Oligoclonal IgG in cerebrospinal fluid detected by isoelectric focusing using PhastSystem

Identification of oligoclonal immunoglobulin G (IgG) in cerebrospinal fluid (CSF) is one of the major laboratory signs in multiple sclerosis (MS). Oligoclonal IgG can also be seen in other immunostimulating central nervous system diseases, e.g. meningitis caused by Borrelia spirochetes. A convenient isoelectric focusing (IEF) method combined with polyethyleneglycol-enhanced (PEG) immunofixation and silverstaining using PhastSystem for detection of oligoclonal IgG bands in serum and unconcentrated spinal fluid was developed. Serum and cerebrospinal fluid samples earlier investigated using agarose IEF combined with immunoblotting and avidin-biotin amplified double-antibody peroxidase staining (= A-IEF) were blindly re-analysed using PhastGel IEF 3-9 modified with addition of Pharmalyte 8-10.5 followed by immunofixation and silver staining (= PhastIEF). PhastSystem IEF using PhastGel had the same capability to separate and visualize oligoclonal IgG bands as the conventional agarose IEF. However, PhastIEF was more convenient and less time-consuming than A-IEF. PhastIEF combined with immunofixation and silver staining using application of standardized amounts of IgG for both the serum and CSF samples (40-60 ng IgG/lane is fast, well-standardized and reproducible. The method is sensitive and uses only a minute volume of unconcentrated cerebrospinal fluid for the investigation of CSF IgG pattern.