At day 6, the CD4/CD8 ratio had changed in the 5 : 1 stimulated samples (non-GVHD 1.02 versus GVHD 3.36; p = 0.052) and PHA stimulated samples (non-GVHD 0.30 versus GVHD 1.33; p = 0.038). Here, CD4 is linked to graft versus host disease.