(A) FasL expression in 3DO cells. Cells were incubated for 15 hours in 96-well plates with medium alone (control) or coated with anti-CD3 MoAb (1 μg/mL). T cells were stained with an antimouse FasL MoAb and an antihamster-FITC. The number shows the percentage of positive cells calculated by Lysis II. Fluorescence intensity versus cell number. (B) RT-PCR analysis of the mouse FasL mRNA transcripts. First-strand cDNA prepared from untreated (line 1) or anti-CD3–treated (line 2) 3DO cells were subjected to PCR with the primers 1 and 2 shown in Fig 2A. A negative control, without cDNA template, was also performed (line 3). The PCR products were separated by electrophoresis on 1.5% agarose gel and stained with ethidium bromide. Marker VI was run for comparison (left line). (C) PCR products obtained using as template the PCR product (0.04 μL) of the experiment shown in (B). Line 1, forward, primer 1, reverse, primer 3; line 2, forward, primer 1, reverse, primer 2; line 3, negative control. The primers are shown in Fig 2A. Marker VI was run for comparison (left line).