Immunochemical Characterization of Immunoglobulins in Serum, Urine, and Cerebrospinal Fluid

Abstract

This chapter focuses on qualitative methods for the assessment and characterization of clonality. The methods include nondenaturing agarose gel electrophoresis (AGE) with immunofixation, capillary zone electrophoresis (CZE) with immunosubtraction, and isoelectric focusing with immunoblotting. All three methods can be used to identify monoclonal, oligoclonal, and polyclonal immunoglobulin populations and to identify the heavy and/or light chains contained in the population. Immunofixation electrophoresis (IFE) and immunosubtraction electrophoresis (ISE) are diagnostic tools used for the identification of monoclonal gammopathies and, conversely, for the confirmation of polyclonal hypergammaglobulinemia. Isoelectric focusing with immunoblotting is a cerebrospinal fluid (CSF) diagnostic test for the identification of oligoclonal bands (OCB) in multiple sclerosis (MS). The monoclonal gammopathies include a spectrum of diseases, from ones that may have little clinical significance to ones that may be rapidly fatal. These include multiple myeloma (MM), Waldenstrom’s macroglobulinemia, smoldering MM, monoclonal gammopathy of undetermined significance (MGUS), primary systemic amyloidosis (AL), lymphoproliferative diseases, and plasmacytomas. High-resolution agarose gel protein electrophoresis (PEL) and CZE fulfill the requirements for a screening procedure for detection of monoclonal proteins. Monoclonal free light chains are uncommon in MGUS and are associated predominantly with MM or AL. The assessment of urine samples by IFE is similar to serum IFE. The major difference is the need to concentrate urine samples to achieve an appropriate protein concentration. The concentration of immunoglobulins is increased in the CSF of patients with inflammatory diseases of the central nervous system, such as MS, neurosyphilis, and acute inflammatory polyradiculoneuropathy.