It engages both Galectin-9 [398] at acidic pH values PSGL-1 (P-selectin glycoprotein ligand-1) [399], which is broadly expressed by leukocytes [400,401,402,403,404] and tumor cells [405], and VSGI3 (V-Set and Immunoglobulin domain containing 3) [406], which is restricted to some non-immune cell types [407,408]. The gene discussed is SELPLG; the disease is neoplasm.