Stimulation by phagocytosis of the deiodination of L-thyroxine in human leukocytes.

Intact human leukocytes actively deiodinate L-[(131)1] thyroxine, producing mainly inorganic (131)1 and chromatographically immobile (131)1-labeled origin material. When phagocytosis is induced, the deiodination is enhanced, a suggestion that deiodination in mediated by a peroxidase-hydrogen peroxide system. l-Thyroxine can serve as a source of iodine for iodination reactions within the leukocyte.