Mer inhibition inhibited endothelial cell apoptosis stimulated by GVHD sera. (A-C) To examine GVHD sera on the apoptosis of ECs, we performed TUNEL staining. ECs were incubated for 24 hours with the sera isolated from patients with or without grade III aGVHD at a level of 0%, 25%, 50%, and 100% (vol/vol) of the total medium, followed by TUNEL staining. Scale bars represent 20 µm. Representative data are from 3 independent experiments. (Ac,Bc,Cc) The statistical analysis indicated the effect of GVHD sera on the EC apoptosis. Results are shown as mean ± SD of statistical analyses from 4 separate experiments. *P < .05; **P < .01. (Da-c) UNC2250 (5 μmol/L) significantly suppressed the EC apoptosis induced by the exposure of sera isolated from patients with grade III aGVHD in ECs at 50% (vol/vol) of the total media. (De) The statistical analysis indicated the effect of exogenous Gas6 or the exposure of sera isolated from patients with grade III aGVHD to ECs on the EC apoptosis. Results are shown as mean ± SD of statistical analyses from 4 separate experiments. *P < .05. (E-F) GVHD sera induced mRNA upregulation of TNF-α and IL-1β, which was inhibited by UNC2250 in ECs. The ECs were incubated for 6 hours with the sera isolated from patients with or without grade III aGVHD at a level of 50% (vol/vol) of the total medium with or without 5 μmol/L UNC2250, followed by real-time PCR. Representative data from 4 similar experiments are shown. Bars are the means ± SD of quantitative densitometric analyses. **P < .01, *P < .05.