Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease characterized by the presence of a plethora of autoantibodies and immune complex formation. Virtually every system and organ can be affected by SLE. Gastrointestinal symptoms are common in SLE patients, and more than half of them are caused by adverse reactions to medications and viral or bacterial infections. Though not as common as lupus nephritis, SLE-related gastrointestinal involvement is clinically important because most cases can be life-threatening if not treated promptly. Lupus mesenteric vasculitis is the most common cause, followed by protein-losing enteropathy, intestinal pseudo-obstruction, acute pancreatitis and other rare complications such as celiac disease, inflammatory bowel diseases, etc. No specific autoantibody is identified as being associated with SLE-related gastroenteropathy. Imaging studies, particularly abdominal computed tomography scans, are helpful in diagnosing some SLE-related gastroenteropathies. Most of these complications have good therapeutic responses to corticosteroids and immunosuppressive agents. Supportive measures such as bowel rest, nutritional support, antibiotics and prokinetic medications are helpful in facilitating functional recovery and improving the outcome.

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Objective Changes in gut microbiota have been linked to systemic lupus erythematosus (SLE), but knowledge is limited. Our study aimed to provide an in‐depth understanding of the contribution of gut microbiota to the immunopathogenesis of SLE. Methods Fecal metagenomes from 117 patients with untreated SLE and 52 SLE patients posttreatment were aligned with 115 matched healthy controls and analyzed by whole‐genome profiling. For comparison, we assessed the fecal metagenome of MRL/lpr mice. The oral microbiota origin of the gut species that existed in SLE patients was documented by single‐nucleotide polymorphism–based strain‐level analyses. Functional validation assays were performed to demonstrate the molecular mimicry of newly found microbial peptides. Results Gut microbiota from individuals with SLE displayed significant differences in microbial composition and function compared to healthy controls. Certain species, including the Clostridium species ATCC BAA‐442 as well as Atopobium rimae, Shuttleworthia satelles, Actinomyces massiliensis, Bacteroides fragilis, and Clostridium leptum, were enriched in SLE gut microbiota and reduced after treatment. Enhanced lipopolysaccharide biosynthesis aligned with reduced branched chain amino acid biosynthesis was observed in the gut of SLE patients. The findings in mice were consistent with our findings in human subjects. Interestingly, some species with an oral microbiota origin were enriched in the gut of SLE patients. Functional validation assays demonstrated the proinflammatory capacities of some microbial peptides derived from SLE‐enriched species. Conclusion This study provides detailed information on the microbiota of untreated patients with SLE, including their functional signatures, similarities with murine counterparts, oral origin, and the definition of autoantigen‐mimicking peptides. Our data demonstrate that microbiome‐altering approaches may offer valuable adjuvant therapies in SLE.

The emerging concept of microbiota contributing to local mucosal homeostasis has fueled investigation into its specific role in immunology. Gut microbiota is mostly responsible for maintaining the balance between host defense and immune tolerance. Dysbiosis of gut microbiota has been shown to be related to various alterations of the immune system. This review focuses on the reciprocal relationship between gut microbiota and innate immunity compartment, with emphasis on gut-associated lymphoid tissue, innate lymphoid cells, and phagocytes. From a clinical perspective, the review gives a possible explanation of how the "gut microbiota-innate immunity" axis might contribute to the pathogenesis of autoimmune diseases like rheumatoid arthritis, spondyloarthritis, and systemic lupus erythematosus.