CD8A and graft versus host disease: Moreover, this same study, which as discussed above demonstrated that human CD8+ T cells alone could not engraft NOG mice, revealed that the transgenic expression of human IL-2 could support CD8+ T cell engraftment and GVHD development, with the authors suggesting that IL-2 from CD4+ T cells facilitates CD8+ T cell engraftment in this model following injection of hPBMCs.