UVC-induced cell death of IL-2-dependent human lymphocytes

We compared the in vitro propensity of human IL-2-dependent lymphocytes (young proliferating and senescent non-proliferating), and resting peripheral blood lymphocytes (PBLs) to undergo UVC-induced apoptosis. The activities of AP-1 (activator protein-1), CRE (cAMP response element) and OCT-1 (octamer-1) transcription factors in all lymphocytes were also assessed. At 24 h after UVC treatment, half of young proliferating T lymphocytes and about a quarter of PBLs and senescent non-proliferating cells were apoptotic, as shown by flow cytometry. However, only in young lymphocytes were both typical DNA 'ladder' and Bcl-2 downregulation evident. The AP-1 transcription factor was activated by UVC in IL-2-dependent young and senescent, but not resting lymphocytes. Taken together, the data show different propensities of resting, proliferating and senescent human lymphocytes to undergo UVC-induced apoptosis and AP-1 activation.