Immunohistochemical evidence for IgA1 involvement in Graves ophthalmopathy

Orbital muscle, adipose tissues, and periorbital muscle from 11 patients with Graves ophthalmopathy were studied with in situ assays using monoclonal antibodies for IgA1, IgA2, IgM, and IgG. Tissue biopsies were taken from varied extraocular muscles and orbital sites. All cases were from patients with severe disease or disease of long duration. Control specimens of extraocular muscle tissues were obtained from nine patients treated for unrelated orbital disorders. Only connective tissue associated with the extraorbital muscles and periorbital muscles showed any reactivity. Of the muscle tissue obtained from patients with Graves disease all exhibited IgA1 positive staining of the endomysium and perimysium, without staining of the muscle fibers themselves. Parallel sections of orbital muscles reacted with anti-IgA2 or anti-IgM antibody failed to demonstrate staining. Control extraocular muscle tissue did not stain with anti-IgM and one control muscle of seven reacted minimally with anti-IgA2. Some reactivity with anti-IgA1 was seen in four of the seven control muscles but this was qualitatively much less than that of muscle tissue from patients with Graves disease. Monoclonal anti-IgG did not stain tissue from the six Graves specimens and three control specimens tested.