Aneta Cheda, Abstract Co-Author: Nothing to Disclose

Ewa M. Nowosielska, Abstract Co-Author: Nothing to Disclose

Jolanta Wrembel-Wargocka, Abstract Co-Author: Nothing to Disclose

Jaroslaw Jazwinski, Abstract Co-Author: Nothing to Disclose

Marek K. Janiak, Presenter: Nothing to Disclose

The reported inhibitory effects of the low-level, low-LET irradiations on the development of tumors may result from stimulation by such exposures of anti-cancer immune mechanisms. In view of the important role of NK cells in anti-tumor surveillance, the aim of the present study was to assess the effect of irradiations with low and higher doses of X-rays on cytotoxic reactions mediated by these cells.

In the study, murine NK cells obtained form spleens of the BALB/c mice were irradiated in vitro with 0.1, 0.2, or 1.0 Gy X-rays or collected from animals exposed to single or fractionated X-rays at the absorbed doses of 0.1, 0.2, or 1.0 Gy. Cytotoxic activity of NK cells was estimated using the 51Cr-release assay and production of IFN-γ by these cells was examined with the ELISA assay. Concanamicin A or the anti-FasL antibody were used to inhibit the perforin- or Fas receptor-mediated cytolytic function of the NK cells, respectively. The in vivo activity of these cells was suppressed by injection of the anti-asialo GM1 antibody.

Cytotoxic activity of the NK cells collected from mice irradiated with both single and fractionated X-rays was significantly stimulated compared to the activity of the counterpart cells obtained from the sham-exposed mice. This effect was totally abrogated by injection of the anti-asialo GM1 antibody. The elevated cytotoxicity was, for the most part, mediated by perforin and FasL. Exposure of mice to all the three doses of X-rays markedly stimulated the IFN-γ production. In contrast, neither the cytotoxic activity nor secretion of IFN-γ were affected by the in vitro irradiations of the NK cells.

The obtained results indicate that both single and fractionated exposures of mice to 0.1, 0.2, or 1.0 Gy X-rays stimulate the anti-tumor activities of NK cells but the effect of the latter irradiations lasts longer than after single exposures.

The obtained results may lead to modification of the standing radiation protection regulations concerning occupational and environmental exposures to ionising radiation.

Cheda, A, Nowosielska, E, Wrembel-Wargocka, J, Jazwinski, J, Janiak, M, Single and Fractionated Exposures to 0.1, 0.2, or 1.0 Gy X-rays Potentiate the Anti-tumor Activit of Murine NK Cells.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5003113.html