Growth hormone enhances natural killer cell activity against glioma

Although it is now known that pituitary hormones activate the immune system, there are still numerous questions to be answered with regard to the mechanisms involved. In this study, which focuses on growth hormone (GH) and natural killer (NK) cells, the latter's antitumor effects on glioma were investigated. Using fluorescein isothiocyanate-labeled rat 9L glioma and NK-receptive YAC-1 cells as target cells and rat splenocytes as effector cells, a cytotoxicity assay was carried out with the fluorescence-activated cell sorter method, which stains dead cells with propidium iodide. The effector cells were pretreated 48 hours in advance with various concentrations of GH. A similar experiment was also carried out in the presence of anti-asialo-GM1 antibodies. When the GH concentration of 9L was 10 to 40 microg/ml, cytotoxicity was confirmed to have been enhanced 17% to 39%. This enhancement disappeared in the presence of anti-asialo-GM1 antibodies. A similar increase in cytotoxic activity was also confirmed in YAC-1 cells. In this experiment we observed GH enhancement of natural killer activity against glioma.