Generation of suppressor cells in normal rats by treatment with spirogermanium, a novel heterocyclic anticancer drug.

Daily oral administration of spirogermanium to Lewis rats resulted in the generation of radiation-resistant (2000 Rad) suppressor cells which inhibited the proliferative response of normal spleen cells to an optimum concentration of concanavalin A. These suppressor cells became evident after three to six days of spirogermanium administration. After one day's treatment, although no suppressor cells could be detected, the response of these cells to concanavalin A was less than 50% of controls. Experiments designed to characterize the cell type(s) responsible for this suppression resulted in the finding that T cell-'depleted' populations of spleen cells were more suppressive than T cell-'enriched' populations. The induction of suppressor cells by spirogermanium and the previously described activity in the adjuvant arthritic rat model suggest therapeutic potential for autoimmune diseases.