Bridgewood C, Russell T, Weedon H, et al. - In Rheumatoid Arthritis, PsA (Psoriatic Arthritis) and OA (Osteoarthritis) patients, researchers analyzed synovial tissue samples to determine the expression of IL-41 protein [Meteorin-like (IL-41) represents a new cytokine that is believed to be immunoregulatory and is highly expressed in psoriatic skin]. They assessed IL-41 generation from healthy enthesis samples, as the enthesis is the primary inflammatory lesion in PsA. They found a high expression of IL-41 in the synovial fluid and synovial tissue of PsA patients (median = 8118 pg/ml) vs OA patients (median = 4720 pg/ml). Overall, PsA synovium exhibited IL-41 expressed on it. The presence, as well as the inducibility of IL-41 at the enthesis, was also reported.