CD8A and neoplasm: However, when human tumor cells release s-MICA into circulation, this not only hinders the recognition of MICA expressing tumors by the immune system, but also leads to a systemic downregulation of NKG2D expression on the surface of γδ T cells and αβ CD8+ T cells, thereby further limiting the anti-tumor activity of these immune cells[12,15,44–46].