Studies of new short‐period method for delayed contact hypersensitivity assay in the guinea pig

Abstract

The enhancement effect of cyclophosphamide on the delayed contact hypersensitivity reaction of chemical compounds was studied in Hartley albino guinea pigs. A series of assay procedures, combining the AP2 test (adjuvant and 24-h occlusive patch 2x test, as previously reported) with intraperitoneal cyclophosphamide administration, were examined. The newly developed method was as follows; cyclophosphamide 200 mg/kg intraperitoneal administration 3 days before the 1st sensitization of the AP2 test (cyclophosphamide, adjuvant and 24-h occlusive patch 2x test: CAP2 test). Comparing the CAP2 test with the AP2 test, the cumulative contact enhancement test (CCET) and the guinea pig maximization test (GPMT), the CAP2 test equally and/or better enabled the detection of allergenicities not only of strong allergens such as bromostyrol, citronellal, p-phenylenediamine and formaldehyde, but also of weak allergens such as benzyl salicylate and p-aminobenzoic acid ethyl ester. Acanthosis and spongiosis in the epidermis and mononuclear cell infiltration into the dermis at the skin reaction site were histopathologically observed. Cyclophosphamide effectively enhanced the delayed contact hypersensitivity reaction of weak allergens.