Enhancement of the delayed-type hypersensitivity reaction by oxazaphosphorines.

Delayed hypersensitivity reactions include tuberculin type, Jones Mote type reactions and contact sensitivity. These reactions are increased in guinea pigs and other species by pretreating the animals with a single dose of up to 300 mg/kg cyclophosphamide (CY). CY also reverses immunological tolerance and other forms of immunological unresponsiveness, including antigenic competition. Regulation of these hypersensitivity responses may be controlled by CY-sensitive B- or T-suppressor cells, depending on the species and the model. CY does not appear to act by increasing IL-2 production in the same way as other anti-cancer agents.