No effects of extremely low frequency magnetic fields found on cytotoxic activities and cytokine production of human peripheral blood mononuclear cells in vitro.

Several epidemiologic studies have suggested an association between exposure to extremely low frequency (ELF) magnetic fields (MFs) and cancer in adults and children. A possible target of MFs is the immune system. The effects of the exposure to ELF MFs on the immunological functions of human peripheral blood mononuclear cells (PBMCs) obtained from healthy male volunteers were assessed by measuring the natural killer (NK) and lymphokine activated killer (LAK) activities and the production of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interleukin-10 (IL-10). The PBMCs were exposed to three different MF: linearly polarized (vertical), circularly polarized, and elliptically polarized, at 50 and 60 Hz. Magnetic flux densities were set at 500, 100, 20, and 2 microT (rms) for vertical field and at 500 microT (rms) for the rotating fields. Using cytotoxicity assay and enzyme-linked immunosorbent assay (ELISA) for cytokine production, we could not find any effects of ELF MFs on the cytotoxic activities and the cytokines production of human PBMCs.

No effect of extremely low-frequency magnetic field observed on cell growth or initial response of cell proliferation in human cancer cell lines.

An effect on the tumor promotion process, as represented by accelerated cell growth, has been indicated as one example of areas that demonstrate the possibility of biological effects of extremely-low frequency magnetic fields. We, therefore, exposed the five cell lines (HL-60, K-562, MCF-7, A-375, and H4) derived from human tumors to a magnetic field for 3 days to investigate the effects on cell growth. Prior to exposure or sham exposure, the cells were precultured for 2 days in low serum conditions. The number of growing cells was counted in a blind manner. To investigate the effect on the initial response of cell proliferation, two cell lines were synchronized in G1 phase by serum starvation and then exposed to a magnetic field for 18 h (H4 cells) or 24 h (MCF-7 cells), both with and without serum stimulation. The rate of DNA synthesis, taken as a measure of the cell proliferation, was determined by following the incorporation of [(3)H]-thymidine into the DNA. Three different magnetic field polarizations at both 50 and 60 Hz were used: linearly polarized (vertical); circularly polarized; and an elliptically polarized field. Magnetic field flux densities were set at 500, 100, 20 and 2 microT (rms) for the vertical field and at 500 microT (rms) for the rotating fields. No effect of magnetic field exposure was observed on either cell growth or the initial response of cell proliferation.