title: Suppression of peripheral blood natural killer cell activity by excess thyroid hormone.
abstract: Natural killer (NK) cells were assessed in patients with hyperthyroxinemia due to Graves' disease or treatment with thyroxine (T4). Cytolytic activity was measured with 51Cr-labeled K562 tumor cells and NK enumeration was by flow cytometry using NKH-1 monoclonal antibody to identify the relevant surface marker. Activity was uniformly decreased in association with hyperthyroxinemia, regardless of the underlying pathology; however, there was no reduction in the number of NKH-1+ cells. NK activity was enhanced by addition of interleukin 2 (IL-2) in both control and patients' cells although the value in the latter instance failed to reach the basal control level. Production of IL-2 by lymphocytes from hyperthyroxinemic subjects, in response to phytohemagglutinin, was also reduced. Since NK cells are thought to act as a defense against viral infections and some malignancies and may play a role in autoregulation of the immune system, this effect of T4 may have significant biological implications.
mesh_terms: D002460:Cell Line; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D006111:Graves Disease / Q000276:immunology*; D006801:Humans; D006981:Hyperthyroxinemia / Q000276:immunology*; D007165:Immunosuppression Therapy; D007376:Interleukin-2 / Q000494:pharmacology; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology*; D008213:Lymphocyte Activation; D012016:Reference Values; D013959:Thyroid Diseases / Q000276:immunology; D013974:Thyroxine / Q000494:pharmacology
chemical_list: D007376:Interleukin-2; D013974:Thyroxine