Specific acquired immune unresponsiveness to contact allergens with cyclophosphamide in the mouse

Treatment with cyclophosphamide (Cy) can modulate the acquisition of allergic contact dermatitis in the mouse. We compared the effect of a single dose of Cy given at different times before or after allergen. Cy one or more days prior to allergen intensified, and Cy several days after allergen inhibited the acquisition of sensitivity. Mice whose immunological response to an allergen had been suppressed by Cy were specifically immunologically tolerant to that allergen, but not to an unrelated allergen. This tolerance probably represents a combination of clone deletion and inhibition; almost certainly it does not depend on the generation of enhancing ('blocking') antibody.