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Antithymocyte globulin was administered to 33 NZB-NZW F1hybrid mice ranging from 36 to 47 weeks of age at the start of treatment. Thirty-one age matched female controls were studied. The ATG had a deleterious effect on survival, but no marked effect on renal histopathologic changes. The ATG did appear to prevent the development of fibrinoid arteritis. We speculate that the decrease in survival rate in the treated animals was related to an exacerbation of an underlying viral disorder.

The capacity of allosensitized thymus-derived lymphocytes to destroy target cells bearing donor alloantigens is modulated by the cellular levels of cyclic AMP and cyclic GMP. Increases in the cyclic AMP levels of attacking lymphocytes by stimulation with prostaglandin E1, isoproterenol, and cholera toxin inhibit lymphocyte-mediated cytotoxicity; whereas, depletion of cyclic AMP with imidazole enhances cytotoxicity. The augmentation of cytotoxicity produced by cholinergic stimulation with carbamylcholine is not associated with alterations in cyclic AMP levels and is duplicated by 8-bromo-cyclic GMP. The effects of activators of adenylate cyclase, cholinomimetic agents, and 8-bromocyclic GMP are upon the attacking and not the target cells and occur at the time of initial interaction of attacking and target cells. Indeed, the level of cyclic nucleotide (cyclic AMP and cyclic GMP) at the time of initial cell-to-cell interaction determines the extent of cytotoxicity.