• Katherine E Bline, Jennifer A Muszynski, Adam J Guess, Somaang Menocha, Melissa D Moore-Clingenpeel, Jill K Popelka, Josey M Hensley, Lisa M Steele, Ian C Goldthwaite, Kathleen J Jedreski, and Mark W Hall.
• The Abigail Wexner Research Institute at Nationwide Children's Hospital, Columbus, OH.
• Pediatr Crit Care Me. 2022 Dec 1; 23 (12): e555e563e555-e563.

ObjectivesImmunoparalysis in children with septic shock is associated with increased risk of nosocomial infections and death. Myeloid-derived suppressor cells (MDSCs) potently suppress T cell function and may perpetuate immunoparalysis. Our goal was to test the hypothesis that children with septic shock would demonstrate increased proportions of MDSCs and impaired immune function compared with healthy controls.DesignProspective observational study.SettingFifty-four bed PICU in a quaternary-care children's hospital.PatientsEighteen children with septic shock and thirty age-matched healthy children.InterventionsNone.Measurements And Main ResultsPeripheral blood mononuclear cells (PBMCs) were isolated from whole blood and stained for cell surface markers to identify MDSCs by flow cytometric analysis, including granulocytic and monocytic subsets. Adaptive and innate immune function was measured by ex vivo stimulation of whole blood with phytohemagglutinin-induced interferon (IFN) γ production and lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α production, respectively. Prolonged organ dysfunction (OD) was defined as greater than 7 days. Children with septic shock had a higher percentage of circulating MDSCs, along with lower LPS-induced TNFα and phytohemagglutinin-induced IFNγ production capacities, compared with healthy controls. A cut-off of 25.2% MDSCs of total PBMCs in initial samples was optimal to discriminate children with septic shock who went on to have prolonged OD, area under the curve equal to 0.86. Children with prolonged OD also had decreased TNFα production capacity over time compared with those who recovered more quickly ( p = 0.02).ConclusionsThis article is the first to describe increased MDSCs in children with septic shock, along with an association between early increase in MDSCs and adverse OD outcomes in this population. It remains unclear if MDSCs play a causative role in sepsis-induced immune suppression in children. Additional studies are warranted to establish MDSC as a potential therapeutic target.Copyright © 2022 by the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies.

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