Roles of plasma proteins and surface negative charge of erythrocytes in erythrocyte aggregation

The effect of plasma proteins (and IgG fragments) and sialic acid content of erythrocytes on the aggregation of human erythrocytes was quantitatively examined by using a rheoscope combined with a television image analyser and a computer. (1) The velocity of erythrocyte aggregation by plasma proteins was increased with increasing in their molecular weight, i.e., IgG less than IgA less than fibrinogen less than IgM. F(ab')2. Fab and Fc could not induce the aggregation. (2) The aggregation induced by fibrinogen was accelerated by IgG and its peptic fragment, F(ab')2, but was unaffected by the plasmic fragments, Fab and Fc. The accelerating effect by IgG and F(ab')2 was inhibited by Fab and Fc. (3) The aggregation of erythrocytes was accelerated by decreasing the sialic acid content (due to the reduction of the electrostatic repulsive force among erythrocytes), and the effect of desialylation on the IgG-induced aggregation was greater than that of desialylation on the fibrinogen-induced aggregation. (4) The roles of plasma proteins and of sialic acid content of erythrocytes on the aggregation of erythrocytes were discussed.