Impaired phagocytosis and susceptibility to infection in pediatric-onset systemic lupus erythematosus.

OBJECTIVES: Impaired function of polymorphonuclear cells (PMNs) in systemic lupus erythematosus (SLE) leads to severe gram-positive and gram-negative bacterial infection, and to major morbidity and mortality. Few studies have focused on the association of impaired function of PMNs and SLE patients' susceptibility to infection. This study aimed to analyze function of PMNs in peroxidase production, chemotaxis, and phagocytosis in pediatric-onset SLE with severe infection.
METHODS: This study compared function of PMNs among pediatric-onset SLE patients with and without histories of severe infection and in normal control subjects. Human peripheral blood PMNs were isolated from patients and controls. Function of PMNs was measured by analyzing peroxidase, chemotaxis, and phagocytic activities. Different disease activity and severity, and drug use in newly diagnosed SLE patients were also compared.
RESULTS: In total, 34 SLE patients (12 patients with severe infection, 22 patients without infection) and 25 healthy controls were analyzed. There were no differences in function of PMNs between SLE patients with or without severe infection. Regardless of infection status, medication, and disease activity, SLE patients had impaired phagocytic ability against Salmonella-specific lipopolysaccharides (LPS) compared with normal controls (p < 0.01). The use of immunosuppressants did not influence phagocytic ability against Salmonella-derived LPS.
CONCLUSIONS: Immunosuppressant agents do not influence phagocytic ability against Salmonella in SLE subjects. Impaired phagocytosis against Salmonella is prominent in pediatric-onset SLE subjects, which may result in the high prevalence of Salmonella infection. There is no deficiency of peroxidase production and chemotaxis activity among SLE subjects.