Significant changes in the composition of the precursor B‐cell compartment in children less than 2 years old

Abstract

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. 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. 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. 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.