In vitro antigen quantification. (a) Flow cytometry of each cell line tested for evaluation of CEA expression qualitatively and quantitatively. For each graph, the red curve corresponds to cells only, the blue curve to cells and secondary FITC-conjugated goat anti-mouse IgG (Fc specific) antibody, and the green curve to cells, primary mouse anti-CEA antibody, and secondary FITC-conjugated goat anti-mouse IgG (Fc specific) antibody. (b) Graph and linear regression equation of control beads used to determine antigen density per cell. The corresponding cell line antigen density is plotted and indicated on the graph.