Reversal by cyclophosphamide of tolerance in contact sensitization. Tolerance induced by prior feeding with DNCB.

Tolerance to DNCB induced by feeding guinea-pigs with the same hapten has been reversed by a single treatment with cyclophosphamide. This is paralleled by a return of the ability of T cells to proliferate in the draining lymph node following sensitization. Certain quantitative differences between this system and that previously described using intravenous DNBSO3 have been revealed. These may indicate some difference between these two mechanisms of tolerance induction.