cAMP dose-response study of TSHR-stimulating monoclonal antibody MS-1. MS-1 was examined for thyroid-stimulating activity at the indicated concentrations. TAb-4 and TAb-8 (5 μg/ml) were used as negative controls. Thyroid stimulation was expressed as a ratio with basal cAMP levels induced by culture medium. More than 200% stimulation above baseline was judged as positive and is shown as a dotted line.