Abstract
Ultrastructure of irradiated lymphocytes in bursa of Fabricius was studied. Twenty four chickens were irradiated by gamma rays at a total dose of irradiation 4.5 Gy and exposure time 12 min 24 s. Histological examination showed occurrence of pyknotic cells in bursa in experimental groups. Electron microscopy of the irradiated bursa revealed typical apoptotic morphology such as chromatin condensation. nuclear fragmentation, formation of apoptotic bodies and phagocytosis of apoptotic cells 6 hour after irradiation. The mitochondria appeared to be morphologically intact in the early stages of cell death. Phagocytosis is supposed to be done by resident macrophages which are mainly located in the medulla of the bursa Fabricii. Although bursa Fabricii like other lymphoid organs has been known to be highly sensitive to irradiation. this work shows high scavenger capability of the mononuclear - phagocyte system in bursa of Fabricii.