Epitope recognition within TSHR residues 317–366 by TAb-4, but not MS-1. MS-1 reacted similarly to both CHO-hTSHR (a) and NC35 (c) cells. However, strong immunoreactivity seen on CHO-hTSHR cells (b) by TAb-4 was lost on NC35 cells (d) lacking TSHR residues 317–366. The thick lines indicate CHO-hTSHR cells in a and b, and NC35 cells in c and d. The thin lines indicate CHO cells. Fluorescence intensity was measured in FL-2.