NKG2D expression over time in culture. (A) Cells were isolated at the stated time points and reverse transcription-polymerase chain reaction (RT-PCR) was performed using NKG2D-specific primers. (B) Cells were stained with antibodies and analyzed by FACS analysis as described in “Materials and methods.” Shown are FACS histograms at either day 0 or at day 21 of culture. Dotted histograms represent isotype control antibodies and solid lines NKG2D. Mean fluorescent intensity (MFI) of NKG2D is shown in the upper right of each histogram. Results are representative of 3 or more experiments.