Cerebrospinal fluid interleukin-6 in progressive Neuro-Behçet's syndrome.

Central nervous system (CNS) involvement in Behçet's disease, usually called neuro-Behçet's syndrome (NB), is one of the most serious complications of the disease. The present study examined cerebrospinal fluid (CSF) interleukin-6 (IL-6) activity in patients with NB to explore its relevance to the progressive CNS disease. Paired CSF and serum specimens were obtained from 11 patients who were diagnosed as having progressive NB based on careful clinical observation and from 11 patients with active Behçet's disease but lacking progressive CNS disease. IL-6 levels in the CSF and sera were determined using IL-6-dependent murine hybridoma MH60.BSF2 cells. All 11 patients with progressive NB showed marked elevation of CSF IL-6 activity [0.18-3.90 U/ml, 1.19 +/- 1.18 (mean +/- SD), normal range, <0.010 U/ml]. In contrast, only 5 of the 11 control patients showed very modest CSF IL-6 activity below 0.10 U/ml, and CSF IL-6 was not detected in the other 6 patients. There was no difference in the serum IL-6 activities of patients with progressive NB and control patients. There was no significant correlation of CSF IL-6 activity with serum IL-6 activity, CSF cell counts, CSF total protein levels, or the CSF/serum albumin quotient. These results indicate that persistent chronic CNS inflammation, as evidenced by the enhanced production of IL-6 within the CNS, plays an important role in the pathogenesis of progressive neuropsychiatric manifestations in Behcet's disease.