Immunosubtraction as a means of typing monoclonal and other proteins in serum and urine.

Serum and urine protein electrophoresis are used primarily to screen for the presence of monoclonal proteins found in conditions such as myeloma, non-Hodgkin's lymphoma, macroglobulinemia, and so on. Having demonstrated the presence of an abnormal band, further testing is required to identify both the immunoglobulin heavy- and light-chain types (e.g., IgG κ). With conventional agarose gel or cellulose acetate electrophoresis, this secondary testing is either by immunofixation (1-3) or immunoelectrophoresis (4). In both methods, serum or urine is electrophoresed, and antibodies to each of the immunoglobulin classes is reacted with the abnormal protein. Insoluble protein-antibody complexes are formed, which can be visualized by staining with dyes such as Coomassie blue. These methods are sensitive, but can be time-consuming and labor-intensive.