Evaluation of niridazole as a suppressant of cellular immunity in chickens.

Niridazole was administered by gavage to 5-week-old chickens at dosage levels of 50, 100, and 200 mg/kg of body weight. The 2 larger dosage levels were toxic and resulted in the death of many of the recipients. The 50 mg/kg dosage level was not lethal, but depressed weight gain. Cellular immune functions were measured by responses of lymphocytes in whole blood to T-cell mitogens and by delayed hypersensitivity reactions to tuberculin. Blastogenic responses to phytohemagglutinin and concanavalin A were reduced in niridazole-treated chickens with responses of controls. Wattle tests measuring delayed hypersensitivity were positive only in control chickens; reactions in niridazole-treated chickens did not differ from nonimmunized controls.