Elevated levels of interleukin-6 in cerebrospinal fluid from patients with systemic lupus erythematosus and central nervous system involvement.

Paired serum and cerebrospinal fluid (CSF) specimens from 14 patients with systemic lupus erythematosus (SLE) and central nervous system (CNS) involvement were studied for interleukin-6 (IL-6) activity using the IL-6-dependent murine hybridoma, MH60.BSF2. We also studied 23 patients with noninflammatory neurologic diseases, and 9 SLE patients without CNS involvement. CSF IL-6 activity was elevated only in SLE patients with CNS involvement, although there was no significant difference in serum IL-6 activity among the 3 groups. CSF IL-6 activity was not correlated with either the CSF-serum albumin quotient (Q albumin; an indicator of blood-brain barrier function) or serum IL-6 activity in SLE patients with CNS involvement. The CSF IL-6 activity decreased significantly when CNS manifestations subsided after successful treatment. These results indicate that determination of CSF IL-6 activity may be useful in the evaluation of CNS disease activity in SLE. Moreover, the data confirm the presence of immune system activation within the CNS in patients with SLE-associated CNS disease.