Killing of human T cells.

(A) Dose-response curve of AP1903-induced killing of Fas-transduced human T cells. Primary human T lymphocytes were retrovirally infected, and transduced cells were immunomagnetically sorted. Cells were incubated with the indicated concentrations of the synthetic dimerizer AP1903, and specific survival was measured as described in “Materials and methods.” Cells analyzed are control LV′V-transduced cells (▵), LV′VFas-transduced cells analyzed after 24 hours (■), and LV′VFas-transduced cells analyzed after 48 hours (●). Values are the mean ± SD of duplicate points (except for LV′V). The result shown is representative of at least 5 independent experiments. (B) Comparison of killing of human T cells engineered with LV′VFas or HSV-tk. Primary human T lymphocytes were transduced with LV′VFas or SFCMM-3 (HSV-tk), immunomagnetically purified and treated with either 10 nM AP1903 or 50 nM GCV for 5 days. Survival was measured as described in “Materials and methods.” Open bars represent untreated cells; filled bars represent cells treated with drug. Values are the mean ± SD of 3 independent points.