title: Significant changes in the composition of the precursor B-cell compartment in children less than 2 years old.
abstract: BACKGROUND
  Defects in early B lymphocyte maturation in bone marrow (BM) compose a characteristic feature of many primary immune deficiencies associated with agammaglobulinemia. To date, only limited data on the composition of the precursor B-cell compartment in BM is available. The aim of this study was to define normal age-related ranges of total B-cell content and distribution of precursor B-cell stages in BM for the future use in clinical diagnostics.
  
  
  METHODS
  Four color flow cytometry was used to analyze the composition of the B-cell compartment in specimens from 59 hematologically healthy children, aged 14 days to 16 years, assigned to six age groups: neonates less than 1 month old, infants >1-12 months old, children >1-2 years old, >2-5 years old, >5-10 years old, and older than 10 years.
  
  
  RESULTS
  Analysis of the composition of the B-cell compartment revealed significant age-related variation in the distribution of individual B-cell maturation stages, most seriously affecting children during first 2 years of life, with the shift from domination of the earliest stages, to gradually increasing content of mature B-cells. Significantly higher proportions of pro-B lymphocytes were observed in neonates than in any other age group.
  
  
  CONCLUSIONS
  Physiological age-related variation in the precursor B-cell compartment composition affects most seriously very young children below the age of 2 years. Proper interpretation of immunophenotyping results performed in cases of suspected early B-cell differentiation defect requires application of adequate reference data.
authors.affiliation: Histocompatibility Laboratory, Children's Memorial Health Institute, Warsaw, Poland. b.piatosa@czd.pl
authors.forename: Barbara
authors.initials: B
authors.lastname: Piątosa
authors.forename: Mariusz
authors.initials: M
authors.lastname: Birbach
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Siewiera
authors.forename: Marek
authors.initials: M
authors.lastname: Ussowicz
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Kałwak
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Drabko
authors.forename: Aneta
authors.initials: A
authors.lastname: Rękawek
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Tkaczyk
authors.forename: Przemysław Norbert
authors.initials: PN
authors.lastname: Kurowski
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015703:Antigens, CD / Q000032:analysis* / Q000276:immunology; D001854:Bone Marrow Cells / Q000166:cytology* / Q000276:immunology; D002454:Cell Differentiation; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping / Q000592:standards*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D054448:Precursor Cells, B-Lymphoid / Q000166:cytology* / Q000276:immunology
chemical_list: D015703:Antigens, CD