Background Interleukin-20 (IL-20) is a pro-inflammatory cytokine that belongs to the IL-10 family of cytokines. Increased expression of IL-20 is found in autoimmune diseased tissue, such as lesional psoriatic skin and synovium from patients with rheumatoid arthritis (RA). A neutralising anti-IL-20 monoclonal antibody (NNC0109-0012) has shown efficacy in phase 2A clinical testing in patients with RA.
Objectives The aim of the present study is to investigate the expression of IL-20 in synovial samples from patients with psoriatic arthritis (PsA).
Methods Three synovial biopsies were obtained during synovectomy from the joints of the hands from patients with PsA. Five ‘normal’ synovial biopsies were obtained during surgical treatment of patients with non-inflamed shoulder disorders, such as subacromial impingement. Samples from eight synovial biopsies from patients with PsA and seven ‘normal’ synovial biopsies were obtained during joint surgery and represented as 2-mm spots on tissue micro array sections. All synovial samples were formalin-fixed and paraffin-embedded. The localisation of IL-20 was analysed in synovial sections by immunohistochemistry using a rabbit polyclonal anti-IL-20 antibody (2313b), and immunoreactivity was visualised with tyramide signal amplification and immunoperoxidase. The specificity of the antibody was verified with IL-20-transfected cells and using antigen pre-absorption and pre-immune IgG control.
Results IL-20 was detected in 6 out of 11 synovial samples from patients with PsA. In 4 of these samples, IL-20 was present in both synovial lining and sublining. In 2 samples, IL-20 was present in the synovial lining, but not in the sublining. The three synovial samples obtained by synovectomy were all positive for IL-20, while IL-20 positive cells were observed in only 3 out of the 8 synovial samples obtained during joint replacement surgery. A few IL-20 positive cells were detected in the lining in one ‘normal’ synovial sample, while 11 out of the 12 ‘normal’ samples were negative for IL-20. The localisation pattern of IL-20 in synovial tissue from patients with PsA was similar to what we have previously observed in synovium from patients with RA. The IL-20 immunoreactivity was completely eliminated following antigen pre-absorption of the antibody.
Conclusions The results demonstrate that IL-20 is differentially expressed in synovial samples from patients with PsA compared with ‘normal’ synovial tissue, and that the distribution of IL-20 in synovium from patients with PsA and RA appears to be similar.
Disclosure of Interest M. Jackerott Shareholder of: Novo Nordisk A/S, Employee of: Novo Nordisk A/S, J. Mandelbaum Shareholder of: Novo Nordisk A/S, Employee of: Novo Nordisk A/S, L.-L. Kruse Shareholder of: Novo Nordisk A/S, Employee of: Novo Nordisk A/S, N. Vendel: None Declared, E. Bartels: None Declared, M. Andersen Employee of: Novo Nordisk A/S, C. Jensen: None Declared, N. Søe: None Declared, H. Bliddahl: None Declared, J. Rømer Shareholder of: Novo Nordisk A/S, Employee of: Novo Nordisk A/S