In addition to this apparent DC-mediated mechanism of GVHD protection, other non-APC mechanisms are likely operative for the Tregs that we studied, because transplant cohorts that received Tregs had more robust protection against xenogeneic GVHD than recipients of Treg-conditioned DC (lowest CD4+ and CD8+ T cell engraftment, lowest posttransplant IFN-γ secretion, and lowest degree of weight loss posttransplant). This evidence concerns the gene CD4 and graft versus host disease.