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. 2004 Jul 8;23(15):3051–3060. doi: 10.1038/sj.emboj.7600302

Figure 6.

Figure 6

RA and IFNγ synergize to kill leukemic, but not normal, T cells in a paracrine mode of action involving TRAIL. (A) Coculture experiment for paracrine death induction performed as outlined at the top. SK-BR-3 effector cells were cocultured for 72 h with Cell Tracker-labeled Jurkat target cells at a 10:1 ratio in the absence or presence of RA and/or IFNγ. Death induced in target cells was analyzed by PI incorporation and FACS analysis; paracrine killed target cells are gated to the right top quadrants, and the left quadrants gate the Cell Tracker-negative effector cells. Numbers indicate the percentage of PI-positive and -negative target cells. (B) Bar graph showing the percentage of dead Jurkat cells in a representative experiment performed as in (A) with SK-BR-3 effector cells in the absence (gray bars) or presence of RA and INFγ (black bars) and presence of neutralizing receptor–Fc chimeras as shown; similar results were obtained in three independent experiments. Note that only the TRAIL receptor chimera inhibits paracrine death. (C) Leukemia cell-selective paracrine death induction analyzed by coculturing SK-BR-3 effector and either Jurkat leukemia (upper panels) or normal CD4+ T (lower panels) target cells as outlined at the top. The effector cells were treated with RA and INFγ for 48 h before labeled target cells were cocultured for a further 24 h at a two-fold excess of effector cells. FACS data are presented as in (A); only the percentage of paracrine death is given.