title: NK cell increase in neonates from the preterm to the full-term period of gestation.
abstract: BACKGROUND
  Several studies have reported differences in lymphocyte phenotype in preterm and full-term neonates as compared to children and adults. However, a detailed description of the immunologic cell populations of neonates corresponding to the gestational age is needed. This will be helpful for clinical practice to find the best way to prevent neonatal infections or strengthen the immune system of newborns with some kind of immunodeficiency.
  
  
  OBJECTIVE
  To study maturation of the immune system throughout gestation, describing the variations of the lymphocyte populations in function of the gestational week when born.
  
  
  METHODS
  We performed a descriptive study in 134 healthy newborns (gestation age 25-42 weeks), quantifying the relative and absolute counts of cell populations in umbilical cord blood obtained during delivery, by a four-color flow cytometry single platform.
  
  
  RESULTS
  We first compared the very-preterm (25-30 weeks), preterm (31-36 weeks) and full-term (37-42 weeks) neonates. We found higher absolute counts of all cell populations in the full-term group and lower absolute and relative values of NK cells in the very-preterm group. After that, we analyzed the lymphocyte populations week to week (from week 31 to 41) and found the lowest values of T cells (CD4+ and CD8+) for week 36. However, lower percentages of CD4+ T cells and higher percentages of NK cells were observed in week 38 and 41.
  
  
  CONCLUSIONS
  We found an increase in cord blood NK cells with gestational age, both in terms of absolute counts and of percentage values. Moreover, the %NK cells showed a pattern opposite to %CD4+ T cells along the studied period.
authors.affiliation: Laboratorio de Inmuno-Biología Molecular, Hospital General Universitario Gregorio Marañón, Madrid, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: Pérez
authors.forename: María Dolores
authors.initials: MD
authors.lastname: Gurbindo
authors.forename: Salvador
authors.initials: S
authors.lastname: Resino
authors.forename: Angel
authors.initials: A
authors.lastname: Aguarón
authors.forename: María Angeles
authors.initials: MA
authors.lastname: Muñoz-Fernández
mesh_terms: D005312:Fetal Blood / Q000166:cytology; D005434:Flow Cytometry / Q000379:methods; D005865:Gestational Age; D006801:Humans; D007107:Immune System / Q000166:cytology / Q000196:embryology*; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood / Q000276:immunology*; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology*; D018655:Lymphocyte Count; D012016:Reference Values; D047929:Term Birth / Q000097:blood / Q000276:immunology*; D013997:Time Factors