CD8A and graft versus host disease: In addition to the recent discovery of the TCF1+ CD8+ T cell subset in the models of GvHD and Graft-versus-leukemia (GvL)44,45, Harris et al. demonstrated that the loss of TCF1 in donor CD8+ T cells reduced the severity and persistence of GvHD symptoms in the MHC-mismatched GvHD model46.