THE BULK OF THE PERIPHERAL B-CELL POOL IN MICE IS STABLE AND NOT RAPIDLY RENEWED FROM THE BONE-MARROW

We have reevaluated the in vivo lifespan of B lymphocytes based on incorporation of the thymidine analogue 5-bromo-2′-deoxyuridine into the DNA of dividing cells. To exclude potential alterations in the turnover of B-lineage cells due to the bromodeoxyuridine incorporation, we performed pulse-chase experiments comparing the appearance and disappearance of bromodeoxyuridine-labeled cells over long periods of time. The data consistently show that more than two-thirds of splenic B cells in adult (>2 months old) mice have a lifetime of several weeks or months, whereas a more rapid tarnover takes place in young (4 week old) mice. Thus, the peripheral B-cell pool is only slowly renewed after it has been initially built up early in life.