Isotype Restriction of Idiotopes found on Human Anti-Carbohydrate Antibodies

Summary

Sharing of idiotopes between IgM and IgG antibodies has been taken as evidence for the integrity of V gene products transferred during isotype switching from μ to γ heavy chains.

Here we describe idiotopes which are exclusively found either on IgM or on IgG antibodies from the same human individual and with the same specificity for the monosaccaride hapten N-acetyl-D-glucosamine (GlcNAc)). Moreover, IgG-restricted idiotopes which occur in high frequency on anti-GlcNAc antibodies of many individuals are also found to be constantly restricted to IgG. Beside the possibility that idiotope composition might be altered more dramatically during isotype switch of anti-GlcNAc B cells compared to other specifities it should be considered that distinct V-genes are used in IgM versus IgG response to GlcNAc.