Reduced frequency of CD56dim CD16pos natural killer cells in pediatric systemic inflammatory response syndrome/sepsis patients

Background: Sepsis continues to be a leading cause of death in infants and children. Natural killer (NK) cells serve as a bridge between innate and adaptive immunity, yet their role in pediatric sepsis has not been well characterized. Methods: We tested the hypothesis that decreased NK cell cytotoxicity is a common feature of pediatric systemic inflammatory response syndrome (SIRS)/sepsis patients by measuring, using flow cytometry, NK cell cytotoxicity and cell surface phenotype in the peripheral blood of 38 pediatric intensive care patients who demonstrated signs and symptoms of SIRS and/or sepsis. Results: NK cell cytotoxicity was significantly reduced in peripheral blood mononuclear cells (PBMCs) of pediatric SIRS/sepsis patients as compared with healthy controls, and the percentage of CD56 dim CD16 + cytotoxic NK cells in PBMCs was lower in patients with SIRS/sepsis than in normal donors. However, on a per cell basis, CD56 dim CD16 + NK cells in patients mediated cytotoxicity as well as those in normal donors. Conclusion: The NK cell dysfunction in pediatric SIRS/sepsis patients reflects a quantitative rather than a qualitative difference from healthy controls.