Abstract:

This experiment was conducted to study the age-related changes in the lymphocyte proliferation and apoptosis during the embryonic and post embryonic development of the Tianfu duck thymus.Sixty five Tianfu ducks were divided into 13 groups as follows: 22，24 and 26 days embryonic stage，and 0 （neonatal stage)，3，5，8，14，17，20，26，29 and 32 weeks after hatching.Proliferating cell nuclear antigen (PCNA) and Caspase-3 immunohistochemisty and light，electron microscopy techniques were used in this study.The results showed that PCNA and Caspase-3 positive lymphocytes were distributed in the thymus.The proliferative rates of thymic lymphocytes in the cortex and medulla decreased significantly from 2226 days embryonic stage，and kept stable from 03，817 and 2632 weeks after hatching，but markedly decreased on 5，8，20 and 26 weeks after hatching.In the same age group，the proliferative rate of lymphocyte in the cortex was higher than that in the medulla.The apoptosis rates of thymic lymphocytes in the cortex and medulla kept unchanged from 22-26 days embryonic stage，then increased from 0-8 weeks after hatching，and kept stable from 8-17 weeks，but rose continually from 20-32 weeks.In the same age group，the apoptosis rate of lymphocytes in the cortex was higher than that in the medulla.The nuclei of apoptotic lymphocytes with swollen mitochondria and broken cristae mitochondriales presented different features.The apoptotic bodies were phagocytized by the macrophages.The proliferation and apoptosis of lymphocytes exist universally during the normal embryonic and post embryonic development of the Tianfu duck thymus which undergoes obvious agerelated changes，and then supervises and controls the development and regression of this organ cooperatively.