Evaluation of CD19+ CD24+CD27 B cell and serum level of interleukin 10 and interleukin 35 in patients with systemic lupus erythematosus

Regulatory B cells (Bregs) maintain immune homeostasis through anti-inflammatory cytokine production, yet their role in systemic lupus erythematosus (SLE) remains poorly understood. This study evaluated concentrations of CD19+CD24 high CD27+ regulatory B cell frequencies and serum interleukin-10 (IL-10) and interleukin-35 (IL-35) in 40 SLE patients compared to 25 normal controls. Patients in this cross-sectional observational study were stratified by SLE Disease Activity Index (SLEDAI) scores into Group I: SLE patients with active disease (≥5) and Group II: SLE patients with inactive disease (≤4) disease groups. CD19+CD24highCD27+ B cells were quantified by flow cytometry, while serum IL-10 and IL-35 levels by enzyme-linked immunosorbent assays. Active SLE patients demonstrated significantly reduced CD19+CD24 highCD27+ B cells (23.20×10⁶) compared to controls (56.40×10⁶, p<0.001). IL-35 levels were markedly decreased in active disease patients (54.04±8.10 pg/ml) versus patients with inactive disease (83.38±20.05 pg/ml) and controls (89.04±10.86 pg/ml, p<0.001). Conversely, IL-10 concentrations were elevated in SLE active patients (4.44±1.27 pg/ml) compared to inactive patients and controls (1.95±0.56 and 2.03±0.61 pg/ml, respectively, p<0.001). Strong correlations were observed between regulatory B cell counts and SLEDAI scores (r=-0.547, p<0.001). In conclusion, active SLE is characterized by impaired regulatory B cell populations and dysregulated cytokine profiles, with reduced IL-35 and elevated IL-10 levels, correlated with disease activity.