SENSITIVITY AND SUBSEQUENT DOWN REGULATION OF SENSITIVITY INDUCED BY CHLOROCRESOL IN GUINEA-PIGS

Chlorocresol has a great potential for contact sensitization in the guinea pig maximization test at the Day-21 challenge; 2 wk later, the reactivity was significantly decreased. Cyclophosphamide (250 mg/kg) was injected i.p., and was used as a modulator for the immune response. When cyclophosphamide was administered 3 days before the 1st challenge, the decrease in reactivity from days 21-35 was reversed. This indicates that the reduction in sensitivity was caused by an immunologic mechanism - probably the formation of suppressor cells. This phenomenon is called down regulation of sensitivity, and it may operate in eczema patients who have lost patch-test reactivity.