Age-Related Decrease in Mouse T Cell Progenitors

Abstract

Mice were given a lethal dose of whole-body γ-radiation and injected with 105 or 106 marrow cells from 10- to 143-week-old syngeneic donors. Nine days later, colony-forming units (CFU) were counted in the spleens of mice given 105 cells, and 15 to 21 days after irradiation thymus weights and in some experiments 3H-thymidine uptake or total thymic cellularity were determined in the recipients of 106 cells. It was found that in the majority of mouse strains studied there were no significant changes with age in marrow CFU. In contrast, thymic regeneration was significantly impaired when the recipients received marrow cells from donors 100 weeks of age or older. These observations and results obtained in dose-response and time-course studies are best explained by an age-related decrease in marrow T cell progenitors; however, certain findings suggest that in addition the proliferative capacity of these stem cells may at times be moderately impaired.