Recombination of Gata1 in vitro affects DC survival. (A) Cell culture efficiency upon tamoxifen (OHT) treatment. Average efficiency (± SEM) from at least 3 independent experiments is plotted. Efficiency is calculated as the ratio between the number of viable cells of treated and nontreated cultures multiplied by 100. The P values are derived from Mann-Whitney statistical analysis of independent samples. (B) mDCs and pDCs were sorted from Flt3-L cultures at day 7 and treated with OHT. Viability was determined by MTT test 2, 3, and 4 days after treatment initiation and calculated as the percentage of the viability of untreated controls. Values are average (± SEM) of 3 independent samples. (C) Analysis of apoptosis in pDCs, mDCs, and non-DCs sorted from the spleen (Figure 1G) and treated ex vivo with OHT for 48 hours. As a positive control for apoptosis, Flt3-L–derived DCs were exposed 24 hours to 1 μM dexamethasone (Flt3-L DCs + Dex). Dot plots are merged from 3 independent experiments; percentages correspond to the average (± SEM). The P values are derived from 2-tailed t tests.