Avian models of autoimmune disease: lessons from the birds.

Many important lessons have been learned from studies of autoimmune diseases in chicken models. It is now quite clear that both cellular and humoral immune responses are important in developing the final picture of autoimmune disease. In the case of the amelanosis of Smyth line (SL) chickens, antibody appears to play the primary role, whereas the sclerosis of University of California/Davis line-200 (UCD-200) birds is mainly mediated by T cells. Chronic thyroiditis of the OS chicken is due to both humoral and cellular effector mechanisms. The Obese strain (OS) chicken is particularly valuable for studies of genetics. Multiple genetic factors converge in producing maximal susceptibility to the development of autoimmune thyroiditis. They include MHC genes responsible for immune recognition; genes affecting thymus development, critical for regulation of the immune response; and genes that control thyroid function, influencing the vulnerability of the target organ to autoimmune attack. The importance of environmental factors, such as dietary iodine, is also strongly supported by studies in the OS chicken. Thus, the birds have provided valuable clues to our understanding of human autoimmune disorders in the past and are expected to do so in the future.