IL-6 and sIL-6R concentration in the cerebrospinal fluid and serum of MS patients

The aim of this study was to determine the concentration of cytokine IL-6 in correlation with its soluble receptor sIL-6R in the serum and CSF of MS patients. The study group consisted of 52 MS patients in clinical stage 2-7 according to the Kurtzke Scale (mean 3.6 +/- 1.8); the disease duration ranged from 2 to 22 years. The levels of interleukin-6 and sIL-6R in serum and CSF were determined using commercial ELISA kits. An significant increase of IL-6 (p=0.03) was found in the serum of MS patients (12.1 +/- 1.8 pg/ml) in comparison to the control group (6.6 +/- 4.5 pg/ml). The concentration of IL-6 in the CSF of MS patients was 13.4 +/- 1.77 pg/ml, and in the majority of patients was higher than in the serum. The highest mean IL-6 concentrations in serum and CSF were found in patients with a longer disease duration, although the differences were not statistically significant. We found some degree of dependence between the serum IL-6 concentration and the level of disability on the Kurtzke scale. The concentrations of sIL-6R in serum (34.0 +/- 39.0 pg/ml) and cerebrospinal fluid (1.4 +/- 3.3 pg/ml) were significantly higher in MS patients than in the controls. IL-6 and its soluble receptors are involved in a complex immunological reaction that is characteristic for MS. However, the significant differences in the results obtained here from those reported in other studies make it rather unlikely that IL-6 and its receptors could be used as surrogate markers of MS activity.