Plasma cells in cerebrospinal fluid and multiple sclerosis: diagnostic yield and clinicobiological correlations.

Cerebrospinal fluid (CSF) cytocentrifugation was performed for plasma cells' demonstration in parallel with white cell count (WCC) and quantitative protein assays. Over a 5-year period, 154 consecutive multiple sclerosis (MS) patients were studied and compared to 28 other inflammatory neurological disease, 85 non-inflammatory neurological disease and 29 non-neurological disease cases. CSF cytology was easy to perform, gave definitive results within 2 h and was abnormal in 80 MS patients, 26 of whom had a normal WCC. Its sensitivity in MS was 0.57, i.e. higher than for WCC (0.45) but lower than for IgG index (0.70) and IgG synthesis rate (0.71). Its specificity was 0.86, not significantly different from specificity of WCC, IgG index and IgG synthesis rate. Plasma cells demonstration in MS CSF was neither a disease activity nor a prognosis marker. It was significantly correlated with pleiocytosis and intrathecal IgG synthesis. If these morphologically defined plasma cells are actual B cells, they could represent circulating individuals of the lymphocyte clones active in MS plaques and have a pathogenetic significance.