INCREASED INTERLEUKIN-6 MESSENGER-RNA EXPRESSION IN BLOOD AND CEREBROSPINAL-FLUID MONONUCLEAR-CELLS IN MULTIPLE-SCLEROSIS

The increased intrathecal production of immunoglobulins within the cer ebrospinal fluid (CSF) compartment commonly observed in multiple scler osis (MS) implicates participation of B cell activating factors. One e ffect of the cytokine interleukin (IL)-6 is induction of immunoglobuli n production by activated B cells. Employing in situ hybridization (IS H) with synthetic oligonucleotide probes, we measured numbers of IL-6 mRNA-expressing mononuclear cells (MNC) in blood and CSF from patients with MS, aseptic meningo-encephalitis (AM), and in blood from patient s with other neurological diseases (OND) and healthy subjects. Numbers of IL-6 mRNA-expressing MNC were elevated in blood (mean frequency 1 per 33 000 MNC) and even further enriched in the CSF (1 per 10 000 MNC ) of MS patients, and to a similar extent in AM patients' blood. Culti vation in the presence of myelin basic protein and proteolipid protein revealed strong augmentation of IL-6 mRNA-positive cells in MS but no t in OND. The results suggest that IL-6 is one of several cytokines wh ich are upregulated in MS, in particular locally in the CSF. A role of IL-6 in MS, whether disease-promoting or protective, remains unclear.