Cytokine production is suppressed in human THP-1 macrophages by direct collisions with energetic heavy-ions and bystander responses due to microbeam irradiation of a limited cell population

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

The radiation effect of heavy-ion on the immune system will be an important factor that affect on the outcome of heavy-ion cancer therapy. The contribution of radiation-induced bystander effect is known to become larger when irradiated with the high-LET heavy-ion. Thus analyzing the effect of heavy-ion on immune cells including bystander effect is important to advance heavy-ion cancer therapy. We irradiated THP-1 macrophages by heavy-ion and analyzed their changes in cytokine production. The cell was used and a very limited part of cell population (approx. 0.45%) was irradiated using heavy-ion microbeam to analyze their bystander response. The cytokine levels were decreased compared with sham-irradiated control in the microbeam irradiated sample as well as broad beam. Thus the very limited cells with microbeam irradiation transferred their radiation signal to the non-irradiated nearby cells and induced bystander effect on the reduction of cytokines production.