title: Phagocytosis of neonatal pathogens by peripheral blood neutrophils and monocytes from newborn preterm and term infants.
abstract: BACKGROUND
  Deficiencies in phagocytosis may contribute to the increased susceptibility of infants to early life infections. Data on phagocytosis of the major neonatal pathogens Staphylococcus epidermidis (SE), Staphylococcus aureus (SA), and Escherichia coli (EC) by preterm infant leukocytes are inconsistent.
  
  
  METHODS
  Cord and <24-h peripheral blood were collected from very preterm (<30.1 wks gestational age (GA)) and term (37-42 wks GA) infants. Monocyte and neutrophil phagocytosis of pHrodo-labeled SE, SA, and EC were analyzed using a small-volume flow cytometry assay, with simultaneous characterization of surface activation marker expression.
  
  
  RESULTS
  Preterm infants had lower proportions of monocytes and neutrophils capable of phagocytosis than term infants, but preterm infant phagocytes had higher phagocytic capacity. Phagocytosis was strongly correlated between cord and <24-h peripheral blood. Supplementation with exogenous complement significantly increased phagocytosis of EC but not of SE or SA. Monocyte human leukocyte antigen (HLA)-DR expression was lower in preterm infants but did not correlate with phagocytosis.
  
  
  CONCLUSIONS
  There is no defect in phagocytosis by monocytes and neutrophils from preterm compared with term infants, although preterm infants possess fewer phagocytes, possibly contributing to susceptibility to bacterial infection. Further investigation into the development of postnatal phagocytic competence is warranted.
authors.affiliation: School of Paediatrics and Child Health, University of Western Australia, Perth, Western Australia, Australia.
authors.forename: Amy
authors.initials: A
authors.lastname: Prosser
authors.forename: Julie
authors.initials: J
authors.lastname: Hibbert
authors.forename: Tobias
authors.initials: T
authors.lastname: Strunk
authors.forename: Chooi Heen
authors.initials: CH
authors.lastname: Kok
authors.forename: Karen
authors.initials: K
authors.lastname: Simmer
authors.forename: Peter
authors.initials: P
authors.lastname: Richmond
authors.forename: David
authors.initials: D
authors.lastname: Burgner
authors.forename: Andrew
authors.initials: A
authors.lastname: Currie
mesh_terms: D004926:Escherichia coli / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000276:immunology*; D009000:Monocytes / Q000276:immunology*; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D013211:Staphylococcus aureus / Q000276:immunology; D013212:Staphylococcus epidermidis / Q000276:immunology; D018709:Statistics, Nonparametric