Figure 3

IL-2 dependence of the immortalized T-cell population and growth advantage of the immortalized T-cell clone over freshly stimulated T cells. (A) Immortalized T cells were cultured in the presence of different IL-2 concentrations (from left: 400 U/mL, 100 U/mL, 50 U/mL and 0 U/mL). After 2 d of culture, cells were stained for the apoptosis marker Annexin V. With declining IL-2 concentrations, the percentage of Annexin V expressing cells increased. (B) Competition experiment to analyze the growth behavior of the immortalized cell population. Primary, freshly stimulated T cells were chosen as a competitor population and set to 90% in the mixed culture, the remaining 10% were immortalized, EGFP-expressing cells (d 0). In total four independent experiments were performed, which are shown in overlay of the individual histogram blots on the day of measurement (d 2, 6 and 8). The immortalized T cells eventually overgrew the competitor cells on d 8 of culture.