Effect of thymectomy, thymectomy and x irradiation, and x irradiation alone on experimentally induced tuberculosis in the chicken

SUMMARY White Leghorn chickens which were thymectomized (Tx), thymectomized x-irradiated (Tx-X), x-irradiated (X), and nontreated (control) were inoculated at 10 weeks of age with a viable culture of Mycobacterium avium . Ten weeks later, tuberculin reactions were evident in almost all of the exposed chickens 48 hours after tuberculin was injected. Although individual chickens reacted with different intensity, detectable difference did not exist among groups. Indirect evidence indicated that the reactions were, in part, due to an Arthus reaction. In thymectomized and thymectomized x-irradiated chickens, there was varying lymphocytic depletion from the spleen. All groups of chickens inoculated with M. avium had granulomas in the liver, spleen, ileocecal junction, thymus, and lung. Although there was no essential difference in the cellular composition of these lesions, caseation necrosis was less prominent and caseous lesions were fewer in the hepatic sections of thymectomized and thymectomized x-irradiated chickens; the lesions at the sites of inoculation were smaller in size. The results provided evidence that thymectomy significantly reduced tissue necrosis in tuberculous granulomas.