Cytotoxicity of tumor necrosis factor for thyroid epithelial cells and its regulation by interferon-gamma

The FRTL-5 line of differentiated rat thyroid epithelial cells was shown to be sensitive to the cytotoxic action of recombinant tumor necrosis factor. The sensitivity of the cells varied with the conditions of culture. It was markedly increased by preincubation with recombinant interferon-gamma, and the magnitude of this enhancement was affected by the presence of thyroid-stimulating hormone. The increased susceptibility of the cells to the cytotoxicity of tumor necrosis factor was clear as early as 2-4 h after the addition of interferon-gamma and greatly preceded the induced expression of major histocompatibility complex class II antigen. Since cells secreting interferon-gamma and tumor necrosis factors may co-exist in inflammatory infiltrates, our observations suggest that these factors may be early mediators of cell destruction in autoimmune thyroid disease.