NK cells have been implicated before in the suppression of GvHD by two mechanisms: either by direct killing of donor T cells, which are activated by alloantigens and may upregulate ligands for NK‐cell receptors DNAM‐1 and NKG2D 16, 17, or by killing host DCs hence inhibiting donor T‐cell proliferation 2. This evidence concerns the gene KLRK1 and graft versus host disease.