IDENTITY OF LIGHT CHAINS OF MONOCLONAL IGG AND MONOCLONAL IGM IN ONE PATIENT

A patient with an IgG myeloma was found to have an elevated monoclonal IgM of the type seen in Waldenstrom's macroglobulinemia. The light chains of the monoclonal IgG and monoclonal IgM were both kappa type. They were indistinguishable by urea starch gel electrophoresis, peptide mapping and amino acid analysis. Optical rotatory dispersion and circular dichroism studies showed that both light chains had similar secondary structure in saline at pH 7·3. Immunofluorescence studies indicated that the two proteins were being synthetized by different plasma cells in the bone marrow. These results provide evidence for a single kind of light polypeptide chain produced by two different clones of plasma cells. © 1969.