Cytotoxic activity of interleukin-2 (IL-2) activated killer cells toward thyroid epithelial cells

We investigated the sensitivity of thyroid epithelial cells (thyrocytes) to IL-2 activated killer cells. The thyrocytes were lysed by autologous and allogeneic IL-2-activated killer cells; there were no differences in sensitivity to the killer cells between normal thyrocytes and thyrocytes from patients with Graves' disease. When thyrocytes were pretreated with recombinant interferon (rIFN) gamma or alpha, the IL-2-activated killer cell-mediated cytotoxicity was depressed and varied inversely with the cell surface expression of class I HLA gene products. The rIFN-gamma pretreatment did not alter the kinetics of thyrocytes lysis by IL-2-activated killer cells. Using cold target competition analysis, rIFN-gamma-pretreated thyrocytes clearly competed less effectively than did untreated cells for lysis of untreated target cells. These results suggest that rIFN-gamma or IFN-alpha pretreatment of thyrocytes may reduce their ability to be recognized by effector cells. These findings suggest that destruction of thyrocytes in autoimmune thyroiditis may be, in part, due to IL-2-activated killer cells and may be regulated by IFN.