Stimulating effect of triiodothyronine on cell-mediated immunity.

The effects in vitro and in vivo of triiodothyronine on certain functions of human lymphocytes and polymorphonuclear granulocytes have been investigated. Triiodothyronine was able to enhance the phagocytic capacity and chemiluminescent activity of polymorphonuclear granulocytes. PHA-P-induced 3H-thymidine incorporation into lymphocytes was significantly increased in the presence of triiodothyronine. A concentration-dependent enhancing effect of triiodothyronine on antibody-dependent enhancing effect of triiodothyronine on antibody-dependent cell-mediated cytotoxicity was also observed.