Dynamics and clinical significance of intestinal intraepithelial lymphocytes

Dietary supplementation with dihydroartemisinin improves intestinal barrier function in weaned piglets with intrauterine growth retardation by modulating the gut microbiota

The aim of this study was to investigate whether dietary dihydroartemisinin (DHA) supplementation could improve intestinal barrier function and microbiota composition in intrauterine growth restriction (IUGR) weaned piglets. Twelve normal birth weight (NBW) piglets and 24 IUGR piglets at 21 d of age were divided into three groups, which were fed a basal diet (NBW-CON and IUCR-CON groups) and an 80 mg/kg DHA diet (IUGR-DHA group). At 49 d of age, eight piglets of each group with similar body weights within groups were slaughtered, and serum and small intestine samples were collected. The results showed that IUGR piglets reduced growth performance, impaired the markers of intestinal permeability, induced intestinal inflammation, decreased intestinal immunity, and disturbed the intestinal microflora. Dietary DHA supplementation increased average daily gain, average daily feed intake, and body weight at 49 d of age in IUGR-weaned piglets (P < 0.05). DHA treatment decreased serum diamine oxidase activity and increased the numbers of intestinal goblet cells and intraepithelial lymphocytes, concentrations of jejunal mucin-2 and ileal trefoil factor 3, and intestinal secretory immunoglobin A and immunoglobin G (IgG) concentrations of IUGR piglets (P < 0.05). Diet supplemented with DHA also upregulated mRNA abundances of jejunal IgG, the cluster of differentiation 8 (CD8), major histocompatibility complex-I (MHC-I), and interleukin 6 (IL-6) and ileal IgG, Fc receptor for IgG (FcRn), cluster of differentiation 8 (CD4), CD8, MHC-I, IL-6 and tumor necrosis factor α (TNF-α), and enhanced mRNA abundance and protein expression of intestinal occludin and ileal claudin-1 in IUGR piglets (P < 0.05). In addition, DHA supplementation in the diet improved the microbial diversity of the small intestine of IUGR piglets and significantly increased the relative abundance of Actinobacteriota, Streptococcus, Blautia and Streptococcus in the jejunum, and Clostridium sensu_ stricto_in the ileum (P < 0.05). The intestinal microbiota was correlated with the mRNA abundance of tight junction proteins and inflammatory response-related genes. These data suggested that DHA could improve the markers of intestinal barrier function in IUGR-weaned piglets by modulating gut microbiota. DHA may be a novel nutritional candidate for preventing intestinal dysfunction in IUGR pigs.

Intestinal location- and age-specific variation of intraepithelial T lymphocytes and mucosal microbiota in pigs

Intraepithelial T lymphocytes (T-IELs) are T cells located within the epithelium that provide a critical line of immune defense in the intestinal tract. In pigs, T-IEL abundances and phenotypes are used to infer putative T-IEL functions and vary by intestinal location and age, though investigations regarding porcine T-IELs are relatively limited. In this study, we expand on analyses of porcine intestinal T-IELs to include additional phenotypic designations not previously recognized in pigs. We describe non-conventional CD8α⁺CD8β^- αβ T-IELs that were most prevalent in the distal intestinal tract and primarily CD16⁺CD27^-, a phenotype suggestive of innate-like activation and an activated cell state. Additional T-IEL populations included CD8α⁺CD8β⁺ αβ, CD2⁺CD8α⁺ γδ, and CD2⁺CD8α^- γδ T-IELs, with increasing proportions of CD16⁺CD27^- phenotype in the distal intestine. Thus, putative non-conventional, activated T-IELs were most abundant in the distal intestine within multiple γδ and αβ T-IEL populations. A comparison of T-IEL and respective mucosal microbial community structures across jejunum, ileum, and cecum of 5- and 7-week-old pigs revealed largest community differences were tissue-dependent for both T-IELs and the microbiota. Between 5 and 7 weeks of age, the largest shifts in microbial community compositions occurred in the large intestine, while the largest shifts in T-IEL communities were in the small intestine. Therefore, results indicate different rates of community maturation and stabilization for porcine T-IELs and the mucosal microbiota for proximal versus distal intestinal locations between 5 and 7 weeks of age. Collectively, data emphasize the intestinal tract as a site of location- and age-specific T-IEL and microbial communities that have important implications for understanding intestinal health in pigs.

Multimodal human thymic profiling reveals trajectories and cellular milieu for T agonist selection

To prevent autoimmunity, thymocytes expressing self-reactive T cell receptors (TCRs) are negatively selected, however, divergence into tolerogenic, agonist selected lineages represent an alternative fate. As thymocyte development, selection, and lineage choices are dependent on spatial context and cell-to-cell interactions, we have performed Cellular Indexing of Transcriptomes and Epitopes by sequencing (CITE-seq) and spatial transcriptomics on paediatric human thymu​​s. Thymocytes expressing markers of strong TCR signalling diverged from the conventional developmental trajectory prior to CD4⁺ or CD8⁺ lineage commitment, while markers of different agonist selected T cell populations (CD8αα(I), CD8αα(II), T_(agonist), T_reg(diff), and T_reg) exhibited variable timing of induction. Expression profiles of chemokines and co-stimulatory molecules, together with spatial localisation, supported that dendritic cells, B cells, and stromal cells contribute to agonist selection, with different subsets influencing thymocytes at specific developmental stages within distinct spatial niches. Understanding factors influencing agonist T cells is needed to benefit from their immunoregulatory effects in clinical use.

Intraepithelial lymphocytes in the pig intestine: T cell and innate lymphoid cell contributions to intestinal barrier immunity

Intraepithelial lymphocytes (IELs) include T cells and innate lymphoid cells that are important mediators of intestinal immunity and barrier defense, yet most knowledge of IELs is derived from the study of humans and rodent models. Pigs are an important global food source and promising biomedical model, yet relatively little is known about IELs in the porcine intestine, especially during formative ages of intestinal development. Due to the biological significance of IELs, global importance of pig health, and potential of early life events to influence IELs, we collate current knowledge of porcine IEL functional and phenotypic maturation in the context of the developing intestinal tract and outline areas where further research is needed. Based on available findings, we formulate probable implications of IELs on intestinal and overall health outcomes and highlight key findings in relation to human IELs to emphasize potential applicability of pigs as a biomedical model for intestinal IEL research. Review of current literature suggests the study of porcine intestinal IELs as an exciting research frontier with dual application for betterment of animal and human health.

Bitter taste receptor T2R38 is expressed on skin-infiltrating lymphocytes and regulates lymphocyte migration

Bitter taste receptors (T2Rs) are G protein-coupled receptors involved in the perception of bitter taste on the tongue. In humans, T2Rs have been found in several sites outside the oral cavity. Although T2R38 has been reported to be expressed on peripheral lymphocytes, it is poorly understood whether T2R38 plays immunological roles in inflammatory skin diseases such as atopic dermatitis (AD). Then, we first confirmed that T2R38 gene expression was higher in lesional skin of AD subjects than healthy controls. Furthermore, skin T2R38 expression levels were correlated with serum thymus and activation-regulated chemokine and IgE levels in AD patients. In lesional skin of AD, section staining revealed that CD3⁺ T cells in the dermis were T2R38 positive. In addition, flow cytometry analysis showed T2R38 expression in skin T cells. Migration assays using T2R38-transduced Jurkat T cell leukemia cells revealed that T2R38 agonists exerted a dose-dependent migration inhibitory effect. Moreover, skin tissue extracts, as well as supernatants of cultured HaCaT keratinocytes, caused T2R38-dependent migration inhibition, indicating that there should be an endogenous ligand for T2R38 in the skin epidermis. These findings implicate T2R38 as a migratory inhibitory receptor on the skin-infiltrating lymphocytes and as a therapeutic target for allergic/inflammatory skin diseases.

Porcine intraepithelial lymphocytes undergo migration and produce an antiviral response following intestinal virus infection

The location of intraepithelial lymphocytes (IELs) between epithelial cells provide a first line of immune defense against enteric infection. It is assumed that IELs migrate only along the basement membrane or into the lateral intercellular space (LIS) between epithelial cells. Here, we identify a unique transepithelial migration of porcine IELs as they move to the free surface of the intestinal epithelia. The major causative agent of neonatal diarrhea in piglets, porcine epidemic diarrhea virus (PEDV), increases the number of IELs entering the LIS and free surface of the intestinal epithelia, driven by chemokine CCL2 secreted from virus-infected intestinal epithelial cells. Remarkably, only virus pre-activated IELs inhibits PEDV infection and their antiviral activity depends on the further activation by virus-infected cells. Although high levels of perforin is detected in the co-culture system, the antiviral function of activated IELs is mainly mediated by IFN-γ secretion inducing robust antiviral response in virus-infected cells. Our results uncover a unique migratory behavior of porcine IELs as well as their protective role in the defense against intestinal infection.

When piglets are infected with intestinal virus, porcine intraepithelial lymphocytes undergo intra-and trans-epithelial migration promoted by chemokines from infected epithelial cells and produce an antiviral response.

The Functional Role of Lactoferrin in Intestine Mucosal Immune System and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), is one of the main types of intestinal inflammatory diseases with intestine mucosal immune disorder. Intestine mucosal immune system plays a remarkable and important role in the etiology and pathogenesis of IBD. Therefore, understanding the intestine mucosal immune mechanism is a key step to develop therapeutic interventions for IBD. Intestine mucosal immune system and IBD are influenced by various factors, such as inflammation, gut permeability, gut microbiota, and nutrients. Among these factors, emerging evidence show that nutrients play a key role in inflammation activation, integrity of intestinal barrier, and immune cell modulation. Lactoferrin (LF), an iron-binding glycoprotein belonging to transferrin family, is a dietary bioactive component abundantly found in mammalian milk. Notably, LF has been reported to perform diverse biological functions including antibacterial activity, anti-inflammatory activity, intestinal barrier protection, and immune cell modulation, and is involved in maintaining intestine mucosal immune homeostasis. The improved understanding of the properties of LF in intestine mucosal immune system and IBD will facilitate its application in nutrition, clinical medicine, and health. Herein, this review outlines the recent advancements on LF as a potential therapeutic intervention for IBD associated with intestine mucosal immune system dysfunction. We hope this review will provide a reference for future studies and lay a theoretical foundation for LF-based therapeutic interventions for IBD by understanding the particular effects of LF on intestine mucosal immune system.

New Insights on CD8+ T Cells in Inflammatory Bowel Disease and Therapeutic Approaches

CD8⁺ T cells are involved in the pathogenesis of inflammatory bowel disease (IBD), a complex multifactorial chronic disease. Here, we present an overview of the current research with the controversial findings of CD8⁺ T cell subsets and discuss some possible perspectives on their therapeutic value in IBD. Studies on the role of CD8⁺ T cells in IBD have contradictory outcomes, which might be related to the heterogeneity of the cells. Recent data suggest that cytotoxic CD8⁺ T cells (Tc1) and interleukin (IL) 17-producing CD8⁺ (Tc17) cells contribute to the pathogenesis of IBD. Moreover, subsets of regulatory CD8⁺ T cells are abundant at sites of inflammation and can exhibit pro-inflammatory features. Some subsets of tissue resident memory CD8⁺ T cells (Trm) might be immunosuppressant, whereas others might be pro-inflammatory. Lastly, exhausted T cells might indicate a positive outcome for patients. The function and plasticity of different subsets of CD8⁺ T cells in health and IBD remain to be further investigated in a challenging field due to the limited availability of mucosal samples and adequate controls.

Recent advances in roles of G-protein coupled receptors in intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) potentially provide the first line of immune defense against enteric pathogens. In addition, there is growing evidence supporting the involvement of IELs in the pathogenesis of gut disorders such as inflammatory bowel diseases. Various kinds of molecules are involved in the dynamics of IELs, such as homing to the intestinal epithelium and retention in the intestinal mucosa. G protein-coupled receptors (GPCRs) comprise the largest family of cell surface receptors and regulate many biological responses. Although some GPCRs, like CCR9, have been implicated to have roles in IEL homing, little is still known regarding the functional roles of GPCRs in IEL biology. In this review, we provide a concise overview of recent advances in the roles of novel GPCRs like GPR55 and GPR18 in the dynamics of IELs.