Immunohistochemical staining of normal and Graves' extraocular muscle.

Extraocular muscle biopsies from normal individuals and five patients with Graves' ophthalmopathy were analyzed by immunohistochemical staining. Fibroblasts in normal extraocular muscle as well as Graves' extraocular muscles expressed HLA-class II antigens, but the muscle cells did not. There was an increase of interstitial tissue in Graves' extraocular muscles but no visible damage to the muscle cells. In four of the biopsies from Graves' patients the cellular reaction was very weak. In the fifth patient the reaction was more pronounced with macrophages predominating, but with few lymphocytes and almost equal amounts of B and T cells. We could not confirm the earlier described specific extraocular muscle antibodies in sera from Graves' patients and conclude that there seems to be an activation of orbital fibroblasts in Graves' ophthalmopathy. This may contribute to the pathogenesis of the disease.