Abstract
The aim of this work was to investigate the apoptosis in normal lymphoid organs of adult chickens and ducks; samples of thymus, spleen and bursa of Fabricius were collected and processed from normal histological techniques as well as immunohistochemistry. Studies were carried out on chickens and ducks of 32 old days. Results showed that The thymus of both chickens and ducks had a few immunopositive cells labeled for caspase-3 and by the Terminal deoxynucleotidyltransferase mediated dUTP Nick End Labeling assay (TUNEL assay) expressed few signals for apoptosis at the corticomedullary junction. However, the spleen expressed numerous apoptotic cells in the peri-ellipsoidal lymphoid sheath, peri-ellipsoidal white pulp and intensive labeling of apoptotic cells in periarteriolar lymphoid sheath and in macrophages in the red pulp. Bursa of chickens, there was apparently normal lymphoid follicle. A few immunopositive cells for caspase-3 were observed in interfollicular epithelium (IFE). TUNEL-positive follicular lymphocytes containing free apoptotic bodies or nuclei with condensed chromatin along with apoptotic bodies in the cytoplasm of macrophages in the follicular cortex and medulla were identified However, the bursa of duck numerous apoptotic bodies in cells of medulla and cells of follicle-associated epithelium FAE. Therefore, we measured the normal distribution and apoptotic cells in the bursa of Fabricius from chickens and ducks order to acquire information for correctly evaluating apoptosis patterns associated with immunopathogenesis in chickens and ducks.

Key words: Apoptosis, caspse-3, bursa, thymus, spleen, TUNEL assay