The Gut Microbiota: Emerging Evidence in Autoimmune and Inflammatory Diseases

Autoimmune diseases (AIDs) are a group of immune-related disorders primarily affecting joints and surrounding tissues, often marked by chronic inflammation and autoimmune activation. Common types include systemic lupus erythematosus, rheumatoid arthritis, multiple sclerosis, autoimmune cardiovascular diseases, and skin conditions. While their pathogenesis is unclear, recent studies suggest that abnormal gut microbiota may contribute. Previous research has shown that various patients with rheumatic disease exhibit altered gut microbiota, characterized by decreased microbial diversity, overall compositional changes, and microbiota-mediated functional alterations. Bacterial species closely associated with AIDs include <i>Prevotella copri</i>, <i>Ruminococcus gnavus</i>, and <i>Ligilactobacillus salivarius</i>. Dysregulated gut microbiota activates host immune responses through multiple mechanisms, including compromised intestinal barrier, systemic translocation, molecular mimicry of self-antigen epitopes, and changes in microbiota-derived metabolites, thereby substantially contributing to the development and progression of AIDs. Microbial metabolites, including short-chain fatty acids, tryptophan metabolites, and bile acid metabolites, are actively involved in driving disease progression. In addition, the therapeutic outcomes and adverse effects of immunotherapeutic agents can be modulated by gut microbiota through their impact on drug biotransformation processes. Clinically, analyzing gut microbiota characteristics can aid in disease diagnosis and prognosis prediction. Therapeutic strategies such as fecal microbiota transplantation, probiotics, prebiotics, and the Mediterranean diet may become effective measures for managing AIDs. This article reviews recent research progress, future directions, and the potential of microbiota-based interventions in treating AIDs.