Cerebrospinal fluid interleukin-6 activity in HIV infection and inflammatory and noninflammatory diseases of the nervous system.

Interleukin-6 (IL-6) activity was measured in the cerebrospinal fluid (CSF) of patients at different stages of human immunodeficiency (HIV) virus infection and of patients with multiple sclerosis (MS) or other inflammatory (OID) and noninflammatory neurological diseases (OND). In the advanced stages of HIV infection and in OID, IL-6 was detected more frequently (80 and 75% of the cases) and at higher concentrations than in the early stages of HIV infection. MS and OND (44, 48, and 44% of cases). Analysis of CSF and paired sera indicated that IL-6 production can be compartmentalized to either of the fluids. Evidence that altered blood-brain barrier functions can, at least in part, influence the CSF IL-6 levels was found in OID patients. No association was evident between intrathecal immunoglobulin synthesis and CSF IL-6 levels. Interleukin-1 (IL-1) levels were detectable in a minority of the samples from neurological patients; one OID patient had high levels of both CSF IL-1 and IL-6.