essential for maintaining FoxP3⁺ Treg and there are no data about the possible role of ILC3 in T1D pathogenesis, the aim of this study was to explore ILC3-Treg link during the development of T1D. Mature diabetic NOD mice had lower frequencies of IL-2-producing ILC3 and Treg in small intestine lamina propria (SILP) compared to prediabetic NOD mice. Similarly, in multiple low doses of streptozotocin (MLDS)-induced T1D in C57BL/6 mice, hyperglycemic mice exhibited lower numbers of ILC3, IL-2⁺ ILC3 and Treg in SILP compared to healthy controls. To boost T1D severity, mice were treated with broad-spectrum antibiotics (ABX) for 14 days prior to T1D induction by MLDS. The higher incidence of T1D in ABX-treated mice was associated with significantly lower frequencies of IL-2⁺ ILC3 and FoxP3⁺ Treg in SILP compared with mice without ABX treatment. The obtained findings show that the lower proportions of IL-2-expressing ILC3 and FoxP3⁺ Treg in SILP coincided with diabetes progression and severity.

The Roles of Innate Lymphoid Cells in the Gastric Mucosal Immunology and Oncogenesis of Gastric Cancer

Innate lymphoid cells (ILCs) are a group of innate immune cells that have garnered considerable attention due to their critical roles in regulating immunity and tissue homeostasis. They are particularly abundant in the gastrointestinal tract, where they have been shown to interact with commensal bacteria, pathogens, and other components of the local microenvironment to influence host immune responses to infection and oncogenesis. Their tissue-residency properties enable gastric ILCs a localized and rapid response to alert and stress, which indicates their key potential in regulating immunosurveillance. In this review, we discuss the current understanding of the role of ILCs in the gastric mucosa, with a focus on their interactions with the gastric microbiota and Helicobacter pylori and their contributions to tissue homeostasis and inflammation. We also highlight recent findings on the involvement of ILCs in the pathogenesis of gastric cancer and the implications of targeting ILCs as a therapeutic approach. Overall, this review provides an overview of the diverse functions of ILCs in gastric mucosa and highlights their potential as targets for future therapies for gastric cancer.

The role of innate lymphocytes in regulating brain and cognitive function

Mounting evidence indicates complex interaction between the immune system and the nervous system, challenging the traditional view about the immune privilege of the brain. Innate lymphoid cells (ILCs) and innate-like T cells are unique families of immune cells that functionally mirror traditional T cells but may function via antigen- and T cell antigen receptor (TCR)-independent mechanisms. Recent work indicates that various ILCs and innate-like T cell subsets are present in the brain barrier tissue, where they play important roles in regulating brain barrier integrity, brain homeostasis and cognitive function. In this review, we discuss recent advances in understanding the intricate roles for innate and innate-like lymphocytes in regulating brain and cognitive function.

Helper innate lymphoid cells as cell therapy for cancer

Although the first cancer immunotherapy was given in the clinic more than a century ago, this line of treatment has remained more of a distant goal than a practical therapy due to limited understanding of the tumour microenvironment and the mechanisms at play within it, which led to failures of numerous clinical trials. However, in the last two decades, the immune checkpoint inhibitors (ICIs) and chimeric antigen receptor-T cell therapies have revolutionized the treatment of cancer and provided proof-of-concept that immunotherapies are a viable option. So far, immunotherapies have majoritarily focused on utilizing T cells; however, T cells are not autonomous but rather function as part of, and therefore are influenced by, a vast cast of other immune cells, including innate lymphoid cells (ILCs). Here, we summarize the role of ILCs, especially helper ILCs, in tumour development, progression and metastasis, as well as their potential to be used as immunotherapy for cancer. By reviewing the studies that used helper ILCs as adoptive cell therapy (ACT), we highlight the rationale behind considering these cells as novel ACT for cancer as well as identify open questions and areas for future research.

PLZF restricts intestinal ILC3 function in gut defense

Group 3 innate lymphoid cells (ILC3s) play important roles in maintaining intestinal homeostasis by protecting the host from pathogen infections and tissue inflammation. The transcription factor PLZF (promyelocytic leukemia zinc finger), encoded by zinc finger BTB domain containing 16 (Zbtb16), is highly and transiently expressed in ILC precursors (ILCPs). However, the role of PLZF in regulating ILC3 development and function remains unknown. Here, we show that PLZF was specifically expressed in mature intestinal ILC3s compared with other ILC subsets. PLZF was dispensable for ILC3 development. However, PLZF deficiency in ILC3s resulted in increased innate interleukin-22 (IL-22) secretion and protection against gut infection and inflammation. Mechanistically, PLZF negatively regulated IL-22 expression by ILC3s in a cell-intrinsic manner by binding to the IL-22 promoter region for transcriptional repression. Together, our data suggest that PLZF restricts intestinal ILC3 function to regulate gut immune homeostasis.

Innate immune cellular therapeutics in transplantation

Successful organ transplantation provides an opportunity to extend the lives of patients with end-stage organ failure. Selectively suppressing the donor-specific alloimmune response, however, remains challenging without the continuous use of non-specific immunosuppressive medications, which have multiple adverse effects including elevated risks of infection, chronic kidney injury, cardiovascular disease, and cancer. Efforts to promote allograft tolerance have focused on manipulating the adaptive immune response, but long-term allograft survival rates remain disappointing. In recent years, the innate immune system has become an attractive therapeutic target for the prevention and treatment of transplant organ rejection. Indeed, contemporary studies demonstrate that innate immune cells participate in both the initial alloimmune response and chronic allograft rejection and undergo non-permanent functional reprogramming in a phenomenon termed "trained immunity." Several types of innate immune cells are currently under investigation as potential therapeutics in transplantation, including myeloid-derived suppressor cells, dendritic cells, regulatory macrophages, natural killer cells, and innate lymphoid cells. In this review, we discuss the features and functions of these cell types, with a focus on their role in the alloimmune response. We examine their potential application as therapeutics to prevent or treat allograft rejection, as well as challenges in their clinical translation and future directions for investigation.

Etiology of end-stage liver cirrhosis impacts hepatic natural killer cell heterogenicity

The natural killer (NK) cell population is a critical component of the innate immune compartment of the liver, and its functions are deeply affected by the surrounding environment. In the late stage of fibrosis, NK cells become dysfunctional, but the influence of disease etiology on NK cell behavior during cirrhosis remains unclear. Using single-cell RNA sequencing (scRNA-seq), we characterized the hepatic NK cells from end-stage cirrhotic livers from subjects with non-alcoholic steatohepatitis (NASH), chronic hepatitis C infection (HCV) and primary sclerosing cholangitis (PSC). Here, we show that although NK cells shared similar dysfunctions, the disease etiology impacts hepatic NK cell heterogeneity. Therapeutical strategies targeting NK cells for the prevention or treatment of fibrosis should consider liver disease etiology in their design.

Strength of CAR signaling determines T cell versus ILC differentiation from pluripotent stem cells

Generation of chimeric antigen receptor (CAR) T cells from pluripotent stem cells (PSCs) will enable advances in cancer immunotherapy. Understanding how CARs affect T cell differentiation from PSCs is important for this effort. The recently described artificial thymic organoid (ATO) system supports in vitro differentiation of PSCs to T cells. Unexpectedly, PSCs transduced with a CD19-targeted CAR resulted in diversion of T cell differentiation to the innate lymphoid cell 2 (ILC2) lineage in ATOs. T cells and ILC2s are closely related lymphoid lineages with shared developmental and transcriptional programs. Mechanistically, we show that antigen-independent CAR signaling during lymphoid development enriched for ILC2-primed precursors at the expense of T cell precursors. We applied this understanding to modulate CAR signaling strength through expression level, structure, and presentation of cognate antigen to demonstrate that the T cell-versus-ILC lineage decision can be rationally controlled in either direction, providing a framework for achieving CAR-T cell development from PSCs.

Controversial role of ILC3s in intestinal diseases: A novelty perspective on immunotherapy

ILC3s have been identified as crucial immune regulators that play a role in maintaining host homeostasis and modulating the antitumor response. Emerging evidence supports the idea that LTi cells play an important role in initiating lymphoid tissue development, while other ILC3s can promote host defense and orchestrate adaptive immunity, mainly through the secretion of specific cytokines and crosstalk with other immune cells or tissues. Additionally, dysregulation of ILC3-mediated overexpression of cytokines, changes in subset abundance, and conversion toward other ILC subsets are closely linked with the occurrence of tumors and inflammatory diseases. Regulation of ILC3 cytokines, ILC conversion and LTi-induced TLSs may be a novel strategy for treating tumors and intestinal or extraintestinal inflammatory diseases. Herein, we discuss the development of ILCs, the biology of ILC3s, ILC plasticity, the correlation of ILC3s and adaptive immunity, crosstalk with the intestinal microenvironment, controversial roles of ILC3s in intestinal diseases and potential applications for treatment.

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.

Involvement of ILC1-like innate lymphocytes in human autoimmunity, lessons from alopecia areata

Here, we have explored the involvement of innate lymphoid cells-type 1 (ILC1) in the pathogenesis of alopecia areata (AA), because we found them to be significantly increased around lesional and non-lesional HFs of AA patients. To further explore these unexpected findings, we first co-cultured autologous circulating ILC1-like cells (ILC1lc) with healthy, but stressed, organ-cultured human scalp hair follicles (HFs). ILClc induced all hallmarks of AA ex vivo: they significantly promoted premature, apoptosis-driven HF regression (catagen), HF cytotoxicity/dystrophy, and most important for AA pathogenesis, the collapse of the HFs physiological immune privilege. NKG2D-blocking or IFNγ-neutralizing antibodies antagonized this. In vivo, intradermal injection of autologous activated, NKG2D+/IFNγ-secreting ILC1lc into healthy human scalp skin xenotransplanted onto SCID/beige mice sufficed to rapidly induce characteristic AA lesions. This provides the first evidence that ILC1lc, which are positive for the ILC1 phenotype and negative for the classical NK markers, suffice to induce AA in previously healthy human HFs ex vivo and in vivo, and further questions the conventional wisdom that AA is always an autoantigen-dependent, CD8 +T cell-driven autoimmune disease.

Retinoic acid receptor activity is required for the maintenance of type 1 innate lymphoid cells

Group 1 innate lymphoid cells (G1-ILCs) are innate immune effectors critical for the response to intracellular pathogens and tumors. G1-ILCs comprise circulating natural killer (NK) cells and tissue-resident type 1 ILCs (ILC1s). ILC1s mainly reside in barrier tissues and provide the initial sources of interferon-γ (IFN-γ) to prime the protecting responses against infections, which are followed by the response of recruited NK cells. Despite such distribution differences, whether local environmental factors influence the behavior of NK cells and ILC1s is unclear. Here, we show that the signaling of retinoic acid (RA), active metabolites of vitamin A, is essential for the maintenance of ILC1s in the periphery. Mice expressing RARα403, a truncated form of retinoic acid receptor α (RARα) that exerts dominant negative activity, in a lymphoid cell- or G1-ILC-specific manner showed remarkable reductions of peripheral ILC1s while NK cells were unaffected. Lymphoid cell-specific inhibition of RAR activity resulted in the reduction of PD-1+ ILC progenitors (ILCPs), but not of common lymphoid progenitors (CLPs), suggesting the impaired commitment and differentiation of ILC1s. Transcriptome analysis revealed that RARα403-expressing ILC1s exhibited impaired proliferative states and declined expression of effector molecules. Thus, our findings demonstrate that cell-intrinsic RA signaling is required for the homeostasis and the functionality of ILC1s, which may present RA as critical environmental cue targeting local type 1 immunity against infection and cancer.

Immunomodulatory Function of Interleukin-15 and Its Role in Exercise, Immunotherapy, and Cancer Outcomes

Exercise has been shown to improve physical and psychosocial outcomes for people across the cancer care continuum. A proposed mechanism underpinning the relationship between exercise and cancer outcomes is exercise-induced immunomodulation via secretion of anti-inflammatory myokines from skeletal muscle tissue. Myokines have the potential to impair cancer growth through modulation of natural killer (NK) cells and CD8+ T cells while improving the effectiveness of cancer therapies. Interleukin-15 (IL-15), one of the most abundant myokines found in skeletal muscle, has a key immunoregulatory role in supporting the proliferation and maturation of T cells and NK cells, which have a key role in the host's immune response to cancer. Furthermore, IL-15 is being explored clinically as an immunotherapy agent with doses similar to the IL-15 concentrations released by skeletal muscle during exercise. Here we review the role of IL-15 within the immune system, examine how IL-15 is produced as a myokine during exercise, and how it may improve outcomes for people with cancer, specifically as an adjuvant or neoadjuvant to immunotherapy. We summarize the available evidence showing changes in IL-15 in response to both acute exercise and training, and the results are inconsistent; higher quality research is needed to advance the understanding of how exercise-mediated increases in IL-15 potentially benefit those who are being treated for, or who have had, cancer.

Homeostasis and immunological function of self-driven memory-phenotype CD4+ T lymphocytes

CD4⁺ T lymphocytes play an essential role in adaptive immune responses. In pathogen infection, naïve CD4⁺ T cells that strongly respond to foreign antigens robustly proliferate to differentiate into effector/memory cells, contributing to elimination of the pathogen concerned. In addition to this conventional T cell activation pathway, naïve T cells can also weakly respond to self antigens in the periphery to spontaneously acquire a memory phenotype through homeostatic proliferation in steady state. Such 'memory-phenotype' (MP) CD4⁺ T lymphocytes are distinguishable from foreign antigen-specific memory cells in terms of marker expression. Once generated, MP cells are maintained by rapid proliferation while differentiating into the T-bet⁺ 'MP1' subset, with the latter response promoted by IL-12 homeostatically produced by type 1 dendritic cells. Importantly, MP1 cells possess innate immune function; they can produce IFN-γ in response to IL-12 and IL-18 to contribute to host defense against pathogens. Similarly, the presence of RORγt⁺ 'MP17' and Gata3^hi 'MP2' cells as well as their potential immune functions have been proposed. In this review, I will discuss our current understanding on the unique mechanisms of generation, maintenance, and differentiation of MP CD4⁺ T lymphocytes as well as their functional significance in various disease conditions.

Gene expression profiling in NOD mice reveals that B cells are highly educated by the pancreatic environment during autoimmune diabetes

AIMS/HYPOTHESIS

B cells play an important role in driving the development of type 1 diabetes; however, it remains unclear how they contribute to local beta cell destruction during disease progression. Here, we use gene expression profiling of B cell subsets identified in inflamed pancreatic tissue to explore their primary functional role during the progression of autoimmune diabetes.

METHODS

Transcriptional profiling was performed on FACS-sorted B cell subsets isolated from pancreatic islets and the pancreatic lymph nodes of NOD mice.

RESULTS

B cells are highly modified by the inflamed pancreatic tissue and can be distinguished by their transcriptional profile from those in the lymph nodes. We identified both a discrete and a core shared gene expression profile in islet CD19⁺CD138^- and CD19⁺CD138⁺ B cell subsets, the latter of which is known to have enriched autoreactivity during diabetes development. On localisation to pancreatic islets, compared with CD138^- B cells, CD138⁺ B cells overexpress genes associated with adhesion molecules and growth factors. Their shared signature consists of gene expression changes related to the differentiation of antibody-secreting cells and gene regulatory networks associated with IFN signalling pathways, proinflammatory cytokines and Toll-like receptor (TLR) activation. Finally, abundant TLR7 expression was detected in islet B cells and was enhanced specifically in CD138⁺ B cells.

CONCLUSIONS/INTERPRETATION

Our study provides a detailed transcriptional analysis of islet B cells. Specific gene signatures and interaction networks have been identified that point towards a functional role for B cells in driving autoimmune diabetes.

The interaction between innate immunity and oral microbiota in oral diseases

INTRODUCTION

Innate immunity serves as the frontline to combat invading pathogens. Oral microbiota is the total collection of microorganisms colonized within the oral cavity. By recognizing the resident microorganisms through pattern recognition receptors, innate immunity is capable of interacting with oral microbiota and maintaining homeostasis. Dysregulation of interaction may lead to the pathogenesis of several oral diseases. Decoding the crosstalk between oral microbiota and innate immunity may be contributory to developing novel therapies for preventing and treating oral diseases.

AREAS COVERED

This article reviewed pattern recognition receptors in the recognition of oral microbiota, the reciprocal interaction between innate immunity and oral microbiota, and discussed how the dysregulation of this relationship leads to the pathogenesis and development of oral diseases.

EXPERT OPINION

Many studies have been conducted to illustrate the relationship between oral microbiota and innate immunity and its role in the occurrence of different oral diseases. The impact and mechanisms of innate immune cells on oral microbiota and the mechanisms of dysbiotic microbiota in altering innate immunity are still needed to be investigated. Altering the oral microbiota might be a possible solution for treating and preventing oral diseases.