High radiosensitivity of the MOLT-4 leukaemic cell line.

Radiation survival of MOLT-4, a leukaemic T-lymphocyte cell line, was measured by counting colonies formed in 0.8 per cent methyl cellulose. The survival curve was a simple exponential and showed the cells to be radiation sensitive, with D0 = 0.49 +/- 0.02 Gy and extrapolation number n = 0.92 +/- 0.09. No increase in survival as measured by colony-forming ability or trypan blue dye exclusion was seen when the dose was split into two fractions, separated by a 5 h incubation period. Electron microscopy and trypan blue dye exclusion showed that 5 h after exposure to high doses, MOLT-4 cells began to die and displayed condensed, marginated chromatin and cellular vesiculation.