Elevated levels of interleukin-6 in serum and cerebrospinal fluid of HTLV-I-associated myelopathy/tropical spastic paraparesis.

A significant elevation of interleukin-6 (IL-6) level was observed both in serum (mean 0.455 +/- 0.251) and in cerebrospinal fluid (CSF) (mean 0.043 +/- 0.016) obtained from 13 patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) when compared to that of either asymptomatic carriers (mean 0.181 +/- 0.074 and 0.021 +/- 0.015, respectively) or controls (mean 0.208 +/- 0.119 and 0.021 +/- 0.015, respectively). The differences were statistically significant between HAM/TSP and asymptomatic carrier for serum (P less than 0.05) or CSF (P less than 0.01). The correlation indexes between serum IL-6 and anti-HTLV-I antibody titers in serum and CSF were 0.61 (P less than 0.06) and 0.67 (P less than 0.05), respectively. Both the cell count and protein level in CSF correlated with CSF IL-6 activity at 0.68 (P less than 0.01) and 0.56 (P less than 0.05), respectively. The results demonstrate that IL-6 may contribute to the production of anti-HTLV-I antibody, and signs of slight inflammation are present in the central nervous system in HAM/TSP.