The present invention is directed to synergic or additive therapies comprising the administration of a VISTA antagonist and a PD-1, PD-L1 or POD-L3 antagonist; or the combination of a VISTA agonist and a -1, PD-L1 or POD-L3 agonist which combinations respectively elicit an additive or synergistic effect at promoting T cell immunity or inhibiting T cell immunity, i.e., CD4, CD8 or Th1 immunity. The agonists and antagonists may be in the same or separate compositions and may be administered together or separately administered in either order.