Based on the findings from early studies, the expression of IDO1 in rheumatoid arthritis synovial fluid41 and subsequent research in a collagen-induced arthritis mouse model that revealed that IDO1 deficiency significantly exacerbated the severity of arthritis symptoms and tissue damage, it can be inferred that the presence of IDO1 may alleviate inflammation. Here, IDO1 is linked to arthritic joint disease.