The combined effects of reduced weightbearing and ionizing radiation on splenic lymphocyte population and function

Purpose: The effects of radiation ++/- hypogravity on immunologic function were investigated using the Partial Weight Suspension (PWS) model (Wagner et al. 2010). Materials and methods: Mice were exposed to 0.5, 1, or 2 Gray (Gy) dose of gamma radiation and then placed in the PWS system for 4, 24, 48 hours, or 4 days. Spleens were excised and white blood cells were prepared for flow cytometry analyses. Results: The combination of PWS ++ radiation (1 and 2 Gy doses only) resulted in decreased cell viability at the 24 h (similar to 16% decrease), 48 h (similar to 20% decrease), and 4 day (similar to 20% decrease) time points, compared to the PWS (no radiation) and no treatment (non-suspended, non-irradiated) groups. The T lymphocyte (thymus-derived) population increased by similar to 10% (24 h, 48 h, and 4 day time points), while the B lymphocyte (bursal or bone marrow-derived) population decreased by similar to 10% (at all time points examined), when mice were exposed to PWS ++ radiation (2 Gy dose only), compared to the PWS or no treatment groups. T cell activation was observed in the PWS group and the 0.5 Gy ++/- PWS groups at the 4 and 24 h time points, compared to the no treatment group. However, T cell activation was significantly suppressed (similar to 85%) at the acute time points in the 2 Gy ++/- PWS groups, comparable to the no treatment group. Conclusions: Ionizing radiation in the absence and presence of simulated hypogravity results in acute lymphocyte dysfunction and compromised immune response.