PATTERNS OF CYTOKINE PRODUCTION IN PSORIATIC SYNOVIUM

Objective. To determine patterns of cytokine production and mRNA expre ssion in synovium from patients with psoriatic arthritis (PsA) and to compare the profile of cytokine production in PsA explants with those derived from rheumatoid (RA) and osteoarthritic (OA) synovia and psori atic skin. Methods. Cytokine levels were measured in supernatants from synovial and dermal explant cultures at Day 10 by ELISA. Cytokine mRN A expression in PsA whole tissue was determined by multi-gene assay. C ytokine levels in explant supernatants were compared between PsA, RA a nd OA, and psoriatic skin. Synovial tissues were scored histologically by a pathologist blinded to the clinical diagnosis. Results. PsA expl ants released elevated levels of interleukin (IL)-1 beta, IL-2, IL-IO, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha, but no t IL-4 or IL-5, A similar pattern of gene expression was detected in w hole synovial tissue. These cytokine levels were greater in PsA than R A, despite higher histopathologic scores in RA explants. Production of IL-1 beta, IFN-gamma, and IL-10 were strongly correlated. Levels of I FN-gamma, IL-1 beta, and IL-10 were higher in psoriatic synovium than psoriatic dermal plaques. Conclusion. The cytokine profile in PsA is c haracterized by the presence of Th1 cytokines and the monokines TNF-al pha and IL-1 beta and very elevated levels of IL-10. The higher levels of these cytokines in PsA compared to RA suggest the presence of diff erent underlying mechanisms.