The article focuses on a research which aims to identify a potential role for the intestinal bacterium Prevotella copri in the pathogenesis of rheumatoid arthritis, noted to be one of the most common autoimmune diseases. It reveals that rheumatoid arthritis is characterized by joint inflammation and suggests that the gut microbiota has the potential to trigger inflammation in the context of pre-existing autoimmunity. Information about Prevotella copri is provided.