Dose-response study of the blocking activity of MS-1. CHO-hTSHR cells were stimulated with MS-1 at the indicated concentrations with or without 100 μU/ml of TSH. Since MS-1 is a TSHR-stimulating monoclonal antibody, the cAMP generated by MS-1 alone was subtracted from the cAMP generated by MS-1 plus TSH. Medium alone produced less than 50 fmol/well cAMP, and TSH (100 μU/ml) generated 2,000 fmol/well.