Abstract
Tritium is a potentially significant source of internal radiation exposure which, at high levels, can be carcinogenic. We evaluated whether single intraperitoneal injection of BALB/c and C57BL/6 mice with tritiated water (HTO) leading to exposure to low (0.01 or 0.1 Gy) and intermediate (1.0 Gy) cumulative whole-body doses of β radiation is immunosuppressive, as judged by enhancement of artificial tumour metastases, functioning of NK lymphocytes and macrophages, circulating cytokine's levels, and numbers of bone marrow, spleen, and peripheral blood cells. We demonstrate that internal contamination of radiosensitive BALB/c and radioresistant C57BL/6 mice with HTO at all the absorbed doses tested did not affect the development of neoplastic colonies in the lungs caused by intravenous injection of syngeneic cancer cells. However, internal exposure of BALB/c and C57BL/6 mice to 0.1 and 0.01 Gy of β radiation, respectively, up-regulated cytotoxic activity of and IFN-γ synthesis in NK lymphocytes and boosted macrophage secretion of nitric oxide. Internal contamination with HTO did not affect the serum levels of pro- (IL-1β, IL-2, IL-6, TNF-α,) and anti-inflammatory (IL-1Ra, IL-4, IL-10) cytokines. In addition, exposure of mice of both strains to low and intermediate doses from the tritium-emitted β-particles did not result in any significant changes in the numbers of bone marrow, spleen, and peripheral blood cells. Overall, our data indicate that internal tritium contamination of both radiosensitive and radioresistant mice leading to low and intermediate absorbed β-radiation doses is not immunosuppressive but may enhance some but not all components of anticancer immunity.