Association of interferon gamma, tumor necrosis factor alpha and interleukin 6 serum levels with systemic lupus erythematosus activity.

We investigated serum level of interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) using an enzyme-linked immunosorbent assay (ELISA) in 59 patients with systemic lupus erythematosus (SLE) and 16 healthy controls. We examined a possible association between serum levels of these cytokines and SLE activity, as well as correlation between IFN-gamma concentration and the level of TNF-alpha and IL-6 and also IL-6 and TNF-alpha. TNF-alpha and IL-6 were detectable in all 59 patients and normal individuals and their level was significantly higher in SLE patients than in the control group (p < 0.001 and p < 0.02, respectively). In contrast IFN-gamma was detectable in 23 (39%) patients and in only 3 (20%) healthy individuals. We found positive correlation between serum concentration of TNF-alpha and IL-6 with SLE activity and no such correlation with IFN-gamma. We also observed positive correlation between serum levels of IFN-gamma and TNF-alpha, IFN-gamma and IL-6 as well as TNF-alpha and IL-6. In conclusion, an increase in the serum levels of TNF-alpha and IL-6 may be useful markers for SLE activity.