The scientific interest in developing anti-galectin-9 mAb is major since this protein participates in various mechanisms of immune escape by tumors: control of T cell survival (212), T cell effector exhaustion and differentiation (82, 201, 213, 214), lymphocyte migration towards the tumor via an endothelial cell reprogramming (45), Treg function (215–220), regulation of antigen presentation (221–223), and myeloid suppressive cells (224). This evidence concerns the gene LGALS9 and neoplasm.