Hemagglutination and the closest distance of approach of normal, neuraminidase- and papain-treated erythrocytes.

By means of potential energy versus distance diagrams, derived from electrophoretic and surface tension data, the minimum distances of approach of normal (NOR) and of neuraminidase-treated (NEU) and papain-treated (PAP) human erythrocytes could be determined. The minimum distances between the actual cell membranes of two opposing red cells are: 184 A (NOR), 111 A (NEU), and 113 A (PAP), which agrees well with the fact that anti-D (Rho) antibodies of the IgG-class (which have a maximum distance of approximately 120 A between the two antibody-active sites) can hemagglutinate NEU and PAP cells, but are incapable of hemagglutinating normal D (Rho)-positive erythrocytes.