Immunoperoxidase staining of cerebrospinal fluid IgG in isoelectric focusing gels: a sensitive new technique.

An isoelectric focusing (IEF) technique using direct peroxidase or peroxidase-antiperoxidase (PAP) overlay staining for detection of cerebrospinal fluid (CSF) oligoclonal IgG is described. The method involves chemical fixation of all proteins in the gel followed by application of peroxidase coupled antiserum as a specific stain. The direct peroxidase system is 4 times and the PAP system 8 times as sensitive as Coomassie blue staining after standard IEF or Coomassie blue staining of immunofixed gels. As little as 0.5 microgram (direct peroxidase) or 0.3 microgram (PAP) of IgG can be detected. Direct peroxidase staining of IgG in IEF gels can be used to examine unconcentrated CSF, with banding patterns similar to those obtained by Coomassie blue staining after standard IEF of concentrated CSF.