Enhancement and restoration of contact sensitivity reactions by isoprinosine.

Isoprinosine (50 mg/kg i.p.) increased the ear swelling reaction in mice sensitized with trinitro-chlorobenzene (picryl chloride) and challenged with the same agent. Enhancements were observed when the drug was administered either simultaneously to the sensitization or to the challenge with picryl chloride. Similar results were obtained when lymphoid cells from sensitized animals were transferred i.v. to normal animals which were then challenged with picryl chloride. Using the same cell transfer system, we found that treatment of cell donors with Isoprinosine (50 mg/kg/day, i.p.) counteracts the inhibition induced by cyclophosphamide. Isoprinosine (50 mg/kg/day, i.p.) inhibited also the generation of antigen-specific suppressor cells induced by picryl-sulfonic acid as shown by transfer to normal recipients of suppressor cells together with lymphoid cells from sensitized animals. These results indicate that Isoprinosine enhances normal contact sensitivity reactions and can counteract, under certain circumstances, antigen-specific as well as nonspecific immunosuppression.