Nature and significance of orbital autoantigens and their corresponding autoantibodies in thyroid-associated ophthalmopathy.

There is now considerable evidence that the pathogenesis of thyroid-associated ophthalmopathy is closely linked to the presence of a shared autoantigen(s) in the thyroid and the eye muscle, against which cytotoxic mechanisms are directed. Although the orbital connective tissue is certainly involved in the orbital inflammatory process, a 64 kDa membrane protein expressed by both the eye muscle and the thyroid and recognized consistently by antibodies in the sera of TAO patients, seems to be the most likely target candidate. While its presence in non ocular skeletal muscle is not as well established, more recent data tend to suggest the existence of a 64 kDa molecule in the three tissues. The availability of a cDNA encoding a 572 amino acid protein corresponding to a MW of 63-64 kDa, which may be the same molecule, will allow us to determine more clearly the structural characteristics of the different molecules proposed as targets. The role of the corresponding autoantibodies in the pathogenesis of the eye disease is far less well defined. Whether they play a role in the induction of the ophthalmopathy or only represent helpful markers remains to be clarified.