Complement activation and humoral immune dysregulation drive progression of pediatric septic shock: a retrospective cohort study.

OBJECTIVE: To investigate the clinical characteristics of pediatric septic shock (SS) and analyze their correlation with immune dysregulation in affected children. METHODS: A retrospective analysis was conducted on 192 pediatric sepsis patients admitted to Children's Hospital of Nanjing Medical University between January 2022 and January 2025. Among these, 54 patients who developed shock were classified into a shock group, and the remaining 138 patients were classified into non-shock group. Laboratory test results (including immune and inflammatory indices) and clinical scores (Acute Physiology and Chronic Health Evaluation II (APACHE II) and sequential organ failure assessment (SOFA) scores) were analyzed. Multivariate logistic regression was applied to verify the predictive role of immune markers for SS, and a nomogram was developed. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the predictive performance of identified immune predictors, and their performance was compared using the Delong test. RESULTS: The shock group showed significantly higher rates of impaired consciousness (74.07% vs 0.00%, P<0.001) and neurological symptoms (38.89% vs 19.57%, P=0.005), along with significantly lower immunoglobulin (Ig) G, complement component 3 (C3) and complement component 4 (C4) levels (all P<0.001) than the non-shock group. Correlation analyses revealed that APACHE II and SOFA scores were negatively associated with IgG, C3, and C4 levels (all P<0.05), with C3 showing additional negative correlations with white blood cell count (WBC) and procalcitonin (PCT), and C4 with PCT. Importantly, IgG, C3 and C4 were identified as independent predictors of shock risk, with C3 demonstrating the highest diagnostic performance in ROC analysis. CONCLUSION: Pediatric SS is characterized by complement activation (reduced C3/C4) and IgG deficiency, which strongly correlate with disease severity. C3 and IgG demonstrated high predictive accuracy for shock progression.