Using a CD4+-dependent, MHC-matched, minor histocompatibility (H) antigen–mismatched chronic GVHD model, they asked whether effector memory CD62L−CD44+CD4+ T cells were more or less likely to induce GVHD than were unfractionated or naïve CD62L+CD44−CD4+ T cells. Here, CD4 is linked to graft versus host disease.