The effects of neuraminidase on concanavalin A agglutination of erythrocytes: evidence for adsorption of neuraminidase to erythrocyte membrane.

Neuraminidase-treated human erythrocytes, but not untreated erythrocytes, were agglutinated by concanavalin A. The degree of concanavalin A agglutinability was not directly related to sialic acid removal by neuraminidase. While maximal sialic acid release was obtained with 5 units neuraminidase/2 x10(9) erythrocytes, maximal concanavalin A agglutination was only obtained after exposure to 20 units neuramindase. Binding of 3H-concanavalin A by erythrocytes was 10-fold higher with rabbit compared to human red cells. Neuraminidase treatment of human erythrocytes caused a relative increase in 3H-concanavalin binding, but the absolute amount was still 10-fold less than that bound to rabbit erythrocytes. Specific adherence of neuraminidase to Con A-Agarose could not be demonstrated. There was no evidence for contamination of the neuraminidase preparation with proteases using a sensitive assay. These studies suggest that neuraminidase absorbs to erythrocytes by a mechanism other than removal of sialic acid.