Abstract: In order to study the expression of Bcl-2 and Bax mRNA and their proteins during the embryonic and post embryonic development of Tianfu duck thymus， 65 Tianfu ducks were divided into 3 groups as follows: 22， 24 and 26 days at embryonic stage， and 0 （neonatal stage）， 3， 5， 8， 14， 17， 20， 26， 29 and 32 weeks after hatching. Immunohistochemisty and in situ hybridization techniques were used in this study. The results showed that Bcl-2 and Bax mRNA and their proteins were distributed in the thymic lymphocytes and epithelial cells. The BCL-2 positive ratios of lymphocytes in the thymic cortex and medulla were not changed from 22 days at embryonic stage to 17 weeks after hatching， but were decreased from 20 to 32 weeks after hatching. The BAX positive ratios of lymphocytes in the thymic cortex and medulla were kept unchanged from 20 to 26 days at embryonic stage and from 8 to 17 weeks after hatching， but were increased from 0 to 8 weeks and from 20 to 32 weeks after hatching. The BCL-2/BAX values of lymphocytes in the thymic cortex and medulla were not changed from 22 to 26 days at embryonic stage and from 8 to 17 weeks after hatching， but were decreased from 0 to 8 weeks and from 20 to 32 weeks after hatching. The change patterns of Bcl-2 mRNA and Bax mRNA positive ratios of lymphocytes in the thymic cortex and medulla were similar to their protein positive ratios， respectively. In each group， the BCL-2 protein， Bcl-2 mRNA positive ratios and BCL-2/BAX value of lymphocytes in the follicle cortex were significantly lower than those in the medulla， while the BAX protein and Bax mRNA positive ratios of lymphocytes in the follicle cortex were significantly higher than those in the medulla， respectively. This study indicated that Bcl-2， Bax genes and their proteins are important modulators for the lymphocyte apoptosis of Tianfu duck thymus.

Key words: duck；thymus；Bcl\, 2；Bax；immunohistochemisty；in situ hybridization