Demonstration in children of oligoclonal IgG bands in unconcentrated CSF using agarose isoelectric focusing and immunolabeling.

Agarose isoelectric focusing, followed by protein transfer to cellulose nitrate membrane and double-antibody avidin-biotin peroxidase staining (avidin-biotin agarose isoelectric focusing), was used to demonstrate oligoclonal IgG bands in unconcentrated cerebrospinal fluid (CSF) and serum; 161 consecutive pediatric patients, ages 6 months to 16 years with a variety of mainly neurologic disorders, were studied. The procedure was standardized for agarose isoelectric focusing (AIF) using 5 microliter specimens containing 125 ng of IgG. Oligoclonal bands were found in the CSF of 12% of the patients; bands were found simultaneously in the CSF and serum of 10% of the patients, mostly those with nervous system infections, but also those with central nervous system tumors, seizures, or migraine. In about 50% of positive cases, oligoclonal bands constituted the only CSF abnormality, reflecting an abnormal humoral immune response within the CSF-central nervous system compartment. Avidin-biotin AIF can be recommended as an integrated part of routine CSF examinations in children.