Trained ILC3 responses promote intestinal defense

ILC3s promote intestinal tuft cell hyperplasia and anthelmintic immunity through RANK signaling

Helminth infections, particularly in developing countries, remain a notable health burden worldwide. Group 3 innate lymphoid cells (ILC3s) are enriched in the intestine and play a critical role in immunity against extracellular bacteria and fungi. However, whether ILC3s are involved in intestinal helminth infection is still unclear. Here, we report that helminth infection reprograms ILC3s, which, in turn, promote anthelmintic immunity. ILC3-derived RANKL [receptor activator of NF-κB (nuclear factor κB) ligand] synergizes with interleukin-13 (IL-13) to facilitate intestinal tuft cell expansion after helminth infection, which further activates the tuft cell-group 2 innate lymphoid cell (ILC2) circuit to control helminth infection. Deletion of RANKL in ILC3s or deletion of RANK or its downstream adaptor RelB in intestinal epithelial cells substantially diminishes tuft cell hyperplasia and dampens anthelmintic immunity. Thus, ILC3s play an indispensable role in protecting against helminth infection through the regulation of intestinal tuft cell hyperplasia and type 2 immunity.

Dietary fuel or fire: Fatty acids rewire gut ILC3s

Long-term consumption of diets high in fats has detrimental impacts on the immune system, but the window necessary for initiating these effects is unclear. In this issue of Immunity, Xiong et al.1 demonstrate that even short-term exposure to saturated fats impairs ILC3 function and renders the intestine vulnerable to inflammation and injury.

Friends to remember: innate immune memory regulation by the microbiota

Innate immune memory (IIM) is the process by which, upon a primary challenge, innate immune cells alter their epigenetic, transcriptional, and immunometabolic profiles, resulting in modified secondary responses. Unlike infections or other immune-system-related diseases, the role of IIM in nonpathogenic contexts is less understood. An increasing body of research has shown that normal microbiota members or their metabolic byproducts induce alternative memory phenotypes, suggesting that memory cells contribute to homeostasis in mucosal areas. In this review, we discuss the newest insights in the emerging field of IIM to the microbiota and the potential of manipulating these long-term responses to promote better mucosal health.

Regulation of innate lymphoid cell by microbial metabolites

Innate lymphoid cells (ILCs) are a unique category of immune cell that lack antigen-specific receptors yet possess the capacity to detect signals from the surrounding tissue. The majority of ILCs reside in the lymphoid and mucosal tissues, maintaining close associations with the microbiota. Beyond the contributions of accessory cells and adaptive immune cells, accumulating studies demonstrate that microbial metabolites serve a crucial role in mediating the relationship between ILCs and the microbiota. In this review, we highlight and summarize the roles of microbial metabolites from different sources in modulating ILC subsets, proposing these metabolites as potential therapeutic mechanisms in ILC-mediated diseases.

Deciphering the Role of Innate Lymphoid Cells Group 3 in the Gut Microenvironment: A Narrative Review of Their Novel Contributions to Autoimmune Disease Pathogenesis

Type 3 Innate lymphoid cells (ILC3s) play a crucial role in intestinal immune function by serving as an innate effector that contributes to early-life defense against pathogens and helps protect the intestines from bacterial infections. ILC3s exert their immune function through cytokine secretion, patrolling actions and the generation of memory ILC3s that aid in repairing epithelial tissue and preserving mucosal barrier integrity. Moreover, dysregulation of ILC3s function has been implicated in the pathogenesis and progression of autoimmune diseases. This comprehensive review aims to explore the interactions between gut microbes, gut microbial metabolites, and diet in relation to ILC3s within the context of the gut microenvironment. Furthermore, the gut microenvironment has the potential to influence distant extra-intestinal sites through immunomodulation, thereby modifying their risk of inflammation. The gut has emerged as a significant focus of autoimmune disease research in recent years. However, the relationship between gut ILC3s and autoimmune diseases remains poorly understood. This paper aims to examine the potential association between ILC3s and autoimmune diseases.

The metabolic sensor LKB1 regulates ILC3 homeostasis and mitochondrial function

Group 3 innate lymphoid cells (ILC3s) are tissue-resident cells that sense environmental cues, control infections, and promote tissue homeostasis at mucosal surfaces. The metabolic sensor liver kinase B1 (LKB1) integrates intracellular stress, metabolism, and mitochondrial function to promote the development and effector functions of a variety of immune cells; however, the role of LKB1 in ILC3 function was unknown. Here, we show that LKB1 is crucial for adult ILC3 homeostasis, cytokine production, and mitochondrial function. ILC3-specific LKB1 deletion resulted in a reduced number of ILC3s and interleukin-22 (IL-22) production. LKB1-deficient ILC3s had decreased survival, mitochondrial dysfunction, cytoplasmic lipid accumulation, and altered bioenergetics. Using LKB1 downstream kinase modulators, we found that LKB1 regulation of ILC3 survival and IL-22 production requires signaling through microtubule affinity-regulating kinases (MARKs). Mechanistically, LKB1 deficiency resulted in increased reactive oxygen species (ROS) production and NFAT2 and PD-1 expression. Our work reveals that metabolic regulation of enteric ILC3 function by an LKB1-dependent signaling network is crucial for intestinal immunity and tissue homeostasis.

Research progress and development potential of oncolytic vaccinia virus

ABSTRACT

Oncolytic virotherapy is a promising therapeutic approach treating tumors, where oncolytic viruses (OVs) can selectively infect and lyse tumor cells through replication, while also triggering long-lasting anti-tumor immune responses. Vaccinia virus (VV) has emerged as a leading candidate for use as an OV due to its broad cytophilicity and robust capacity to express exogenous genes. Consequently, oncolytic vaccinia virus (OVV) has entered clinical trials. This review provides an overview of the key strategies used in the development of OVV, summarizes the findings from clinical trials, and addresses the challenges that must be overcome in the advancement of OVV-based therapies. Furthermore, it explores potential future strategies for enhancing the development and clinical application of OVV, intending to improve tumor treatment outcomes. The review aims to facilitate the further development and clinical adoption of OVV, thereby advancing tumor therapies.

There's no place like home: How local tissue microenvironments shape the function of innate lymphoid cells

Innate lymphoid cells (ILC) have emerged as critical immune effectors with key roles in orchestrating the wider immune response. While ILC are relatively rare cells they are found enriched within discrete microenvironments, predominantly within barrier tissues. An emerging body of evidence implicates complex and multi-layered interactions between cell types, tissue structure and the external environment as key determinants of ILC function within these niches. In this review we will discuss the specific components that constitute ILC-associated microenvironments and consider how they act to determine health and disease. The development of holistic, integrated models of ILC function within complex tissue environments will inform new understanding of the contextual cues and mechanisms that determine the protective versus disease-causing roles of this immune cell family.

Cellular and Molecular Mechanisms of Innate Memory Responses

There has been an increasing effort to understand the memory responses of a complex interplay among innate, adaptive, and structural cells in peripheral organs and bone marrow. Trained immunity is coined as the de facto memory of innate immune cells and their progenitors. These cells acquire epigenetic modifications and shift their metabolism to equip an imprinted signature to a persistent fast-responsive functional state. Recent studies highlight the contribution of noncoding RNAs and modulation of chromatin structures in establishing this epigenetic readiness for potential immune perturbations. In this review, we discuss recent studies that highlight trained immunity-mediated memory responses emerging intrinsically in innate immune cells and as a complex interplay with other cells at the organ level. Lastly, we survey epigenetic contributors to trained immunity phenotypes-specifically, a recently discovered regulatory circuit coordinating the regulation of a key driver of trained immunity.

Effects of Yeast β-Glucan Supplementation on Calf Intestinal and Respiratory Health

The physiological functions of newborn calves are undeveloped, especially the immune system, making them susceptible to infections. In recent years, the theory of trained immunity has attracted attention and provided new strategies to prevent unknown infections in animals. This study investigated the effects of feeding yeast β-glucan on the intestinal and respiratory health of calves during the suckling period. Newborn Holstein calves (average birth weight: 36.18 ± 0.61 kg, mean ± SE) were randomly assigned to two groups: the PO (Per Os) group (n = 22) and the CON (Control) group (n = 22). Calves in the PO group were fed a yeast β-glucan solution (0.1 g/mL, 65 mg/kg body weight) at 3 and 6 days of age, respectively, while calves in the CON group received equal volumes of sterile saline orally at the same time. Blood and fecal samples were collected at 7 and 30 days of age, respectively. The results showed that (1) Compared to the CON group, being fed yeast β-glucan resulted in an inflammatory response after 24 h of the second administration, including increased gene expression of interleukin-6 (IL-6, p < 0.01), interleukin-1 beta (IL-1β, p < 0.01), and malonaldehyde (MDA, p < 0.001) content. Also, stimulation with β-glucan increased the concentrations of secreted immunoglobulin A (sIgA, p < 0.01) and defensins (p < 0.05) in the rectal feces. (2) Pre-stimulation with yeast β-glucan effectively reduced the incidence of diarrhea (p < 0.05) and bovine respiratory disease (BRD, p < 0.05) from day 31 to day 60. (3) At 30 days of age, the pre-stimulated calves had significantly lower serum DAO (p < 0.001) and MDA levels (p < 0.05), while they had higher levels of serum IL-6 (p < 0.01) and fecal slgA (p < 0.05) than calves in the CON group. (4) Pre-stimulation with yeast β-glucan altered the intestinal bacterial community; the Beta diversity results showed that the CON group and the PO group were clustered separately in the principal coordinate analysis (PCoA) graph. Obviously, the PO group sample points were more clustered. In conclusion, this study highlights the potential of yeast β-glucan-induced trained immunity to improve calf health during the suckling period. The findings offer new insights into the prevention of intestinal and respiratory infections in calves.

Immune Memory: A New Frontier in Treating Recurrent Inflammatory Skin Diseases

The recurrence of inflammatory skin diseases represents a significant challenge in clinical practice, primarily mediated by immune memory. In inflammatory skin diseases, immune memory encompasses adaptive immune memory, trained immunity, and inflammatory memory, which are conducted by adaptive immune cells, innate immune cells, and structural cells, respectively. Adaptive immune memory is established through gene rearrangement, leading to antigen-specific immune memory. In contrast, trained immunity and inflammatory memory are formed through epigenetic and metabolic reprogramming, resulting in non-specific immune memory. Different types of immune memory work synergistically to aggravate localized inflammation in recurrent inflammatory skin diseases. However, immune memory in specific cells, such as macrophages, may also play an immunoregulatory role under certain conditions. We reviewed the immune memory mechanisms in different inflammatory skin diseases and discussed future strategies for targeted regulation of the molecular mechanisms underlying immune memory, such as targeted biological agents and epigenetic modifications. Additionally, we explored the potential for precise regulation of immune memory and its application in personalized treatment for recurrent inflammatory skin diseases.

Period circadian clock 3 is crucial for regulation of IL-22-producing type 3 innate lymphoid cells by flavonoids from Shen Ling Bai Zhu San to alleviate colitis

Type 3 Innate lymphoid cells (ILC3s) functions bear complex response during Inflammatory bowel diseases (IBD). Here, our study first analyzed the main pharmacological components in Shen Ling Bai Zhu San n-butanol extracts (S-Nb), and then explored whether S-Nb administrated immune response of ILC3s, and how it regulates ILC3s. Shen Ling Bai Zhu San (SLBZS) or S-Nb were administrated for 7 days to analyze the frequency of ILC3s and their produced cytokine. Using siRNA technology to knock down the expression of period circadian clock 2 (Per2) and period circadian clock 3 (Per3) and Anti-IL-22 antibody was supplied to mice, then detecting the moderator effect of S-Nb on colitis. The most class of S-Nb is flavonoids, with a content of approximately 48%. Oral administration of S-Nb enhanced the production of NCR+ILC3s and IL-22 produced by ILC3s, but did not alter IL-17A. Surprisingly, knocking down the expression of Per3 instead of Per2 inhibited the modulation effect of S-Nb on colitis and reduced IL-22 production, whether originating from NCR+ILC3s or NCR-ILC3s. After neutralizing the expression of IL-22 in mice, S-Nb was deprived of ability to alleviate colitis. The reason why S-Nb alleviates colitis is by enhancing the expression of Per3 via flavonoids, which in turn promotes the secretion of IL-22+ILC3s in intestine.

A panoramic view of cell population dynamics in mammalian aging

To elucidate aging-associated cellular population dynamics, we present PanSci, a single-cell transcriptome atlas profiling >20 million cells from 623 mouse tissues across different life stages, sexes, and genotypes. This comprehensive dataset reveals >3000 different cellular states and >200 aging-associated cell populations. Our panoramic analysis uncovered organ-, lineage-, and sex-specific shifts in cellular dynamics during life-span progression. Moreover, we identify both systematic and organ-specific alterations in immune cell populations associated with aging. We further explored the regulatory roles of the immune system on aging and pinpointed specific age-related cell population expansions that are lymphocyte dependent. Our "cell-omics" strategy enhances comprehension of cellular aging and lays the groundwork for exploring the complex cellular regulatory networks in aging and aging-associated diseases.

Postbiotics From Lactobacillus Johnsonii Activates Gut Innate Immunity to Mitigate Alcohol-Associated Liver Disease

Prolonged alcohol consumption disrupts the gut microbiota and the immune system, contributing to the pathogenesis of alcohol-associated liver disease (ALD). Probiotic-postbiotic intervention strategies can effectively relieve ALD by maintaining gut homeostasis. Herein, the efficacy of heat-killed Lactobacillus johnsonii (HKLJ) in mitigating alcoholic liver damage is demonstrated in mouse models of ALD. The gut-liver axis is identified as a pivotal pathway for the protective effects of L. johnsonii against ALD. Specifically, HKLJ is found to upregulate the expression of intestinal lysozymes, thereby enhancing the production of immunoregulatory substances from gut bacteria, which subsequently activated the Nucleotide-binding oligomerization domain 2 (NOD2)-interleukin (IL-23)-IL-22 innate immune axis. The elevated IL-22 upregulated the antimicrobial peptide synthesis to maintain intestinal homeostasis and moreover activated the Signal transducer and activator of Transcription3 (STAT3) pathway in the liver to facilitate the repair of hepatic injuries. The heat-killed L. johnsonii provoked immunity helps correct the gut microbiota dysbiosis, specifically by reversing the reduction of butyrate-producing bacteria (such as Faecalibaculum rodentium) and the expansion of opportunistic pathogens (such as Helicobacter sp. and Pichia kudriavzevii) induced by ethanol. The findings provide novel insights into the gut microbiota-liver axis that may be leveraged to enhance the treatment of ALD.

Group 3 Innate Lymphoid Cells: A Potential Therapeutic Target for Steroid Resistant Asthma

Asthma is a chronic airway inflammatory disease that affects millions globally. Although glucocorticoids are a mainstay of asthma treatment, a subset of patients show resistance to these therapies, resulting in poor disease control and increased morbidity. The complex mechanisms underlying steroid-resistant asthma (SRA) involve Th1 and Th17 lymphocyte activity, neutrophil recruitment, and NLRP3 inflammasome activation. Recent studies provided evidence that innate lymphoid cells type 3 (ILC3s) might be potential therapeutic targets for non-eosinophilic asthma (NEA) and SRA. Like Th17 cells, ILC3s play crucial roles in immune responses, inflammation, and tissue homeostasis, contributing to disease severity and corticosteroid resistance in NEA. Biologics targeting ILC3-related pathways have shown promise in managing Th2-low asthma, suggesting new avenues for SRA treatment. This review aims to explore the risk factors for SRA, discuss the challenges and mechanisms underlying SRA, consolidate current findings on innate lymphoid cells, and elucidate their role in respiratory conditions. We present the latest findings on the involvement of ILC3s in human diseases and explore their potential mechanisms in SRA development. Furthermore, we review emerging therapeutic biologics targeting ILC3-related pathways in managing NEA and SRA. This review highlights current challenges, and emerging therapeutic strategies, and addresses a significant gap in asthma research, with implications for improving the management of steroid-resistant asthma.

ScRNA-seq reveals trained immunity-engaged Th17 cell activation against Edwardsiella piscicida-induced intestinal inflammation in teleost

Mucosal immunity typically involves innate and adaptive immune cells, while the cellular mechanism of teleost's intestinal immune cells that engages gut homeostasis against bacterial infection remains largely unknown. Taking advantage of the enteric fish pathogen (Edwardsiella piscicida) infection-induced intestinal inflammation in turbot (Scophthalmus maximus), we find that β-glucan training could mitigate the bacterial infection-induced intestinal inflammation. Through single-cell transcriptome profiling and cellular function analysis, we identify that E. piscicida infection could tune down the activation of intestinal Th17 cells, while β-glucan-training could preserve the potential to amplify and restore the function of intestinal Th17 cells. Moreover, through pharmacological inhibitor treatment, we identify that Th17 cells are essential for ameliorating bacterial infection-induced intestinal inflammation in teleost. Taken together, these results suggest a new concept of trained immunity activation to regulate the intestinal Th17 cells' function, which might contribute to better developing strategies for maintaining gut homeostasis against bacterial infection.

Therapeutic potential of Astragalus membranaceus-Pueraria lobata decoction for the treatment of chemotherapy bowel injury

Intestinal mucositis (IM) is one of the most serious side effects of the chemotherapeutic agent irinotecan (CPT-11). Astragalus membranaceus-Pueraria lobata decoction is from the ancient medical book Zhengzhihuibu, has been reported to be used for the treatment of diabetes and hypertension. However, the beneficial effect and mechanism of AP on chemotherapy intestinal mucositis (CIM) remain largely unknown. This study aimed to investigate the efficacy and mechanism of Astragalus membranaceus-Pueraria lobata decoction (AP) in treating CIM. The beneficial effect and mechanism of AP on chemotherapy intestinal mucositis (CIM) were detected using Drosophila model, and combination with RT qPCR, transcriptomics. AP supplementation could significantly alleviate the CPT-11-induced body injury in Drosophila, such as increasing the survival rate, recovering the impaired digestion, improving the movement, and repairing the reproduction and developmental processes. Administration of AP remarkably alleviated the IM caused by CPT-11, including inhibiting the excretion, repairing the intestinal atrophy, improving the acid-base homeostasis imbalance, and inhibiting the disruption of intestinal structure. Mechanistic studies revealed that the protective role of AP against CPT-11 induced intestinal injury was regulated mainly by inhibiting immune-related Toll and Imd pathways, and enhancing the antioxidant capacity. Taken together, these results suggest that AP may be a novel agent to relieve CIM.

Innate lymphoid cells in immunoglobulin E-mediated food allergy

PURPOSE OF REVIEW

Recognition of the importance of innate lymphoid cells (ILCs) in the immune mechanisms of food allergy has grown in recent years. This review summarizes recent findings of ILCs in immunoglobulin E (IgE)-mediated food allergy. New research on ILCs in the context of the microbiome and other atopic diseases are also considered with respect to how they can inform understanding of the role of ILCs in food allergy.

RECENT FINDINGS

ILCs can mediate allergic and tolerogenic responses through multiple pathways. A novel subset of interleukin (IL)-10 producing ILC2s are associated with tolerance following immunotherapy to grass pollen, house dust mite allergy and lipid transfer protein allergy. ILC2s can drive food allergen-specific T cell responses in an antigen-specific manner. A memory subset of ILC2s has been identified through studies of other atopic diseases and is associated with effectiveness of response to therapy.

SUMMARY

The role of ILCs in food allergy and oral tolerance is relatively understudied compared to other diseases. ILCs can modulate immune responses through several mechanisms, and it is likely that these are of importance in the context of food allergy. Better understanding of theses pathways may help to answer fundamental questions regarding the development of food allergy and lead to novel therapeutic targets and treatment.

Trained immunity of intestinal tuft cells during infancy enhances host defense against enteroviral infections in mice

Innate immune cells have been acknowledged as trainable in recent years. While intestinal tuft cells are recognized for their crucial roles in the host defense against intestinal pathogens, there remains uncertainty regarding their trainability. Enterovirus 71 (EV71), a prevalent enterovirus that primarily infects children but rarely infects adults. At present, there is a significant expansion of intestinal tuft cells in the EV71-infected mouse model, which is associated with EV71-induced interleukin-25 (IL-25) production. Further, we found that IL-25 pre-treatment at 2 weeks old mouse enabled tuft cells to acquire immune memory. This was evidenced by the rapid expansion and stronger response of IL-25-trained tuft cells in response to EV71 infection at 6 weeks old, surpassing the reactivity of naïve tuft cells in mice without IL-25-trained progress. Interestingly, IL-25-trained intestinal tuft cells exhibit anti-enteroviral effect via producing a higher level of IL-25. Mechanically, IL-25 treatment upregulates spermidine/spermine acetyl-transferase enzyme (SAT1) expression, mediates intracellular polyamine deficiency, further inhibits enterovirus replication. In summary, tuft cells can be trained by IL-25, which supports faster and higher level IL-25 production in response to EV71 infection and further exhibits anti-enteroviral effect via SAT1-mediated intracellular polyamine deficiency. Given that IL-25 can be induced by multiple gut microbes during human growth and development, including shifts in gut flora abundance, which may partially explain the different susceptibility to enteroviral infections between adults and children.

Inflammatory tissue priming: novel insights and therapeutic opportunities for inflammatory rheumatic diseases

Due to optimised treatment strategies and the availability of new therapies during the last decades, formerly devastating chronic inflammatory diseases such as rheumatoid arthritis or systemic sclerosis (SSc) have become less menacing. However, in many patients, even state-of-the-art treatment cannot induce remission. Moreover, the risk for flares strongly increases once anti-inflammatory therapy is tapered or withdrawn, suggesting that underlying pathological processes remain active even in the absence of overt inflammation. It has become evident that tissues have the ability to remember past encounters with pathogens, wounds and other irritants, and to react more strongly and/or persistently to the next occurrence. This priming of the tissue bears a paramount role in defence from microbes, but on the other hand drives inflammatory pathologies (the Dr Jekyll and Mr Hyde aspect of tissue adaptation). Emerging evidence suggests that long-lived tissue-resident cells, such as fibroblasts, macrophages, long-lived plasma cells and tissue-resident memory T cells, determine inflammatory tissue priming in an interplay with infiltrating immune cells of lymphoid and myeloid origin, and with systemically acting factors such as cytokines, extracellular vesicles and antibodies. Here, we review the current state of science on inflammatory tissue priming, focusing on tissue-resident and tissue-occupying cells in arthritis and SSc, and reflect on the most promising treatment options targeting the maladapted tissue response during these diseases.

Vaccination with O-linked Mannans Protects against Systemic Candidiasis through Innate Lymphocyte Populations

Candida spp. are the fourth leading cause of bloodstream infections in hospitalized patients and the most common cause of invasive fungal infection. No vaccine against Candida spp. or other fungal pathogens of humans is available. We recently discovered the Blastomyces Dectin-2 ligand endoglucanase 2 that harbors antigenic and adjuvant functions and can function as a protective vaccine against that fungus. We also reported that the adjuvant activity, which is mediated by O-mannans decorating the C terminus of Blastomyces Dectin-2 ligand endoglucanase 2, can augment peptide Ag-induced vaccine immunity against heterologous agents, including Cryptococcus, Candida, and influenza. In this article, we report that the O-linked mannans alone, in the absence of any antigenic peptide, can also protect against systemic candidiasis, reducing kidney fungal load and increasing survival in a Dectin-2-dependent manner. We found that this long-term glycan-induced protection is mediated by innate lymphocyte populations including TCR-γδ+ T cells, innate lymphoid cells, and NK cells that subsequently activate and release reactive oxygen species from neutrophils and monocytes. Our findings suggest that Blastomyces O-mannan displayed by Eng2 induces a form of protective trained immunity mediated by innate lymphocyte populations.

Vaccine induced mucosal and systemic memory NK/ILCs elicit decreased risk of SIV/SHIV acquisition

SIV and HIV-based envelope V1-deleted (ΔV1) vaccines, delivered systemically by the DNA/ALVAC/gp120 platform, decrease the risk of mucosal SIV or SHIV acquisition more effectively than V1-replete vaccines. Here we investigated the induction of mucosal and systemic memory-like NK cells as well as antigen-reactive ILC response by DNA/ALVAC/gp120-based vaccination and their role against SIV/SHIV infection. ΔV1 HIV vaccination elicited a higher level of mucosal TNF-α+ and CD107+ memory-like NK cells than V1-replete vaccination, suggesting immunogen dependence. Mucosal memory-like NK cells, systemic granzyme B+ memory NK cells, and vaccine-induced mucosal envelope antigen-reactive IL-17+ NKp44+ ILCs, IL-17+ ILC3s, and IL-13+ ILC2 subsets were linked to a lower risk of virus acquisition. Additionally, mucosal memory-like NK cells and mucosal env-reactive IFN-γ+ ILC1s and env- reactive IL-13+ ILC2 subsets correlated with viral load control. We further observed a positive correlation between post-vaccination systemic and mucosal memory-like NK cells, suggesting vaccination enhances the presence of these cells in both compartments. Mucosal and systemic memory-like NK cells positively correlated with V2-specific ADCC responses, a reproducible correlate of reduced risk of SIV/HIV infection. In contrast, an increased risk was associated with the level of mucosal PMA/Ionomycin-induced IFN-γ+ and CD107+ NKG2A-NKp44- ILCs. Plasma proteomic analyses demonstrated that suppression of mucosal memory-like NK cells was linked to the level of CCL-19, LT-α, TNFSF-12, and IL-15, suppression of systemic env-reactive granzyme B+ memory-like NK cells was associated with the level of OLR1, CCL-3, and OSM, and suppression of IL-17+ ILCs immunity was correlated with the level of IL-6 and CXCL-9. In contrast, FLT3 ligand was associated with promotion of protective mucosal env-reactive IL-17+ responses. These findings emphasize the importance of mucosal memory-like NK cell and envelope- reactive ILC responses for protection against mucosal SIV/SHIV acquisition.

The crosstalk between ILC3s and adaptive immunity in diseases

RORγt+ group 3 innate lymphoid cells (ILC3s), the innate counterpart of Th17 cells, are enriched in the mucosal area and lymphoid tissues. ILC3s interact with a variety of cells through their effector molecules and play an important role in the host defense against a spectrum of infections. Recent studies suggest that the extensive crosstalk between ILC3s and adaptive immune cells, especially T cells, is essential for maintaining tissue homeostasis. Here we discuss recent advances in the crosstalk between ILC3s and adaptive immune responses in multiple tissues and diseases. Understanding how ILC3s engage with adaptive immune cells will enhance our comprehension of diseases and facilitate the identification of novel therapeutic targets.

Paeoniae Decoction restores intestinal barrier dysfunction by promoting the interaction between ILC3 and gut flora

BACKGROUND

Intestinal barrier dysfunction is a significant contributor to the recurrence and refractory of ulcerative colitis (UC). Promoting the interaction between group 3 innate lymphoid cells (ILC3s) and gut flora is a valuable strategy for mucosal repair. Paeoniae decoction (PD) is a compound commonly used in clinical treatment of UC, but its exact mechanism remains unclear.

PURPOSE

We aimed to investigate the protective effect of PD on intestinal mucosal injury induced by dextran sulfate sodium (DSS) in chronic colitis, as well as to elucidate its potential mechanism.

METHODS

C57BL/6 mice were induced with chronic colitis by 2 % DSS and divided into four groups: control group, model group, PD low dose (4 g/kg), and high dose (8 g/kg) group. The effectiveness of PD in treating chronic colitis mice was evaluated based on changes in body weight, colon length, colon pathological tissue scores, and the mRNA levels of inflammatory factors IL-6 and IL-1β. The expressions of intestinal epithelial tight junction proteins (ZO-1 and Occludin), IL-22, and MUC2 were observed using immunofluorescence and RT-PCR. Additionally, the proportion of ILC3 and natural cytotoxicity receptor (NCR)+ ILC3 in the colon were detected using flow cytometry. Furthermore, UHPLC-QE-MS was utilized to identify chemical components of PD and network pharmacology was employed to predict potential pathways for PD intervention in UC. Subsequently, MNK-3 cells (ILC3 in vitro cell line) and NCM460 cells were used to verify the network pharmacology results. Finally, the effects of PD on UC gut flora have been explored using in vitro fermentation and 16S rDNA techniques.

RESULTS

The results showed that PD significantly restored body weight and colon length in mice with chronic colitis, while also reducing colon inflammatory cell infiltration and the expression of IL-6 and IL-1β. Additionally, PD notably promoted the expression of MUC2, ZO-1, Occludin, and IL-22, as well as increasing the ratio of ILC3 and NCR+ILC3. UHPLC-QE-MS analysis identified 443 components of PD, and network pharmacology suggested that PD could target the aryl hydrocarbon receptor (AHR) signaling pathway, which was confirmed by MNK-3 cells and in vitro fermentation experiments. Furthermore, MNK-3-conditioned medium (CM) increased the expression of ZO-1 and Occludin in NCM460 cells. In addition, 16S rDNA results indicated that PD promoted the abundance of Lactobacillales, thus contributing to mucosal damage repair by activating the AHR signal in ILC3s.

CONCLUSION

In summary, our study demonstrates that PD repairs intestinal mucosal damage in chronic colitis by regulating the interaction of gut flora with ILC3, and the specific mechanism is related to the activation of AHR signaling pathway.

Sirtuin 6 inhibits group 3 innate lymphoid cell function and gut immunity by suppressing IL-22 production

Introduction

Group 3 innate lymphoid cells (ILC3s) are enriched in the intestinal mucosa and play important roles in host defense against infection and inflammatory diseases. Sirtuin 6 (SIRT6) is a nicotinamide adenine dinucleotide (NAD+)- dependent deacetylase and has been shown to control intestinal epithelial cell differentiation and survival. However, the role of SIRT6 in ILC3s remains unknown.

Methods

To investigate the role of SIRT6 in gut ILC3s, we generated SIRT6 conditional knockout mice by crossing Rorccre and Sirt6flox/flox mice. Cell number and cytokine production was examined using flow cytometry. Citrobacter rodentium infection and dextran sodium sulfate-induced colitis models were used to determine the role of SIRT6 in gut defense. RT-qPCR, flow cytometry and immunohistochemistry were used to assess the intestinal inflammatory responses.

Results

Here we show that SIRT6 inhibits IL-22 expression in intestinal ILC3s in a cell-intrinsic manner. Deletion of SIRT6 in ILC3s does not affect the cell numbers of total ILC3s and subsets, but results in increased IL-22 production. Furthermore, ablation of SIRT6 in ILC3s protects mice against Citrobacter rodentium infection and dextran sodium sulfate-induced colitis. Our results suggest that SIRT6 may play a role in ILC3 function by regulating gut immune responses against bacterial infection and inflammation.

Discussion

Our finding provided insight into the relation of epigenetic regulators with IL-22 production and supplied a new perspective for a potential strategy against inflammatory bowel disease.

The role of trained immunity in sepsis

Sepsis is defined as a life-threatening organ dysfunction syndrome caused by dysregulated host response to infection, characterized by a systemic inflammatory response to infection. The use of antibiotics, fluid resuscitation, and organ support therapy has limited prognostic benefit in patients with sepsis, and its incidence is not diminishing, which is attracting increased attention in medicine. Sepsis remains one of the most debilitating and expensive illnesses. One of the main reasons of septic mortality is now understood to be disruption of immune homeostasis. Immunotherapy is revolutionizing the treatment of illnesses in which dysregulated immune responses play a significant role. This "trained immunity", which is a potent defense against infection regardless of the type of bacteria, fungus, or virus, is attributed to the discovery that the innate immune cells possess immune memory via metabolic and epigenetic reprogramming. Here we reviewed the immunotherapy of innate immune cells in sepsis, the features of trained immunity, and the relationship between trained immunity and sepsis.

Commensal microbe regulation of skin cells in disease

Human skin is the host to various commensal microbes that constitute a substantial microbial community. The reciprocal communication between these microbial inhabitants and host cells upholds both the morphological and functional attributes of the skin layers, contributing indispensably to microenvironmental and tissue homeostasis. Thus, disruption of the skin barrier or imbalances in the microbial communities can exert profound effects on the behavior of host cells. This influence, mediated by the microbes themselves or their metabolites, manifests in diverse outcomes. In this review, we examine existing knowledge to provide insight into the nuanced behavior exhibited by the microbiota on skin cells in health and disease states. These interactions provide insight into potential cellular targets for future microbiota-based therapies to prevent and treat skin disease.

Human CD127 negative ILC2s show immunological memory

ILC2s are key players in type 2 immunity and contribute to maintaining homeostasis. ILC2s are also implicated in the development of type 2 inflammation-mediated chronic disorders like asthma. While memory ILC2s have been identified in mouse, it is unknown whether human ILC2s can acquire immunological memory. Here, we demonstrate the persistence of CD45RO, a marker previously linked to inflammatory ILC2s, in resting ILC2s that have undergone prior activation. A high proportion of these cells concurrently reduce the expression of the canonical ILC marker CD127 in a tissue-specific manner. Upon isolation and in vitro stimulation of CD127-CD45RO+ ILC2s, we observed an augmented ability to proliferate and produce cytokines. CD127-CD45RO+ ILC2s are found in both healthy and inflamed tissues and display a gene signature of cell activation. Similarly, mouse memory ILC2s show reduced expression of CD127. Our findings suggest that human ILC2s can acquire innate immune memory and warrant a revision of the current strategies to identify human ILC2s.

OLFM4 modulates intestinal inflammation by promoting IL-22+ILC3 in the gut

Group 3 innate lymphoid cells (ILC3s) play key roles in intestinal inflammation. Olfactomedin 4 (OLFM4) is highly expressed in the colon and has a potential role in dextran sodium sulfate-induced colitis. However, the detailed mechanisms underlying the effects of OLFM4 on ILC3-mediated colitis remain unclear. In this study, we identify OLFM4 as a positive regulator of IL-22+ILC3. OLFM4 expression in colonic ILC3s increases substantially during intestinal inflammation in humans and mice. Compared to littermate controls, OLFM4-deficient (OLFM4-/-) mice are more susceptible to bacterial infection and display greater resistance to anti-CD40 induced innate colitis, together with impaired IL-22 production by ILC3, and ILC3s from OLFM4-/-mice are defective in pathogen resistance. Besides, mice with OLFM4 deficiency in the RORγt compartment exhibit the same trend as in OLFM4-/-mice, including colonic inflammation and IL-22 production. Mechanistically, the decrease in IL-22+ILC3 caused by OLFM4 deficiency involves the apoptosis signal-regulating kinase 1 (ASK1)- p38 MAPK signaling-dependent downregulation of RAR-related orphan receptor gamma (RORγt) protein. The OLFM4-metadherin (MTDH) complex upregulates p38/RORγt signaling, which is necessary for IL-22+ILC3 activation. The findings indicate that OLFM4 is a novel regulator of IL-22+ILC3 and essential for modulating intestinal inflammation and tissue homeostasis.

Shaoyao decoction improves damp-heat colitis by activating the AHR/IL-22/STAT3 pathway through tryptophan metabolism driven by gut microbiota

ETHNOPHARMACOLOGICAL RELEVANCE

The efficacy of Shaoyao Decoction (SYD), a traditional Chinese medicine prescription, in treating damp-heat colitis is established, but its underlying mechanism remains to be elucidated.

AIM OF THE STUDY

Our study aims to investigate the effect and mechanism of action of SYD in treating damp-heat colitis.

MATERIALS AND METHODS

A mouse model of damp-heat colitis was induced and treated with SYD via gavage for seven days. The therapeutic efficacy of SYD was assessed through clinical indicators and histopathological examinations. The inflammatory factors and oxidative stress parameters were detected by ELISA and biochemical kits. We also analyzed alterations in the gut microbiome via 16 S rRNA gene sequencing and quantified serum indole derivatives using targeted tryptophan metabolomics. Western blotting and immunofluorescence were used to detect the expressions of AHR, CYP1A1, STAT3 and tight junction (TJ) proteins. The ELISA kit was utilized to detect the content of antibacterial peptides (Reg3β and Reg3γ) in colon. The immunohistochemistry was employed to detect the expressions of proliferating cell nuclear antigen (PCNA) protein.

RESULTS

SYD effectively alleviated symptoms in mice with damp-heat colitis, including body weight loss, shortened colon, elevated DAI, enlarged spleen, and damage to the intestinal mucosa. SYD notably reduced IL-6, TNF-α, IL-1β and MDA levels in colon tissues, while increasing IL-10 and T-AOC levels. Furthermore, SYD mitigated gut microbiota disturbance, restored microbial tryptophan metabolite production (such as IA, IAA, and IAld), notably increased the protein levels of AHR, CYP1A1 and p-STAT3 in colon tissue, and elevated the IL-22 level. Moreover, the expression levels of Reg3β, Reg3γ, occludin, ZO-1 and PCNA were increased in SYD group.

CONCLUSION

Our study showed that SYD ameliorates damp-heat colitis by restructuring gut microbiota structure, enhancing the metabolism of tryptophan associated with gut microbiota to activate the AHR/IL-22/STAT3 pathway, thereby recovering damaged intestinal mucosa. This research offers novel insights into the therapeutic mechanisms of SYD on damp-heat colitis.

Transcription factor Tox2 is required for metabolic adaptation and tissue residency of ILC3 in the gut

Group 3 innate lymphoid cells (ILC3) are the major subset of gut-resident ILC with essential roles in infections and tissue repair, but how they adapt to the gut environment to maintain tissue residency is unclear. We report that Tox2 is critical for gut ILC3 maintenance and function. Gut ILC3 highly expressed Tox2, and depletion of Tox2 markedly decreased ILC3 in gut but not at central sites, resulting in defective control of Citrobacter rodentium infection. Single-cell transcriptional profiling revealed decreased expression of Hexokinase-2 in Tox2-deficient gut ILC3. Consistent with the requirement for hexokinases in glycolysis, Tox2-/- ILC3 displayed decreased ability to utilize glycolysis for protein translation. Ectopic expression of Hexokinase-2 rescued Tox2-/- gut ILC3 defects. Hypoxia and interleukin (IL)-17A each induced Tox2 expression in ILC3, suggesting a mechanism by which ILC3 adjusts to fluctuating environments by programming glycolytic metabolism. Our results reveal the requirement for Tox2 to support the metabolic adaptation of ILC3 within the gastrointestinal tract.

Emerging role of gut microbiota in autoimmune diseases

Accumulating studies have indicated that the gut microbiota plays a pivotal role in the onset of autoimmune diseases by engaging in complex interactions with the host. This review aims to provide a comprehensive overview of the existing literatures concerning the relationship between the gut microbiota and autoimmune diseases, shedding light on the complex interplay between the gut microbiota, the host and the immune system. Furthermore, we aim to summarize the impacts and potential mechanisms that underlie the interactions between the gut microbiota and the host in autoimmune diseases, primarily focusing on systemic lupus erythematosus, rheumatoid arthritis, Sjögren's syndrome, type 1 diabetes mellitus, ulcerative colitis and psoriasis. The present review will emphasize the clinical significance and potential applications of interventions based on the gut microbiota as innovative adjunctive therapies for autoimmune diseases.

Group 3 innate lymphoid cells: A trained Gutkeeper

Group 3 innate lymphoid cells (ILC3s) are tissue-resident immune lymphocytes that critically regulate intestinal homeostasis, organogenesis, and immunity. ILC3s possess the capacity to "sense" the inflammatory environment within tissues, especially in the context of pathogen challenges that imprints durable non-antigen-specific changes in ILC3 function. As such, ILC3s become a new actor in the emerging field of trained innate immunity. Here, we summarize recent discoveries regarding ILC3 responses to bacterial challenges and the role these encounters play in triggering trained innate immunity. We further discuss how signaling events throughout ILC3 ontogeny potentially control the development and function of trained ILC3s. Finally, we highlight the open questions surrounding ILC3 "training" the answers to which may reveal new insights into innate immunity. Understanding the fundamental concepts behind trained innate immunity could potentially lead to the development of new strategies for improving immunity-based modulation therapies for inflammation, infectious diseases, and cancer.

Extrinsic and intrinsic drivers of natural killer cell clonality

Clonal expansion of antigen-specific lymphocytes is the fundamental mechanism enabling potent adaptive immune responses and the generation of immune memory. Accompanied by pronounced epigenetic remodeling, the massive proliferation of individual cells generates a critical mass of effectors for the control of acute infections, as well as a pool of memory cells protecting against future pathogen encounters. Classically associated with the adaptive immune system, recent work has demonstrated that innate immune memory to human cytomegalovirus (CMV) infection is stably maintained as large clonal expansions of natural killer (NK) cells, raising questions on the mechanisms for clonal selection and expansion in the absence of re-arranged antigen receptors. Here, we discuss clonal NK cell memory in the context of the mechanisms underlying clonal competition of adaptive lymphocytes and propose alternative selection mechanisms that might decide on the clonal success of their innate counterparts. We propose that the integration of external cues with cell-intrinsic sources of heterogeneity, such as variegated receptor expression, transcriptional states, and somatic variants, compose a bottleneck for clonal selection, contributing to the large size of memory NK cell clones.

New insights into ILC2 memory

Group 2 Innate Lymphoid Cells (ILC2s) are innate lymphocytes involved in type 2 immunity. ILC2s are abundant at the barrier tissues and upon allergen exposure, respond to epithelial-derived alarmins by producing type 2 cytokines (e.g., IL-5 and IL-13). Upon activation, some of these activated ILC2s acquire immunological memory and can mount enhanced responses upon further allergen encounters. Here, we review recent findings of the cellular and molecular mechanisms underlying immune memory in ILC2s both in mice and humans and discuss the implications of memory ILC2s in the context of allergic diseases.

Inflammatory Memory in Chronic Skin Disease

Inflammation is a hallmark of remitting-relapsing dermatological diseases. Although a large emphasis has been placed on adaptive immune cells as mediators of relapse, evidence in epithelial and innate immune biology suggests that disease memory is widespread. In this study, we bring to the fore the concept of inflammatory memory or nonspecific training of long-lived cells in the skin, highlighting the epigenetic and other mechanisms that propagate memory at the cellular level. We place these findings in the context of psoriasis, a prototypic flaring disease known to have localized memory, and underscore the importance of targeting memory to limit disease flares.

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

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

IMPORTANCE

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

A Panoramic View of Cell Population Dynamics in Mammalian Aging

To elucidate the aging-associated cellular population dynamics throughout the body, here we present PanSci, a single-cell transcriptome atlas profiling over 20 million cells from 623 mouse tissue samples, encompassing a range of organs across different life stages, sexes, and genotypes. This comprehensive dataset allowed us to identify more than 3,000 unique cellular states and catalog over 200 distinct aging-associated cell populations experiencing significant depletion or expansion. Our panoramic analysis uncovered temporally structured, organ- and lineage-specific shifts of cellular dynamics during lifespan progression. Moreover, we investigated aging-associated alterations in immune cell populations, revealing both widespread shifts and organ-specific changes. We further explored the regulatory roles of the immune system on aging and pinpointed specific age-related cell population expansions that are lymphocyte-dependent. The breadth and depth of our 'cell-omics' methodology not only enhance our comprehension of cellular aging but also lay the groundwork for exploring the complex regulatory networks among varied cell types in the context of aging and aging-associated diseases.

Disease-associated astrocyte epigenetic memory promotes CNS pathology

Disease-associated astrocyte subsets contribute to the pathology of neurologic diseases, including multiple sclerosis and experimental autoimmune encephalomyelitis1-8 (EAE), an experimental model for multiple sclerosis. However, little is known about the stability of these astrocyte subsets and their ability to integrate past stimulation events. Here we report the identification of an epigenetically controlled memory astrocyte subset that exhibits exacerbated pro-inflammatory responses upon rechallenge. Specifically, using a combination of single-cell RNA sequencing, assay for transposase-accessible chromatin with sequencing, chromatin immunoprecipitation with sequencing, focused interrogation of cells by nucleic acid detection and sequencing, and cell-specific in vivo CRISPR-Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP-citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) that is used by histone acetyltransferase p300 to control chromatin accessibility. The number of ACLY+p300+ memory astrocytes is increased in acute and chronic EAE models, and their genetic inactivation ameliorated EAE. We also detected the pro-inflammatory memory phenotype in human astrocytes in vitro; single-cell RNA sequencing and immunohistochemistry studies detected increased numbers of ACLY+p300+ astrocytes in chronic multiple sclerosis lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, multiple sclerosis. These findings may guide novel therapeutic approaches for multiple sclerosis and other neurologic diseases.

RORα is required for expansion and memory maintenance of ILC1s via a lymph node-liver axis

Type 1 innate lymphoid cells (ILC1s) possess adaptive immune features, which confer antigen-specific memory responses against haptens and viruses. However, the transcriptional regulation of memory ILC1 responses is currently not known. We show that retinoic acid receptor-related orphan receptor alpha (RORα) has high expression in memory ILC1s in murine contact hypersensitivity (CHS) models. RORα deficiency diminishes ILC1-mediated CHS responses significantly but has no effect on memory T cell-mediated CHS responses. During sensitization, RORα promotes sensitized-ILC1 expansion by suppressing expression of cell-cycle repressors in draining lymph nodes. RORα programs gene-expression patterns related to cell survival and is required for the long-term maintenance of memory ILC1s in the liver. Our findings reveal RORα to be a key transcriptional factor for sensitized-ILC1 expansion and long-term maintenance of memory ILC1s.

Innate Lymphoid Cells and Their Role in the Immune Response to Infections

Over the past decade, a group of lymphocyte-like cells called innate lymphoid cells (ILCs) has gained considerable attention due to their crucial role in regulating immunity and tissue homeostasis. ILCs, lacking antigen-specific receptors, are a group of functionally differentiated effector cells that act as tissue-resident sentinels against infections. Numerous studies have elucidated the characteristics of ILC subgroups, but the mechanisms controlling protective or pathological responses to pathogens still need to be better understood. This review summarizes the functions of ILCs in the immunology of infections caused by different intracellular and extracellular pathogens and discusses their possible therapeutic potential.

Role of trained innate immunity against mucosal cancer

Mucosal tissues are frequent targets of both primary and metastatic cancers. This has highlighted the significance of both innate and adaptive anti-cancer immunity at mucosal sites. Trained innate immunity (TII) is an emerging concept defined as enhanced reactivity of innate leukocytes long after a previous stimulation that induces prolonged epigenetic, transcriptional, and metabolic changes. Trained innate leukocytes can respond to heterologous targets due to their lacking of antigen-specificity in most cases. Emerging experimental and clinical data suggest that certain microbes or their products induce TII in mucosal-associated innate leukocytes which endows heterologous anti-tumor innate immunity, in both prophylactic and therapeutic scenarios. In this mini-review, we summarize updated findings on the significance of TII in mucosal cancers. We also attempt to raise a few key questions critical to our further understanding on the roles of TII in mucosal cancers, and to the potential application of TII as anti-cancer strategy.

Ginsenoside Rk3 modulates gut microbiota and regulates immune response of group 3 innate lymphoid cells to against colorectal tumorigenesis

The gut microbiota plays a pivotal role in the immunomodulatory and protumorigenic microenvironment of colorectal cancer (CRC). However, the effect of ginsenoside Rk3 (Rk3) on CRC and gut microbiota remains unclear. Therefore, the purpose of this study is to explore the potential effect of Rk3 on CRC from the perspective of gut microbiota and immune regulation. Our results reveal that treatment with Rk3 significantly suppresses the formation of colon tumors, repairs intestinal barrier damage, and regulates the gut microbiota imbalance caused by CRC, including enrichment of probiotics such as Akkermansia muciniphila and Barnesiella intestinihominis, and clearance of pathogenic Desulfovibrio. Subsequent metabolomics data demonstrate that Rk3 can modulate the metabolism of amino acids and bile acids, particularly by upregulating glutamine, which has the potential to regulate the immune response. Furthermore, we elucidate the regulatory effects of Rk3 on chemokines and inflammatory factors associated with group 3 innate lymphoid cells (ILC3s) and T helper 17 (Th17) signaling pathways, which inhibits the hyperactivation of the Janus kinase-signal transducer and activator of transcription 3 (JAK-STAT3) signaling pathway. These results indicate that Rk3 modulates gut microbiota, regulates ILC3s immune response, and inhibits the JAK-STAT3 signaling pathway to suppress the development of colon tumors. More importantly, the results of fecal microbiota transplantation suggest that the inhibitory effect of Rk3 on colon tumors and its regulation of ILC3 immune responses are mediated by the gut microbiota. In summary, these findings emphasize that Rk3 can be utilized as a regulator of the gut microbiota for the prevention and treatment of CRC.

Disease-associated astrocyte epigenetic memory promotes CNS pathology

Astrocytes play important roles in the central nervous system (CNS) physiology and pathology. Indeed, astrocyte subsets defined by specific transcriptional activation states contribute to the pathology of neurologic diseases, including multiple sclerosis (MS) and its pre-clinical model experimental autoimmune encephalomyelitis (EAE) 1-8 . However, little is known about the stability of these disease-associated astrocyte subsets, their regulation, and whether they integrate past stimulation events to respond to subsequent challenges. Here, we describe the identification of an epigenetically controlled memory astrocyte subset which exhibits exacerbated pro-inflammatory responses upon re-challenge. Specifically, using a combination of single-cell RNA sequencing (scRNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), chromatin immunoprecipitation with sequencing (ChIP-seq), focused interrogation of cells by nucleic acid detection and sequencing (FIND-seq), and cell-specific in vivo CRISPR/Cas9-based genetic perturbation studies we established that astrocyte memory is controlled by the metabolic enzyme ATP citrate lyase (ACLY), which produces acetyl coenzyme A (acetyl-CoA) used by the histone acetyltransferase p300 to control chromatin accessibility. ACLY + p300 + memory astrocytes are increased in acute and chronic EAE models; the genetic targeting of ACLY + p300 + astrocytes using CRISPR/Cas9 ameliorated EAE. We also detected responses consistent with a pro-inflammatory memory phenotype in human astrocytes in vitro ; scRNA-seq and immunohistochemistry studies detected increased ACLY + p300 + astrocytes in chronic MS lesions. In summary, these studies define an epigenetically controlled memory astrocyte subset that promotes CNS pathology in EAE and, potentially, MS. These findings may guide novel therapeutic approaches for MS and other neurologic diseases.

Single-Cell Transcriptional Analysis of Lamina Propria Lymphocytes in the Jejunum Reveals Innate Lymphoid Cell-like Cells in Pigs

Pigs are the most suitable model to study various therapeutic strategies and drugs for human beings, although knowledge about cell type-specific transcriptomes and heterogeneity is poorly available. Through single-cell RNA sequencing and flow cytometry analysis of the types in the jejunum of pigs, we found that innate lymphoid cells (ILCs) existed in the lamina propria lymphocytes (LPLs) of the jejunum. Then, through flow sorting of live/dead-lineage (Lin)-CD45+ cells and single-cell RNA sequencing, we found that ILCs in the porcine jejunum were mainly ILC3s, with a small number of NK cells, ILC1s, and ILC2s. ILCs coexpressed IL-7Rα, ID2, and other genes and differentially expressed RORC, GATA3, and other genes but did not express the CD3 gene. ILC3s can be divided into four subgroups, and genes such as CXCL8, CXCL2, IL-22, IL-17, and NCR2 are differentially expressed. To further detect and identify ILC3s, we verified the classification of ILCs in the porcine jejunum subgroup and the expression of related hallmark genes at the protein level by flow cytometry. For systematically characterizing ILCs in the porcine intestines, we combined our pig ILC dataset with publicly available human and mice ILC data and identified that the human and pig ILCs shared more common features than did those mouse ILCs in gene signatures and cell states. Our results showed in detail for the first time (to our knowledge) the gene expression of porcine jejunal ILCs, the subtype classification of ILCs, and the markers of various ILCs, which provide a basis for an in-depth exploration of porcine intestinal mucosal immunity.

Unravelling the immunobiology of innate lymphoid cells (ILCs): Implications in health and disease

Innate lymphoid cells (ILCs), a growing class of immune cells, imitate the appearance and abilities of T cells. However, unlike T cells, ILCs lack acquired antigen receptors, and they also do not undergo clonal selection or proliferation in response to antigenic stimuli. Despite lacking antigen-specific receptors, ILCs respond quickly to signals from infected or damaged tissues and generate an array of cytokines that regulate the development of adaptive immune response. ILCs can be categorized into four types based on their signature cytokines and transcription factors: ILC1, ILC2, ILC3 (including Lymphoid Tissue inducer- LTi cells), and regulatory ILCs (ILCregs). ILCs play key functions in controlling and resolving inflammation, and variations in their proportion are linked to various pathological diseases including cancer, gastrointestinal, pulmonary, and skin diseases. We highlight current advancements in the biology and classification of ILCs in this review. Additionally, we provide a thorough overview of their contributions to several inflammatory bone-related pathologies, including osteoporosis, rheumatoid arthritis, periodontitis, and ankylosing spondylitis. Understanding the multiple functions of ILCs in both physiological and pathological conditions will further mobilize future research towards targeting ILCs for therapeutic purposes.

Gut microbiota-mediated IL-22 alleviates metabolic inflammation

Low-grade chronic inflammation, also known as metabolic inflammation, promotes the development of metabolic diseases. Increasing evidence suggests that changes in gut microbes and metabolites disrupt the integrity of the gut barrier and exert significant effects on the metabolism of various tissues, including the liver and adipose tissue, thereby contributing to metabolic inflammation. We observed that IL-22 is a key signaling molecule that serves as a bridge between intestinal microbes and the host, effectively alleviating metabolic inflammation by modulating the host immunomodulatory network. Here, we focused on elucidating the underlying mechanisms by which the gut microbiota and their metabolites reduce inflammation via IL-22, highlighting the favorable impact of IL-22 on metabolic inflammation. Furthermore, we discuss the potential of IL-22 as a therapeutic target for the management of metabolic inflammation and related diseases.

Cardinal features of immune memory in innate lymphocytes

The ability of vertebrates to 'remember' previous infections had once been attributed exclusively to adaptive immunity. We now appreciate that innate lymphocytes also possess memory properties akin to those of adaptive immune cells. In this Review, we draw parallels from T cell biology to explore the key features of immune memory in innate lymphocytes, including quantity, quality, and location. We discuss the signals that trigger clonal or clonal-like expansion in innate lymphocytes, and highlight recent studies that shed light on the complex cellular and molecular crosstalk between metabolism, epigenetics, and transcription responsible for differentiating innate lymphocyte responses towards a memory fate. Additionally, we explore emerging evidence that activated innate lymphocytes relocate and establish themselves in specific peripheral tissues during infection, which may facilitate an accelerated response program akin to those of tissue-resident memory T cells.

ILC3: a case of conflicted identity

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

Trained immunity: a cutting edge approach for designing novel vaccines against parasitic diseases?

The preventive situation of parasitosis, a global public health burden especially for developing countries, is not looking that good. Similar to other infections, vaccines would be the best choice for preventing and controlling parasitic infection. However, ideal antigenic molecules for vaccine development have not been identified so far, resulting from the complicated life history and enormous genomes of the parasites. Furthermore, the suppression or down-regulation of anti-infectious immunity mediated by the parasites or their derived molecules can compromise the effect of parasitic vaccines. Comparing the early immune profiles of several parasites in the permissive and non-permissive hosts, a robust innate immune response is proposed to be a critical event to eliminate the parasites. Therefore, enhancing innate immunity may be essential for designing novel and effective parasitic vaccines. The newly emerging trained immunity (also termed innate immune memory) has been increasingly recognized to provide a novel perspective for vaccine development targeting innate immunity. This article reviews the current status of parasitic vaccines and anti-infectious immunity, as well as the conception, characteristics, and mechanisms of trained immunity and its research progress in Parasitology, highlighting the possible consideration of trained immunity in designing novel vaccines against parasitic diseases.