The ability of VISTA to modulate the functions of cells of the lymphoid and myeloid lineage and the expression of VISTA/PSGL-1/VSIG3/galectin-9 molecules in a wide range of cells of the tumor microenvironment, as well as data on the presence of specific modulations to the immune response with the participation of VISTA in the context of the selective role of pH, expands the possibilities of finding and developing effective immunotherapeutic drugs. The gene discussed is LGALS9; the disease is neoplasm.