Increased Serum Interleukin-2 Levels Are Associated with Abnormal Peripheral Blood Natural Killer Cell Levels in Patients with Active Rheumatoid Arthritis

Objective. To investigate the relationship between serum interleukin-2 (IL-2) levels and disease activity, absolute numbers of peripheral lymphocyte subsets, autoantibodies, and associated cytokines in patients with rheumatoid arthritis (RA). Methods. This study included 106 patients with RA, evaluated their disease activity (DAS28 score), and divided them into disease remission (DAS28≤2.6), low disease activity (DAS28≤3.2), and moderate-high disease activity (DAS28>3.2) groups. Flow cytometry was used to detect the absolute numbers of peripheral lymphocyte subpopulations and CD4+ T cell subsets in each group, and serum cytokine levels were measured using cytometric bead array. Results. Serum IL-2 levels in RA patients were positively correlated with disease activity and rheumatoid factor titers (p