Spontaneous aggregation of washed human erythrocytes in isotonic media of reduced ionic strength. Conclusions about the spatial arrangement of the N-terminal part of the glycophorins.

Aggregation measurements of washed human erythrocytes (RBC) were made in an NaCl-PBS solution under laminar shear conditions. An artificial aggregation was caused by decreased pH and reduced ionic strength and characterized by collision efficiency, i. e. the probability of permanent aggregate formation. It was found that aggregation increases with reduced ionic strength and decreased pH value of the medium. Aggregation can be inhibited by addition of human serum albumin and neuraminidase treatment (removal of sialic acids). As calculations show, the results cannot be explained by the force balance between electrostatic repulsion and attraction due to dispersion forces. It was assumed that this type of aggregation involves reversible changes of the surface structure of RBC. Possible conclusions for the arrangement of the glycophorins of the glycocalyx (surface coat) are discussed.