PDCD1 and graft versus host disease: In the mice that received the anti-PD-1 + anti-CTLA-4 combination significantly reduced survival was noted compared to the control group, and when compared to the anti-PD-1 or anti-CTLA-4 single agent groups (Figure 2A), with some animals terminated as soon as 11 days after the start of treatment due to the onset of Grade 3 adverse signs, including moderate rough coats and hunching, in addition to weight loss (Supplementary Figure 4), and just 6 out of 20 mice (30%) surviving until the end of the study with mild (Grade 0-1) or moderate (Grade 2) symptoms of GvHD.