TSH receptor antibody induction of thyroglobulin release from human thyroid cell monolayers

We investigated the influence of TSH receptor antibody (TRA), as detected by inhibition of 125I-bTSH binding to detergent solubilized porcine TSH receptors, on in-vitro thyroglobulin (hTg) production using normal thyroid cells in monolayer. Secretion of hTg into the culture medium was analysed by a non-competitive enzyme immunosorbent (ELISA) technique utilizing two murine monoclonal antibodies. Basal hTg release (mean +/- SD 124 +/- 27 ng/10(5) cells/6 d, n = 5) was stimulated by bTSH (10, 10(2), 10(3) microU/ml) in a dose related manner (mean +/- SD 191 +/- 24, 587 +/- 80, 695 +/- 66 ng/10(5) cells/6 d, respectively). IgG (2 mg/ml) from seven patients with hyperthyroid Graves' disease, and known titres of TRA, similarly enhanced production of hTg, in a dose and time-dependent manner, when compared to control IgG. The degree of induction varied from a 140-230% increase in total hTg release over a 6-day incubation period. There was a direct correlation between the degree of 125I-bTSH binding inhibitory activity and the hTg response (r = 0.9, P less than 0.01). These data demonstrate that TSH receptor antibodies enhance hTg release from human thyroid cell monolayers and allow an assessment to be made of antibody-activated post receptor mechanisms.