ABSTRACT
@EN Thyrotropin receptor-blocking antibodies (TRBAb) from the patients with autoimmune atrophic thyroiditis inhibit thyroid stimulation of thyrotropin (TSH) and thyroid stimulating antibody at the receptor level. However, it has been reported
that
there
are some TRBAb which bind to the other sites, not TSH receptor, or block post-receptor processes. These findings suggest that there may be heterogeous TRBAb in autoimmune atrophic thyrodiditis. In order to investigate the heterogeneity of TRBAb
in
terms
of its mechanism of action, we classified TRBAb according to TSH binding inhibitor immunoglobulin (TBII) and thyroid stimulation blocking antibody (TSBAb) activities and measured the change of TSBAb activity after absorption with guinea pig fat
cell
membrane. The prevalences of TBII and TSBAb was 45% (36/80) and 60% (48/80), respectively. Immunoglobulins G from TBII-positive group were all positive for TSBAb activity but 27.3% (12/44) of TBII-negative group also had TSBAb activity.
Therefore,
we
divided TRBAb into at least 2 groups, that is, both TBII and TSBAb-positive (45%), TBII-negative but TSBAb-positive group (15%). After absorption with guinea pig fat cell membrane, TSBAb activities were decreased by more than 50% in both TBII and
TSBAb-positive group, while among the patients of TBII-negative but TSBAb-positive group TSBAb activities were decreased in some (3/7) but not in others (4/7). From these results, we speculate that there are at least two types of TRBAb in
autoimmune
atrophic thyroiditis. Most of them are TSH receptor-mediated but some TRBAb particularly from TBII-negative but TSBAb-positive group are directed against other sites than that of TSH binding or block post-receptor signal transduction (J Kor Soc
Endocrinol 8:404~413, 1993).
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