DNT (Double-Negative T) cells are a subpopulation of CD3 positive and CD4/CD8 negative T-cells normally present in human peripheral blood, accounting for 1-10％ of all T cells. DNT cells express CD3 molecules and αβ- or γδ- T cell receptors (TCR) on their surfaces, but not CD4 or CD8 molecules. They do not bind invariant Natural Killer T (iNKT) cell-specific αGalCer-loaded CD1d tetramers, and thus are different from conventional T cells, NK cells, and NKT cells. DNT cells highly express cell surface receptors such as NKG2D and DNAM-1, and specifically recognize target cells expressing the corresponding ligands in an MHC-unrestricted manner. They kill target cells by secreting a variety of cytotoxic molecules and cytokines, but do not cause graft-versus-host disease (GvHD) and host-versus-graft response (HvGR).