Age-related trends in pediatric B-cell subsets.

There are few studies of the developmental changes in B-cell subsets in children. Recent data from adult populations demonstrate that alterations to B-cell subsets have functional consequences and can be helpful diagnostically. Comparable studies in children have been hindered by the lack of normative data and by significant changes with age. This study evaluated B-cell subsets by 4-color flow cytometry in 47 children of different ages. The use of a 4-color platform is compatible with broad use in clinical laboratories. We found that there are rapid changes in the B-cell compartment in infancy and early childhood. Total B-cell numbers decline early in life, and this correlates with a decline in transitional B cells and naïve B cells. The decline is most rapid between 1 and 5 years of age, with a slower decline later in childhood. In contrast, nonswitched and switched memory B cells both increase during the 1st 5 years of life. The decline in B-cell numbers did not occur until after 1 year of age, suggesting that the period after birth is a unique developmental window. These data provide a reference set for further studies on B-cell dysfunction in pediatric disorders. The changes occurring in early childhood document the need for age-related assessments and serve to underscore the B-cell-specific kinetics of immunologic development in humans.