Expression of the Lu and B-CAM antigens in CHO cells. CHO cells were transfected with plasmid containing Lu^a (pcDNA-Lu^a), Lu^b (pcDNA-Lu^b), or B-CAM (pcDNA-B-CAM) cDNAs or with the pcDNA3 vector alone as a negative control. Expression of the Lu^a, Lu^b, and B-CAM antigens was determined by flow cytometry analysis using anti-Lu^a human antisera, LM342 monoclonal anti-Lu^b, and G253 monoclonal anti–B-CAM. The relative numbers of positive cells in the selected windows are indicated as percentages.