gms | German Medical Science

Background: A major impediment for future manned deep space missions is the radiation environment, with one of the primary hazards being heavy ions. It is well known that heavy ions with high-linear energy transfer (LET) have higher relative biological effectiveness and greater effects in vivo and in vitro than low-LET radiations. Radiation-induced destruction of the immune systems is the primary cause of infection and death. Immune cells use cytokines as one of trigger specific activation pathways and effector mechanisms, because cytokines have the potential to trigger many cells and lead to an amplification of the immune response. The natural killer (NK) cells derived cytokines has been shown to promote antigen presentation to CD8+ T cells and may be involved in promoting B cell production of specific IgG subtypes. The aim of present study is to estimate the biological risks from space radiation encountered by cosmonauts for long-term duration in space.

Materials and methods: The Kun-Ming strain mice were whole-body irradiated by ¹²C⁶⁺ ion with 0, 0.01, 0.05, 0.075, 0.2, 0.3, 0.5, 0.75, 1 or 2Gy, at a dose rate of 1 Gy/min. At 35 days after irradiation, the thymus and spleen weights were measured, the natural killer (NK) cells activity of spleen was determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT), and the Interferon-γ (IFN-γ) levels in serum and thymus were detected with enzyme-linked immunosorbent assays (ELISA).

Results: The results showed that the thymus weight, IFN-γ levels in serum and the activity of splenic NK-cells had significantly ascended at dose of 0.05Gy. With doses increasing, the weight of spleen still ascended but weight of thymus, IFN-γ level and NK-cells activity declined.

Conclusions: These results suggested that the dose of 0.05Gy irradiation should have stimulary function to immunity in mice; the immunity of body declined with doses increasing.