TSCM cells, featured by CD45RA+ CD45RO− CD27+ CD28+ CCR7+ CD62L+ CD95+ CD122+ CD127+, were first discovered in mouse models of human graft versus host disease (GVHD) in 2005 and isolated in vitro in 2013 [5, 17–21]. Here, CCR7 is linked to graft versus host disease.