Specific suppressor cells have been demonstrated in mice tolerant to the thymus-dependent antigen HGG. Transfer of normal thymocytes, normal spleen cells, or immune spleen cells into these tolerant mice did not restore immunocompetence to HGG. Furthermore, the transfer of tolerant spleen cells into normal recipients abrogated the response of these recipients to subsequent challenge with immunogenic HGG. Spleen cells removed from mice 5, 8, or 11 wk after the induction of tolerance specifically suppressed the response of normal spleen cells in an adoptive cell transfer system. The extent of suppression appears to be dependent upon how long after the induction of tolerance the cells were removed from the tolerant donors and how soon after transfer the recipients were challenged.

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