Involvement of bystander effect in suppression of the cytokine production induced by heavy-ion broad beams

重粒子線誘発バイスタンダー効果が生体免疫能に与える影響

武藤 泰子; 舟山 知夫; 横田 裕一郎; 小林 泰彦

Muto, Yasuko; Funayama, Tomoo; Yokota, Yuichiro; Kobayashi, Yasuhiko

The heavy-ion beams for cancer therapy may stimulate immune cells and affect on the immune system. We irradiated immune cells using heavy-ion beams and analyzed changes in production of TNF-, important cytokines for the cancer treatment. THP-1 macrophages were irradiated using carbon-ion broad-beams. To examine the bystander response after heavy-ion irradiation, a very small fraction of the cell population was irradiated using heavy-ion microbeams. When cells were irradiated with 5 Gy that did not cause severe damage, cytokine levels were reduced after both microbeam irradiation and broad-beam irradiation. TNF- production of macrophages with the nitric oxide (NO) inhibitor-treatment increased after carbon-ion broad-beam. NO was involved in the radiation-induced suppression of TNF- production. The suppression of cytokine production arose after irradiation with heavy-ions, and may also be induced in the surrounding non-irradiated cells via the bystander effect.