Objective:To investigate the expression of apoptosis-related protein Fas/FasL and BcL-2 and their significance in Hashimoto’s thyroiditis (HT) and diffuse toxic goiter(DTG).Methods:Immunohistochemical staining(S-P method) was used to detect expression of apoptosis-related protein in formalin-fixed and paraffin-embeded tissues from 30 cases of HT

25 cases of DTG

and 22 normal thyroid tissues.Results:Fas-positive thyrocytes were observed in HT and DTG

while expression of Fas protein in normal thyroid tissues was negative.The positive rates of Fas expression were 40% and 60% in HT and DTG respectively

compared with the normal thyroid tissues

there was a significant difference ( P <0.01).FasL-positive thyrocytes and BcL-2-positive thyrocytes were observed in HT

DTG and the normal thyroid tissues

but there was not a significant difference in intensity of FasL-positive staining ( P >0.05).Expressions of BcL-2 in normal thyroid tissues and DTG were stronger

while no significant correlation was found between them.In HT the staining of follicles for BcL-2 was very weak

and there was significant difference compared with that in the normal thyroid tissues and DTG.Conclusion:LIU Chun

et al (Department of Internal Medicine

College of Clinical Medicine

Chongqing Medical University) Abstract Objective:To investigate the expression of apoptosis-related protein Fas/FasL and BcL-2 and their significance in Hashimoto’s thyroiditis (HT) and diffuse toxic goiter(DTG).Methods:Immunohistochemical staining(S-P method) was used to detect expression of apoptosis-related protein in formalin-fixed and paraffin-embeded tissues from 30 cases of HT

25 cases of DTG

and 22 normal thyroid tissues.Results:Fas-positive thyrocytes were observed in HT and DTG

while expression of Fas protein in normal thyroid tissues was negative.The positive rates of Fas expression were 40% and 60% in HT and DTG respectively

compared with the normal thyroid tissues

there was a significant difference ( P <0.01).FasL-positive thyrocytes and BcL-2-positive thyrocytes were observed in HT

DTG and the normal thyroid tissues

but there was not a significant difference in intensity of FasL-positive staining ( P >0.05).Expressions of BcL-2 in normal thyroid tissues and DTG were stronger

while no significant correlation was found between them.In HT the staining of follicles for BcL-2 was very weak

and there was significant difference compared with that in the normal thyroid tissues and DTG.Conclusion:Our results suggest that the follicular cells in HT undergo apoptosis through expression of Fas/FasL and interaction between them.The down-regulation of BcL-2 expression in thyrocytes can decrease BcL-2-mediated suppression for apoptosis.Overexpression of BcL-2 in DTG could render thyrocytes resistant to Fas/FasL-mediated apoptosis.We conclude that the expression of apoptosis-related protein plays an important role in the pathogenesis of HT and DTG.