T cell–specific cytotoxicity of ara-G. Exponentially growing cultures of CEM (▪), Raji (▾), and ML-1 (♦) were incubated with the indicated concentration of ara-G for 3 hours. (A) Cells were washed free of drug, resuspended in warmed drug-free medium for 72 hours and, at the end of incubation, the cell number was counted and expressed as a percent of control. Data points represent mean of 2 independent experiments conducted in triplicate. (B) Cells were resuspended in drug-free medium for 72 hours. At the end of incubation, MTS reagent was added and the obtained absorbance at 490 nm was measured and expressed as a percent of control. Data points represent mean of 2 independent experiments conducted in quadruplicate. (C) Cells were washed free of drug, embedded in soft agar, and expressed as a percentage of colonies formed in untreated samples. Data points represent mean of 2 independent experiments conducted in triplicate.