Identification of multiple isolated lymphoid follicles on the antimesenteric wall of the mouse small intestine

The pathogenesis of West Nile virus-associated lymphohistiocytic proliferative cutaneous lesions of American alligators (Alligator mississippiensis)

"Pix" is one of the most common skin defects that reduce the quality of crocodilian leather. The name is derived from their resemblance to pit marks made by an ice pick. Histologically, each "pix" is associated with a focal dermal accumulation of immune cells, specifically lymphocytes and histiocytes. Consequently, these defects have been termed lymphohistiocytic proliferative cutaneous lesions (LPCLs). In farmed American alligators (Alligator mississippiensis), LPCLs have been associated with seropositivity against West Nile virus (WNV) and the presence of viral genome in the skin. Despite this association, the nature and pathogenesis of LPCLs remain unclear. Using immunohistochemistry and in situ hybridization, we unravel the microanatomy of LPCLs of alligators and localize WNV genome within the lesions. Our results show that LPCL lesions consist of de novo follicular aggregates of lymphocytes segregated into B- and T-cell zones, like tertiary lymphatic follicles of mammals and birds. Furthermore, the presence of WNV genome was highlighted by in situ hybridization in the macrophages of LPCLs, gut-associated lymphoid tissues, and the spleen. Our results suggest that LPCLs may form in American alligators' skin as part of a generalized lymphofollicular proliferation, likely as an immune response against WNV infection.

The role of gut flora-driven Th cell responses in preclinical rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder with an immune pathogenesis that evolves over decades. Preclinical RA (PreRA) represents a dynamic immune phase preceding clinical RA, marked by the loss of autoimmune tolerance, the appearance of tissue-invasive effector T cells, and the production of autoantibodies (such as antibodies against citrullinated proteins and rheumatoid factors). Extensive research has demonstrated that gut microbiota influence mucosal T-cell responses, driving the progression of PreRA through multiple mechanisms, including altered intestinal permeability, gene-environment interactions, bacterial antigenic specificity, molecular mimicry, and metabolite production. Environmental risk factors such as smoking, hormonal changes, and high-sodium (Na) diets, may contribute to RA pathogenesis via the gut microbiome. The next challenge in RA research lies in developing therapeutic strategies to intervene during the asymptomatic autoimmune phase, where dietary adjustments, natural compounds, probiotics, and other approaches could effectively modulate gut flora to prevent or delay RA onset.

Long-acting injectable nanoparticle formulation for sustained release of anti-TNF-α antibody therapeutic in ulcerative colitis treatment

Inflammatory bowel diseases (IBD) are chronic, remitting, and relapsing conditions of the gastrointestinal tract with incompletely elucidated etiology. The anti-TNF-α mAbs represent one of aflash nanocomplexation and flash nanoprecipitation process, resulting in particles with a narrow size distribution and tunable release profile, with the longest in vitro release lasting over four months. These mAb-releasing NPs are then incorporated into hyaluronic acid hydrogel microparticles (MPs) to enhance tissue retention, thus extending the duration of mAb release in vivo. A single i.m. injection of the LAI can maintain the serum mAb level above the therapeutically effective concentration for over 100 days in healthy mice. In a 9-week study using a dextran sulfate-induced chronic colitis model, the anti-TNF-α LAI formulation demonstrates substantial therapeutic efficacy and a better safety profile than free mAb injections. This work demonstrates the effectiveness of this LAI system in maintaining a persistent serum mAb level and its potential as a versatile, safer, and effective delivery system for antibody therapeutics.

Barrier-Strengthening Effects of Cannabidiol on Porcine Peyer's Patches

Cannabidiol (CBD), a major non-psychoactive cannabinoid of the Cannabis sativa L. plant, has demonstrated anti-inflammatory effects in various studies. However, the therapeutic use of CBD is still limited. Despite its potential, little is known about the molecular mechanisms of CBD on epithelial integrity, particularly concerning effects in native intestinal tissue. To accomplish this, our study aimed to investigate the effects of CBD ex vivo on the follicle-associated epithelium of Peyer's Patches (PP) and villus epithelium (VE) from porcine intestine. To measure the epithelial barrier, the Ussing chamber technique was employed, followed by immunoblotting and confocal laser-scanning immunofluorescence microscopy of tight junction proteins and specific receptors. The results revealed that CBD significantly strengthens the epithelial barrier of PP by upregulation of sealing tight junction proteins, including occludin, claudin-1, -3, and -7. Additionally, the study showed the potential of CBD to decrease the expression of Tumor necrosis factor alpha (TNFɑ) receptor 1 (TNFR-1) in PP that plays a key role in chronic inflammatory diseases. The study highlights the potential of CBD in the prevention of inflammatory conditions and underlines the important role of PP as a target for bioactive compounds.

Intestinal tissue-resident memory T cells: Characteristics, functions under physiological and pathological conditions and spatial specificity

BACKGROUND

Tissue-resident memory T (TRM) cells are a distinct subset of memory T cells that persist in non-lymphoid tissues, providing localized and rapid immune responses to infection and malignancy. Unlike circulating memory T cells, TRM cells have unique homing and functional characteristics that are shaped by the tissue microenvironment. In the gut, TRM cells play a pivotal role in maintaining mucosal immunity, exhibiting phenotypic and functional heterogeneity in different intestinal compartments and in response to aging and pathological conditions.

AIM OF REVIEW

This review aims to systematically examine the definition, spatial heterogeneity and functional roles of intestinal TRM (iTRM) cells. It highlights their contributions to physiological immunity, their involvement in pathological processes such as inflammatory bowel disease (IBD) and colorectal cancer (CRC), and their age-related dynamics. The review also explores emerging therapeutic implications of modulating iTRM cells for intestinal health and disease management. KEY SCIENTIFIC CONCEPTS OF REVIEW: iTRM cells are defined by surface markers like CD69 and CD103, transcriptional regulators such as Hobit, Runx3, Blimp-1, as well as cytokine signals including TGF-β, IFN-β, IL-12. They exhibit spatial and functional heterogeneity across intestinal layers (epithelium versus lamina propria) and regions (small intestine versus colon). In IBD, iTRM cells play a dual role, contributing to both inflammation and tissue repair, whereas in CRC, specific subsets of iTRM cells (e.g., CD8+ CD103+ CD39+) are associated with enhanced antitumor immunity. Aging impacts iTRM functionality, with shifts in the CD4+/CD8+ ratio and reduced cytokine production in elderly individuals. Insights into the metabolic, transcriptional, and environmental regulation of iTRM cells provide avenues for targeted therapies in intestinal diseases, cancer immunotherapy, and interventions to delay intestinal aging.

Biomarker expression level changes within rectal gut-associated lymphoid tissues in spinal cord-injured rats

Neurogenic bowel dysfunction (NBD) is common after spinal cord injury (SCI). Gut-associated lymphoid tissue (GALT), an organized structure within the mucosal immune system, is important for the maintenance of gut homeostasis and body health and serves as the first line barrier/defense against diet antigens, commensal microbiota, pathogens, and toxins in mucosal areas. The current study examined gene expression levels along six segments of anorectal tissue using real-time polymerase chain reaction (RT-PCR) in uninjured rats (28-day sham surgical controls) and at both 28- and 42-days post-T9 contusion injury. Consistent with our previous report of functional regional differences in the ano-rectum, we demonstrate the existence of GALTs located primarily within the segment at 3-4.5 cm from the rectal dentate line (termed rectal GALTs-rGALTs) in shams with upregulated gene expression levels of multiple biomarkers, including B cell and T cell-related genes, major histocompatibility complex (MHC) class II molecules, and germinal center (GC)-related genes, which was further confirmed by histologic examination. In the same rectal tissue segment following T9 SCI, inflammation-related genes were upregulated at 28 days post-injury (DPI) indicating that microbial infection and inflammation of rGALTs modified structure and function of rGALTs, while at 42 DPI rGALTs exhibited resolution of inflammation and impaired structure/function for extrafollicular B cell responses. Taken together, our data suggest that rGALTs exists in rat rectum for homeostasis of gut microbiota/barrier. SCI induces microbial infection and inflammation in rectal tissues containing rGALTs, which could contribute to development of SCI-related gut microbiome dysbiosis, NBD, and systemic diseases.

Organismal mucosal immunology: A perspective through the eyes of game theory

In complex organisms, functional units must interact cohesively to maintain homeostasis, especially within mucosal barriers that house diverse, specialized cell exposed to constant environmental challenges. Understanding how homeostasis at mucosal barriers is maintained and how its disruption can lead to autoimmune diseases or cancer, requires a holistic view. Although omics approaches and systems immunology have become powerful tools, they are not without limitations; interpretations may reflect researchers' assumptions, even if other explanations exist. In this perspective, I propose that applying game theory concepts to mucosal immunology could help interpret complex data, offering fresh perspectives and supporting the exploration of alternative scenarios. By framing the mucosal immune system as a network of strategic interactions with multiple possible outcomes, game theory, which analyzes strategic interactions and decision-making processes, could illuminate novel cell types and functions, cell interactions, and responses to pathogens and commensals, leading to a more comprehensive understanding of immune homeostasis and diseases. In addition, game theory might encourage researchers to consider a broader range of possibilities, reduce the risk of myopic thinking, and ultimately enable a more refined and comprehensive understanding of the complexity of the immune system at mucosal barriers. This perspective aims to introduce game theory as a complementary framework for mucosal immunologists, encouraging them to incorporate these concepts into data interpretation and system modeling.

Transient PU.1 low fetal progenitors generate lymphoid progeny that contribute to adult immunity

Hematopoietic stem cells and multipotential progenitors emerge in multiple, overlapping waves of fetal development. Some of these populations seed the bone marrow and sustain adult B- and T-cell development long-term after birth. However, others are present transiently, but whether they are vestigial or generate B and T cells that contribute to the adult immune system is not well understood. We now report that transient fetal progenitors distinguished by expression of low levels of the PU.1 transcription factor generated activated and memory T and B cells that colonized and were maintained in secondary lymphoid tissues. These included the small and large intestines, where they may contribute to the maintenance of gut homeostasis through at least middle age. At least some of the activated/memory cells may have been the progeny of B-1 and marginal zone B cells, as transient PU.1low fetal progenitors efficiently generated those populations. Taken together, our data demonstrate the potential of B- and T-cell progeny of transient PU.1low fetal progenitors to make an early and long-term contribution to the adult immune system.

Group 3 innate lymphoid cells in intestinal health and disease

The gastrointestinal tract is an immunologically rich organ, containing complex cell networks and dense lymphoid structures that safeguard this large absorptive barrier from pathogens, contribute to tissue physiology and support mucosal healing. Simultaneously, the immune system must remain tolerant to innocuous dietary antigens and trillions of normally beneficial microorganisms colonizing the intestine. Indeed, a dysfunctional immune response in the intestine underlies the pathogenesis of numerous local and systemic diseases, including inflammatory bowel disease, food allergy, chronic enteric infections or cancers. Here, we discuss group 3 innate lymphoid cells (ILC3s), which have emerged as orchestrators of tissue physiology, immunity, inflammation, tolerance and malignancy in the gastrointestinal tract. ILC3s are abundant in the developing and healthy intestine but their numbers or function are altered during chronic disease and cancer. The latest studies provide new insights into the mechanisms by which ILC3s fundamentally shape intestinal homeostasis or disease pathophysiology, and often this functional dichotomy depends on context and complex interactions with other cell types or microorganisms. Finally, we consider how this knowledge could be harnessed to improve current treatments or provoke new opportunities for therapeutic intervention to promote gut health.

Early life imprinting of intestinal immune tolerance and tissue homeostasis

Besides its canonical role in protecting the host from pathogens, the immune system plays an arguably equally important role in maintaining tissue homeostasis. Within barrier tissues that interface with the external microenvironment, induction of immune tolerance to innocuous antigens, such as commensal, dietary, and environmental antigens, is key to establishing immune homeostasis. The early postnatal period represents a critical window of opportunity in which parallel development of the tissue, immune cells, and microbiota allows for reciprocal regulation that shapes the long-term immunological tone of the tissue and subsequent risk of immune-mediated diseases. During early infancy, the immune system appears to sacrifice pro-inflammatory functions, prioritizing the establishment of tissue tolerance. In this review, we discuss mechanisms underlying early life windows for intestinal tolerance with a focus on newly identified RORγt+ antigen-presenting cells-Thetis cells-and highlight the role of the intestinal microenvironment in shaping intestinal immune system development and tolerance.

Early life microbiome influences on development of the mucosal innate immune system

The gut microbiota is well known to possess immunomodulatory capacities, influencing a multitude of cellular signalling pathways to maintain host homeostasis. Although the formation of the immune system initiates before birth in a sterile environment, an emerging body of literature indicates that the neonatal immune system is influenced by a first wave of external stimuli that includes signals from the maternal microbiota. A second wave of stimulus begins after birth and must be tightly regulated during the neonatal period when colonization of the host occurs concomitantly with the maturation of the immune system, requiring a fine adjustment between establishing tolerance towards the commensal microbiota and preserving inflammatory responses against pathogenic invaders. Besides integrating cues from commensal microbes, the neonatal immune system must also regulate responses triggered by other environmental signals, such as dietary antigens, which become more complex with the introduction of solid food during the weaning period. This "window of opportunity" in early life is thought to be crucial for the proper development of the immune system, setting the tone of subsequent immune responses in adulthood and modulating the risk of developing chronic and metabolic inflammatory diseases. Here we review the importance of host-microbiota interactions for the development and maturation of the immune system, particularly in the early-life period, highlighting the known mechanisms involved in such communication. This discussion is focused on recent data demonstrating microbiota-mediated education of innate immune cells and its role in the development of lymphoid tissues.

Review of yeast culture concerning the interactions between gut microbiota and young ruminant animals

Microorganisms inhabit the gastrointestinal tract of ruminants and regulate body metabolism by maintaining intestinal health. The state of gastrointestinal health is influenced not only by the macro-level factors of optimal development and the physiological structure integrity but also by the delicate equilibrium between the intestinal flora and immune status at the micro-level. Abrupt weaning in young ruminants causes incomplete development of the intestinal tract resulting in an unstable and unformed microbiota. Abrupt weaning also induced damages to the microecological homeostasis of the intestinal tract, resulting in the intestinal infections and diseases, such as diarrhea. Recently, nutritional and functional yeast culture has been researched to tackle these problems. Herein, we summarized current known interactions between intestinal microorganisms and the body of young ruminants, then we discussed the regulatory effects of using yeast culture as a feed supplement. Yeast culture is a microecological preparation that contains yeast, enriched with yeast metabolites and other nutrient-active components, including β-glucan, mannan, digestive enzymes, amino acids, minerals, vitamins, and some other unknown growth factors. It stimulates the proliferation of intestinal mucosal epithelial cells and the reproduction of intestinal microorganisms by providing special nutrient substrates to support the intestinal function. Additionally, the β-glucan and mannan effectively stimulate intestinal mucosal immunity, promote immune response, activate macrophages, and increase acid phosphatase levels, thereby improving the body's resistance to several disease. The incorporation of yeast culture into young ruminants' diet significantly alleviated the damage caused by weaning stress to the gastrointestinal tract which also acts an effective strategy to promote the balance of intestinal flora, development of intestinal tissue, and establishment of mucosal immune system. Our review provides a theoretical basis for the application of yeast culture in the diet of young ruminants.

Mast cells help organize the Peyer's patch niche for induction of IgA responses

Peyer's patches (PPs) are lymphoid structures situated adjacent to the intestinal epithelium that support B cell responses that give rise to many intestinal IgA-secreting cells. Induction of isotype switching to IgA in PPs requires interactions between B cells and TGFβ-activating conventional dendritic cells type 2 (cDC2s) in the subepithelial dome (SED). However, the mechanisms promoting cDC2 positioning in the SED are unclear. Here, we found that PP cDC2s express GPR35, a receptor that promotes cell migration in response to various metabolites, including 5-hydroxyindoleacetic acid (5-HIAA). In mice lacking GPR35, fewer cDC2s were found in the SED, and frequencies of IgA+ germinal center (GC) B cells were reduced. IgA plasma cells were reduced in both the PPs and lamina propria. These phenotypes were also observed in chimeric mice that lacked GPR35 selectively in cDCs. GPR35 deficiency led to reduced coating of commensal bacteria with IgA and reduced IgA responses to cholera toxin. Mast cells were present in the SED, and mast cell-deficient mice had reduced PP cDC2s and IgA+ cells. Ablation of tryptophan hydroxylase 1 (Tph1) in mast cells to prevent their production of 5-HIAA similarly led to reduced PP cDC2s and IgA responses. Thus, mast cell-guided positioning of GPR35+ cDC2s in the PP SED supports induction of intestinal IgA responses.

The immunoglobulin A isotype of the Arabian camel (Camelus dromedarius) preserves the dualistic structure of unconventional single-domain and canonical heavy chains

Introduction

The evolution of adaptive immunity in Camelidae resulted in the concurrent expression of classic heterotetrameric and unconventional homodimeric heavy chain-only IgG antibodies. Heavy chain-only IgG bears a single variable domain and lacks the constant heavy (CH) γ1 domain required for pairing with the light chain. It has not been reported whether this distinctive feature of IgG is also observed in the IgA isotype.

Methods

Gene-specific primers were used to generate an IgA heavy chain cDNA library derived from RNA extracted from the dromedary's third eyelid where isolated lymphoid follicles and plasma cells abound at inductive and effector sites, respectively.

Results

Majority of the cDNA clones revealed hallmarks of heavy chain-only antibodies, i.e. camelid-specific amino acid substitutions in framework region 1 and 2, broad length distribution of complementarity determining region 3, and the absence of the CHα1 domain. In a few clones, however, the cDNA of the canonical IgA heavy chain was amplified which included the CHα1 domain, analogous to CHγ1 domain in IgG1 subclass. Moreover, we noticed a short, proline-rich hinge, and, at the N-terminal end of the CHα3 domain, a unique, camelid-specific pentapeptide of undetermined function, designated as the inter-α region. Immunoblots using rabbit anti-camel IgA antibodies raised against CHα2 and CHα3 domains as well as the inter-α region revealed the expression of a ~52 kDa and a ~60 kDa IgA species, corresponding to unconventional and canonical IgA heavy chain, respectively, in the third eyelid, trachea, small and large intestine. In contrast, the leporine anti-CHα1 antibody detected canonical, but not unconventional IgA heavy chain, in all the examined tissues, milk, and serum, in addition to another hitherto unexplored species of ~45 kDa in milk and serum. Immunohistology using anti-CHα domain antibodies confirmed the expression of both variants of IgA heavy chains in plasma cells in the third eyelid's lacrimal gland, conjunctiva, tracheal and intestinal mucosa.

Conclusion

We found that in the dromedary, the IgA isotype has expanded the immunoglobulin repertoire by co-expressing unconventional and canonical IgA heavy chains, comparable to the IgG class, thus underscoring the crucial role of heavy chain-only antibodies not only in circulation but also at the mucosal frontiers.

Gut immune microenvironment and autoimmunity

A variety of immune cells or tissues are present in the gut to form the gut immune microenvironment by interacting with gut microbiota, and to maintain the gut immune homeostasis. Accumulating evidence indicated that gut microbiota dysbiosis might break the homeostasis of the gut immune microenvironment, which was associated with many health problems including autoimmune diseases. Moreover, disturbance of the gut immune microenvironment can also induce extra-intestinal autoimmune disorders through the migration of intestinal pro-inflammatory effector cells from the intestine to peripheral inflamed sites. This review discussed the composition of the gut immune microenvironment and its association with autoimmunity. These findings are expected to provide new insights into the pathogenesis of various autoimmune disorders, as well as novel strategies for the prevention and treatment against related diseases.

Immunostimulating Commensal Bacteria and Their Potential Use as Therapeutics

The gut microbiome is intimately intertwined with the host immune system, having effects on the systemic immune system. Dysbiosis of the gut microbiome has been linked not only to gastrointestinal disorders but also conditions of the skin, lungs, and brain. Commensal bacteria can affect the immune status of the host through a stimulation of the innate immune system, training of the adaptive immune system, and competitive exclusion of pathogens. Commensal bacteria improve immune response through the production of immunomodulating compounds such as microbe-associated molecular patterns (MAMPs), short-chain fatty acids (SCFAs), and secondary bile acids. The microbiome, especially when in dysbiosis, is plastic and can be manipulated through the introduction of beneficial bacteria or the adjustment of nutrients to stimulate the expansion of beneficial taxa. The complex nature of the gastrointestinal tract (GIT) ecosystem complicates the use of these methods, as similar treatments have various results in individuals with different residential microbiomes and differential health statuses. A more complete understanding of the interaction between commensal species, host genetics, and the host immune system is needed for effective microbiome interventions to be developed and implemented in a clinical setting.

The interplay between Epstein-Barr virus DNA and gut microbiota in the development of arthritis in a mouse model

Epstein-Barr virus (EBV) DNA may influence the development of autoimmune diseases by increasing the production of proinflammatory cytokines. Such cytokines have been associated with inducing the dysbiosis of colonic microbiota, which, in turn, is a risk factor for autoimmune diseases such as rheumatoid arthritis (RA). Therefore, we investigated the role that EBV DNA may play in modulating the intestinal microbiota and consequent exacerbation of arthritis in a mouse model. Mice were treated with collagen (arthritis-inducing agent), EBV DNA and collagen, EBV DNA, or water. Fecal samples were collected from arthritic and control mice, and 16S rRNA sequencing was performed to determine the effect of EBV DNA on the composition of colonic microbiota. EBV DNA causes a change in the alpha diversity of the microbiota resulting in an increased Chao1 microbial richness and decreased Shannon diversity index in the RA mouse model. In addition, the abundance of particular genera/genus clusters was significantly altered among the various groups, with the EBV DNA-exacerbated arthritic group having the highest number of altered genera/genus cluster abundances. This group also had the highest number of cells co-expressing IL-17A, FOXP3, and IFNγ in the colons. Antimicrobial-cleared mice transplanted with fecal samples from EBV DNA-exacerbated arthritic mice showed a higher incidence and enhanced severity of RA compared to those transplanted with fecal samples from water or collagen-treated mice. IMPORTANCE Epstein-Barr virus (EBV) DNA alters the composition and diversity of the gut microbiota in a rheumatoid arthritis (RA) mouse model. These induced changes are associated with enhanced severity of symptoms. This better understanding of the various factors involved in the development of RA will possibly help in creating individualized treatments for RA patients including target mediators triggered by viral DNA. Given that a large swathe of the population harbors EBV, a significant proportion of subjects with arthritis may benefit from possible approaches that target EBV or mediators triggered by this virus.

Microbial energy metabolism fuels an intestinal macrophage niche in solitary isolated lymphoid tissues through purinergic signaling

Maintaining macrophage (MΦ) heterogeneity is critical to ensure intestinal tissue homeostasis and host defense. The gut microbiota and host factors are thought to synergistically guide intestinal MΦ development, although the exact nature, regulation, and location of such collaboration remain unclear. Here, we report that microbial biochemical energy metabolism promotes colony-stimulating factor 2 (CSF2) production by group 3 innate lymphoid cells (ILC3s) within solitary isolated lymphoid tissues (SILTs) in a cell-extrinsic, NLRP3/P2X7R-dependent fashion in the steady state. Tissue-infiltrating monocytes accumulating around SILTs followed a spatially constrained, distinct developmental trajectory into SILT-associated MΦs (SAMs). CSF2 regulated the mitochondrial membrane potential and reactive oxygen species production of SAMs and contributed to the antimicrobial defense against enteric bacterial infections. Collectively, these findings identify SILTs and CSF2-producing ILC3s as a microanatomic niche for intestinal MΦ development and functional programming fueled by the integration of commensal microbial energy metabolism.

Building better barriers: how nutrition and undernutrition impact pediatric intestinal health

Chronic undernutrition is a major cause of death for children under five, leaving survivors at risk for adverse long-term consequences. This review focuses on the role of nutrients in normal intestinal development and function, from the intestinal epithelium, to the closely-associated mucosal immune system and intestinal microbiota. We examine what is known about the impacts of undernutrition on intestinal physiology, with focus again on the same systems. We provide a discussion of existing animal models of undernutrition, and review the evidence demonstrating that correcting undernutrition alone does not fully ameliorate effects on intestinal function, the microbiome, or growth. We review efforts to treat undernutrition that incorporate data indicating that improved recovery is possible with interventions focused not only on delivery of sufficient energy, macronutrients, and micronutrients, but also on efforts to correct the abnormal intestinal microbiome that is a consequence of undernutrition. Understanding of the role of the intestinal microbiome in the undernourished state and correction of the phenotype is both complex and a subject that holds great potential to improve recovery. We conclude with critical unanswered questions in the field, including the need for greater mechanistic research, improved models for the impacts of undernourishment, and new interventions that incorporate recent research gains. This review highlights the importance of understanding the mechanistic effects of undernutrition on the intestinal ecosystem to better treat and improve long-term outcomes for survivors.

Role of microbiota short-chain fatty acids in the pathogenesis of autoimmune diseases

There is emerging evidence that microbiota and its metabolites play an important role in helath and diseases. In this regard, gut microbiota has been found as a crucial component that influences immune responses as well as immune-related disorders such as autoimmune diseases. Gut bacterial dysbiosis has been shown to cause disease and altered microbiota metabolite synthesis, leading to immunological and metabolic dysregulation. Of note, microbiota in the gut produce short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate, and remodeling in these microbiota metabolites has been linked to the pathophysiology of a number of autoimmune disorders such as type 1 diabetes, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis, celiac disease, and systemic lupus erythematosus. In this review, we will address the most recent findings from the most noteworthy studies investigating the impact of microbiota SCFAs on various autoimmune diseases.

B Lymphocyte Development in the Bursa of Fabricius of Young Broilers is Influenced by the Gut Microbiota

Chickens have been used as a valuable and traditional model for studies on basic immunology. B lymphocytes were first identified in the bursa of Fabricius (BF) of broilers. The microbiota is important for immune system development and function. However, the effect of the microbiota on mediating B cell development and its regulatory mechanism is poorly elucidated. Here, we show that the gut microbiota is associated with the development of bursal B cells in young chickens. Changing patterns of both the alpha diversity and the expression of the B cell marker Bu-1α in the gut microbiota were related to the ages of chickens at different growth phases. Further correlation analysis revealed the marked correlation between the relative abundances of Intestinimonas, Bilophila, Parasutterella, Bacteroides, Helicobacter, Campylobacter, and Mucispirillum and the expression of Bu-1α. In antibiotic-treated chickens, BF and B cell development had aberrations as the relative abundance of the microbiota in early life decreased. These findings were consistent with Spearman's correlation results. Single-cell transcriptome analysis indicated that the heterogeneity in the cellular composition and developmental trajectory of bursal B cells from antibiotic-treated chickens was large. We found a novel subpopulation of unnamed B cells and identified Taf1 as a new pivotal regulator of B cell lineage differentiation. Therefore, we provide novel insights into the regulatory role of the gut microbiota in B cell development in early life and the maturation of host humoral immunity. IMPORTANCE In this study, we used young broilers to investigate the relationship between their gut microbiota and bursal B cell development. We characterized the important variables, microbes, B cells, and immunoglobulins during the posthatch development of birds. We also identified several candidate taxa in the cecal contents associated with B cells. Our study provides a rich resource and cell-cell cross talk model supporting B cell differentiation from the bursa in vitro at single-cell resolution. Furthermore, we determined a new pivotal regulator (Taf1) of B cell differentiation. We believe that our study makes a significant contribution to the literature because our findings may elucidate the role of the gut microbiota in B cell differentiation. This study also serves as a basis for developing new strategies that modulate B cell differentiation to prevent diseases.

Cecum axis (CecAx) preservation reveals physiological and pathological gradients in mouse gastrointestinal epithelium

The mouse cecum has emerged as a model system for studying microbe-host interactions, immunoregulatory functions of the microbiome, and metabolic contributions of gut bacteria. Too often, the cecum is falsely considered as a uniform organ with an evenly distributed epithelium. We developed the cecum axis (CecAx) preservation method to show gradients in epithelial tissue architecture and cell types along the cecal ampulla-apex and mesentery-antimesentery axes. We used imaging mass spectrometry of metabolites and lipids to suggest functional differences along these axes. Using a model of Clostridioides difficile infection, we show how edema and inflammation are unequally concentrated along the mesenteric border. Finally, we show the similarly increased edema at the mesenteric border in two models of Salmonella enterica serovar Typhimurium infection as well as enrichment of goblet cells along the antimesenteric border. Our approach facilitates mouse cecum modeling with detailed attention to inherent structural and functional differences within this dynamic organ.

B cell expansion hinders the stroma-epithelium regenerative cross talk during mucosal healing

Therapeutic promotion of intestinal regeneration holds great promise, but defining the cellular mechanisms that influence tissue regeneration remains an unmet challenge. To gain insight into the process of mucosal healing, we longitudinally examined the immune cell composition during intestinal damage and regeneration. B cells were the dominant cell type in the healing colon, and single-cell RNA sequencing (scRNA-seq) revealed expansion of an IFN-induced B cell subset during experimental mucosal healing that predominantly located in damaged areas and associated with colitis severity. B cell depletion accelerated recovery upon injury, decreased epithelial ulceration, and enhanced gene expression programs associated with tissue remodeling. scRNA-seq from the epithelial and stromal compartments combined with spatial transcriptomics and multiplex immunostaining showed that B cells decreased interactions between stromal and epithelial cells during mucosal healing. Activated B cells disrupted the epithelial-stromal cross talk required for organoid survival. Thus, B cell expansion during injury impairs epithelial-stromal cell interactions required for mucosal healing, with implications for the treatment of IBD.

Asymmetric mucosal structure, mesenteric versus antimesenteric, in mouse, rat, and human small intestines

The morphology of the small intestinal mucosa is reflected by the degree of stimuli. Previous studies have come to different conclusion about whether the mucosa is equally symmetrical. The aim of the study is to investigate whether there are structural differences in the mesenteric versus antimesenteric mucosa in mice, rats, and humans. Jejunal biopsies from mice and rats were saved. Samples from human small intestine were obtained from patients undergoing Roux-en-Y gastric bypass surgery. Fixed samples were used to morphologically evaluate villus height and enlargement factor due to villi. The number of goblet cells, mast cells, enteroendocrine cells, and Paneth cells were histologically analyzed in the villus structure. Cell turnover was analyzed by Ki-67 staining. There was a significant increased villi height and villus enlargement factor antimesenterically in mice, rats, and human small intestines. The distribution of goblet cells, mast cells, and Paneth cells were equal while the number of enteroendocrine cells was increased antimesenteric in the human samples. The crypt mitotic activity was almost 20% higher in the antimesenteric part of jejunum. In summary we found longer villi, greater surface enlargement, and increased number of enteroendocrine cells as well as increased cell turnover antimesenterically. These differences may be of importance in understanding normal gastrointestinal physiology in health and disease.

MHC II - EGFP knock-in mouse model is a suitable tool for systems and quantitative immunology

Immunology is a rapidly evolving field of research with sophisticated models and methods. However, detailed data on total immune cell counts and population distributions remain surprisingly scarce. Nevertheless, recently established quantitative approaches could help us understand the overall complexity of the immune system. Here, we studied a major histocompatibility complexclass II - enhanced green fluorescent protein knock-in mouse model to precisely identify and manipulate lymphoid structures. By combining flow cytometry with light sheet microscopy, we quantified MHC II⁺ populations of the small intestine and associated individual mesenteric lymph nodes, with 36.7 × 10⁶ cells in lamina propria, 3.0 × 10⁵ cells in scattered lymphoid tissue and 1.1 × 10⁶ cells in Peyer's patches. In addition to these whole-organ cell counts, we assessed approximately 1 × 10⁶ total villi in the small intestine and 450 scattered lymphoid tissue follicles. By direct noninvasive microscopic observation of a naturally fully translucent mouse organ, the cornea, we quantified 12 ± 4 and 35 ± 7 cells/mm² Langerhans- and macrophage-like populations, respectively. Ultimately, our findings show that flow cytometry with quantitative imaging data analysis enables us to avoid methodological discrepancies while gaining new insights into the relevance of organ-specific quantitative approaches for immunology.

Clonal IgA and IgG autoantibodies from individuals at risk for rheumatoid arthritis identify an arthritogenic strain of Subdoligranulum

The mucosal origins hypothesis of rheumatoid arthritis (RA) proposes a central role for mucosal immune responses in the initiation or perpetuation of the systemic autoimmunity that occurs with disease. However, the connection between the mucosa and systemic autoimmunity in RA remains unclear. Using dual immunoglobulin A (IgA) and IgG family plasmablast-derived monoclonal autoantibodies obtained from peripheral blood of individuals at risk for RA, we identified cross-reactivity between RA-relevant autoantigens and bacterial taxa in the closely related families Lachnospiraceae and Ruminococcaceae. After generating bacterial isolates within the Lachnospiraceae/Ruminococcaceae genus Subdoligranulum from the feces of an individual, we confirmed monoclonal antibody binding and CD4⁺ T cell activation in individuals with RA compared to control individuals. In addition, when Subdoligranulum isolate 7 but not isolate 1 colonized germ-free mice, it stimulated T_H17 cell expansion, serum RA-relevant IgG autoantibodies, and joint swelling reminiscent of early RA, with histopathology characterized by antibody deposition and complement activation. Systemic immune responses were likely due to mucosal invasion along with the generation of colon-isolated lymphoid follicles driving increased fecal and serum IgA by isolate 7, because B and CD4⁺ T cell depletion not only halted intestinal immune responses but also eliminated detectable clinical disease. In aggregate, these findings demonstrate a mechanism of RA pathogenesis through which a specific intestinal strain of bacteria can drive systemic autoantibody generation and joint-centered antibody deposition and immune activation.

Clonal IgA and IgG autoantibodies from individuals at risk for rheumatoid arthritis identify an arthritogenic strain of Subdoligranulum

The mucosal origins hypothesis of rheumatoid arthritis (RA) proposes a central role for mucosal immune responses in the initiation or perpetuation of the systemic autoimmunity that occurs with disease. However, the connection between the mucosa and systemic autoimmunity in RA remains unclear. Using dual immunoglobulin A (IgA) and IgG family plasmablast-derived monoclonal autoantibodies obtained from peripheral blood of individuals at risk for RA, we identified cross-reactivity between RA-relevant autoantigens and bacterial taxa in the closely related families Lachnospiraceae and Ruminococcaceae. After generating bacterial isolates within the Lachnospiraceae/Ruminococcaceae genus Subdoligranulum from the feces of an individual, we confirmed monoclonal antibody binding and CD4⁺ T cell activation in individuals with RA compared to control individuals. In addition, when Subdoligranulum isolate 7 but not isolate 1 colonized germ-free mice, it stimulated T_H17 cell expansion, serum RA-relevant IgG autoantibodies, and joint swelling reminiscent of early RA, with histopathology characterized by antibody deposition and complement activation. Systemic immune responses were likely due to mucosal invasion along with the generation of colon-isolated lymphoid follicles driving increased fecal and serum IgA by isolate 7, because B and CD4⁺ T cell depletion not only halted intestinal immune responses but also eliminated detectable clinical disease. In aggregate, these findings demonstrate a mechanism of RA pathogenesis through which a specific intestinal strain of bacteria can drive systemic autoantibody generation and joint-centered antibody deposition and immune activation.

The porcine large intestine contains developmentally distinct submucosal lymphoid clusters and mucosal isolated lymphoid follicles

Gut-associated lymphoid tissues (GALT) serve as key priming sites for intestinal adaptive immune responses. Most of our understanding of GALT function and development arises from studies in mice. However, the diversity, structure and cellular composition of GALT differs markedly between mammalian species and the developmental window in which distinct GALT structures develop in large mammals remains poorly understood. Given the importance of pigs as models of human disease, as well as their role in livestock production, we adapted a recently developed protocol for the isolation of human GALT to assess the diversity, development and immune composition of large intestinal GALT in neonatal and adult pigs. We demonstrate that the large intestine of adult pigs contains two major GALT types; multifollicular submucosal GALT that we term submucosal lymphoid clusters (SLC) which develop prenatally, and as yet undescribed mucosal isolated lymphoid follicles (M-ILF), which arise after birth. Using confocal laser microscopy and flow cytometry, we additionally assess the microanatomy and lymphocyte composition of SLC and M-ILF, compare them to jejunal Peyer's patches (PP), and describe the maturation of these structures. Collectively, our results provide a deeper understanding of the diversity and development of GALT within the porcine large intestine.

Comparison of the performance of MS enteroscope series and Japanese double- and single-balloon enteroscopes

BACKGROUND

Small intestine disease endangers human health and is not easy to locate and diagnose.

AIM

To observe the effect of the MS series of small intestine endoscopes on the gastrointestinal tract, the changes in serum gastrin levels and intestinal tissue, and the time required for the examination.

METHODS

In vivo experiments in 20 Living pigs were conducted, Bowel preparation was routinely performed, Intravenous anesthesia with propofol and ketamine was applied, the condition of the small intestine was observed and the detection time of the MS series of small intestine endoscopes were recorded, The changes in intestinal tissue using the MS series of small intestine endoscopes observed and compared before and after the examination, Venous blood (3-5 mL) from pigs was collected before and after the experiment; changes in intestinal tissue after use of the MS series of small intestine endoscopes observed after examination. After completion of each type of small intestine endoscope experiment, the pigs were allowed to rest and the next type of small intestine endoscope experiment was performed after 15 days of normal feeding. The detection time data of the single-balloon small intestine endoscope and double-balloon small intestine endoscope were collected from four hospitals.

RESULTS

One case of Ascarislumbricoides, one of suspected Crohn's disease, one small intestinal diverticulum and one anesthesia accident were observed in pigs. The small intestine showed no differences in the MS series of small intestine endoscopes and there were no differences in serum gastrin between the groups (P > 0.05). The time required for inspection was recorded, and the overall detection time for the Japanese small intestine endoscopes was approximately 1.68 ± 0.16 h.

CONCLUSION

Intestinal ascariasis is a common disease in pigs. Some pigs have abnormal intestinal variation. After continuous upgrade and improvement, the MS-3 and MS-4 small intestine endoscope appear superior in terms of detection time.

Functional Analysis of the Transcriptional Regulator IκB-ζ in Intestinal Homeostasis

BACKGROUND

The Toll-like receptor signaling pathway contributes to the regulation of intestinal homeostasis through interactions with commensal bacteria. Although the transcriptional regulator IκB-ζ can be induced by Toll-like receptor signaling, its role in intestinal homeostasis is still unclear.

AIMS

To investigate the role of IκB-ζ in gut homeostasis.

METHODS

DSS-administration induced colitis in control and IκB-ζ-deficient mice. The level of immunoglobulins in feces was detected by ELISA. The immunological population in lamina propria (LP) was analyzed by FACS.

RESULTS

IκB-ζ-deficient mice showed severe inflammatory diseases with DSS administration in the gut. The level of IgM in the feces after DSS administration was less in IκB-ζ-deficient mice compared to control mice. Upon administration of DSS, IκB-ζ-deficient mice showed exaggerated intestinal inflammation (more IFN-g-producing CD4⁺ T cells in LP), and antibiotic treatment canceled this inflammatory phenotype.

CONCLUSION

IκB-ζ plays a crucial role in maintaining homeostasis in the gut.

Setd2 determines distinct properties of intestinal ILC3 subsets to regulate intestinal immunity

Subsets of group 3 innate lymphoid cells (ILC3s) are heterogeneous in development and function and play differential roles in intestinal immunity. Histone modifications are involved in the fate commitment of immune cells, including ILC3s. Here, we report that deletion of Setd2, histone H3K36 methyltransferase, in ILC3s results in increased generation of NKp46⁺ILC3s with enhanced cytotoxic signatures and tumor-suppressive capacity. Meanwhile, Rag1^-/-Rorc^CreSetd2^flox/flox mice have fewer CCR6⁺ILC3s and less defective solitary intestinal lymphoid tissue formation, accompanied by reduced granulocyte-macrophage colony-stimulating factor (GM-CSF) production by NKp46^-ILC3s and decreased CD11b⁺CD103⁺ dendritic cell accumulation. The deficiency of Setd2^-/-NKp46^-ILC3s may contribute to disturbed RORγt⁺Treg homeostasis and intestinal inflammation in Rag1^-/-Rorc^CreSetd2^flox/flox mice upon T cell reconstitution. Setd2 regulates genome accessibility imprinting gene mRNA expression, with a more profound effect on NKp46⁺ILC3s than NKp46^-ILC3s. Therefore, Setd2 determines distinct chromatin status and transcriptomic programs of ILC3 subsets to affect their function and intestinal immunity.

B cell class switching in intestinal immunity in health and disease

The gastrointestinal tract is colonized by trillions of commensal microorganisms that collectively form the microbiome and make essential contributions to organism homeostasis. The intestinal immune system must tolerate these beneficial commensals, whilst preventing pathogenic organisms from systemic spread. Humoral immunity plays a key role in this process, with large quantities of immunoglobulin (Ig)A secreted into the lumen on a daily basis, regulating the microbiome and preventing bacteria from encroaching on the epithelium. However, there is an increasing appreciation of the role of IgG antibodies in intestinal immunity, including beneficial effects in neonatal immune development, pathogen and tumour resistance, but also of pathological effects in driving chronic inflammation in inflammatory bowel disease (IBD). These antibody isotypes differ in effector function, with IgG exhibiting more proinflammatory capabilities compared with IgA. Therefore, the process that leads to the generation of different antibody isotypes, class-switch recombination (CSR), requires careful regulation and is orchestrated by the immunological cues generated by the prevalent local challenge. In general, an initiating signal such as CD40 ligation on B cells leads to the induction of activation-induced cytidine deaminase (AID), but a second cytokine-mediated signal determines which Ig heavy chain is expressed. Whilst the cytokines driving intestinal IgA responses are well-studied, there is less clarity on how IgG responses are generated in the intestine, and how these cues might become dysfunctional in IBD. Here, we review the key mechanisms regulating class switching to IgA vs IgG in the intestine, processes that could be therapeutically manipulated in infection and IBD.

Gut microbiome-immune system interaction in reptiles

Reptiles are ectothermic amniotes in a world dominated by endotherms. Reptiles originated more than 300 million years ago and they often dwell in polluted environments which may expose them to pathogenic micro-organisms, radiation and/or heavy metals. Reptiles also possess greater longevity and may live much longer than similar-sized land mammals, for example, turtles, tortoises, crocodiles and tuatara are long-lived reptiles living up to 100 years or more. Many recent studies have emphasized the pivotal role of the gut microbiome on its host; thus, we postulated that reptilian gut microbiome and/or its metabolites and the interplay with their robust immune system may contribute to their longevity and overall hardiness. Herein, we discuss the composition of the reptilian gut microbiome, immune system-gut microbiome cross-talk, antimicrobial peptides, reptilian resistance to infectious diseases and cancer, ageing, as well the current knowledge of the genome and epigenome of these remarkable species. Preliminary studies have demonstrated that microbial gut flora of reptiles such as crocodiles, tortoises, water monitor lizard and python exhibit remarkable anticancer and antibacterial properties, as well as comprise novel gut bacterial metabolites and antimicrobial peptides. The underlying mechanisms between the gut microbiome and the immune system may hold clues to developing new therapies overall for health, and possible extrapolation to exploit the ancient defence systems of reptiles for Homo sapiens benefit.

Dendritic cell functions in the inductive and effector sites of intestinal immunity

The intestine is constantly exposed to foreign antigens, which are mostly innocuous but can sometimes be harmful. Therefore, the intestinal immune system has the delicate task of maintaining immune tolerance to harmless food antigens while inducing tailored immune responses to pathogens and regulating but tolerating the microbiota. Intestinal dendritic cells (DCs) play a central role in these functions as sentinel cells able to prime and polarize the T cell responses. DCs are deployed throughout the intestinal mucosa but with local specializations along the gut length and between the diffuse effector sites of the gut lamina propria (LP) and the well-organized immune inductive sites comprising isolated lymphoid follicles (ILFs), Peyer's patches (PPs), and other species-specific gut-associated lymphoid tissues (GALTs). Understanding the specificities of each intestinal DC subset, how environmental factors influence DC functions, and how these can be modulated is key to harnessing the therapeutic potential of mucosal adaptive immune responses, whether by enhancing the efficacy of mucosal vaccines or by increasing tolerogenic responses in inflammatory disorders. In this review, we summarize recent findings related to intestinal DCs in steady state and upon inflammation, with a special focus on their functional specializations, highly dependent on their microenvironment.

Akkermansia muciniphila – obiecujący kandydat na probiotyk nowej generacji

W ostatnich czasach można zaobserwować duży wzrost zainteresowania relacjami między człowiekiem a mikroorganizmami zasiedlającymi jego organizm. Licznie występują w oraz na ciele człowieka, a ich liczba przekracza liczbę komórek ludzkiego organizmu. Udoskonalenie technik badawczych pozwala lepiej zrozumieć molekularne podłoże tych oddziaływań, co być może pozwoli na wykorzystanie w terapiach tych mikroorganizmów, które korzystnie wpływają na organizm człowieka. W artykule podsumowano dotychczasową wiedzę na temat fizjologii licznie występującej w przewodzie pokarmowym bakterii Akkermansia muciniphila i jej wpływu na organizm gospodarza. Opisano właściwości A. muciniphila, jej funkcjonowanie w środowisku przewodu pokarmowego oraz relacje (zarówno antagonistyczne jak i symbiotyczne) z innymi tam bytującymi mikroorganizmami. Przedstawiono także mechanizmy oddziaływania A. muciniphila na barierę jelitową, układ immunologiczny oraz metabolizm energetyczny gospodarza. Ponadto opisano jej rolę w patogenezie i terapii chorób, w tym m.in. cukrzycy typu 2, nieswoistego zapalenia jelit, zaburzeń neurologicznych, astmy, a także jej wpływ na odpowiedź pacjenta na terapie przeciwnowotworowe oparte na działaniu układu odpornościowego. Duże zainteresowanie tą bakterią, a także przytoczone wyniki badań, w tym tych sprawdzających bezpieczeństwo jej stosowania, wskazują, że A. muciniphila może być obiecującym kandydatem na probiotyk nowej generacji. Niewątpliwie jednak przed dopuszczeniem A. muciniphila do powszechnego stosowania konieczne są dalsze badania z udziałem ludzi, a także wnikliwa ocena bezpieczeństwa jej stosowania.

Antinuclear antibodies produced in HLA-DR transgenic humanized mice developed chronic graft-versus-host disease

Background

Chronic graft versus host disease (GVHD) has been reported in humanized mice after the implantation of human hematopoietic stem cells (hu-HSC). As such, humanized mice have been applied to a mouse model of chronic GVHD; however, B-cell activation and autoantibody production did not occur, and the clinical features of chronic GVHD were not sufficiently reproduced. The purpose of this study was to establish an improved humanized mouse model with chronic GVHD using HLA-DR transgenic NOD/Shi-scid, IL-2RγKO (NOG) mice.

Methods

CD34-positive cells were isolated from blood extracted from HLA-DRB1∗0405-positive umbilical cords using magnetic cell isolation. Then these were transplanted into NOG-Iab KO, HLA-DR 0405 Tg mice aged 8–16 weeks. GVHD symptoms were observed 26 weeks after transplantation. Histological findings of the skin, lung, liver, and spleen were compared with those of non-humanized mice. Antinuclear antibodies (ANA) were measured by indirect immunofluorescence using sera isolated 26 weeks after transplantation.

Results

Although GVHD symptoms were not observed in humanized (hu-HSC) NOG-Iab KO, HLA-DR 0405 Tg mice during the observation period, histological findings of human T-cell infiltration were observed in the skin, liver, and lung, suggesting that GVDH was present; human tingible body macrophages or clusters of BCL-6-positive human B-cells were observed in the spleen. Furthermore, human IgG ANA with peripheral or homogeneous staining patterns were also detected in the sera.

Conclusion

Hu-HSC NOG-Iab KO, HLA-DR 0405 Tg mice differed from conventional models in terms of B-cell activation and ANA production. This study is the first to report on B-cell activation and autoantibody production in humanized mice with chronic GVHD, suggesting that hu-HSC NOG-Iab KO, HLA-DR 0405 Tg mice could be applied to a new humanized mouse model of chronic GVHD.

Spatial gene expression maps of the intestinal lymphoid follicle and associated epithelium identify zonated expression programs

The intestine is lined with isolated lymphoid follicles (ILFs) that facilitate sampling of luminal antigens to elicit immune responses. Technical challenges related to the scarcity and small sizes of ILFs and their follicle-associated epithelium (FAE) impeded the characterization of their spatial gene expression programs. Here, we combined RNA sequencing of laser capture microdissected tissues with single-molecule transcript imaging to obtain a spatial gene expression map of the ILF and its associated FAE in the mouse small intestine. We identified zonated expression programs in both follicles and FAEs, with a decrease in enterocyte antimicrobial and absorption programs and a partial induction of expression programs normally observed at the villus tip. We further identified Lepr+ subepithelial telocytes at the FAE top, which are distinct from villus tip Lgr5+ telocytes. Our analysis exposes the epithelial and mesenchymal cell states associated with ILFs.

Regulation of neonatal IgA production by the maternal microbiota

Infants are born without an established gut microbiota, which develops rapidly after birth and is shaped by the maternal microbiota. However, how the maternal microbiota, through shaping the neonatal microbiota, would affect the establishment of a strong immune system in neonates remains unclear. Here, we show mechanistically how the maternal microbiota regulates the de novo production of neonatal IgA.

Infants are prone to enteric infections due to an underdeveloped immune system. The maternal microbiota, through shaping the neonatal microbiota, helps establish a strong immune system in infants. We and others have observed the phenomenon of enhanced early neonatal immunoglobulin A (IgA) production in preweaning immunocompetent mice nursed by immunodeficient dams. Here, we show that this enhancement of IgA in neonates results from maternally derived microbiota. In addition, we have found that the neonatal IgA production can be induced by Lactobacillus reuteri, which is enriched in the milk of immunodeficient dams. Moreover, we show that while the production of neonatal IgA is dependent on neonatal T cells, the immunodeficient maternal microbiota-mediated enhancement of neonatal IgA has a T cell–independent component. Indeed, this enhancement may be dependent on type 3 innate lymphoid cells in the neonatal small intestinal lamina propria. Interestingly, maternal microbiota-induced neonatal IgA does not cross-react with common enteric pathogens. Future investigations will determine the functional consequences of having this extra IgA.

Application of NGS Technology in Understanding the Pathology of Autoimmune Diseases

NGS technologies have transformed clinical diagnostics and broadly used from neonatal emergencies to adult conditions where the diagnosis cannot be made based on clinical symptoms. Autoimmune diseases reveal complicate molecular background and traditional methods could not fully capture them. Certainly, NGS technologies meet the needs of modern exploratory research, diagnostic and pharmacotherapy. Therefore, the main purpose of this review was to briefly present the application of NGS technology used in recent years in the understanding of autoimmune diseases paying particular attention to autoimmune connective tissue diseases. The main issues are presented in four parts: (a) panels, whole-genome and -exome sequencing (WGS and WES) in diagnostic, (b) Human leukocyte antigens (HLA) as a diagnostic tool, (c) RNAseq, (d) microRNA and (f) microbiome. Although all these areas of research are extensive, it seems that epigenetic impact on the development of systemic autoimmune diseases will set trends for future studies on this area.

Redefining the Role of Lymphotoxin Beta Receptor in the Maintenance of Lymphoid Organs and Immune Cell Homeostasis in Adulthood

Lymphotoxin beta receptor (LTβR) is a promising therapeutic target in autoimmune and infectious diseases as well as cancer. Mice with genetic inactivation of LTβR display multiple defects in development and organization of lymphoid organs, mucosal immune responses, IgA production and an autoimmune phenotype. As these defects are imprinted in embryogenesis and neonate stages, the impact of LTβR signaling in adulthood remains unclear. Here, to overcome developmental defects, we generated mice with inducible ubiquitous genetic inactivation of LTβR in adult mice (iLTβR^Δ/Δ mice) and redefined the role of LTβR signaling in organization of lymphoid organs, immune response to mucosal bacterial pathogen, IgA production and autoimmunity. In spleen, postnatal LTβR signaling is required for development of B cell follicles, follicular dendritic cells (FDCs), recruitment of neutrophils and maintenance of the marginal zone. Lymph nodes of iLTβR^Δ/Δ mice were reduced in size, lacked FDCs, and had disorganized subcapsular sinus macrophages. Peyer`s patches were smaller in size and numbers, and displayed reduced FDCs. The number of isolated lymphoid follicles in small intestine and colon were also reduced. In contrast to LTβR^-/- mice, iLTβR^Δ/Δ mice displayed normal thymus structure and did not develop signs of systemic inflammation and autoimmunity. Further, our results suggest that LTβR signaling in adulthood is required for homeostasis of neutrophils, NK, and iNKT cells, but is dispensable for the maintenance of polyclonal IgA production. However, iLTβR^Δ/Δ mice exhibited an increased sensitivity to C. rodentium infection and failed to develop pathogen-specific IgA responses. Collectively, our study uncovers new insights of LTβR signaling in adulthood for the maintenance of lymphoid organs, neutrophils, NK and iNKT cells, and IgA production in response to mucosal bacterial pathogen.

Suppression of plasmacytoid dendritic cell migration to colonic isolated lymphoid follicles abrogates the development of colitis

BACKGROUND

Dendritic cells (DCs) play a pivotal role in maintaining immunological homeostasis by orchestrating innate and adaptive immune responses via migration to inflamed sites and the lymph nodes (LNs). Plasmacytoid DCs (pDCs) have been reported to accumulate in the colon of inflammatory bowel disease (IBD) patients and dextran sulfate sodium (DSS)-induced colitis mice. However, the role of pDCs in the progression of colonic inflammation remains unclear.

METHODS

80 compounds in natural medicines were searched for inhibitors of pDC migration using bone marrow-derived pDCs (BMpDCs) and conventional DCs (BMcDCs). BALB/c mice were given 3% DSS in the drinking water to induce acute colitis. Compounds, which specifically inhibited pDC migration, were administrated into DSS-induced colitis mice.

FINDINGS

Astragaloside IV (As-IV) and oxymatrine (Oxy) suppressed BMpDC migration but not BMcDC migration. In DSS-induced colitis mice, the number of pDCs was markedly increased in the colonic lamina propria (LP), and the expression of CCL21 was obviously observed in colonic isolated lymphoid follicles (ILFs). As-IV and Oxy reduced symptoms of colitis and the accumulation of pDCs in colonic ILFs but not in the colonic LP. Moreover, in a BMpDC adoptive transfer model, BMpDC migration to colonic ILFs was significantly decreased by treatment with As-IV or Oxy.

INTERPRETATION

pDCs accumulated in the colon of colitis mice, and As-IV and Oxy ameliorated colitis by suppressing pDC migration to colonic ILFs. Accordingly, the selective inhibition of pDC migration may be a potential therapeutic approach for treating colonic inflammatory diseases.

Influence of immunomodulatory drugs on the gut microbiota

Immunomodulatory medications are a mainstay of treatment for autoimmune diseases and malignancies. In addition to their direct effects on immune cells, these medications also impact the gut microbiota. Drug-induced shifts in commensal microbes can lead to indirect but important changes in the immune response. We performed a comprehensive literature search focusing on immunotherapy/microbe interactions. Immunotherapies were categorized into 5 subtypes based on their mechanisms of action: cell trafficking inhibitors, immune checkpoint inhibitors, immunomodulators, antiproliferative drugs, and inflammatory cytokine inhibitors. Although no consistent relationships were observed between types of immunotherapy and microbiota, most immunotherapies were associated with shifts in specific colonizing bacterial taxa. The relationships between colonizing microbes and drug efficacy were not well-studied for autoimmune diseases. In contrast, the efficacy of immune checkpoint inhibitors for cancer was tied to the baseline composition of the gut microbiota. There was a paucity of high-quality data; existing data were generated using heterogeneous sampling and analytic techniques, and most studies involved small numbers of participants. Further work is needed to elucidate the extent and clinical significance of immunotherapy effects on the human microbiome.

Human gut-associated lymphoid tissues (GALT); diversity, structure, and function

Gut-associated lymphoid tissues (GALT) are the key antigen sampling and adaptive immune inductive sites within the intestinal wall. Human GALT includes the multi-follicular Peyer's patches of the ileum, the vermiform appendix, and the numerous isolated lymphoid follicles (ILF) which are distributed along the length of the intestine. Our current understanding of GALT diversity and function derives primarily from studies in mice, and the relevance of many of these findings to human GALT remains unclear. Here we review our current understanding of human GALT diversity, structure, and composition as well as their potential for regulating intestinal immune responses during homeostasis and inflammatory bowel disease (IBD). Finally, we outline some key remaining questions regarding human GALT, the answers to which will advance our understanding of intestinal immune responses and provide potential opportunities to improve the treatment of intestinal diseases.

GPR34-mediated sensing of lysophosphatidylserine released by apoptotic neutrophils activates type 3 innate lymphoid cells to mediate tissue repair

Neutrophils migrate rapidly to damaged tissue and play critical roles in host defense and tissue homeostasis. Here we investigated the mechanisms whereby neutrophils participate in tissue repair. In an intestinal epithelia injury model, neutrophil depletion exacerbated colitis and associated with reduced interleukin (IL)-22 and limited activation of type 3 innate lymphoid cells (ILC3s). Co-culture with neutrophils activated ILC3s in a manner dependent on neutrophil apoptosis. Metabolomic analyses revealed that lysophosphatidylserine (LysoPS) from apoptotic neutrophils directly stimulated ILC3 activation. ILC3-specific deletion of Gpr34, encoding the LysoPS receptor GPR34, or inhibition of downstream PI3K-AKT or ERK suppressed IL-22 production in response to apoptotic neutrophils. Gpr34-/- mice exhibited compromised ILC3 activation and tissue repair during colon injury, and neutrophil depletion abrogated these defects. GPR34 deficiency in ILC3s limited IL-22 production and tissue repair in vivo in settings of colon and skin injury. Thus, GPR34 is an ILC3-expressed damage-sensing receptor that triggers tissue repair upon recognition of dying neutrophils.

Acute Radiation Syndrome and the Microbiome: Impact and Review

Study of the human microbiota has been a centuries-long endeavor, but since the inception of the National Institutes of Health (NIH) Human Microbiome Project in 2007, research has greatly expanded, including the space involving radiation injury. As acute radiation syndrome (ARS) is multisystemic, the microbiome niches across all areas of the body may be affected. This review highlights advances in radiation research examining the effect of irradiation on the microbiome and its potential use as a target for medical countermeasures or biodosimetry approaches, or as a medical countermeasure itself. The authors also address animal model considerations for designing studies, and the potential to use the microbiome as a biomarker to assess radiation exposure and predict outcome. Recent research has shown that the microbiome holds enormous potential for mitigation of radiation injury, in the context of both radiotherapy and radiological/nuclear public health emergencies. Gaps still exist, but the field is moving forward with much promise.

Tertiary Lymphoid Structures: Diversity in Their Development, Composition, and Role

Lymph node stromal cells coordinate the adaptive immune response in secondary lymphoid organs, providing both a structural matrix and soluble factors that regulate survival and migration of immune cells, ultimately promoting Ag encounter. In several inflamed tissues, resident fibroblasts can acquire lymphoid-stroma properties and drive the formation of ectopic aggregates of immune cells, named tertiary lymphoid structures (TLSs). Mature TLSs are functional sites for the development of adaptive responses and, consequently, when present, can have an impact in both autoimmunity and cancer conditions. In this review, we go over recent findings concerning both lymph node stromal cells and TLSs function and formation and further describe what is currently known about their role in disease, particularly their potential in tolerance.

Group 3 Innate Lymphoid Cells Program a Distinct Subset of IL-22BP-Producing Dendritic Cells Demarcating Solitary Intestinal Lymphoid Tissues

Solitary intestinal lymphoid tissues such as cryptopatches (CPs) and isolated lymphoid follicles (ILFs) constitute steady-state activation hubs containing group 3 innate lymphoid cells (ILC3) that continuously produce interleukin (IL)-22. The outer surface of CPs and ILFs is demarcated by a poorly characterized population of CD11c⁺ cells. Using genome-wide single-cell transcriptional profiling of intestinal mononuclear phagocytes and multidimensional flow cytometry, we found that CP- and ILF-associated CD11c⁺ cells were a transcriptionally distinct subset of intestinal cDCs, which we term CIA-DCs. CIA-DCs required programming by CP- and ILF-resident CCR6⁺ ILC3 via lymphotoxin-β receptor signaling in cDCs. CIA-DCs differentially expressed genes associated with immunoregulation and were the major cellular source of IL-22 binding protein (IL-22BP) at steady state. Mice lacking CIA-DC-derived IL-22BP exhibited diminished expression of epithelial lipid transporters, reduced lipid resorption, and changes in body fat homeostasis. Our findings provide insight into the design principles of an immunoregulatory checkpoint controlling nutrient absorption.

Effects of a Low Dose of T-2 Toxin on the Percentage of T and B Lymphocytes and Cytokine Secretion in the Porcine Ileal Wall

Plant materials used in the production of pig feed are frequently contaminated with mycotoxins. T-2 toxin is a secondary metabolite of selected Fusarium species, and it can exert a harmful influence on living organisms. Most mycotoxins enter the body via the gastrointestinal tract, and they can modulate the gut-associated lymphoid tissue (GALT) function. However, little is known about the influence of low T-2 toxin doses on GALT. Therefore, the aim of this study was to evaluate the effect of T-2 toxin administered at 50% of the lowest-observed-adverse-effect level (LOAEL) on the percentage of CD2+ T cells, CD4+ T helper cells, CD8+ cytotoxic T cells, CD4+CD8+ double-positive T cells, TCRγδ+ cells, CD5+CD8- B1 cells, and CD21+ B2 cells, and the secretion of proinflammatory (IFN-γ, IL-1β, IL-2, IL-12/23p40, IL-17A), anti-inflammatory, and regulatory (IL-4, IL-10, TGF-β) cytokines in the porcine ileal wall. The results of the study revealed that T-2 toxin disrupts the development of tolerance to food antigens by enhancing the secretion of proinflammatory and regulatory cytokines and decreasing the production of anti-inflammatory TGF-β. T-2 toxin triggered the cellular response, which was manifested by an increase in the percentage of CD8+ T cells and a decrease in the percentage of B2 and Tγδ lymphocytes.