Validated analysis of CD137L expression in AML cell lines. (A) The indicated AML cell lines including THP-1 cells with validated authenticity were analyzed by FACS for CD137L and HLA class I expression using specific mAb (shaded peaks) and isotype control (open peaks). (B) RNA from the cell lines was extracted, reverse transcribed, and investigated for CD137L expression by RT-PCR analysis of equal mRNA levels; 18S rRNA served as control.