Serum IL-2 levels are associated with disease activity and related to dyslipidaemia and the immunological profile in systemic lupus erythematosus

Introduction Systemic lupus erythematosus (SLE) is an autoimmune disorder characterised by multisystem involvement, frequently including cardiovascular manifestations. Interleukin 2 (IL-2), a key cytokine in immune regulation, plays a pivotal role in maintaining tolerance by promoting regulatory T cell function. The relationship between serum IL-2 levels and specific SLE features remains incompletely defined. The aim of our study was to investigate the associations between serum IL-2 concentrations and disease activity, inflammatory markers, autoantibody profiles as well as cardiovascular and metabolic parameters in a well-characterised cohort of patients with SLE. Methods In this cross-sectional study, 235 patients with SLE were recruited and characterised, including assessment of autoantibody profiles, disease activity indices (SLE Disease Activity Index-2000 (SLEDAI-2K)), Damage Index and remission status. Cardiovascular characteristics were evaluated, encompassing lipid profiles, insulin resistance indices and carotid ultrasound parameters such as plaque presence, intima-media thickness and arterial stiffness. Serum IL-2 concentrations were quantified using an ultrasensitive technique, the Single Molecule Array (Simoa). Multivariable linear regression was conducted to examine the associations between circulating IL-2 levels and clinical as well as cardiovascular manifestations of SLE. Results In multivariable analyses, serum IL-2 levels showed significant positive associations with inflammatory markers including C reactive protein and IL-6. Disease activity, assessed by SLEDAI-2K, was positively correlated with IL-2 levels. Positive and significant associations were also noted, after adjustment for covariates, between IL-2 and specific autoantibodies, including anti-DNA, anti-Sjögren’s syndrome antigen A (SSA), anti-Sjögren’s syndrome antigen B (SSB), anti-Smith (Sm) and antiribosome. Regarding cardiovascular disease factors, triglycerides were positively associated with IL-2 whereas high-density lipoprotein-cholesterol exhibited an inverse relationship. Conclusion Significant correlations exist between serum IL-2 levels and markers of inflammation, lipid profile, disease activity and specific autoantibody profiles in patients with SLE. These findings underscore the pivotal role of IL-2 in SLE immunopathogenesis, reflecting its intricate involvement in modulating both inflammatory responses and metabolic pathways.