[A double monoclonal IgG1-kappa and IgG3-lambda with electrophoretically same mobility in a single patient].

The serum from a 78-year-old male (SY) with abdominal aneurysm was shown to contain monoclonal protein (MP) of IgG. Immunoelectrophoresis (IEP) and immunofixation electrophoresis (IFE) of SY serum revealed MP reacted with both of anti kappa and anti lambda antisera. To see whether the monoclonal IgG molecule possesses both types of light chains, an attempt to separate MPs isolated by zone electrophoresis was made by affinity chromatography using anti kappa and anti lambda Sepharose 4 B conjugates. Immunodiffusion (ID) of these separated MPs showed that kappa type of MP (MP-kappa) was IgG1, while lambda type of MP (MP-lambda) was IgG3. For preparation of anti-idiotype antibodies (Aid) against MP-lambda, antisera against MP-lambda raised in rabbits by immunization with affinity-chromatographic purified MP-lambda was absorbed with solid phase normal human serum. ID and IFE of these MPs (original MP, MP-lambda and MP-kappa) revealed MP-kappa did not react with Aid, suggesting idiotype of MP-kappa was different from that of MP-lambda. These results indicate that two types of MPs derived from different B cell clones happen to have same mobility electrophoretically.