Deficiency of IL-22-binding protein enhances the ability of the gut microbiota to protect against enteric pathogens

Therapeutic activation of IL-22-producing innate lymphoid cells enhances host defenses to Clostridioides difficile infection

Clostridioides difficile causes debilitating colitis via secreted toxins that disrupt the intestinal barrier, and toxemia is associated with severe disease. Thus, therapies that fortify the intestinal barrier will reduce the severity of infection. Innate lymphoid cells (ILCs) are critical in the defense against acute C. difficile infection and represent a promising therapeutic target to limit disease. Here, we report that oral administration of the Toll-like receptor (TLR) 7 agonist R848 limits intestinal damage and protects mice from lethal C. difficile infection without impacting pathogen burden or altering the intestinal microbiome. R848 induced interleukin (IL)-22 secretion by ILCs, leading to STAT3 phosphorylation in the intestinal epithelium and increased stem cell proliferation. Genetic ablation of ILCs, IL-22, or epithelial-specific STAT3 abrogated R848-mediated protection. R848 reduced intestinal permeability following infection and limited systemic toxin dissemination. Combined, these data identify an immunostimulatory molecule that activates IL-22 production in ILCs to enhance host tissue defenses following C. difficile infection.

Novel insights into immune-gut microbiota interactions in colorectal cancer: a Mendelian randomization study

BACKGROUND

The relationship between immune cells and colorectal cancer (CRC) development has been extensively studied; however, the mediating role of gut microbiota in this relationship remains poorly understood.

METHODS

We utilized summary data from genome-wide association studies (GWAS) to analyze 731 immune cell phenotypes, 473 gut microbiota, and CRC-related data. A two-step mediation analysis was employed to identify mediating gut microbiota. The primary analysis method was inverse variance weighting (IVW), supplemented by MR-Egger, simple mode, weighted median, and weighted mode analyses. Robustness of the results was ensured through systematic sensitivity analyses.

RESULTS

Our analysis identified 13 immune cell phenotypes significantly associated with CRC, including 10 protective factors and 3 risk factors. Additionally, 13 gut microbiota showed significant associations with CRC, comprising 8 protective factors and 5 risk factors. Mediation analysis revealed that 4-gut microbiota (1 order, 1 family, 1 genus, and 1 unclassified) mediated the relationship between immune cells and CRC. For instance, unclassified CAG - 977 mediated the effects of FSC-A on NK and NKT %lymphocyte on CRC risk, with mediation proportions of 11% and 12.3%, respectively. Notably, 22.3% of the protective effect of EM CD8br %CD8br on CRC was mediated through order Francisellales.

CONCLUSION

This study provides evidence for a potential causal relationship between immune cells, gut microbiota, and CRC, highlighting the mediating role of specific gut microbiota. These findings offer new insights into the pathogenesis of CRC and may inform future therapeutic strategies.

Fiber- and acetate-mediated modulation of MHC-II expression on intestinal epithelium protects from Clostridioides difficile infection

Here, we explore the relationship between dietary fibers, colonic epithelium major histocompatibility complex class II (MHC-II) expression, and immune cell interactions in regulating susceptibility to Clostridioides difficile infection (CDI). We find that a low-fiber diet increases MHC-II expression in the colonic epithelium, which, in turn, worsens CDI by promoting the development of pathogenic CD4+ intraepithelial lymphocytes (IELs). The influence of dietary fibers on MHC-II expression is mediated by its metabolic product, acetate, and its receptor, free fatty acid receptor 2 (FFAR2). While acetate activation of FFAR2 on epithelial cells helps resist CDI, it does not directly regulate MHC-II expression. Instead, MHC-II is regulated by FFAR2 in type 3 innate lymphoid cells (ILC3s). Acetate enhances interleukin-22 (IL-22) production by ILC3s, which then suppresses MHC-II expression on the colonic epithelium. In conclusion, a low-fiber diet reduces acetate-induced IL-22 production by ILC3s, leading to increased MHC-II on the colonic epithelium. This change affects recovery from CDI by expanding the population of pathogenic CD4+ IELs.

Novel insight into MDA-7/IL-24: A potent therapeutic target for autoimmune and inflammatory diseases

Melanoma differentiation-associated gene-7 (MDA-7)/interleukin-24 (IL-24) is a pleiotropic member of the IL-10 family of cytokines, and is involved in multiple biological processes, including cell proliferation, cell differentiation, tissue fibrosis, the inflammatory response, and antitumor activity. MDA-7/IL-24 can regulate epithelial integrity, homeostasis, mucosal immunity and host resistance to various pathogens by enhancing immune and inflammatory responses. Our recent study revealed the mechanism of MDA-7/IL-24 in promoting airway inflammation and airway remodeling through activating the JAK/STAT3 and ERK signaling pathways in bronchial epithelial cells. Herein, we summarize the cellular sources, inducers, target cells, signaling pathways, and biological effects of MDA-7/IL-24 in several allergic and autoimmune diseases. This review also synopsizes recent advances in clinical research targeting MDA-7/IL-24 or its receptors. Based on these advancements, we emphasize its potential as a target for immunotherapy and discuss the challenges of developing immunotherapeutic drugs targeting MDA-7/IL-24 or its receptors in autoimmune and inflammatory disorders.