Studies on the intrathecal humoral immunity in multiple sclerosis

Abstract

The most frequent immunological change which occurs in multiple sclerosis (MS) is the oligoclonal pattern of IgG in electrophoresis of the concentrated cerebrospinal fluid (CSF)^1-3. This peculiar pattern is not seen at the electrophoresis of the paired serum. There are numerous studies supporting the assumption that these oligoclonal IgG are locally produced in the central nervous system of MS patients. In a recent study of 80 patients, we have observed this restricted heterogeneity by agar gel electrophoresis in 61 cases (76%) (Table 1). Several formulae have been proposed to estimate this local biosynthesis, but the IgG index is the most commonly used⁴. The index takes into account the influence of the serum concentration and the permeability of the blood-CSF barrier. The latter factor is assessed by the gradient of albumin between the two compartments. In our hands 66% of the cases had an increased IgG index whereas 76% had an oligoclonal pattern. One key question remains to know whether the local biosynthesis of IgG has a pathogenic significance. In addition to the study of IgG, we have investigated the local production of other immunoglobulin (Ig) classes, namely IgM, IgA, IgE and looked for the occurrence of immune complexes (IC) in the CSF.