Determination of apoptosis levels in reduced serum conditions. The percentage viability of EBV and H. pan BHRF1 Ramos-BL transfectants compared to vector controls in medium containing A) 10% serum or B) 0.1% serum over a 4 day period. The % viability was determined daily by acridine orange fluorescence. The data plotted are the means three experiments carried out in triplicate ± standard error. Statistical analysis was performed using ANOVA and Tukey's pairwise comparison on data normalised by arcsine transformation.