The effect of cyclophosphamide on the allergic contact reaction in guinea pig: dose effects and influence on peripheral blood.

Single intraperitoneal injections of cyclophosphamide were administered 6 days before testing guinea pigs sensitized to oxazolone in order to study the effects on inflammatory cell populations in blood and dermis. Skin tests were assessed macroscopically (erythema and oedema) and microscopically (counting of the dermal inflammatory cell infiltrate). At the highest dose (300 mg/kg) the allergic contact reaction was augmented with increases in erythema and oedema and the mononuclear dermal infiltrate. At the lowest dose (75 mg/kg), redness and oedema and all components of the dermal inflammatory cell infiltrate decreased. Total and differential white blood counts up to 20 days after administration of cyclophosphamide showed that a dose-dependent leukopenia maximal around 6 days occurred. During the leukopenia the differential count showed a lymphocytosis with a marked granulocyte depletion. The augmentation of the contact allergic reaction produced at the highest dose of cyclophosphamide occurs despite a marked peripheral blood leukopenia. Cyclophosphamide's effects at the lower dose would appear to be of a non-specific anti-inflammatory nature.