CD4 and graft versus host disease: High proportions of Tregs in the graft may also aid immune tolerance, improving immune reconstitution during thymic-independent homeostatic expansion of mature donor T cells and/or thymic-dependent T-cell production.26, 27, 28 In our study, there was a trend towards less aGvHD and fewer deaths because of GvHD (1 vs 9) in patients receiving grafts with higher Treg/CD4+ T-cell ratios, suggesting that that lower incidence of NRM in this group is due, at least in part, to reduced GvHD-related mortality.