The mild and transient acute GVHD was reflected by transient body weight loss and low clinical GVHD score at approximately 7 days after HCT (Figure 1A), but no obvious tissue damage was observed in recipients of STAT3–/– donor T cells at 7 and 100 days after HCT (Figure 1, D and E, and Supplemental Figure 1, B and C). The gene discussed is STAT3; the disease is graft versus host disease.