LAUSR

Background While the role of adaptive immune system in pathogenesis of systemic lupus erythematosus (SLE) has been well characterized, there is paucity of literature on innate immunity in these patients. There are limited data on neutrophil function in pediatric lupus. In this study we analyzed neutrophilic functions in a cohort of pediatric lupus from North India. Objectives To evaluate phagocytic and oxidative burst activity of neutrophils in patients with pediatric-onset SLE Methods This prospective study was carried out at a tertiary care center in North India in patients with SLE during the period July 2017 to December 2018. Diagnosis of lupus was based on SLICC 2012 criteria and patients who had disease onset below 18 years were included. Controls were age matched children attending the outpatient clinic of department. Disease activity was measured by SELENA-SLEDAI score. Phagocytic activity was estimating using the pH Rhodo Escherichia coli (E coli) BioParticles kit by flow cytometry. Phagocytic function was measured as% phagocytic activity of neutrophils, delta mean fluorescent intensity (ΔMFI), and stimulation index (SI). Oxidative burst activity was performed by Dihydrorhodamine (DHR) flow cytometry assay and% positivity neutrophils, ΔMFI, and SI were calculated. Results Eighty-seven children with lupus (63 girls; 24 boys) comprised the study group. 44 healthy controls were also enrolled. Disease onset was 8.52±2.95 years whereas age at enrolment was 12.34±5.67 years. Phagocytic activity in neutrophils SLE and controls were 76.59 ± 20.70%; 91.30 ± 4.47%; p<0.001 respectively. ΔMFI phagocytosis in patients with SLE and control were 0.09 (005-0.16), 0.18 (0.15, 0.22); (p.= 0.002) respectively. SI of phagocytosis in patients with SLE and controls were 2.79 (1.92, 3.93); 5.00 (4.50, 6.12); p<0.001. SLEDAI score was negatively correlated with phagocytic function in neutrophils in patients with SLE. Oxidative burst activity of neutrophils in patients with SLE and controls in form of%positivity on neutrophils were 84.03±17.36%, 92.26± 5.49; p<0.001 respectively. ΔMFI and SI on DHR between patients and healthy controls were comparable. There was no difference in oxidative burst activity between active and inactive SLE patients. Two patients showed a double peak in DHR flow cytometry consistent with mosaic pattern associated with a probable carrier state for X-linked chronic granulomatous disease. Both oxidative burst activity and phagocytic activity did not show significant correlation with the dose of prednisolone. Conclusion This study suggests that there is impaired neutrophil function in childhood SLE and also there may be a correlation between neutrophil dysfunction and disease activity. The E.coli based phagocytic functions of neutrophils were significantly reduced in pediatric SLE patients compared to healthy controls. Phagocytic activity of neutrophil was significantly lower in patients with disease activity and coexistent infection in patients with pediatric SLE. Oxidative burst activity was reduced in patients with pediatric SLE compared to healthy controls. However, there was no significant correlation of oxidative burst activity to the age, disease activity and coexistent infections. References [1] Wu S-A, Yeh K-W, Lee W-I et al. Impaired phagocytosis and susceptibility to infection in pediatric-onset systemic lupus erythematosus. Lupus.2013;22(3):279–88. [2] Marini R, Condino-Neto A, Appenzeller S et al. Superoxide release in juvenile systemic lupus erythematosus. Rheumatol Int.2012;32(7):1977–83.Abstract THU0510 – Figure 1 Phagocytic functions in patients with active SLE versus inactive diseaseAbstract THU0510 – Figure 2 Correlation of SLEDAI and phagocytic activity Acknowledgement None Disclosure of Interests None declared