RADIATION RESPONSE OF MOUSE LYMPHOID AND MYELOID CELL-LINES .2. APOPTOTIC DEATH IS SHOWN BY ALL LINES EXAMINED

The mode of death induced by gamma-irradiation in a panel of 10 mouse lymphoid or myeloid cell lines was examined. Four of these lines were known to lose viability (membrane integrity) rapidly after irradiation , whilst the others were known to lose viability considerably more slo wly. However, based on the criteria of morphology and DNA degradation pattern, all 10 lines showed apoptotic death. The occurrence of apopto sis after irradiation in rapid-dying lymphoid cell lines was consisten t with published results, whilst the demonstration of apoptosis in slo w-dying lines was unexpected. Cells of the slow-dying lymphoid lines u nderwent one or more mitoses prior to death, a feature also reported f or fibroblastoid cell lines. However, the occurrence of radiation-indu ced necrosis in fibroblasts suggests that the pathways leading to 'mit otic death' differ between fibroblastoid and lymphoid cell lines.