Refined characterization and reference values of the pediatric T- and B-cell compartments

Work in the past years has led to a refined phenotypical description of functionally distinct T- and B-cell subsets. Since both lymphocyte compartments are established and undergo dramatic changes during childhood, redefined pediatric reference values of both compartments are needed. In a cohort of 145 healthy children, aged 0–18 years, the relative and absolute numbers of the various T- and B-cell subsets were determined. In addition, we found that besides thymic output, naive (CD27+CD45RO−) T-cell proliferation contributed significantly to the establishment of the naive T-cell compartment. At birth, regulatory (CD25+CD127−CD4+) T cells (Tregs) mainly had a naive (CD27+CD45RO−) phenotype whereas ‘memory or effector-like’ (CD45RO+) Tregs accumulated slowly during childhood. Besides the CD27+IgM+IgD+ memory B-cell population, the recently identified CD27−IgG+ and CD27−IgA+ memory B-cell populations were already present at birth. These data provide reference values of the T- and B-cell compartments during childhood for studies of immunological disorders or immune reconstitution in children.