Thyroid epithelial cell proliferation in xenotransplanted human toxic nodular goitre is increased by Graves' IgG

Human toxic nodular goitre tissue was xenotransplanted to athymic mice. Transplant function was analysed as 18-h thyroid transplant uptake of iodide-125 at day 21 and again at 10 weeks after transplantation. Graves' IgG or IgG from healthy donors was given intraperitoneally daily day 22-35. Epithelial cell proliferation in thyroid tissue transplants from human toxic nodular goitre and from normal thyroid glands was analysed by continuous [3H]thymidine administration for 4 days between day 21 and 24 and for 12 days between day 21 and 33 in separate series given daily injections of Graves' IgG or normal IgG during the same period. After administration of Graves' IgG, the 18-h iodide-125 uptake by the toxic nodular tissue transplants was 7 times higher at 10 weeks than at 3 weeks. Control IgG gave a corresponding 1.6-fold increase. The fraction of labelled cells after [3H]thymidine incorporation was 18 and 56% in toxic nodular goitre transplants and 4 and 48% in normal thyroid tissue transplants after daily Graves' IgG administration for 4 and 12 days, respectively, but only 1.3% in both types of tissue transplants after administration of normal IgG. Graves' IgG therefore seems to be able to stimulate cell proliferation in toxic nodular goitre tissue.