The electrophoretic mobility of human red cell ghosts decreases in the presence of chicken serum. The decrease is not directly due to the presence of adsorbed material but to a change which is catalyzed by the foreign substance. It is suggested that abnormal serum materials resulting from disease may serve as catalysts.
Fragments of broken cells have the same mobility as whole cells at first, then decrease even in pure salt suspension, while the whole cells remain essentially unchanged for hours.
The results suggest that the slow change of whole cells, the change of ghosts in the presence of foreign serum, and the change of fragments are all manifestations of the same modification of structure or composition of the cell surface.