Figure 1: The effect of co-culture on cellular viability. Thymocytes were cocultured with either TEC or OP9-DL1 cells at a ratio of 1:25 or cultured alone as a control for 96 hours. A) Viability of the thymocytes was assessed by trypan blue exclusion every 24 hours. Thymocytes cultured alone resulted in the largest decrease in cell viability over time, whereas in co-culture with OP9- DL1 cells thymocyte viability over 96 hours in culture was maintained. n=4, *p≤ 0.0001 and **p=0.001 by analysis of variance and p< 0.05 by Dunnett’s simultaneous test versus time 0. B) Representative flow histograms where 10,000 events were acquired and apoptosis of the cells was determined by annexin V/PI staining. C) There was a significantly lower spontaneous apoptosis in OP9-DL1 cocultures when compared to TEC co-cultures (n=4, p=0.009 by paired student T-test).