Detection of the human erythrocyte surface antigen gerbich by flow cytometry using human antibodies and phycoerythrin for extreme immunofluorescence sensitivity

We used indirect immunofluorescence and flow cytometry to detect the human erythrocyte surface antigen Gerbich. The procedure consisted of sequential erythrocyte-labeling with human antibody to Gerbich, biotinylated goat anti-human IgG and finally phycoerythrin-conjugated streptavidin. With maximal excitation of phycoerythrin at 546 nm, an increase in the fluorescence sensitivity was achieved. All erythrocytes from normal controls had detectable Gerbich antigen with little variation in antigen density between individuals. Six Gerbich-negative patients had no detectable antigen. By diluting the erythrocytes, as few as 0.1% antigen-positive cells in an antigen-negative population could be detected. These studies indicate that flow cytometry is a useful technique for the detection of erythrocyte surface antigens.