B-CELL LIFE-SPAN - A REVIEW

Debate has surrounded the subject of B cell life span since it was fir st measured in mice in the early 1970s. In the 25 years which have pas sed since then, it has become increasingly apparent that the methods e mployed to measure rates of B cell turnover, such as [H-3]-thymidine l abelling, cell transfer or cell ablation, brought about significant di sruptions to normal physiology which in themselves might have affected B cell turnover. More recently the use of bromodeoxyuridine has overc ome many of these methodological difficulties and has allowed rates of B cell renewal to be measured within B cell subpopulations defined by multiparameter flow cytometry. Such studies have largely resolved the issue, concluding that about 85% of peripheral B cells are phenotypic ally mature and display first-order exponential kinetics defined by a half-life of 5-6 weeks, whilst the remainder are short-lived with a li fe span of several days. This review examines both traditional and rec ent methods and discusses the influence of age, self-tolerance and ran domnes in the overall shaping of a kinetically stable mature B cell po pulation.