Expression of ABO antigens on HeLa cells.

HeLa cells were transfected with either human A-transferase (A), B-transferase (B), or a “control” O-transferase (C), as previously described,24 and analyzed by specific mAb (as indicated in “Materials and methods”) and flow cytometry. Dark gray indicates cell populations stained with specific Ab and FITC-labeled secondary Ab; light gray indicates cell populations stained with a secondary reagent only; white indicates cells without any staining.