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.