AB0162 Expression of interleukin-20 and its receptor chains IL-20R1, IL-20R2 and IL-22R in synovium from patients with rheumatoid arthritis

Background Interleukin-20 (IL-20) signals via the IL-20R1/IL-20R2 and IL-20R2/IL-22R1 heterodimeric receptor complexes. Elevated expression of IL-20 has been demonstrated in synovial tissue from patients with rheumatoid arthritis (RA). In the rat CIA model blockade of IL-20 has been shown to reduce disease activity. Neutralisation of IL-20 may provide a new beneficial therapy for patients with RA Objectives To analyse the expression and localisation of IL-20 and the receptor chains IL-20R1, IL-20R2 and IL-22R in RA synovial tissue biopsies using immunohistochemistry and double-immunofluorescence Methods Synovial biopsies from patients with RA or osteoarthritis were obtained during joint replacement surgery or synovectomy and normal, non-inflamed synovial samples were obtained during impingement surgery. Immunohistochemistry and double-immunofluorescence staining on paraffin-embedded sections using microwave treatment between the primary antibodies and tyramide streptavidin amplification were performed with antibodies for IL-20 (rabbit polyclonal 2313b, Novo Nordisk), IL-20R1 (mouse monoclonal MAB11761, R&D), IL-20R2 (goat polyclonal AF1788, R&D) or IL-22R (goat polyclonal BAF2770, R&D) and antibodies recognising T-cell markers CD3, CD4 and CD8; DC-markers CD1a, CD11c, CD123, CD83 and CD303; the macrophage marker CD68; endothelial marker CD31 and the fibroblast-like synoviocyte marker CD55. The specificity of primary antibodies was validated in sections of cells transfected with IL-20, or one of the two receptor complexes IL-20R1/IL-20R2 and IL-22R/IL-20R2 Results Immunohistochemical staining revealed that IL-20 was present in inflammatory cells in RA synovial biopsies compared with low or no immunoreactivity in normal or OA synovium as previously reported (2). In RA joint replacement and synovectomy tissues IL-20–positive (+) cells were identified in both the areas of the lining layer and the sublining layer. IL-20+ cells located in the area of the lining layer co-stained with CD1a and CD4, which indicates that IL-20 is located in a subpopulation of immature DCs. Interestingly, in the RA samples obtained during synovectomy the IL-20+ cells in lymphoid aggregates co-stained with the T-cell marker CD3. All three IL-20 receptor chains were expressed in both the lining and the sublining layers, and were all co-localised with CD31+ endothelial cells. Subpopulations of IL-20R1+ and IL-20R2+ cells were observed in the lining layer and co-localised with either CD6