Objective To investigate the relationship between the TRAb-producing cell precursors and different clinical stages of Graves' disease.Methods Peripheral lymphocytes were infected with Epstein-Barr virus,a kind of lymphocyte precursor stimulator,and were stimulated to produce TRAb.Results Of the total wells containing Ig-producing B cell precursors,there were 34.6% and 29.1% from 2 untreated patients,30% from 1 relapsing patient and only 1.3% and 3.8% from 2 healthy controls that secreted TRAb,respectively.As for the wells containing B cell precursors from 2 remission patients with undetectable TRAb in circulation,the percentage (10.7%) of TRAb-containing wells from one was higher than that from the other (5.3%).And the latter had similar percentage of TRAb-positive wells with the controls.The isotype of TRAb in supernatants of our EBV-transformed B lymphocytes was predominantly IgM.Conclusion The frequencies of TRAb-specific precursors were different at three distinct clinical stages of the disease.