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Expression and activity of beta-defensins and LL-37 in the developing human lung

Timothy D Starner1, Birgitta Agerberth, Gudmundur H Gudmundsson

  • 1Department of Pediatrics, University of Iowa, Iowa City, IA 52242, USA. timothy-starner@uiowa.edu

Journal of Immunology (Baltimore, Md. : 1950)
|January 22, 2005
PubMed

Insights

Human beta-defensins (HBDs) are key to neonatal lung immunity. Lower HBD-2 levels in premature infants may increase their susceptibility to pulmonary infections.

Area of Science:

  • Immunology
  • Neonatal Medicine
  • Pulmonology

Background:

  • Neonatal innate immunity is immature, increasing infection susceptibility.
  • The lung is a primary pathogen entry point in neonates.
  • Human beta-defensins (HBDs) and LL-37 are crucial for pulmonary innate immunity.

Purpose of the Study:

  • To investigate the developmental regulation and expression of HBDs and LL-37 in neonatal pulmonary tissues.
  • To determine the role of these antimicrobial factors in neonatal innate immunity.
  • To assess the antimicrobial activity of HBDs against neonatal sepsis-causing bacteria.

Main Methods:

  • Analysis of HBD-2, HBD-1, HBD-3, and LL-37 mRNA expression in neonatal lung and airway epithelial cultures.
  • Investigation of the effects of IL-1beta and dexamethasone on HBD expression.
  • Quantification of HBD-2 in neonatal tracheal aspirates.
  • Assessment of antimicrobial activity and salt sensitivity of HBDs.

Main Results:

  • HBD-2 was the predominant beta-defensin in the neonatal lung.
  • HBD-2 expression was developmentally regulated, induced by IL-1beta, and suppressed by dexamethasone.
  • HBD-2 levels in tracheal aspirates correlated positively with gestational age.
  • HBD-1 expression was lower than HBD-2 and induced by dexamethasone.
  • HBD-3 and LL-37 were not detected in airway epithelial cultures.
  • Each antimicrobial peptide displayed distinct antimicrobial activity and salt sensitivity.

Conclusions:

  • HBD-2 is a key developmentally regulated antimicrobial factor in the neonatal lung.
  • Decreased HBD-2 levels in premature infants may contribute to their heightened susceptibility to pulmonary infections.
  • These findings highlight the importance of HBDs in neonatal pulmonary defense.

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