Adhesion and rouleau formation of red cells in a shear flow

Red blood cells form rouleau at lower shear rates, convection being important in determining the rates of growth of these compliant and flexible structures. The rouleau can be disrupted into separated cells when the shear rates in flow are sufficiently high. Because relatively sophisticated computational models of cell-cell interactions in flow are now being advanced, with virtual-reality rendering for visualization, better quantitative information about rouleau formation is important for providing space-time images and aggregation-rate data of rouleau formation for comparison with such models. We provide here some such quantitative information on aggregation rate determined with a dilute RBC suspension observed in vitro in a flow chamber with a simple Hele-Shaw geometry. At a steady shear rate, following initial adhesion of some individual red cells to the glass wall, growth of wall-attached rouleau is observed while the number of single adherent red cells remains relatively constant. Rouleau adherent to the wall tend to align their major axis parallel to the steady flow.