Increased IL-18 in patients with systemic lupus erythematosus: relations with Th-1, Th-2, pro-inflammatory cytokines and disease activity. IL-18 is a marker of disease activity but does not correlate with pro-inflammatory cytokines.

OBJECTIVE: The aim of this study was to investigate the imbalance between Th-1 and Th-2 cytokines in systemic lupus erythematosus patients (SLE) and to asses if any of these cytokines could be related to disease activity.
METHODS: Twenty SLE patients and 20 healthy individuals were investigated. Blood samples were collected to evaluate, using ELISA method, serum levels of a wide array of cytokines including: Th-1 type cytokines (Interleukin (IL)-12, Interferon (IFN)-gamma), Th-2 cytokines (IL-4, IL-10), pro-inflammatory cytokines (tumor necrosis factor (TNF)-alpha, IL-1beta and IL-18). Disease activity was assessed using the SLE Disease Activity Index (SLEDAI). Data were evaluated using the Mann-Whitney and Spearman's rank tests.
RESULTS: The SLE patients group had a higher IL-4, IL-10, IL-12 and IL-18 serum concentration compared to the normal control group. IL-18 was negatively correlated with IL-4 and positively correlated with IFN-gamma. No serum cytokine level was correlated with disease activity except for IL-18, which was found strongly correlated with "active disease", defined as SLEDAI > 8 points. IL-18 showed no correlation with pro-inflammatory cytokines.
CONCLUSIONS: Our results show that Th-1 as well Th-2 cytokines can be elevated in SLE patients suggesting that lupus is a complex disease that may be supported by different cytokine patterns in different time-points. Only IL-18 has been found to be disease-activity related. The role of IL-18 in the pathogenesis of SLE might be important through apoptosis-mediating properties.