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Interleukin-20 expressed in lesions, tissue in patients with psoriasis, PsA
Interleukin-20 was expressed in psoriatic skin lesions and synovial tissue in patients with both psoriasis and psoriatic arthritis at levels similar to those in rheumatoid arthritis synovium in a recent prospective study.
Researchers evaluated 11 patients with active psoriatic arthritis (PsA) and chronic plaque psoriasis who were treated with 7.5 mg alefacept for 12 weeks. Skin and synovial biopsies were taken before therapy, and then skin biopsies were obtained at weeks 1 and 6. Additional synovial biopsies were taken after 4 and 12 weeks. Synovial biopsies from 10 patients with rheumatoid arthritis (RA) served as controls.
Expression of interleukin-20 (IL-20) was measured at baseline in controls via immunohistochemical analysis.Digital image analysis evaluated stained synovial tissue sections. Double staining was conducted on anti-IL-20 antibodies together with CD68 (macrophages) and CD 55 (fibroblast-like synoviocytes, FLS) to determine the phenotype of IL-20 cells in PsA synovial tissue.Semi-quantitative analysis was conducted on IL-20 expression in six skin sections.
Both PsA and RA synovial tissue expressed IL-20, which was co-expressed by CD68 and CD55 in inflamed PsA synovium. FLS correlated with the expression. Six weeks after treatment, IL-20 expression in skin lesions of PsA patients decreased (P=.04) and had a positive correlation with the Psoriasis Area and Severity Index (PASI). Alefacept did not affect IL-20 expression in PsA synovium.
“This study is the first to investigate the effects of alefacept treatment on IL-20 expression in paired synovial tissue and psoriatic lesional skin of patients with PsA and psoriasis,” the researchers said. “While IL-20 expression in PsA synovium was not affected by alefacept treatment, its expression in lesional skin was significantly decreased after treatment.
“It remains to be established whether the observed effects of alefacept are specific for IL-20 or also are seen with other members of the IL-10 sub-family, namely IL-19 or IL-24.”