ULBP1 and acute lymphoblastic leukemia: ALL cells escape from NK cell recognition and cytotoxicity by downregulating the ligands of the NK cell-activating receptors (MICA/B, ULBP1, and NEC-2) [119], resist phagocytosis by upregulating the CD47 “do not eat me signal” [105], and avoid a T cell response by triggering selected inhibitory checkpoints (TIM-3, CD200R) [5].