ABSTRACT
Cell destruction in Hashimoto's thyroiditis (HT) involves autoantibodies and cytotoxic T lymphocytes. Thyrocytes maintenance occurs by pro-apoptotic, anti-apoptotic and cell proliferation balance. OBJECTIVES: To characterize factors related to the mechanisms of apoptosis and cell proliferation in thyroid cells and intrathyroid lymphocytic infiltrate in HT. METHODS: We assessed lymphocytic infiltrate and thyroid cells from HT and normal thyroid by immunohistochemical analysis of cell proliferation (Ki-67), antiproliferation (p27Kip1), pro-apoptosis (Fas, Fas-ligand, BID) and anti-apoptosis (MCL-1, BCL2) markers. RESULTS: Lymphocytic infiltrate presented BCL2 and MCL-1 higher expression, Ki-67 and p27kip1 balance. Thyrocytes exhibited Fas and FasL balance, higher BID expression; MCL-1, BCL-2, Ki-67 similar to the normal thyroid. T4 and higher lymphocytes BID expression were associated. CONCLUSIONS: In lymphocytic infiltrate predominated anti-apoptosis in relation to pro-apoptosis except for BID. Thyrocytes presented pro-apoptosis and anti-apoptosis balance and cell proliferation similar to normal thyroid. T4-associated BID expression in HT lymphocytes suggests the influence of thyroid hormone as a signal to up-regulate the BID pro-apoptotic protein and thus increase lymphocytic apoptosis rates.
