KLRD1 and neoplasm: Key molecules for tumor immunosurveillance as identified in knockout mouse models comprise interferon-γ (IFNγ) (12), IL-12 (13) perforin (14, 15), TRAIL (tumor necrosis factor related apoptosis-inducing ligand) (16–19), and its corresponding apoptosis-inducing receptors DR4 and DR5 (20), the recombination activating genes RAG1 (21), and RAG2 (12), which are required for T cell development, the T cell receptor (22), and the activating NK cell receptor NKG2D (23).