Interleukin 33 (IL-33), a member of the IL-1 family and a ligand of the orphan receptor ST2, plays key roles in innate and adaptive immunity. We examined the associations between IL-33/ST2 levels and clinical manifestations of patients with active adult-onset Still's disease (AOSD).
Blood samples were collected from 40 patients with active AOSD, 28 patients with rheumatoid arthritis (RA), and 27 healthy controls (HC). The serum levels of IL-33 and soluble ST2 were determined using ELISA. Expression levels of IL-33 and ST2 in biopsy specimens obtained from 34 AOSD patients with rash were immunohistochemically investigated.
IL-33 levels of patients with AOSD were higher than those of patients with RA and HC. Soluble ST2 levels of patients with AOSD were higher than those of HC, but not of patients with RA. Serum IL-33 levels correlated with systemic score, erythrocyte sedimentation rate, ferritin levels, and aspartate transaminase levels. However, serum soluble ST2 levels correlated only with ferritin levels. The numbers of inflammatory cells expressing IL-33 and ST2 were elevated in skin lesions of patients with AOSD compared to HC, but did not differ from those of the skin lesions of eczema or psoriasis.
We found significantly higher serum IL-33 and soluble ST2 levels in patients with active AOSD. Results indicate that the IL-33/ST2 signaling pathway may play a role in the pathogenesis of the acute inflammation and skin manifestations associated with AOSD.