[Expression of apoptosis-related proteins in Hashimoto's thyroiditis and its pathological significance]

To explore the role and significance of apoptosis-related proteins in the pathogenesis and pathological changes in Hashimoto's thyroiditis (HT).

Apoptotic level in thyroid tissue specimens from 17 patients with HT and 17 patients with nontoxic goiter (NTG) was evaluated by TUNEL method. Expression and distribution of Fas, FasL, Bcl-2 and Bax proteins in the specimens were investigated with immunohistochemical methods.

A high percentage of apoptosis (32.5% +/- 12.3%) was observed by TUNEL method in thyroid follicles from HT specimens in comparison with that from NTG specimens (1.3% +/- 0.7%, P < 0.01). Positive rates of Fas, FasL, Bcl-2 and Bax in thyroid cells of NTG (35% approximately 47%) were significantly lower than those in thyroid cells of HT (88% approximately 94%, P < 0.01). The intensity of positive immunostaining for Fas, FasL, Bcl-2 and Bax in thyroid cells of HT was significantly higher than that of the controls (P < 0.01). Apoptosis and strongly positive immunostained thyroid cells with HT for Fas, FasL and Bax were mainly distributed in follicles adjacent to lymphocytic infiltrates, whereas strongly positive stained thyroid cells for Bcl-2 were mainly located in the area remote from the infiltrating lymphocytes. Staining of infiltrating lymphocytes for Fas, FasL, Bcl-2 and Bax was weak.

Thyroid follicles in HT specimens exhibited high apoptotic levels. The high expression of apoptosis-related proteins Fas, FasL, Bcl-2 and Bax in thyrocytes of HT and weak expression in infiltrating lymphocytes accounted for thyroid follicle destruction and diffuse lymphocytic infiltration in HT.