Detection of IgG Oligoclonal Bands in Unconcentrated CSF by Isoelectric Focusing in Ultrathin Polyacrylamide Gel, Direct Antiserum Immunofixation and Silver Nitrate Staining

Abstract

Isoelectric focusing of proteins in ultrathin polyacrylamide gel (0.4 mm), followed by direct immunofixation with monospecific antisera and silver nitrate staining, is a highly specific, sensitive and simple method for the detection of oligoclonal IgG in unconcentrated CSF samples. The ultrathin polyacrylamide gels have several advantages, i.e. significantly smaller amounts of reagents are required, and thinner gel can be more efficiently cooled, resulting in higher resolution and shorter running, washing, staining and destaining times. Direct immunofixation in the gel, a time-saving and simple step, increases the sensitivity and specificity of the method. We reduced the samples to 5-10 microliters. For the present method, the optimal concentration of IgG was 0.025-0.030 g/l. It is possible to detect oligoclonal IgG bands at an IgG concentration corresponding to the applied amount of 80-100 ng. In our testing of this method, oligoclonal bands in CSF specimens were clearly demonstrated in 33 (97%) out of 34 patients with definite multiple sclerosis, in 16 (42%) out of 38 patients with infectious diseases of the central nervous system and in 11 (18%) out of 58 patients with other neurological disorders. The method appears to be a useful alternative for the demonstration of oligoclonal IgG bands in unconcentrated CSF samples, and can be recommended for use in the CSF laboratory routine.