Background: Programmed death-1 (PD-1) is an immuneregulatory molecule functioning by ‎down-regulating immune responses. PD-1 is present on follicular helper T cells (TFH) and is important ‎in the formation of plasma cells.PD-1 exists in a bioactive soluble form (sPD-1) and is thought to be ‎implicated in disease activity in rheumatoid arthritis (RA). ‎ Objectives: to measure the levels of soluble programmed death-1(sPD-1) in RA patients and to ‎correlate it with clinical and laboratory parameters of disease activity and severity.‎ Method: We measured sPD-1 at in plasma (n = 60) and synovial fluid (SF) (n = 24) from patients ‎with RA. We tested for correlations with the Disease Activity Score using 28 joint counts (DAS28), the ‎Health Assessment Questionnaire(HAQ)score, immunoglobulin M rheumatoid factor (IgM-RF), anti-‎cyclic citrullinated peptide(anti-CCP) antibodies, C-reactive protein (CRP) and total Sharp score (TSS). ‎We also measured sPD-1 in plasma from healthy volunteers (HV) (n = 30). ‎ Results: In RA, sPD-1 concentrations in plasma (mean 1416.9 pg/ml) and SF (mean 1503.9 ‎pg/ml) were increased compared with HV (median 165 pg/mL)(all p