The Effect of Methotrexate on the Production of Antibodies against Attenuated Distemper Virus in the Dog¹

Methotrexate is a potent inhibitor of antibody production in the dog at dose levels that are not in themselves productive of serious toxicity. In the absence of antibody production inoculation with the attenuated virus of distemper vaccine causes a fatal illness. The production of a fatal illness by this usually benign vaccine virus illustrates the heightened hazard of infection in subjects whose immunologic responsiveness is reduced by chemotherapy.