Age-related low expression of HLA-DR molecules on monocytes of term and preterm newborns with and without signs of infection.

Objectives: Presentation of human leucocyte antigen (HLA) molecules is an important part of an efficient immune response. Since bacterial infections are more common in newborns, we hypothesized that the level of HLA-DR expression may influence the host defense system.

Study Design: HLA-DR expression on monocytes was examined by flow cytometry during the first week of life of term and preterm neonates with and without signs of infection and of adults.

Results: HLA-DR expression of term and preterm newborns with or without signs of infection was lower compared with adults during the first day of life (p<0.0001). Prematurity correlates with lower expression in neonates with gestational age less than 32 weeks (p=0.0008). HLA-DR expression in neonates with signs of infection was decreased compared to healthy neonates (p=0.0196). Maternal conditions such as preeclampsia, prenatal treatment with steroids and mode of delivery had no influence on the expression of HLA-DR. In contrast, newborns with respiratory distress syndrome but without signs of infection showed reduced HLA-DR expression (p=0.0370).

Conclusion: Low HLA-DR expression on monocytes contributes to impaired neonatal host defense, especially in preterm neonates.