Pediatric systemic lupus erythematosus: phagocytic defect and oxidase activity of neutrophils.

ABSTRACT

BACKGROUND: There are limited data on neutrophil function in pediatric-onset systemic lupus erythematosus (pSLE) patients. This study aimed to evaluate phagocytosis and oxidase activity of neutrophils in patients with pSLE. PATIENTS AND METHODS: Eighty-seven patients with pSLE and 44 controls were enrolled. Phagocytic activity was assayed using pHrodoTMRed E. coli BioParticles Phagocytosis Kit by flow cytometry. Determination of NADPH oxidase activity was carried out by Dihyrdrorhodamine-123 (DHR-123) flow cytometry assay. RESULTS: Phagocytic activity of patients' neutrophils (mean 76.59%) was lower than that in controls (91.30%) (p < 0.001). Median delta median fluorescence intensity (ΔMFI) and stimulation index (SI) in patients (ΔMFI 0.09; SI 2.79) were also decreased compared to controls (ΔMFI 0.18; SI 5.00) (p < 0.002; p < 0.001 respectively). Disease activity showed an inverse correlation with phagocytic activity. Oxidase activity was also significantly low (SI DHR < 40) in 16% of patients. No significant correlation was found between oxidative burst and disease activity. CONCLUSION: Neutrophil function is impaired in patients with pSLE, as evidenced by the markedly reduced phagocytic activity. Phagocytic activity is also inversely correlated with disease activity. The oxidative activity was also reduced but not significantly. IMPACT Neutrophil phagocytic function is impaired in pediatric-onset systemic lupus erythematosus (pSLE). There is an inverse correlation between disease activity in pSLE and phagocytic activity. NADPH oxidase activity in patients with pSLE did not show significant correlation with disease activity.