Crit Care. 2025 Dec 22. doi: 10.1186/s13054-025-05758-0. Online ahead of print.
ABSTRACT
PURPOSE: Humoral immunity proteins-immunoglobulins, complement proteins, and antimicrobial peptides-have key antimicrobial and immunomodulatory functions in sepsis. We hypothesised that their circulating levels are lower in non-survivors, potentially resulting in impaired bacterial clearance and persistent or recurrent infections.
METHODS: We performed a systematic review and meta-analysis evaluating differences in humoral immunity proteins between survivors and non-survivors in adult patients with sepsis. PubMed and Embase were searched without date restrictions. Random-effects meta-analyses were used to estimate pooled standardised mean differences (SMD) with 95% confidence intervals (CI). Sensitivity analyses included data from the MIMIC-IV ICU database, and further supplemented by three proteomic studies.
RESULTS: Thirty-six studies including 6,330 patients were analysed. Thirteen reported on immunoglobulins, 17 on complement proteins, and 7 on the antimicrobial peptide heparin-binding protein (HBP). Survivors had significantly higher levels of complement proteins C3 (SMD 0.53 [0.07-0.99]) and C4 (SMD 0.51 [0.09-0.94]) compared to non-survivors. Conversely, C4a (SMD – 1.17 [-1.77 to – 0.56]) and IgA (SMD – 0.21 [-0.39 to – 0.03]) were significantly lower in survivors. No differences were found for IgG (SMD 0.00 [-0.18 to 0.18]), IgM (SMD – 0.02 [-0.13 to 0.08]), C5, C5a, or HBP. Sensitivity analyses using MIMIC-IV (n = 2,452) and proteomic datasets supported these findings. Proteomic data revealed early depletion of classical complement components (C3, C4B) and regulatory proteins in non-survivors.
CONCLUSION: Sepsis non-survivors exhibit lower C3 and C4 levels and higher C4a, consistent with complement activation and/or depletion. Complement proteins may serve as potential biomarkers and therapeutic targets in sepsis.
PMID:41430733 | DOI:10.1186/s13054-025-05758-0