Differential expression of antimicrobial polypeptides in cord blood samples of preterm and term infants

Aim To determine levels of antimicrobial polypeptides (AMP) in cord blood of term and preterm neonates and to investigate influencing factors. Methods In a single‐centre study, n = 139 preterm infants and n = 36 term infants were included. AMP levels were analysed in supernatants of whole cord blood cultures with a standardised concentration of 5 × 106 white blood cells/mL via enzyme‐linked immunosorbent assay (ELISA). Results Lactoferrin, human neutrophil peptides (HNP) 1–3 and bacterial permeability‐increasing protein (BPI) expression in cord blood of preterm infants were influenced by the cause of preterm delivery, that is increased levels in infants with clinical amniotic infection. AMP levels also weakly correlated with white blood cell and neutrophil count at birth. In the whole cohort, no association between gestational age or birthweight with AMP levels was found. In the subgroup of infants without clinical amniotic infection (n = 77 preterm infants, n = 36 healthy term infants), we noted a weak correlation between gestational age and lactoferrin, calprotectin and HNP1‐3 levels. In addition to that, we observed higher levels of lactoferrin and HNP1‐3 in large‐for‐gestational‐age infants. Conclusion Our study confirms that several factors influence cord blood AMP levels which underlines the difficulties of using AMP levels as biomarkers of immunological response.