The asymmetric IgG non-precipitating antibody. Localization of the oligosaccharide involved, by concanavalin A interaction

Binding to Con A-Sepharose 4B of the low-affinity Fab fragment from sheep IgG1 anti-Dnp non-precipitating antibody was previously determined. This communication reports the results obtained when the concanavalin A interaction with Fd' fragments and L chains from non-precipitating and precipitating antibodies was examined. When Fd' fragments and L chains from non-precipitating and precipitating antibodies were tested as inhibitors of the binding of 125I-labelled concanavalin A to guinea pig erythrocytes, inhibition of such binding was only achieved by Fd' fragments from non-precipitating antibodies. Forty eight per cent of this Fd' fragment was bound by Con A-Sepharose 4B. From these results and our previous studies we conclude that mannose and/or glucose residues must be present and exposed at the Fd' fragment from the low-affinity Fab arm of sheep IgG1 anti-Dnp non-precipitating antibody. Glycosylation differences may explain the difference in precipitation behaviour of the 2 types of antibody.