Rapid typing of serum paraproteins by immunoblotting without antigen-excess artifacts.

In this new immunoblotting procedure for determining the heavy-chain class and light-chain type of monoclonal serum immunoglobulins, proteins are transferred from agarose electrophoretic gels to nitrocellulose by brief capillary blotting. Paraproteins transferred are detected with appropriate horseradish peroxidase-conjugated antisera to light chain and heavy chain. Examination of 121 serum specimens probably containing a paraprotein (as detected by protein staining) by immunoblotting and by immunofixation gave the same results for 116 specimens: paraproteins were typed in 103 specimens and their presence was excluded in 13. Immunoblotting required one repeat analysis (as compared with 22 for immunofixation). In only 100 min we could type as many as 10 paraproteins, and the procedure did not show antigen-excess artifacts. These results suggest that immunoblotting may be preferable to immunofixation for routine typing of paraproteins.