Frequency of circulating B cell subpopulations in umbilical cord blood and venous blood

Background: The intrauterine and early extrauterine development represents a “window of opportunity” in the immuno-logical development. The underlying mechanisms are still poorly understood. The aim of this study was to provide reference values B cell subpopulations in cord blood of term newborns, juveniles and in adults to find the spectrum of their physiological age-related variation. Methods In this study, we used flow cytometry to evaluate human B lymphocytes and subpopulations in cord blood (n = 10), in peripheral blood from healthy juveniles aged 1 to 17 years (n = 20) and from donors 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 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.