Immunoglobulin G in multiple sclerosis brain.

We extracted free and bound IgG from plaques and normal-appearing white matter of multiple sclerosis (MS) brains. By isoelectric focusing (IEF), three patterns of IgG distribution were seen: (A) a restricted high-pI distribution with a specific band at low pH, (B) a restricted high-pI pattern, and (C) a broad pI pattern similar to that of the unbound IgG extracted at neutral pH. In one MS brain, we compared the IEF pattern of plaque material with that of normal-appearing white matter (NAWM); the low-pH extract of plaque material (PM) had a restricted pattern at high pI. In another MS brain, a specific band of bound IgG was found. These data suggest that MS lesions expose an antigen(s) unique to MS. B cells consequently might be stimulated by a disease-related antigen(s) in the MS lesion.