Insights into the Role of Commensal-Specific T Cells in Intestinal Inflammation

Mucosal Immunity to Gut Fungi in Health and Inflammatory Bowel Disease

The gut microbiome is a diverse microbial community composed of bacteria, viruses, and fungi that plays a major role in human health and disease. Dysregulation of these gut organisms in a genetically susceptible host is fundamental to the pathogenesis of inflammatory bowel disease (IBD). While bacterial dysbiosis has been a predominant focus of research for many years, there is growing recognition that fungal interactions with the host immune system are an important driver of gut inflammation. Candida albicans is likely the most studied fungus in the context of IBD, being a near universal gut commensal in humans and also a major barrier-invasive pathogen. There is emerging evidence that intra-strain variation in C. albicans virulence factors exerts a critical influence on IBD pathophysiology. In this review, we describe the immunological impacts of variations in C. lbicans colonisation, morphology, genetics, and proteomics in IBD, as well as the clinical and therapeutic implications.

Reciprocal Interactions Between Regulatory T Cells and Intestinal Epithelial Cells

It has been well established that Foxp3+ regulatory T cells (Treg cells) play a crucial role for immune repression and tolerance, protecting the body from autoimmunity and inflammation. Previous studies indicate that intestinal Treg cells are one specialized population of Treg cells, distinct from those in other organ compartments, both functionally and phenotypically. Specific external and internal signals, particularly the presence of microbiota, shape these Treg cells to better cooperate with the gut ecosystem, controlling intestinal physiology. The integrity of intestinal epithelial barrier represents a key feature of gut immune tolerance, which can be regulated by multiple factors. Emerging evidence suggests that bidirectional interactions between gut epithelium and resident T cells significantly contribute to intestinal barrier function. Understanding how Treg cells regulate intestinal barrier integrity provides insights into immune tolerance-mediated mucosal homeostasis, which can further illuminate potential therapeutic strategies for treating inflammatory bowel disease and colon cancer.