Analysis of soluble interleukin 6 receptor in cerebrospinal fluid in inflammatory and non-inflammatory conditions

The objective of this study was to investigate the pathophysiological roles of soluble interleukin 6 receptor (sIL-6R) in cerebrospinal fluid (CSF). C SF was obtained from patients suspected with meningitis. Eight patients wit hout any meningeal signs or symptoms were enrolled as controls, An addition al 34 CSF samples were collected to measure both biologically active and im munoreactive sIL-6R, All CSF samples were proven to be aseptic, IL-6 and sI L-6R were measured using specific ELISAs, Patients were divided into three groups on the basis of cell number in CSF; inflammatory group (cell number >5 mu l, mean 241 +/- 363.1, n = 61); noninflammatory group (cell number le ss than or equal to 5 mu l, mean = 2.1 +/- 1.7, n = 12) and controls (cell number less than or equal to 5 mu l, mean = 0.3 +/- 1.7, n = 8), Among thes e three groups, the differences in protein (F (2,78) = 8.274, P < 0.0001) a nd IL-6 concentration (F (2,78) = 6.475, P < 0.001) were statistically sign ificant but those of sIL-6R concentration were not. There were only weak co rrelations between log (sIL-6R) versus log (cell number) (r = 0.23, P = 0.0 75), log (protein) (r = 0.239, P = 0.0358) and log (IL-6) (r = 0.27, P = 0. 0167), Amounts of immunoreactive and biologically active sIL-6R were closel y correlated (r = 0.62, n = 34, P < 0.005). It was concluded that sIL-6R is present constitutively in CSF and its level may not increase significantly in inflammatory conditions; infiltrating cells in CSF are not the main sou rce of sIL-6R; and sIL-6R in CSF can bind IL-6. (C) 2000 Academic Press.