MEASUREMENT OF THYROID-STIMULATING IMMUNOGLOBULINS IN A NEW CELL-LINETRANSFECTED WITH A FUNCTIONAL HUMAN TSH RECEPTOR (JPO9 CELLS), COMPARED WITH AN ASSAY USING FRTL-5 CELLS

OBJECTIVE Most bioassays used to measure thyroid stimulating antibodie s (TSAb) rely on the ability of patient sera to generate cAMP in cultu red cells of non-human origin. The cell line most commonly used has be en the rat thyroid cell line, FRTL-5. Recently, a new cell line (JPO9) possessing a transfected human TSH receptor has been developed. The a im of this study was to evaluate the JPO9 cells by comparing them with the widely used FRTL-5 cells, using the method of H-3-adenine incorpo ration for the direct measurement of intracellular cAMP.DESIGN The abi lity of patient sera to generate cAMP production in JPO9 and FRTL-5 ce lls was used as the index of thyroid stimulation. The specificity of t he assay was determined using sera from patients with autoimmune thyro id and non-thyroid autoimmune diseases. PATIENTS We studied sera from 28 patients with newly diagnosed Graves' disease, 72 patients with Gra ves' disease at various stages of treatment, 8 patients with Hashimoto 's thyroiditis, 40 patients with a variety of non-thyroid autoimmune d iseases and 42 control subjects. MEASUREMENTS The intracellular H-3-cA MP generated in JPO9 cells following preincubation with H-3-adenine an d subsequent incubation with patient or control sera, was used as a me asure for TSAb. The results obtained with these cells were compared to those obtained with the widely used FRTL-5 cells and they were also c orrelated with the measurement of TSH binding inhibitory immunoglobuli ns by a conventional radioreceptor assay. RESULTS JPO9 cells were more sensitive and had a wider range of response to bovine TSH (bTSH) than had FRTL-5 cells (10(-7)-10(-2) U/ml compared to 10(-5)-10(-3) U/ml r espectively). Unlike FRTL-5 cells, JPO9 cells respond well to unmodifi ed serum and grow constitutively in the absence of TSH, thereby not re quiring TSH deprivation prior to assay. The TSAb values obtained with both cell lines correlated well (r = 0.87). The JPO9 cells responded s pecifically to Graves' sera (23 out of 28 newly diagnosed patients wer e positive), whereas no patients with Hashimoto's thyroiditis and only 4 of 40 patients with non-thyroid autoimmune diseases gave low positi ve results for the presence of TSAb. CONCLUSIONS The JPO9 cells provid e similar diagnostic information to FRTL-5 cells in patients with auto immune thyroid disease. However, because they are more sensitive, grow faster, have less fastidious growth requirements and respond to unext racted sera, compared to FRTL-5 cells, we conclude that the JPO9 cells are preferable for the measurement of TSAb.