AGE-RELATED EVENTS IN ACTIVE T-LYMPHOCYTE SUBPOPULATION - A MORPHOLOGICAL-STUDY

The incorporation of 5-bromo-2'-deoxyuridine (BrdU) into the DNA of ac tive T lymphocytes from healthy aged donors was evaluated after in vit ro PHA stimulation by means of light microscopy, electron microscopy a nd flow cytometry. The percentage of BrdU-labelled cells differed mark edly between aged and young donors after 48 h of PHA stimulation, due to an enlarged early S phase compartment. In contrast, after 72 h the percentage of positive cells was quite similar in both age groups and no significant differences in the distribution within S phase nor chan ges in the patterns of ultrastructural localization of DNA replicon si tes were observed. Our study provides evidence that an altered synchro nization and a substantial delay in the in vitro cell proliferation oc cur in this peculiar T subpopulation as a consequence of the ageing pr ocess.