Morphological changes induced in human red cells by rabbit univalent antibody

In an attempt to study size and shape variations induced in red cells by fixation of relatively large amounts of antibody protein in the absence of haemagglutination, microscopic analysis has been performed on human O red cells incubated with rabbit univalent anti-human red cell antibodies. These were obtained by recombining half-molecules of anti-red cell γG-immunoglobulin with half-molecules of non-specific γG-immunoglobulin.

Changes in cell morphology accounted essentially for a diameter increase during incubation at 37° in the presence of the recombined fraction. These changes were a progressive variation towards the sphere and then the disk shape. The amount of univalent material effective in determining such variation was estimated to be near to 45,000 molecules/cell, i.e. about twice the amount of bivalent molecules per cell giving 50 per cent agglutination.

The possibility that the mechanism of action of either the bivalent γG-immunoglobulin antibody or the recombined univalent molecule might be the same in respect to cytotoxicity is discussed.