Ontogeny of Circulating B Cell Subpopulations from Birth to Adulthood

Background: The intrauterine and early extrauterine development represents a “window of opportunity” in the immunological development. The underlying mechanisms are still poorly understood. The aim of this study was to provide reference values on B cell subpopulations in cord blood of term newborns, and peripheral venous blood of juveniles and adults to analyze the potential spectrum of their physiological age-related variation. Methods: Flow cytometry was used to evaluate human B lymphocytes and subpopulations in cord blood (n = 10), and peripheral blood from healthy children and adolescence, further called juveniles, aged 1 to 17 years (n=20) and adults aged 24 to 62 years (n = 10). Results: Our findings showed increasing frequencies of IgM memory B cells, class-switched memory B cells, marginal zone B cells and plasmablasts, from cord blood to peripheral blood of juveniles and adults. In contrast, the percentage of naïve B cells was higher in newborns than in juveniles and adults. The frequencies of immature B cells were similar in all three groups and B1 cell were similar in cord blood and peripheral blood of adults. Interestingly, transitional B cells frequencies were similar in cord blood and adults but significantly lower in juveniles. Conclusions: The frequencies of circulating B cell subpopulation are subject to considerable changes during ontogeny, reflecting overlying effects of maturation and of the acquisition of an adaptive immune memory.