Chronologic Study of the T-Virus in Chicks. I. Development of Lesions

Abstract

SUMMARY The development of the lesions associated with the T-virus in chicks was studied by microscopic examination of selected tissues at 24-hour intervals after intraperitoneal injection with macerated infected liver. On day 1 postinjection (PI), the bursa of Fabricius was smaller in the injected chicks than in the uninjected, and lympholysis occurred in the lymphoid follicles of the injected. On day 2 PI, primitive mesenchymal cells (PMC) were proliferating under the capsule of the spleen. On day 3 PI, the first PMC were observed in the liver, kidney, and lungs. On day 4 PI, the bursa contained many PMC, and PMC had obliterated the erythropoietic elements in the bone marrow. By day 5 PI, the normal architecture of the bursa and spleen had been disarranged. By day 6 PI, foci of PMC had so proliferated that they formed small macroscopic white spots on the surface of the liver, spleen, and pancreas. By day 7 PI, about 1/8 of the normal parenchyma of the liver had been replaced with PMC, and PMC were first seen in the thymus. Loss of mature lymphocytes was marked in all tissue as the disease progressed. Terminally, there was a proliferation of primitive mesenchymal cells around the blood vessels and in the centers of the lymphoid follicles. The spleen weighed significantly (P<0.05) more in injected chicks than in uninjected in the terminal stages, though the liver weighed less in injected chicks than in uninjected throughout the infection.