Gene expression response in human peripheral blood exposed to x-rays or neutrons ex vivo

The detonation of an improvised nuclear device would produce prompt radiation consisting of both photons (gamma-rays) and neutrons. While much effort in recent years has gone into the development of radiation biodosimetry methods suitable for mass triage, the possible effect of neutrons on the endpoints studied has remained largely uninvestigated. We have used a novel neutron irradiator with an energy spectrum based on that 1-1.5 km from the epicenter of the Hiroshima blast to begin examining the effect of neutrons on global gene expression, and the impact this may have on the development of gene expression signatures for radiation biodosimetry. We have exposed peripheral blood from healthy human donors to 0, 0.1, 0.3, 0.5, or 1 Gy of neutrons ex vivo using our neutron irradiator, and compared the transcriptomic response 24 h later to that resulting from exposure to 0.1, 0.3, 0.5, 1, 2 or 4 Gy of photons (x-rays). Initially, aliquots of blood were exposed to doses of 0.25, 0.5 or 1 Gy neutrons or 1, 2, or 4 Gy x-rays, or treated as a mock-irradiated control, and RNA was harvested 24 hours later. Six different donors were used in this part of the study. Later, six additional donors were recruited, and their blood was exposed to a lower range of doses: control, 0.1, 0.3, 0.5, or 1 Gy x-rays or neutrons. One each of the 0.5 Gy neutron, 1 Gy x-ra,y and control samples were lost in processing, resulting in a total of 92 samples in the overall study