Oral toleragens in rheumatoid arthritis

Rheumatoid arthritis (RA) is a common inflammatory and destructive arthropathy. Its precise pathogenesis remains unknown but there is evidence to suggest it is an autoimmune disease. Recently, a number of candidate autoantigens have been identified in RA. Modulating the immune response to the autoantigens by oral tolerance may lead to safer and more effective treatment. Oral tolerance is a state of systemic immune suppression to an antigen induced by oral feeding of the same antigen. In animal models, oral feeding with pathogenic antigens prevents and reduces the severity of autoimmune diseases. Even in diseases where the pathogenic autoantigens are unknown, bystander suppression can be induced using antigens present in the anatomical vicinity. Hence, oral tolerance has been advocated as a treatment strategy for autoimmune diseases including RA. Clinical trials of chicken and bovine type II collagen, a major constituent of articular cartilage, produced conflicting results in RA. This review examines the scientific basis of oral tolerance, discusses the apparent discrepancy in clinical trial results and looks at the future prospect.