Aggregation and sedimentation of mixtures of erythrocytes with different properties

The rouleau formation of erythrocytes and the erythrocyte sedimentation were examined for mixture of different kinds of the cells suspended in isotonic phosphate-buffered saline containing 1 or 2 g/dl dextran T-70 (MW = 70,400) and 4 g/dl albumin, using a low shear rheoscope and the Westergren method, respectively. The deformability of cells was decreased by treating with diamide, diazene-dicarboxylic acid bis[N,N-dimethylamide], and the sialic acid content of cells, i.e., the surface negative charge, was reduced by treating with neuraminidase. (1) The rate of rouleau formation was decreased in cells with decreased deformability, while it was increased in cells with reduced sialic acid content. The rate changed in proportion to the ratio of the modified cells to normal cells. (2) The erythrocyte sedimentation was also decreased in cells with decreased deformability, while it was increased in cells with reduced sialic acid content. Furthermore, the erythrocyte sedimentation changed almost proportionally to the ratio of the modified cells to normal cells. (3) When normal deformable cells were mixed with cells with decreased deformability, the deformable cells seemed to settle faster than the less deformable cells, though the difference was not significant. (4) When normal cells were mixed with cells with reduced sialic acid content, the cells with less sialic acid settled significantly faster than those with more sialic acid. The present experiment may conclude that erythrocyte aggregation is induced preferentially among more deformable cells and/or among less negatively charged cells with weaker electrostatic repulsive force, and then the formed aggregates settle faster.