Antigen-induced cyclophosphamide-resistant suppressor T cells inhibit the in vitro generation of cytotoxic cells from one-way mixed leukocyte reactions.

Mice sensitized against a tumor allograft and given cyclophosmamide 6 days later failed to generate an immune response to the allograft. Spleen cells derived from these mice suppressed the generation of cytotoxic T cell response by normal spleen cells in mixed leukocyte cultures. The suppressor cells were not specific, thymus dependent, and resistant to 2000 R.