To further investigate the possible association of NKG2D and 2B4 in CIK cells, we used the mouse mastocytoma cell line (P815), which expresses the Fc receptor on the surface that can easily recognize and bind the respective antibodies, e.g., anti-NKG2D, anti-2B4, in our experimental setup. This evidence concerns the gene KLRK1 and mastocytoma.