Distinct Humoral Immune Profiles in Non-Hospitalized Pediatric Systemic Lupus Erythematosus with Autoimmune Flare versus Bacterial Pneumonia

Humoral immune dysfunction plays a pivotal role in the immunopathogenesis of systemic lupus erythematosus (SLE) and serves as a useful tool for differentiating disease activity from infectious processes in pediatric patients. In routine clinical settings the pediatric SLE flares and bacterial infections frequently present with overlapping clinical features and creating diagnostic uncertainty and potentially delaying appropriate treatment. This study evaluated multiple humoral immune indicators that including complement proteins (C3 and C4), total complement activity (CH50), autoantibodies (anti–double-stranded DNA and antinuclear antibodies), and serum immunoglobulins (IgG, IgM, and IgA). The analysis included two groups of ambulatory children aged 5–10 years: one group experiencing SLE disease activity (n = 30) and another with SLE complicated by bacterial pneumonia (n = 30). Laboratory measurements were performed using nephelometric, enzyme-linked immunosorbent assay, and immunoturbidimetric techniques. Children with active SLE exhibited pronounced reductions in C3, C4, and CH50 levels and along with significantly increased anti-dsDNA titers, reflecting active immune complex–driven inflammation. patients diagnosed with bacterial pneumonia demonstrated elevated IgM and IgA levels which is consistent with an infection-related humoral immune response. Receiver operating characteristic analysis showed that a combined assessment of C3, C4, and anti-dsDNA provided high diagnostic accuracy in distinguishing disease flare from infection (AUC = 0.92). humoral immune marker evaluation represents a practical outpatient tool for differentiating SLE flares from bacterial infections and guiding appropriate therapy in pediatric patients.