BACKGROUND: IL-33 has recently been found to be the specific ligand of ST2, an IL-1 receptor family member that is selectively expressed on Th2 cells and mediates Th2 response. This study aimed to measure serum levels of soluble form of ST2 (sST2) and IL-33 in patients with systemic lupus erythematosus (SLE) and to examine its association with disease activity. METHODS: Seventy SLE patients were evaluated for disease activity determined by SLE disease activity index (SLEDAI), serological features (anti-dsDNA antibody, C3 and C4) and 57 patients were evaluated longitudinally on a second occasion. IL-33 and sST2 were measured by sandwich ELISA in the 127 SLE serum samples and compared to 28 age- and sex-matched healthy controls. RESULTS: Serum sST2 level was significantly higher in SLE patients with active disease (0.51+0.18 ng/mL) compared to those with inactive disease (0.42+0.08 ng/mL) [P=0.006] and to normal controls (0.36+0.13 ng/mL) [P<0.001]. sST2 level correlated significantly and positively with SLEDAI, level of anti-dsDNA antibody and prednisolone dosage and negatively with C3 and remained significantly predictive of active disease after adjustment for prednisolone use in logistic regression analysis (odds ratio=4.6, P=0.01). sST2 level was sensitive to change in disease activity in longitudinal evaluation and not influenced by age, gender, and renal function. Elevated serum IL-33 was comparable in frequency (4.3% vs 7.1%, P=0.62) and levels (P=0.53) between SLE patients and controls. CONCLUSION: Elevated serum sST2 level in SLE patients was found to correlate with disease activity and was sensitive to change, suggesting a potential role as surrogate marker of disease activity.published_or_final_versionThe 15th Medical Research Conference (15th MRC), Department of Medicine, University of Hong Kong, Hong Kong, 16 January 2010. In Hong Kong Medical Journal, 2010, v. 16 n. 1, suppl. 1, p. 46, abstract no. 7
