Adhesion of human red blood cells and surface charge of the membrane

To elucidate the mechanism by which red blood cells (RBC) participate in thrombus formation, we investigated the mechanism of adhesion between human RBC. Our study showed that the morphology of RBC was changed by various cationic reagents, inducing adhesion between RBC. When RBC suspended in PBS buffer containing sodium phosphate (PBS(Na)) or potassium phosphate (PBS(K)) were treated with cationic reagents, stronger adhesion occurred between RBC treated with the latter. When concentrations of the reagents were low, adhesion was released and the RBC resumed its original morphology after washing. However, when the concentrations of reagents were high, the morphology did not normalize, although the adhesion was released. When fresh RBC were treated with cationized ferritin (CF), CF bound to the periphery of RBC membranes and induced adhesion. However, when RBC were induced to adhere strongly by a cationic reagent, no binding of CF to the membrane was not observed. When RBC were treated with CF, bindings between substances outside the membranes and bindings between the membranes and substances outside the membranes were observed. When RBC treated with neuraminidase to remove 85-90% of sialic acid were treated with the cationic reagents, both adhesion between RBC and morphological change were reduced. When RBC were pretreated with polyclonal antibody against human RBC membrane band 3 protein, treatment with the cationic reagents did not induce adhesion and morphological change of RBC. Further, when RBC induced to adhere by the cationic reagents were treated with the polyclonal antibody against band 3, in the case of weak adhesion, the adhesion was released and the RBC resumed its original morphology. However, in the case of strong adhesion, the morphology did not return to normal although the adhesion was released. These results suggest that the adhesion between RBC induced by cationic reagents was due to changes in the charge on the membrane surface, involving polysaccharide chains and membrane surface proteins.