Elevated anti-alpha-galactosyl antibody titres. A marker of progression in autoimmune thyroid disorders and in endocrine ophthalmopathy?

The titres of anti-alpha-galactosyl antibodies were measured by passive haemagglutination in 50 control subjects and in 128 patients presenting with various thyroid disorders. Titres of control subjects ranged from 1/10 to 1/80, regardless of age and blood group. Elevated titres (greater than 1/80) were constantly noted in 6/6 patients with progressive exophthalmos, in 5/5 patients with untreated Graves' disease, and in 11/12 patients with progressive nontoxic goitre. By contrast, the titres were within the normal range in primary myxoedema (17 patients) and in residual exophthalmos (11 patients), whereas they were only erratically increased in 1/31 patients with treated or cured Graves' disease and in 5/36 patients with nonprogressive nontoxic goitre. Finally, elevated titres were also found in 3/7 patients presenting with autoimmune thyroiditis. No correlations could be established between elevated titres and the thyrotropin binding inhibiting immunoglobulin activity, the antithyroglobulin antibody titres or the antimicrosomal antibody titres. As in the control subjects, the anti-alpha-galactosyl antibodies mainly belonged to the IgG class. Affinity purified anti-alpha-galactosyl antibodies were capable of binding to trypsinized human and porcine thyroid cells in culture, as shown by indirect immunofluorescence. On the other hand, they were not able to react with untreated thyroid cells. The data show that the measurement of anti-alpha-galactosyl antibody titres could represent an easy and useful tool to determine whether an autoimmune thyroid disorder is in progression. Besides, they suggest that some of the antigenic determinants implicated in the enhanced production of anti-alpha-galactosyl antibodies are present, but normally hidden, within the cell surface of thyroid cells.