Effect of ionizing radiation (6 Gy) on p53 and p21/WAF1 levels in freshly isolated (F) and PHA-stimulated (P) lymphocytes from 2 individuals. Cells were irradiated followed by incubation at 37°C in 5% CO₂ for 2 hours before preparation of extracts. C3 represents extracts from unirradiated C3ABR cells. A total of 20 μg of protein was loaded in each lane of a 12% SDS-PAGE gel. β-actin was used as a loading control.