Similar to the observation in the tumour model (Supplementary Fig. 5i,j), effector memory CTLs were the major population and had the highest expression of perforin and granzyme B in the target tissues of the GVHD model (Supplementary Fig. 6g,h), indicating their roles in GVHD pathogenesis. The gene discussed is GZMB; the disease is graft versus host disease.