[Electron microscopic detection of blood group antigen A on human erythrocytes by means of ferritin- and gold-labelled protectin of helix pomatia].

By means of ferritin- and gold-labelled protectin from the albumen gland of the edible snail Helix pomatia the blood group antigen A was located on human erythrocytes of groups A1, A2 and A1B. With erythrocytes of groups O and B the reaction is negative. The antigen is focally distributed on the outer surface of the cell membrane. Cells from groups A1 and A1B have an antigen A concentration about 4 times greater than A2 cells. The numbers of particles after tagging with ferritin or gold are comparable. The gold particles show an extremely high contrast and are therefore very suitable for the immunoelectron microscopic localization of antigens.