Immunologic Studies of Poisonous Anacardiaceae: Ⅰ.Production of Tolerance and Desensitization to Poison Ivy and Oak Urushiols Using Esterifed Urush-iol Derivatives in Guinea Pigs

The development of contact sensitivity to poison ivy urushiol in Hartley guinea pigs was inhibited by i.v.injection of the diacetate esters of poison ivy and oak urushiols into guinea pigs 2 weeks prior to attempted sensitization with homolongous antigen. Immune tolerance to urushiols of poison ivy and oak developed in 80% or more of the treated animals and persisted for the duration of the study, 8 weeks. The tolerance was immunologically specific for urushiols since the tolerant animals were sensitizable to the umrelated sensitizer 2.4-dinitrochlorobenzene.Guinea pigs already sensitive to urushiol were also desensitized or hyposensitizied by i.v.injection of urushiol acetates in increasing doses. After receiving the equivalent of 16 mg of poison ivy and oak urushiols in the acetate from over a period of 12 weeks, 54% of a group of guinea pigs were desensitized to poison ivy. All of the remaining 46% of the guinea pigs still sensitive to poison ivy were substantially hyposensitized (no longer responded to 1.5 or 0.80 μg test doses of PDC). A control group of guinea pigs was not hyposensitized by injections of vehicle, and remained highly sensiteive throughout the 15 week study. The majority of treated animals (>80%) were also hyposensitized to poison sumac and cashew nut shell liquid allergens.