Abstract
We investigated a possible association between serum concentrations of tumour necrosis factor α (TNF-α), interleukin-6 (IL-6) and their soluble receptors (sTNF-α-Rp55 and sIL-6R) using an enzyme-linked immunosorbent assay (ELISA) in 55 patients with systemic lupus erythematodes (SLE) and 16 healthy controls. We also examined a possible association between the serum levels of these peptides and SLE activity, as well as TNF-α and IL-6 concentrations and the levels of their soluble receptors. The median concentrations of TNF-α, sTNF-α-Rp55 and IL-6 were significantly higher in SLE patients than in normal individuals. In contrast, there was no difference between the serum level of sIL-6R in both groups. We found positive correlations between the serum concentrations of TNF-α and IL-6 as well as their soluble receptors and disease activity. There were also correlations between TNF-α and sTNF-α-Rp55 as well as IL-6 and sIL-6R serum levels in SLE patients but there were no such correlations in the normal control group. In conclusion, an increase in the serum levels of TNF-α, sTNF-α-Rp55 and IL-6 may become useful markers for SLE activity. Patients with SLE have sIL-6R serum concentration similar to that as in normal individuals. However, it correlates with disease activity and the level of IL-6.