Therapeutic monoclonal antibodies mimicking paraproteins in immunofixation electrophoresis: migration profiles of 21 commonly used agents.

OBJECTIVES: Therapeutic monoclonal antibodies (t-mAbs) are increasingly used in oncology, hematology, autoimmune diseases, and inflammatory disorders. Because most of these agents are monoclonal immunoglobulins, they may be detected by serum immunofixation electrophoresis (IFE) and mimic pathological monoclonal proteins. METHODS: We analyzed the electrophoretic migration profiles of 21 therapeutic monoclonal antibodies using agarose gel immunofixation electrophoresis on the Hydrasys 2 system (Sebia). Each antibody was diluted in serum previously confirmed to be free of monoclonal components. RESULTS: All antibodies produced detectable bands on IFE with characteristic migration profiles. Migration patterns were mainly associated with the isoelectric point (pI) of the molecules. Antibodies with high pI values showed cathodic migration in the gamma region, whereas antibodies with lower pI values migrated more anodically toward the beta-gamma interface. Three migration groups were identified according to electrophoretic behavior. CONCLUSIONS: Therapeutic monoclonal antibodies can generate bands that mimic monoclonal gammopathies on IFE. Knowledge of their migration profiles may help laboratories distinguish treatment-related interference from pathological paraproteins and improve interpretation of electrophoretic results.