Kinetics of adhesive interaction in vitro of human erythrocytes in plasma

The initial step in rouleaux formation, the stacking of two red blood cells, is mechanically a process of three stages, compression, sliding, and creeping. Although this has been thoroughly described for cells in synthetic polymer solutions the present work was undertaken to analyze the process for cells in normal plasma, in order to lay the basis for comparison for ongoing studies of blood from patients with blood disorders. For each experiment a small amount of blood was diluted in its own plasma. A drop from the suspension was then placed on a coverslip, the coverslip covered with paraffin oil in a chamber, and the chamber quickly placed on the stage of an inverted microscope for observation and cinemicroscopy. Twenty-four doublet formations in blood plasma from five subjects were analyzed. After two cells make rim to rim contact, they move closer together by deformation of the contiguous rims to a straight line boundary (compression). Then one of the cells moves up over the other and begins the process of registration which previous work has established as a sliding interaction. The peak sliding velocity (on average 0.35 micron/sec) occurs near halfway to complete overlap. Sliding almost completely stopped just before full overlap, which was achieved very slowly (creeping). The several forces involved during sliding were identified, the force balance was examined, and from the variation of the velocity of sliding it was concluded that the medium between the touching membranes exhibits shear-rate-dependent viscosity.