Ly49G2 receptor blockade reduces tumor burden in a leukemia model but not in a solid tumor model.

Background :
NK cell activity is regulated in part by inhibitory receptors that bind to MHC class I molecules. This is possible to enhance NK cell cytotoxicity against tumor cells by preventing the interaction of these inhibitory receptors with their MHC class I ligands.
Results :
In this study, we determinend that Ly49G2 is an inhibitory receptor in AKR mice for self-MHC class I, and AKR Ly49G2 has an identical sequence to BALB/c Ly49G2. Blockade of Ly49G2 receptors in vivo resulted in decreased growth of BW-Sp3 lymphoma cells when the tumor cells were given i.v. but not when the tumor cells were inoculated into the flank forming a solid tumor. However, NK cells were involved in inhibiting the growth of BW-Sp3 tumor cells in the flank.
Conclusion :
These data demonstrate that the effectiveness of inhibitory receptor blockade depends upon the tissue location of the tumor cells.