Distribution of IL-10 family cytokines in serum and synovial fluid of patients with inflammatory arthritis reveals different contribution to systemic and joint inflammation.

Evidence exists that IL-10 family cytokines may be involved in the pathogenesis of rheumatoid arthritis (RA). We sought to determine whether these cytokines are involved in psoriatic arthritis (PsA). We conducted a prospective study on patients with PsA, RA, and osteoarthritis (OA); healthy controls (HC) were also included. We analyzed IL-20, IL-24, and IL-19 serum and synovial fluid (SF) levels and change of serum levels following treatment with biological agents. IL-20 serum levels were increased in PsA and RA compared with OA patients and HC, and with matched SF levels. IL-24 serum levels in PsA, RA, and OA patients were higher than those in HC and also with respect to matched SF in PsA. IL-19 serum levels were higher in HC and OA compared with PsA and RA patients; IL-19 SF levels were higher in PsA and RA compared with OA patients, and in PsA compared with RA patients. PsA and RA patients showed a reduction of IL-19 serum levels after biological treatment. Therefore, IL-19 seems to be mainly involved in the joint inflammation, whereas IL-20 and IL-24 appear to participate mostly in the systemic responses. These findings may allow to further the comprehension of the contribution of these cytokines to the inflammatory response involved in chronic arthritis, as well as to develop novel therapeutic strategies. This article is protected by copyright. All rights reserved.