Abstract Background: Programmed cell death-1 (PD-1) is an immunoreceptor that negatively regulates
antigen receptor signaling and plays a critical role in the immunoregulation of autoimmune diseases.
Aim of the work: This study aimed to measure the plasma and synovial fluid levels of soluble programmed
death-1(sPD-1) in rheumatoid arthritis (RA) patients and to correlate them with the clinical
and laboratory characteristics, disease activity, functional status and radiological severity.
Patients and methods: We measured sPD-1 in the plasma (n=60) and synovial fluid (SF) samples
(n=24) from 60 RA patients and in the plasma from healthy control (n=30). In the patients, disease
activity score using 28 joint counts (DAS28) and the health assessment questionnaire (HAQ)
score were assessed; immunoglobulin-M rheumatoid factor (IgM-RF) titer, anti-cyclic citrullinated
peptide (anti-CCP) antibodies titer and C-reactive protein (CRP) levels were measured and total Sharp
Results: In RA patients both plasma and SF sPD-1 levels (1416.9±1037.9 pg/ml and
1503.9±1129.48 pg/ml respectively) were highly significantly increased compared to its plasma level
in the healthy control (165±26.11 pg/mL) (p