Assay of Thyrotropin Receptor Antibodies with Recombinant Human Thyrotropin Receptor Expressed on Chinese Hamster Ovary Cells / 대한내분비학회지

ABSTRACT

Thyroid stimulating antibody which results in the development of hyperthyroidism and goiter in Graves' patients used to be measured by using rat thyroid cells, FRTL-5. However, this assay has disadvantages decreased sensitivity due to differences in species, and fastidious culture conditions for FRTL-5 cells. Thus, we recently created stably transfected Chinese hamster ovary(CHO) cells containing the human TSH receptor(hTSHR-CHO) and developed optimal conditions for the measurement of thyroid stimulating antibody using hTSHR-CHO cells. In this study, to evaluate the clinical relevance of thyroid stimulating antibody measurement using hTSHR-CHO cells, we measured thyroid stimulating antibody activities of IgGs from Graves' disease and other thyroid disease using hTSHR-CHO cells, and compared to those of thyroid stimulating antibody assays using FRTL-5 cells. 1) The cut off value of positive thyroid stimulating antibody activity measured in hTSHR-CHO cells was 145%(above the mean +2SD) which was lower than 165% in FRTL-5 cells. The intra-assay and inter-assay variances were 3.9% to 9.0% and 12.7% to 1.6%, respectively. 2) Thyroid stimulating antibody activity was detected in 90% of patients with untreated Graves' disease when patients initially presented. Further, in patients seen initially but already under therapy, 75% had positive values if they were hyperthyroid but only 43% had IgGs with activity if they were euthyroid. Patients in clinical remission after therapy showed positive values in 23% of cases. Only 2 of 25 patients with Hashimoto's thyroiditis showed weak thyroid stimulating antibody activity, none of 18 patients with nodular nontoxie goiter, 1 of 15 patients with primary myxedema, and 2 of 33 control patients with no thyroid disease. Thus, the detection frequency and specificity of the assay with hTSHR-CHO cells was excellent for this type bioassay.3) The detection frequency of thyroid stimulating antibody activity by hTSHR-CHO cells assay system(90%) was higher than that by FRTL-5 cells assay system(66%) in untreated Graves' patients. Those two activities were positively correlated with each other(r=0.52, p<0.001). However, some IgGs showed discrepancy of the thyroid stimulating antibody activity measured in hTSHR-CHO cells and in FRTL-5 cells; 56 of 87 patients were positive in both cells system, 8 of 87 were negative in both cells system, 1 of 87 was only positive in FRTL-5 cells and 22 of 87 were only positive in hTSHR-CHO cell system. Thus, 73%(22/30) of IgGs showing negative values of thyroid stimulating antibody activities in FRTL-5 cells were detected its activities in hTSHR-CHO cells system.In summary, thyroid stimulating antibody assay with hTSHR-CHO cells exhibited so excellent sensitivity and specificity that this technique should be used for clinical practice as well as basic research.