Electron microscopic investigation of cell surface antigens using a multivalent hybrid antibody with double specificity.

Multivalent hybrid antibody (MHA) complexes with double specificity were prepared by combining two different antibodies, one specific against ferritin (Fer), the other against horseradish peroxidase using protein A from Staphylococcus aureus (SpA). Electron microscopy of mouse spleen lymphocytes and thymocytes (the latter coated with mouse anti-Thy-1 antibody) reacted with anti-HRP/SpA/anti-mIg complex and HRP showed the pattern of surface Ig receptors visualized by the specific peroxidase labelling. When IgG anti-Fer/SpA/IgG-anti-mIg complex was applied to the same cellular stuff, better resolution and higher accuracy were obtained although the distribution was similar. Surface Thy-1 alloantigen and Fe receptors (charged with hIgG) were simultaneously detected on the thymocyte surface by using in the same way a mixture of anti-Fer/SpA/anti-Thy-1 and anti-HRP/SpA/anti-Fab. The concomitant ultrastructural visualization of Thy-1 (with Fer) and Fc (with HRP) on mouse thymocytes clearly showed that their distribution was mainly independent and that the amount of Thy-1 antigen prevailed. These data show that electron microscopy with a mixture of MHA may be a useful technique for the concomitant location of two antigenic determinants on the cell surface.