Fig 1. Time course of blood (A) lymphocyte and (B) neutrophil depression after graded doses of WBI in NHPs.
The incidence of severe neutropenia at 7 days occurred only at doses exceeding 3 Gy. The lymphocytes responded with a rapid drop in counts within the first day after WBI. The neutrophils on the other hand showed a delayed response after 4 days, consistent with initial radiation sterilization of myeloid progenitors in the bone marrow and the turnover of mature cells. By day 7, a clear radiation dose-dependent depression of the blood cell counts was observed. The grey shaded regions in the plots correspond with severe lymphopenia and/or neutropenia (below 0.5 x 106 cells/mL). These radiation dose-response relationships correspond to a predominant and significant feature of ARS.