Transferrin receptors and natural killer cell lysis. A study using Colo 205 cells exposed to 60 Hz electromagnetic...

The role of target cell transferrin receptors (TfR) in natural killer (NK) cell-induced cytolysis has been studied using Colo 205 cells in which prior exposure to 60 Hz electromagnetic fields produced constitutive expression of maximum numbers of TfR. It was found that NK cell cytolysis was decreased in those cells expressing the highest levels of TfR, while cells expressing the lowest level of TfR were lysed to the greatest extent. Furthermore, pretreatment of target cells with, and the continued presence in the assay medium of, iron transferrin produced, in general, only a slight decrease in cytolysis. Incubation of cells with apotransferrin also produced only a slight decrease in cytolysis, while incubation with zinc transferrin produced a greater decrease in cytolysis. This latter effect was particularly dramatic for cells that had been exposed previously to either a 60 Hz magnetic field alone (1.0 gauss) or to a combined electric + magnetic field (current density 300 mA/m2, 1.0 gauss). In addition to indicating a discordance between TfR expression on target cells and their sensitivity to NK cell cytolysis, the data presented provide a further indication of cellular membrane changes produced by exposure to 60 Hz electromagnetic fields.