A pharmaceutically acceptable agent able to acidify the cell cytoplasm, for the manufacture of a pharmaceutical composition useful for causing immunosuppression in a person or animal, where an effective amount of the agent is administered in an essentially non-dissociated form to the person or animal, and where the agent is admixed with a carrier to adjust the pH of the composition to the pH range 6.1 to 7.0. A pharmaceutical composition is also disclosed.
