In contrast to the chimeric mice with exclusive hematopoietic STAT1 deficiency, we found that donor T cell activation was not increased in the Β6.Stat1+/+→Stat1Poison chimeric recipient mice upon induction of GVHD following retransplantation compared with that observed in the Β6.Stat1+/+→Stat1+/+ chimeric mice (Figure 2C). This evidence concerns the gene STAT1 and graft versus host disease.