The effect of  Belimumab combined with conventional treatment on NK cell count in childhood systemic lupus erythematosus

Objective To investigate the effect of belimumab combined with conventional therapy on natural killer (NK) cells counts and its correlation with clinical response in childhood systemic lupus erythematosus (cSLE). Methods A retrospective analysis was conducted on 46 cSLE patients treated with belimumab plus standard therapy for 48 weeks. NK cell counts, complement levels, SLEDAI-2K scores, and steroid doses were assessed at baseline, 24, and 48 weeks. Statistical analyses included paired t-test, Wilcoxon test, Pearson/Spearman correlation, and minimal clinically important difference (MCID) calculation. Results NK cell counts increased from 72.0 ± 56.6 cells/µL at baseline to 185.6 ± 84.5 cells/µL at week 48 (P < 0.05). Complement C3 and C4 levels also improved significantly. SLEDAI-2K scores decreased from 16.4 to 2.1 (P < 0.05), with 88.1% achieving low disease activity. Steroid dose was reduced in over 90% of patients. NK cell increase strongly correlated with both complement recovery (ρ = 0.68, P < 0.05) and disease activity improvement (ρ = 0.69, P < 0.05). Conclusions Belimumab combined with conventional therapy may enhance NK cell counts, improve serological and clinical outcomes, and facilitate steroid tapering in cSLE. Further prospective controlled studies are needed to confirm these findings.