Thymolysis induced by EN3638 and other drugs and its relation to immunosuppression

The effect on the thymus of EN3638, an oxime derivative of salicylic acid, was investigated because the drug has immunosuppressive properties. It caused a moderate reduction in thymic weight of normal adult and weanling rats and it retarded the regeneration of the thymus that follows acute corticosteroid-induced involution. These effects of EN3638 were not mediated by the adrenal nor due to the salicylate part of the molecule. At high dose levels, the drug also reduced slightly the weight of spleen and lymph nodes and the rate of body growth. Thymolytic doses of EN3638 were also immunosuppressive for experimental allergic encephalomyelitis (EAE). At doses that caused equivalent degrees of thymolysis. EN3638 was somewhat more potent for suppression of EAE than cyclophophosphamide or hydrocortisone.