Proliferative activity and cell cycle of peripheral blood lymphocytes (PBL) at late time after chronic radiation exposure in man

Cell cycle check-points exert control over the cell's genetic stability. Exposure to ionizing radiation leads to a delay in cell cycle and reduction in proliferative activity of irradiated cells with various DNA injuries. Previous studies on animals involving chronic exposure in the range of 0.01-0.5 Gy/day revealed inhibition of hemopoiesis, changes in cell cycle duration and proliferation of hemopoietic cells. The present study showed an increase in the number of peripheral blood leucocytes with delayed cell cycle in exposed persons 60 years after the onset of chronic exposure (average cumulative dose to red bone marrow was 1.15 Gy). It is assumed that the effect observed can be associated with genomic instability of hemopoietic stem cells (HSC). Increased numbers of proliferating PBL were also noted in exposed individuals at late time after radiation exposure.