A clonal strain of rat thyroid cell (FRTL-5) in continuous culture has been used to investigate the effect of IgG preparations derived from the sera of a patient with Graves' disease and a patient with thyroid carcinoma on the synthesis of thyroglobulin. In the culture medium on the surface of cover glass, we obtained a single layer of the rat thyroid epithelial cells. After fixation by Bouin's solution and immunohistochemical stain (PAP method), we determined quantitatively the thyroglobulin (Tg) positive ...