Suppression of Thyroid Cell Growth by Serum IgG in Graves' Disease

Summary

To determine whether serum immunoglobulin in addition to epidermal growth factor (EGF) augment growth in human thyroid cells, effects of these factors on thyrocytes were tested using IgG derived from 34 patients with Graves' disease and 12 normal subjects. The cell growth was estimated by [³H]-thymidine uptake, cell cycle determined by FACS analysis and the expression of c-fos mRNA in monolayer thyrocytes enzymatically prepared from Graves' thyroid. The addition of IgG taken from patients with Graves' disease inhibited the [³H]-thymidine uptake compared to that taken from control subjects. IgG taken from Graves' disease suppressed EGF-induced increase of S + G₂/M phase in cell cycle and the expression of c-fos mRNA, while those taken from normal subjects did not affect at all. [³H]-thymidine uptake was more suppressed by IgG from patients with a smaller-sized goiter than by those with a larger-sized one. There was a negative correlation between the suppression of [³H]-thymidine up-take and levels of TBII (p < 0.05). There was no correlation between the degree of suppression and the levels of T₃, T₄, TSAb, TSBAb or MCHA. Thus, in conclusion, IgG derived from sera of Graves' may inhibit the growth of Graves' thyrocytes, leading to the determination of the goiter size.

Key words

Thyroid Cell - Graves' Disease - IgG - Growth - Cell Cycle - c-fos