Low-dose gamma-rays and simulated solar particle event protons modify splenocyte gene and cytokine expression patterns

The goal was to investigate the t helper (th) response in splenocytes of mice exposed to low-dose/low-dose-rate (ldr) γ-rays,simulated solar particle event protons (sspe),or combination of both. c57bl/6 mice were exposed to ldr γ-radiation ( 57co) to a total dose of 0. 05 gray (gy) at 0. 024 cgy/h,either with or without subsequent exposure to 2 gy sspe protons. expression of genes related to th cells was evaluated immediately after exposure (day 0). on day 21,intra- and extracellular cytokine production was assessed after activation with anti-cd3 monoclonal antibodies (mab) or phorbol 12-myristate 13-acetate/ionophore (pma/i). five genes were significantly modulated on day 0 in one or more of the irradiated groups compared to controls (p < 0. 05): ccl11,ccr5,cd80,inha,and il9. on day 21,numbers of cells positive for interferon-γ were high in the ldr + sspe group versus 0 gy and ldr γ-rays (p < 0. 05),but there was no difference in il-2 and tnf-α. levels of secreted cytokines after anti-cd3 mab activation were high for 5 (mip-1α,gm-csf,ifn-γ,tnf-α,il-13) and low for 2 (il-7,il-9) in all irradiated groups. priming with ldr photons had a significant effect on ifn-γ and il-17 compared to sspe protons alone; il-2 was low only in the ldr + sspe group. the cytokine patterns after anti-pma/i activation were different compared to anti-cd3 mab and with fewer differences among groups. the data show that total-body exposure to space-relevant radiation has profound effects on th cell status and that priming with ldr γ-rays can in some cases modulate the response to sspe.