Constitutive inhibition of NK cells by GR: reversal by histamine.
One hundred thousand NK cell-enriched lymphocytes were admixed with 105 GR or 105 CML cells and assayed for cytotoxicity against K562 cells (104 cells/well) in a 16-hour assay. The cell cultures were treated with culture medium (■) or histamine (10 μmol/L, ▪). The results are expressed as the mean percent of baseline cytotoxicity against K 562 cells (control, part A), where the cytotoxicity of NK cell-enriched lymphocytes of each donor was set to 100% (mean baseline cytotoxicity of all donors: 49.2 cell lysis percent, range 32-74). Part B (IL-2) shows results obtained in parallel experiments in which cells were treated with IL-2 (100 U/mL, 16 hours), and the cytotoxicity of IL-2–activated lymphocytes of individual donors was set to 100% (mean IL-2–induced cytotoxicity: 59.2 cell lysis percent, range 38-85). Data are percent of control cytotoxicity (mean ± SEM) of NK cells incubated with GR from 9 healthy donors, or CML cells obtained from 9 CML patients in stable disease with 100% Ph+ cells. Statistics by Mann-WhitneyU test. Lymph (medium) versus lymph + GR (medium):P < .005 (control), P < .005 (IL-2); lymph + GR (medium) versus lymph + GR (histamine):P < .05 (control), P < .01 (IL-2); lymph + GR (medium) versus lymph + CML (medium):P < .005 (control), P < .005 (IL-2).
