SPI-CI expression in effector cells. (A) Complementary DNA of in vitro–activated CD8⁺ T cells was analyzed for SPI-CI expression by RT-PCR for 40 cycles. Purified CD8⁺ T cells were cultured for 24 hours in the presence of the indicated (nanograms per milliliter) amounts of platebound α-CD3 Ab in combination with platebound α-CD28 Ab (5 μg/mL). (B) Complemenatary DNA of LAK cells and several T-cell clones was analyzed for SPI-CI expression by RT-PCR for 30, 35, and 40 cycles (top panel) and GAPDH PCR for 22, 25, and 28 cycles (bottom panel). (C) Expression of SPI-CI and SPI-6 protein in LAK cells. LAK cells were further separated by FACS using cell-specific antibodies into NK, NKT, and T cells and analyzed for SPI-CI (top panel), SPI-6 expression (middle panel), and ERK-2 (bottom panel) expression.