Immunohistochemical Evidence for IgE Involvement in Graves' Orbitopathy

Orbital muscle and adipose tissues from seven Graves' orbitopathy patients were studied with in situ assays for IgE. The cases varied in disease severity and site biopsied. Two monoclonal and one polyclonal anti-IgE reagents produced similar results. Identically prepared monoclonal anti-IgM and anti-IgG antibodies and tissues obtained from five patients treated for unrelated orbital disorders were used as controls. Graves' tissues exhibited extravasated leukocytes and leukocyte-rich vessels. These leukocytes were mostly lymphoid. Some basophils and mast cells were identified and polymorphonuclear cells were abundant within vessels of adipose tissue. IgE-positive material was found in association with the majority of leukocytes and with muscle fibers. Parallel sections reacted with anti-IgM antibody were negative, whereas anti-IgG produced diffuse staining with no specific structures highlighted. Control, non-Graves' tissues had no evidence of immune cell activity and were either negative or displayed reactions with anti-IgE reagents that were in most cases different from those of Graves' tissue. Serum IgE was measured in six of the seven patients and was elevated in the two patients with fulminating disease.