Elevated anti-galactosyl antibody titers in endemic goiter

Anti-Gal is a human polyclonal antibody that constitutes approximately 1% o f the circulating immunoglobulin G (IgG), interacts specifically with the m ammalian carbohydrate alpha-galactosyl epitope. Furthermore, it was found t o mimic irt vitro thyrotropin (TSH) effects regarding stimulation for cycli c adenosine monophosphate (cAMP) synthesis, I-125 uptake, and cellular prol iferation on cultured porcine thyrocytes and on Graves' disease thyrocytes, but not on normal human thyrocytes. As immune activation in sporadic and e ndemic goiters might play a secondary role in regulating thyrocyte prolifer ation and function, we evaluated anti-Gal titers in endemic goiter. Serum w as obtained from 109 Chagas'-negative patients living in an endemic goiter area of Brazil (Grao Mogol, MG) and 160 controls. The patients were divided into 3 groups, according to their goiter size (World Health Organization [ WHO] classification): grade 0 (group 1, n = 24), grade I-II (group 2, it = 41), and grade III-TV (group 3, rt = 44). Anti-Gal was assessed by a radioi mmunological procedure (results expressed as the percentage of bound radioa ctivity/total activity [%B/T]). The antibody titer was significantly more e levated in group 1 (mean +/- SEM: 9.27% +/- 0.80%), in group 2 (mean +/- SE M: 16.17% +/- 0.97%), and in group 3 (20.97% +/- 1.30%) than in normal cont rols (6.46% +/- 0.33%). Analysis of the male and female data separately for anti-Gal titer did not substantially alter these results. We concluded tha t the anti-Gal titer is higher in patients with endemic goiter and presente d a possible relationship with the size of goiter. Whether these antibodies contribute to the pathogenesis of the disease needs further clarification.