KLRK1 and leukemia: Leukemia cells that express MICA are lysed in vitro by NK cells via NKG2D engagement with the sera of patients, but not of healthy donors as the latter contain elevated levels of seric soluble MICA (sMICA), which impairs NKG2D-mediated immune surveillance of leukemia by triggering internalization of surface NKG2D [39].