Lack of isotype exclusion and expression of aberrant lambda light chain on secreted MOPC-315 myeloma proteins.
The presence of aberrant lambda 1 light (L) chain fragment (lambda 1 F) on the secreted myeloma protein of MOPC-315 has been demonstrated by serological and immunochemical methods. We developed a highly sensitive radioimmunoassay that utilizes exquisitely specific xenogeneic anti-lambda 1 antibodies to detect the minute amounts of lambda 1 F on lambda 2-bearing MOPC-315 myeloma proteins. In addition, structural evidence that lambda 1 F is present on MOPC-315 myeloma protein was demonstrated by subjecting 125I-labeled MOPC-315 myeloma protein to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions followed by autoradiography. The relative amounts of lambda 1 F and lambda 2-chain on MOPC-315 myeloma were measured by two independent methods. The molar ratio of lambda 1 F to lambda 2 was calculated to be 1:68 by radioimmunoassay and 1:80 by analytical SDS-PAGE. This represents the first demonstration that an aberrant L-chain fragment combines with a heavy chain and is secreted in association with antigen-binding myeloma proteins. The implications of these results on L-chain isotype exclusion are discussed.
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D000818:Animals; D000912:Antibodies, Neoplasm / Q000032:analysis*; D000918:Antibody Specificity; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D007147:Immunoglobulin Light Chains / Q000032:analysis*; D007146:Immunoglobulin lambda-Chains / Q000032:analysis*; D051379:Mice; D008807:Mice, Inbred BALB C; D009194:Myeloma Proteins / Q000276:immunology*; D010954:Plasmacytoma / Q000276:immunology*
D000912:Antibodies, Neoplasm; D007147:Immunoglobulin Light Chains; D007146:Immunoglobulin lambda-Chains; D009194:Myeloma Proteins