The silencing of SPI-CI and SPI-6 in CMT-93 affects cytolysis. (A) Expression of SPI-CI (top panel), SPI-6 (middle panel), and ERK-2 (bottom panel) after selection of CMT93 lines expressing siRNA constructs against SPI-CI and SPI-6 (RS) or a control vector (con). (B) Northern blot with total RNA from CMT93 and CMT93-RS, probed with the sense 19 nucleotide targeting both SPI-CI and SPI-6. (C) RS-transfected CMT93 (CMT93-RS), control-transfected CMT93 (CMT93-con), and CMT93 were labeled with ⁵¹Cr-chromate for 1 hour and incubated with an E1A-specific CTL clone in the presence of the relevant epitope. After 5 hours, the released label was determined, which served as a measure for lysis. (D) CMT93-RS and CMT93 were labeled with ⁵¹Cr-chromate for 1 hour and incubated with LAK cells. After 5 hours, the released label was determined, which served as a measure for lysis. Similar data were obtained when CMT-con was tested in comparison with CMT93-RS. (E) CMT93 and CMT93-RS were incubated at 37°C with different concentrations of purified LAK granules. After 1 hour, cells were harvested and membrane integrity was measured using propidium iodide. Similar data were obtained when CMT-con was tested in comparison with CMT93-RS.