Expression of K2P5.1 potassium channels on CD4+ T lymphocytes correlates with disease activity in rheumatoid arthritis patients

Expression levels of K2P5.1 were measured by RT-PCR in the peripheral blood of 58 patients with RA and correlated with disease activity parameters (C-reactive protein levels, erythrocyte sedimentation rates, disease activity score (DAS28) scores). Twenty patients undergoing therapy change were followed-up for six months. Additionally, synovial fluid and synovial biopsies were investigated for T lymphocytes expressing K2P5.1.K2P5.1 expression levels in CD4+ T cells show a strong correlation to DAS28 scores in RA patients. Similar correlations were found for serological inflammatory parameters (erythrocyte sedimentation rate, C-reactive protein). In addition, K2P5.1 expression levels of synovial fluid-derived T cells are higher compared to peripheral blood T cells. Prospective data in individual patients show a parallel behaviour of K2P5.1 expression to disease activity parameters during a longitudinal follow-up for six months.Disease activity in RA patients correlates strongly with K2P5.1 expression levels in CD4+ T lymphocytes in the peripheral blood in cross-sectional as well as in longitudinal observations. Further studies are needed to investigate the exact pathophysiological mechanisms and to evaluate the possible use of K2P5.1 as a potential biomarker for disease activity and differential diagnosis.Rheumatoid arthritis (RA) is a chronic inflammatory disease which is characterized by pain, swelling and progressive destruction of multiple joints. The systemic nature of RA causes, next to loss of joint function, substantially decreased quality of life and increased mortality of patients. Current treatments are mainly based on immunosuppressive disease-modifying antirheumatic drugs, among them the rapidly expanding family of biologic agents [1]. Close monitoring of disease activity is mandatory for the evaluation of treatment efficacy as a substantial percentage of patients do not respond adequately to first-line therapy. In these cases, as well as in patients with