THYROID-HORMONE POTENTIATES THE ANTIVIRAL ACTION OF INTERFERON-GAMMA IN CULTURED HUMAN-CELLS

Human interferon-gamma (hIFN gamma) exhibits a number of biological ef fects, including antiviral activity in homologous cells. The antiviral activity of recombinant (r) hIFN gamma, estimated by inhibition of ve sicular stomatitis virus yield, was potentiated up to 120-fold in huma n fibroblast (BG-9) cells exposed to free L-T-4 (0.5 X 10(-10) mol/L). Thyroid hormone alone did not induce the antiviral state in BG-9 cell s. L-T-3 also potentiated the antiviral action of rhIFN gamma, but D-T -4 and D-T-3 were ineffective, The antiviral effect of hIFN alpha in B G-9 cells was not influenced by thyroid hormone. Exposure of rhIFN gam ma-treated BG-9 cells to L-T-4 for only 3 h was sufficient to potentia te hIFN gamma-mediated antiviral activity. Similar potentiation by L-T -4 of the antiviral effect of rhIFN gamma in HeLa cell cultures was al so observed. Although the mechanism of potentiation of rhIFN gamma act ion by thyroid hormone is incompletely understood, the absence of anti viral activity of thyroid hormone alone indicates that the iodothyroni ne effect does not depend upon hormonal action on genes able to be sti mulated by IFN gamma.