TSH receptor antibody (TRAb) activity using chicken thyroid receptor (c-TRAb) and porcine thyroid receptor (p-TRAb) was determined by the incubation of 125I-bovine TSH with each receptor. Both c-TRAb and p-TRAb activity in
LATS positive and negative Graves' sera were compared. 15 out of 39
LATS positive sera and 4 out of 46
LATS negative sera had positive c-TRAb activity. On the other hand, all
LATS positive sera and 33 out of 46
LATS negative sera had positive p-TRAb activity. No relationship between c-TRAb and p-TRAb activity was observed, and there was also no correlation between c-TRAb and
LATS activity. Changes in c-TRAb, p-TRAb and
LATS activity in the
clinical course of patients with
Graves' disease were examined. These activities were parallel in some cases, but in others they were not. A weak c-TRAb activity was observed in 4 out of 29
Hashimoto's disease, but all cases with
thyroid cancer and
subacute thyroiditis showed no activity. Sera with positive c-TRAb activity did not stimulate chicken thyroid in chick bioassay. These results suggest that some cases of TRAb in
Graves' disease (mainly
LATS) inhibit TSH binding to chicken thyroid receptor (non-mammalian species) in the same way as mammalian thyroid, but may not have any stimulatory action on
thyroid hormone synthesis. It is interesting to note that TRAb including
LATS have the similar effect on
TSH receptor even in nonmammalian species.