Immune function and host defense in rodents exposed to 60-Hz magnetic fields

This study was conducted to evaluate the influence of subchronic exposure to pure, linearly polarized 60-Hz magnetic fields (MF) on the host immune response in mice. The experimental design was as follows: three groups were exposed continuously (18.5 hr/day) to MF at field strengths of 0.02, 2, or 10 gauss (G), one group was exposed intermittently (1 hr on/1 hr off) to MF at a field strength of 10 G, and one group served as a sham control. Experimental endpoints included spleen and thymus weights and cellularity, antibody-forming cell (AFC) response, delayed-type hypersensitivity (DTH) response, splenic lymphocyte subset analysis, susceptibility to infection with Listeria monocytogenes, and natural killer (NK) cell activity. No differences in body weight, lymphoid organ weight, or lymphoid organ cellularity were observed in any MF-exposed group in comparison to sham controls. Likewise, no statistically significant differences were found in comparisons of AFC responses. Isolated statistically significant differences from control were observed in MF-exposed mice in the DTH assay, although no clear dose-related pattern of altered activity was seen. Splenic lymphocyte subset parameters examined were within normal limits in all groups, and no differences between control and MF-exposed mice were found. Host resistance to bacterial infection was not altered at any MF exposure examined in this study. Finally, although apparently dose-related, statistically significant alterations were observed in an initial study of NK cell function, repeat studies failed to demonstrate a consistent pattern of alteration.