Neopterin concentrations in serum and cerebrospinal fluid in HTLV-I infected individuals.

The concentration of neopterin was measured in serum samples taken from individuals infected with HTLV-I: 5 from asymptomatic individuals, 1 from a patient with adult T-cell leukaemia and 30 from patients with tropical spastic paraparesis (TSP). In addition, cerebrospinal fluid (CSF) was available from 22 of the TSP patients and neopterin concentrations were determined in these. Elevated levels of neopterin were found in only 3 of the 36 HTLV-I-positive serum samples, all from TSP patients, but significantly elevated neopterin levels were observed in 12 of the 22 CSF samples. The localisation of the elevated neopterin concentrations to the CSF of patients with TSP suggests a marked degree of activation of the cell-mediated immune system intrathecally. This provides further evidence in favour of powerful immune mechanisms operating centrally in the pathogenesis of TSP.