[Mechanism of radiation death of human peripheral blood lymphocytes, assessed by the DNA-comet method].

Radiation-induced death of human peripheral blood lymphocytes (HPBL) was studied using the comet assay. It has been shown that gamma-irradiation induced simultaneously two forms of death, necrosis and apoptosis which may be discriminated by the comet assay. Three groups of comets formed by HPBL are specified: symmetric/slowly asymmetric comets attributed to viable cells (C0/C1-class of comets); comets reminding "tear-drop" (C3/C4-class of comets) which are characterized by decreased total fluorescence of comet and formed by dying/dead (necrotic or apoptotic) cells; intermediate form of comets (C2-class), containing head, tail and attributed to cells committed to apoptosis (containing high molecular weight fragments of DNA). Kinetics of C2-comets permits detection of early stage of apoptotic death of irradiated HPBL.