Immunological studies of an atypical (myeloma) immunoglobulin.

An 8S myeloma component, isolated from serum of a patient with myelomatosis is described, which appears to have no antigenic determinants in common with human, α-, δ-, γ- or μ-polypeptide chains as revealed by immuno-electrophoresis and Ouchterlony gel diffusion analysis. The myeloma protein migrates in the fast γ-region on electrophoresis at pH 8.6 and has an elution volume on Sephadex G-200 similar to that of 6.5S IgA. The isolated myeloma component has an approximate molecular weight of 200,000 and a total carbohydrate content of 10.7 per cent. Reduction with β-mercaptoethanol and acid dissociation yields light polypeptide chains of Type L and a carbohydrate-rich component, in the ratio of 1:4. Antisera specific to determinants on the heavy chains of the myeloma protein showed no reaction with the immunoglobulins A, D, G or M. Instead unique determinants were found on the heavy polypeptide chains.