Soluble ST2 is increased in systemic lupus erythematous and is a potential marker of lupus nephritis

Objective To investigate the role of the interleukin IL-33/ST2 axis in systemic lupus erythematosus (SLE). Methods Serum concentrations of IL-33 and sST2 were measured by sandwich ELISA in SLE patients (n=111) compared to sex-and age-matched healthy controls (n=36). The serum concentrations of IL-33 and sST2 were correlated with various clinical and biological parameters. The expressions of IL-33 and ST2L were investigated in kidney sections by immunohistochemistry in lupus nephritis patients (n=23) and controls (n=10). Results Serum levels of IL-33 were significantly higher in SLE patients (11.64 +/- 3.141 pg/mL) than in controls (1.043 +/- 0.8526 pg/mL) (p<0.0001). Similarly, the serum concentrations of sST2 were significantly higher in SLE patients (34.013 +/- 2.043 pg/mL) than in controls (25.278 +/- 2.258 pg/mL) (p=0.046). sST2, but not IL-33, correlated significantly with disease activity index (SLEDAI). In addition, serum levels of sST2 were significantly higher in patients with lupus nephritis (45.438 +/- 5.661 pg/mL) that in SLE patients without renal involvement (30.691 +/- 1.941 pg/mL) (p=0.016). The immunoreactivity of IL-33 in renal biopsies of patients with lupus nephritis was not increased compared to controls, while the glomerular expression of ST2L was significantly higher in nephritis patients compared to controls. Conclusion Although IL-33 and sST2 levels are both increased in SLE, sST2 represents a surrogate marker of disease activity and complications of nephritis.