House, R. V. and McCormick, D. L. Modulation of Natural Killer Cell Function after Exposure to 60 Hz Magnetic Fields: Confirmation of the Effect in Mature B6C3F₁ Mice.

In a previous study, we demonstrated that subchronic exposure to pure, linearly polarized 60 Hz magnetic fields (MFs) at flux densities ranging from 0.002 to 1.0 mT induced a modest but statistically significant and reproducible suppression of NK cell activity in young adult B6C3F₁ mice. NK cell activity in mice declines with age and is known to be suboptimal in older animals. The present study was designed to determine if the same MF exposure regimens will suppress NK cell activity in mature (i.e. more than 1 year old) animals. Extending our previous findings, a modest suppressive effect of MFs on NK cell activity in B6C3F₁ mice was found when subchronic exposure was initiated in animals held in quarantine for 1 year prior to exposure. These data demonstrate that MF exposure suppresses NK cell activity in both young and mature adult B6C3F₁ mice. However, because chronic exposure to the same MF parameters used in the NK function studies does not increase the incidence of neoplasia in B6C3F₁ mice, this statistically significant inhibition of NK cell function appears to be of limited biological significance.