Decreased Human Leukocyte Antigen DR on Circulating Monocytes Expression After Severe Pediatric Trauma: An Exploratory Report

OBJECTIVES: Major trauma in adults induces immune dysfunction, with diminished expression of human leukocyte antigen-DR on circulating monocytes. No pediatric data are available. This study described the kinetics of human leukocyte antigen-DR on circulating monocytes following major pediatric trauma and relationships between human leukocyte antigen-DR on circulating monocytes and outcomes. DESIGN: Prospective observational study. SETTING: PICU and trauma unit at a tertiary-care university hospital in South Africa. PATIENTS: Children between 1 month and 13 years hospitalized for severe brain trauma or trauma with an Injury Severity Score greater than or equal to 16, from November 2016 to March 2017. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We included 36 children. Median (interquartile range) age and Injury Severity Score were 7 years (4.9-10.5 yr) and 25 years (22.7-30 yr), respectively. Blood samples (n = 83) for standardized human leukocyte antigen-DR on circulating monocytes measurement were collected at days 1-2, 3-4, and 8-9 after injury (D1, D3, and D8, respectively). On D1, median (interquartile range) human leukocyte antigen-DR on circulating monocytes was markedly reduced relative to normal values (7,031 [5,204-11,201] antibodies per cell). There was a significant increase in human leukocyte antigen-DR on circulating monocytes from D1 to D8. Although all patients with secondary infections (n = 8; 22%) had human leukocyte antigen-DR on circulating monocytes less than 15,000 antibodies per cell at D3, human leukocyte antigen-DR on circulating monocytes levels were not associated with the occurrence of secondary infections (p = 0.22). At D3, human leukocyte antigen-DR on circulating monocytes was significantly higher in patients discharged home (n = 21) by Day 30 after trauma compared with those who died or were still hospitalized (n = 14) (p = 0.02). CONCLUSIONS: Pediatric severe trauma induced an early and dramatic decrease in human leukocyte antigen-DR on circulating monocytes expression. This alteration of innate immunity was not associated with the occurrence of secondary infection, possibly due to a lack of statistical power. However, human leukocyte antigen-DR on circulating monocytes at Day 3 is a potential indicator of those at high risk of secondary infection and worse outcomes.