Immunogenicity and antigenicity of immunoglobulins: detection of human immunoglobulin light-chain carbohydrate, using concanavalin A

Concanavalin A binding to glycoprotein bands on nitrocellulose blots was used to detect mannose, sorbose, N-acetylgalactosamine and/or glucose residues on 100% (31/31) of human Bence Jones protein light chains, following sodium dodecyl sulphate-polyacrylamide gel electrophoresis. All (20/20) light chains form IgG myeloma proteins and light chains from a preparation of normal polyclonal human IgG were also bound by concanavalin A. The specificity of concanavalin A for glycoproteins was demonstrated by its binding to human Fc fragments and a human monoclonal anti-Rhesus D antibody (REG-A), but not to human albumin pFc' fragments and aglycosylated REG-A derived from cells grown in the presence of the glycosylation inhibitor tunicamycin. These results suggest that all Bence Jones proteins and light chains from myeloma IgG proteins contain mono- or oligosaccharides linked O-glycosidically to serine or threonine residues.