Children with moderate burns had lower surface expression of HLA-DR on circulating monocytes early after injury, alongside a stronger-than-normal whole-blood response to bacterial lipopolysaccharide, according to a prospective observational study of 23 pediatric burn patients and seven healthy controls. The mixed pattern did not resemble uniform immune suppression: cells carrying a phenotypic marker associated with monocyte immune competence appeared less active in one respect, while the integrated capacity of blood to produce tumor necrosis factor alpha, or TNF-α, after laboratory stimulation was heightened. Small burns covering less than 15% of total body surface area, or TBSA, did not differ significantly from controls on the group-level analyses. The findings were reported for burns spanning 15% to 30% TBSA, with a prespecified enrollment tolerance that allowed inclusion up to 32% TBSA.

The researchers prospectively enrolled children aged 6 months to 15 years who were admitted to the pediatric burn service at UF Health Shands Children’s Hospital between December 2023 and July 2025. The cohort included 14 children with small burns and nine with moderate burns. Seven healthy controls younger than 16 were undergoing elective pediatric surgery. The investigators collected blood from burn patients on hospital day 2, with a window of one day either side, and obtained later samples when clinically feasible. Control blood was collected in the operating room after induction of anesthesia and before surgery. Because sampling times were partly determined by each child’s clinical course, serial specimens were not available from every participant at every interval, and the number included in each immune assay varied.

Monocyte HLA-DR was measured by flow cytometry in circulating CD14-positive monocytes. The researchers converted median fluorescence intensity into the average number of anti-HLA-DR antibodies bound per cell, a measure reported as ABC. This analysis included seven controls, 11 small-burn patients and six moderate-burn patients. Median HLA-DR expression was significantly lower in the moderate-burn group than in healthy controls, while the small-burn group did not differ significantly from either comparison group after statistical correction for multiple comparisons. The estimated Hodges–Lehmann location shift between the moderate-burn and control groups was minus 22,939 ABC, with an exact 96.50% confidence interval from minus 33,104 to minus 12,039. Individual values varied considerably, including substantial overlap between the small-burn and moderate-burn groups.

The investigators also assessed whether burn injury altered circulating myeloid-derived suppressor cells, or MDSCs, a heterogeneous collection of immature myeloid cells described in the study as having immunosuppressive activity. Flow-cytometric phenotyping of peripheral blood mononuclear cells was performed approximately one week after injury in seven controls, six small-burn patients and six moderate-burn patients. Total MDSCs and three subsets—monocytic, polymorphonuclear and early MDSCs—showed considerable person-to-person variation. Some measures appeared numerically higher in the moderate-burn group, but neither total frequencies, subset frequencies nor absolute subset counts differed significantly among the three groups. Absolute total MDSC counts were numerically higher in moderate-burn patients, with a median of 253,685 compared with 161,336 in controls and 117,892 in the small-burn group, but the difference was not statistically significant.

Functional responsiveness was tested with a whole-blood TNF-α ELISpot assay. Diluted blood was incubated for 24 hours with or without LPS, and spots representing TNF-α-secreting cells were counted and characterized. The day-2 analysis included seven controls, seven small-burn patients and eight moderate-burn patients. LPS increased the number of spots, their size and total expression within every cohort, demonstrating that all three groups retained the capacity to respond to the stimulus. Among stimulated samples, however, the moderate-burn group produced the strongest responses. Stimulated spot-forming units, spot size and total expression were significantly higher than in controls, while total expression was also significantly higher than in the small-burn group. The small-burn cohort did not differ significantly from controls.

The magnitude of the acute functional differences was appreciable. The estimated shift in stimulated spot-forming units between moderate-burn patients and controls was 294, with an exact 95.99% confidence interval of 36 to 506. The corresponding shifts were 1.203 for stimulated spot size, with a confidence interval of 0.3966 to 2.521, and 2,503 for total expression, with a confidence interval of 974.7 to 3,686. Compared with small-burn patients, the estimated difference in total expression was 2,229, with a confidence interval of 403.2 to 3,473. These results indicate that the heightened response was specific to the moderate-burn group in this cohort rather than evidence of a general rise in every burned child.

Exploratory analyses suggested that immune measures might also differ among children with and without inpatient complications, defined in the study as graft loss, wound infection, gastrointestinal infection or bacteremia. Among burn patients with available data, those who experienced complications had larger burns: a median of 25% TBSA, compared with 11% among those without complications. Those with complications also had lower day-2 monocyte HLA-DR expression, with a median of 28,603 ABC versus 40,910 ABC. Whole-blood LPS-induced TNF-α responses did not differ significantly by complication status. These observations were exploratory, and burn size was greater in the complication group, making it difficult to separate the independent effects of severity, clinical interventions and immune markers.

Only three moderate-burn patients provided samples for a descriptive comparison at six to eight weeks after injury. Their later samples showed lower spot-forming units and total TNF-α expression than their acute day-2 samples, while spot size appeared similar. The small and incomplete dataset was not subjected to inferential testing and cannot establish how immune responsiveness changes during recovery. It nevertheless points toward a possible difference between acute and later responses. More broadly, the assays captured different immune domains: monocyte HLA-DR was a cell-specific phenotypic measurement, whereas whole-blood ELISpot responses reflected an integrated cytokine response from multiple blood-cell populations and did not identify the cellular source of TNF-α.

The study has important limitations. It was conducted at a single center with modest, assay-specific sample sizes, making it underpowered for modest differences and limiting generalizability. Nonsignificant results should not be interpreted as proof of equivalence. The cohort was predominantly male, no healthy control was African American, controls underwent diverse elective operations, and burn care—including surgery, transfusion, antibiotics, nutritional support and intensive care—varied with severity. The study was not designed to isolate those interventions’ effects. Burn depth was mixed, longitudinal sampling was incomplete, T-regulatory cells were not measured, and broader cytokine profiling and leukocyte functions such as phagocytosis, reactive oxygen species production and migration were not systematically assessed. All 30 participants were ultimately discharged in stable condition, and the research characterized early immune patterns rather than establishing that any marker predicts infection or other outcomes. Taken together, the results indicate that moderate pediatric burns were associated with concurrent phenotypic and functional innate immune alterations, rather than a uniformly weakened immune response.

Subject of Research: Early innate immune alterations in children with small and moderate burn injuries

Article Title: Moderate pediatric burn injury is associated with reduced monocyte HLA-DR expression and heightened whole-blood LPS-induced TNF-α responses

Article References: Wiggins, W. B., Rincon, J. C., Hernández-Ríos, M., Polcz, V., Rodhouse, C., Yoham, A. L., Richter, S., Cabral, A., Moldawer, L. L., Efron, P. A., Maile, R., & Larson, S. D. (2026). Moderate pediatric burn injury is associated with reduced monocyte HLA-DR expression and heightened whole-blood LPS-induced TNF-α responses. Frontiers in Pediatrics, 14, Article 1967322. https://doi.org/10.3389/fped.2026.1967322

Image Credits: AI Generated

DOI: 10.3389/fped.2026.1967322

Keywords: pediatric burns, innate immunity, monocyte HLA-DR, TNF-alpha, lipopolysaccharide, ELISpot, flow cytometry, myeloid-derived suppressor cells, immune dysregulation, Moderate, pediatric, burn