Increased Levels of Soluble ST2 in Patients with Active Newly Diagnosed ANCA-Associated Vasculitis

Objective. ST2, a member of the interleukin-1 receptor family, is selectively expressed on Th2 cells and mediates important Th2 functions. IL-33 is a specific ligand of ST2. The aim of the study was to determine whether serum levels of soluble ST2 (sST2) or IL-33 predict activity of the disease in patients with ANCA-associated vasculitides (AAV). Methods. 139 AAV patients and 62 controls were studied. IL-33 and sST2 in the blood were measured with a commercially available ELISA. Results. Newly diagnosed AAV patients had higher sST2 levels than controls (P < 0.01). Levels of sST2 were significantly higher in active newly diagnosed AAV patients than in patients with remission (P < 0.001). IL-33 levels were higher in AAV patients than in the control groups (P = 0.002). However, serum IL-33 levels were not increased in patients with active AAV compared to patients in remission. IL-33 levels were higher in patients with granulomatosis with polyangiitis than in patients with microscopic polyangiitis (P = 0.012). Conclusions. Serum sST2, but not serum IL-33, may be a marker of activity in AAV patients.