Immunological properties of cephalexin-induced delayed type hypersensitivity reaction in guinea pigs

Immunological properties of delayed-type hypersensitivity (DTH) reaction induced by cephalexin (CEX) in guinea pigs were investigated. The animals were immunized with CEX using Freund's complete adjuvant. The time course of CEX-induced erythema showed some differences compared with that of classical DTH reaction. The erythema appeared at 6 h after intradermal administration of CEX, reached maximum size at 12 to 24 h and to be visible until 72 h. By enzyme-linked immunosorbent assay, anti-CEX antibody was detected in only one of 15 animals tested. Normal animals (recipients) which had received immune sera from CEX-sensitized animals (donors) showed no skin reaction to CEX. In contrast, reaction to CEX was observed in recipient animals which had received a local transfer of lymphocytes or T cells from CEX sensitized animals. In immunopharmacological study, cyclosporin A suppressed the skin reaction but cyclophosphamide did not. Administration of carrageenan, an inhibitor of macrophage function, had no effect on expression of the reaction. Post administration (1 or 15 h) of clemastine, an anti-histamine drug, did not affect the reaction. By histological examination, the infiltrating cell-types at the reaction site were mainly composed of mononuclear cells and neutrophils, but no basophils, indicating that CEX-induced DTH reaction is tuberculin-type DTH and not a cutaneous basophil hypersensitivity reaction.