Induction of experimental allergic encephalomyelitis and tumor occurrence in rats treated with 4-dimethylaminoazobenzene and 3,4-benzpyrene.

Antagonisms between 2 simultaneously developing processes were studied by inducing experimental allergic encephalomyelitis in rats bearing liver tumors produced by feeding 4-dimethylaminobenzene (4-DAB) or in nontumorous rats which either received the 4-DAB tumorigenic diet or were treated with a tumorigenic dose of 3,4-benzpyrene. It was shown that tumorous and pretumorous rats were less susceptible to sensitization with the encephalitogenic vaccine. The occurrence of 4-DAB liver tumors was lower if the en cephalitogenic vaccine was injected within about 1 month after the end of the azo dye feeding. The results are discussed in view of the assumption that processes similar to the competition of antigens may be the cause of described antagonisms.