FACS analysis of BOSC23 cells using 8G5. BOSC23 cells were transiently trans-fected with an expression vector encoding either CEACAM1 (red curve) or an irrelevant protein (control transfectant: black curve). Binding of 8G5 was detected with a PE-conjugated secondary antibody. A positive signal was obtained only with CEACAM1 transfected cells.

Members of the CEA family were expressed on BOSC cells after transient transfection with expression vectors containing either the cDNA of CEACAM1, 5, 6, 7, 8, 19, 20 or 21. Recognition of CEACAM3 and 4 was tested on stably trans-fected HeLa (CEACAM3) and CHO cells (CEACAM4). Expression of the constructs was confirmed with monoclonal antibodies known to recognise the corresponding proteins (CEACAM1, 3, 4: D14HD11; CEACAM5: 26/3/13; CEACAM6: 9A6; CEACAM7: BAC2; CEACAM8: 2H6; CEACAM19-21: anti-myc; green curves). An irrelevant monoclonal antibody served as a nega-tive control (black curves). For specificity testing, protein G-purified 8G5 was tested on all CEACAM transfectants. A posi-tive signal was only obtained with CEACAM1-expressing cells (red curves).