Dynamic regulation of innate lymphoid cells in the mucosal immune system

Proportions of IgA antibodies targeting glycosylated epitopes of secreted Escherichia coli mucinase YghJ in initial plasmablast response differ from salivary and intestinally secreted IgA

Mucosal infections normally cause an immune response including activation of antigen-specific B cells in regional mucosa-associated lymphoid tissue. After recirculation of plasmablasts, and maturation at mucosal surfaces or bone marrow, plasma cells produce secretory or systemic IgA. It remains uncertain to what extent secretory and systemic IgA share the same target specificities. For vaccine candidate optimization, it is important to know whether IgA targeting of glycosylated epitopes of a protein antigen vary between mucosal and systemic sites. We evaluated glycosylated epitope specificity of systemic and mucosally secreted IgA against YghJ, a potential vaccine candidate antigen secreted by most pathogenic Escherichia coli. IgA from intestinal lavage, saliva, serum, and blood-derived antibody in lymphocyte supernatants (ALS) were collected from 21 volunteers following experimental infection with enterotoxigenic E. coli. Methods for preparing IgA from saliva and ALS were developed, and multiplex bead flow cytometric immunoassays were used to determine levels of IgA targeting natively glycosylated YghJ and estimating what proportion of these antibodies specifically targeted glycosylated epitopes. Following infection, anti-YghJ IgA levels increased substantially for most volunteers across all four specimen types. Target specificity of ALS IgA correlated well with serum IgA, but not with mucosally secreted IgA. Furthermore, glycosylation-specific proportion of salivary IgA was higher than, and did not correlate with, intestinally secreted IgA. These results indicate a new degree of complexity to our understanding of epitope-targeting and tissue specificity of mucosal antibody responses. Our findings also suggest that all features of an intestinal IgA response may not be well reflected in serum, saliva, or ALS, which are commonly used proxy specimens for evaluating intestinal immune responses.

The development of a human Brucella mucosal vaccine: What should be considered?

Brucellosis is a chronic infectious disease that is zoonotic in nature. Brucella can infect humans through interactions with livestock, primarily via the digestive tract, respiratory tract, and oral cavity. This bacterium has the potential to be utilized as a biological weapon and is classified as a Category B pathogen by the Centers for Disease Control and Prevention. Currently, there is no approved vaccine for humans against Brucella, highlighting an urgent need for the development of a vaccine to mitigate the risks posed by this pathogen. Brucella primarily infects its host by adhering to and penetrating mucosal surfaces. Mucosal immunity plays a vital role in preventing local infections, clearing microorganisms from mucosal surfaces, and inhibiting the spread of pathogens. As mucosal vaccine strategies continue to evolve, the development of a safe and effective mucosal vaccine against Brucella appears promising.This paper reviews the immune mechanism of mucosal vaccines, the infection mechanism of Brucella, successful Brucella mucosal vaccines in animals, and mucosal adjuvants. Additionally, it elucidates targeting and optimization strategies for mucosal vaccines to facilitate the development of human vaccines against Brucella.

Implications of innate lymphoid cells in oral diseases

Innate lymphoid cells (ILCs), as newly discovered antigen-independent innate immune cells, respond promptly to stimuli by secreting effector cytokines to exert effector functions similar to those of T cells. ILCs predominantly reside at mucosal sites and play critical roles in defending against infections, maintaining mucosal homeostasis, regulating inflammatory and immune responses, and participating in tumorigenesis. Recently, there has been a growing interest in the role of ILCs in oral diseases. This review outlines the classifications and the major characteristics of ILCs, and then comprehensively expatiates the research on ILCs in oral cancer, primary Sjogren's syndrome, periodontal diseases, oral lichen planus, oral candidiasis, Behcet's disease, and pemphigus vulgaris, aiming at summarising the implications of ILCs in oral diseases and providing new ideas for further research.

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.

Research progress in the development of natural-product-based mucosal vaccine adjuvants

Mucosal vaccines have great potential and advantages in preventing infection caused by multiple pathogens. In developing mucosal vaccines, the biggest challenge comes from finding safe and effective adjuvants and drug delivery systems. Great progress has been made in the generation of mucosal adjuvants using detoxified bacterial toxin derivatives, pathogen-related molecules, cytokines, and various vaccine delivery systems. However, many problems, relating to the safety and efficacy of mucosal vaccine adjuvants, remain. Certain natural substances can boost the immune response and thus could be used as adjuvants in vaccination. These natural-product-based immune adjuvants have certain advantages over conventional adjuvants, such as low toxicity, high stability, and low cost of production. In this review, we summarize the latest natural-product-based immune adjuvants, and discuss their properties and clinical applications.

Intestinal Escherichia coli and related dysfunction as potential targets of Traditional Chinese Medicine for respiratory infectious diseases

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) has saved countless lives and maintained human health over its long history, especially in respiratory infectious diseases. The relationship between the intestinal flora and the respiratory system has been a popular research topic in recent years. According to the theory of the "gut-lung axis" in modern medicine and the idea that "the lung stands in an interior-exterior relationship with the large intestine" in TCM, gut microbiota dysbiosis is a contributing factor to respiratory infectious diseases, and there is potential means for manipulation of the gut microbiota in the treatment of lung diseases. Emerging studies have indicated intestinal Escherichia coli (E. coli) overgrowth in multiple respiratory infectious diseases, which could exacerbate respiratory infectious diseases by disrupting immune homeostasis, the gut barrier and metabolic balance. TCM is an effective microecological regulator, that can regulate the intestinal flora including E. coli, and restore the balance of the immune system, gut barrier, and metabolism.

AIM OF THE REVIEW

This review discusses the changes and effects of intestinal E. coli in respiratory infection, as well as the role of TCM in the intestinal flora, E. coli and related immunity, the gut barrier and the metabolism, thereby suggesting the possibility of TCM therapy regulating intestinal E. coli and related immunity, the gut barrier and the metabolism to alleviate respiratory infectious diseases. We aimed to make a modest contribution to the research and development of new therapies for intestinal flora in respiratory infectious diseases and the full utilization of TCM resources. Relevant information about the therapeutic potential of TCM to regulate intestinal E. coli against diseases was collected from PubMed, China National Knowledge Infrastructure (CNKI), and so on. The Plants of the World Online (https://wcsp.science.kew.org) and the Plant List (www.theplantlist.org) databases were used to provide the scientific names and species of plants.

RESULTS

Intestinal E. coli is a very important bacterium in respiratory infectious diseases that affects the respiratory system through immunity, the gut barrier and the metabolism. Many TCMs can inhibit the abundance of E. coli and regulate related immunity, the gut barrier and the metabolism to promote lung health.

CONCLUSION

TCM targeting intestinal E. coli and related immune, gut barrier, and metabolic dysfunction could be a potential therapy to promote the treatment and prognosis of respiratory infectious diseases.

Gastric immune homeostasis imbalance: An important factor in the development of gastric mucosal diseases

The gastric mucosal immune system is a unique immune organ independent of systemic immunity that not only maintains nutrient absorption but also plays a role in resisting the external environment. Gastric mucosal immune disorder leads to a series of gastric mucosal diseases, including autoimmune gastritis (AIG)-related diseases, Helicobacter pylori (H. pylori)-induced diseases, and various types of gastric cancer (GC). Therefore, understanding the role of gastric mucosal immune homeostasis in gastric mucosal protection and the relationship between mucosal immunity and gastric mucosal diseases is very important. This review focuses on the protective effect of gastric mucosal immune homeostasis on the gastric mucosa, as well as multiple gastric mucosal diseases caused by gastric immune disorders. We hope to offer new prospects for the prevention and treatment of gastric mucosal diseases.

The Role of Innate Lymphoid Cells in Cancer Development and Immunotherapy

Innate Lymphoid Cells (ILCs) are an elusive type of innate immune cell that was only discovered recently. Their tissue residency and dependency makes them a niche group of cells that bridge the adaptive and innate immune system. The nomenclature and classification of ILCs have been challenging due to their heterogeneity. The currently agreed ILC classification splits the cells into two categories including cytotoxic and helper ILCs. The tumour microenvironment is often hostile for immune cells. Remodeling the microenvironment and regulating other immune cells—achieved by ILCs-can enhance anti-tumor effects. How ILCs regulate other immune cells in the tumor microenvironment remains to be understood. Here we review current understanding of the role of ILCs in the tumor microenvironment. ILCs recruit CD8 positive T and memory T cells in PDAC, ILCs are also able to help CD108 positive B cells migrate toward tumour locations. In NSCLC, ILC3s are seen helping resident macrophages enhancing the mucus immunity to cancer cells. We then highlight the roles of cytokines and immune checkpoint pathways in ILCs and its implication in immunotherapy.

Imbalanced distribution of group 2 innate lymphoid cells (ILCs) and ILC precursors in peripheral blood of patients with primary biliary cholangitis

Innate lymphoid cells (ILCs), a novel group of innate immune cells, play a key role in the early immune response via rapidly reacting to signals expressed by tissue-resident cells. ILCs contribute to some autoimmune diseases. We aim to investigate the proportions of circulating ILC subgroups in patients with primary biliary cholangitis (PBC). Overall, 48 patients with PBC and 24 healthy controls (HCs) were enrolled. Circulating ILCs and cytokine production were detected by flow cytometry. The proportions of total ILCs, ILC precursors (ILCPs), and ILCP/ILC2 ratio increased and that of ILC2s decreased in patients with PBC. ILC2 proportion was negatively correlated with gamma-glutamyl transpeptidase (GGT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). The proportion of ILCPs and ILCP/ILC2 ratio were positively correlated with alkaline phosphatase, GGT, ALT, and AST. ILC2 proportion was significantly decreased in the ursodeoxycholic acid (UDCA) -non-responder group compared with the UDCA-responder group, whereas the proportion of ILCPs and ILCP/ILC2 were ratio significantly increased. The proportions of CD38⁺ ILC2s, CD38⁺ ILCPs, CD45RO⁺ ILC2s, and CD45RO⁺ ILCPs were significantly higher in patients with PBC than in HCs. Levels of IL-17A producing ILCs were higher in patients with PBC than in HCs. PBC is accompanied by alterations in circulating ILCs. The proportions of ILC2s, ILCPs, and ILCP/ILC2 ratio were associated with the PBC disease activity. The proportions of ILCPs and ILCP/ILC2 ratio may reflect the UDCA treatment failure in patients with PBC. ILC2s and ILCPs from patients with PBC get activated, these cells may be involved in the pathogenesis of PBC.

Trained immunity in the mucosal diseases

Immune memory is well known as a signature of the adaptive immune system. Recently, enhanced responses to subsequent triggers are also observed in innate immune system, termed trained immunity (TI). Awakening of innate immune memory is required for host defense, such as anti-pathogen and anti-tumor responses. However, hyper-reactivation of trained innate immune cells also gives rise to undesirable inflammation. Mucosa immune system serves as the first defense line against pathogens. Trained immunity of mucosal immune system is tightly associated with the outcomes of mucosal diseases. In this review, we discuss the role of trained immunity in mucosal-associated diseases and the underlying mechanisms. We summarize the metabolic and epigenetic changes of trained immune cells and highlight their potential in clinical treatment. This article is categorized under: Infectious Diseases > Molecular and Cellular Physiology.

Enterovirus 71 Antagonizes Antiviral Effects of Type III Interferon and Evades the Clearance of Intestinal Intraepithelial Lymphocytes

Enterovirus 71 (EV71) is the major pathogen causing severe neurological complications and hand, foot, and mouth disease. The intestinal mucosal immune system has a complete immune response and immune regulation mechanism, consisting of densely arranged monolayer intestinal epithelial cells (IECs) and intestinal intraepithelial lymphocytes (iIELs) distributed among the IECs, which constitute the first line of intestinal mucosa against infection of foreign pathogens. As an enterovirus, EV71 is transmitted by the intestinal tract; however, the mechanisms it uses to evade the immunosurveillance of the intestinal mucosal immune system are still incompletely clarified. The present study investigated how EV71 evades from recognizing and eliminating IECs, iIELs, and iNK cells. We found that EV71 infection induced a higher level of type III interferons (IFN-λ) than type I interferons (IFN-β) in IECs, and the addition of IFN-λ markedly restricted EV71 replication in IECs. These results indicate that IFN-λ plays a more important role in anti-EV71 intestinal infection. However, EV71 infection could markedly attenuate the antiviral responses of IFN-λ. Mechanistically, 2A protease (2Apro) and 3C protease (3Cpro) of EV71 inhibited the IFN-λ production and IFN-λ receptor expression and further decreased the response of IECs to IFN-λ. In addition, we found that EV71-infected IECs were less susceptible to the lysis of intestinal NK (iNK) cells and CD3⁺iIELs. We revealed that the viral 2Apro and 3Cpro could significantly reduce the expression of the ligands of natural killer group 2D (NKG2D) and promote the expression of PD-L1 on IECs, rendering them to evade the recognition and killing of iNK and CD3⁺iIELs. These results provide novel evasion mechanisms of EV71 from intestinal mucosal innate immunity and may give new insights into antiviral therapy.