Induction of an adaptive response in human blood lymphocytes exposed to radiofrequency fields: Influence of the universal mobile telecommunication system (UMTS) signal and the specific absorption rate

The induction of an adaptive response (AR) was examined in human peripheral blood lymphocytes exposed to non-ionizing radiofrequency fields (RF). Cells from nine healthy human volunteers were stimulated for 24 h with phytohaemagglutinin and then exposed for 20 h to an adaptive dose (AD) of a 1950 MHz RF UMTS (universal mobile telecommunication system) signal used for mobile communications, at different specific absorption rates (SAR) of 1.25, 0.6, 0.3, and 0.15 W/kg. This was followed by treatment of the cells at 48 h with a challenge dose (CD) of 100 ng/ml mitomycin C (MMC). Lymphocytes were collected at the end of the 72 h total culture period. The cytokinesis-block method was used to record the frequency of micronuclei (MN) as genotoxicity end-point. When lymphocytes from six donors were pre-exposed to RF at 0.3 W/kg SAR and then treated with MMC, these cells showed a significant reduction in the frequency of MN, compared with the cells treated with MMC alone: this result is indicative of induction of AR. The results from our earlier study indicated that lymphocytes that were stimulated for 24 h, exposed for 20 h to a 900 MHz RF GSM (global system for mobile communication) signal at 1.25 W/kg SAR and then treated with 100 ng/ml MMC, also exhibited AR. These overall data suggest that the induction of AR depends on RF frequency, type of the signal and SAR. Further characterization of RF-induced AR is in progress.