Fig. 2.

NK cells eliminate partially reprogrammed cells in vitro. (A) i4F MEFs were reprogrammed in vitro with doxycycline (Dox; 1 μg/ml) for 11 days. From days 2 to 6, primed NK cells were added to the medium and cells were then co-cultured for 5 days in co-culture medium. On day 11, iPSC colonies were scored by AP staining. (B,C) Quantification (B) and representative images (C) of NK cells co-cultured with i4F MEFs with or without doxycycline at E:T (NK:MEF) ratios of 0.5:1, 2.3:1 and 4.5:1. Data pooled from two independent experiments. (D) Delta mean fluorescent intensity (ΔMFI) of the total H60, MULT1, ICAM1, RAE1 and CD155 expression in i4F MEFs reprogrammed with doxycycline (1 μg/ml) at different time points (n=3). (E) Co-culture experiment in which primed NK cells were seeded in Transwells (TW) at an NK:MEF ratio of 1:1 to avoid cell–cell contact (n=3). (F) Co-culture experiment using ConA to disrupt the function of lytic granules secreted by NK cells at an NK:MEF ratio of 1:1 (n=4). (G) Co-culture experiment using the blocking antibody anti-NKG2D, which was added to the medium on days 2 and 4 of reprogramming (n=4). All data are mean±s.d.; *P<0.05, **P<0.001, ***P<0.001, ****P<0.0001 evaluated using the unpaired two-tailed Student's t-test (B,E-G) or one-way ANOVA (D). ns, not significant.