The Fas overexpression on SECs in the GvHD group was further confirmed by RT-PCR: 14 days after transplantation, relative expression of FAS gene in GvHD group was 0.2536±0.021 vs 0.0852±0.013 in the BMT group (n = 3, P<0.001, Figure 6F). Here, FAS is linked to graft versus host disease.