Effects of estradiol on the development of the bursa of Fabricius in Japanese quail.

ABSTRACT

Effects of androgens on the development of the bursa of Fabricius are better understood than those of estradiol, despite the known sensitivity of the bursa to estradiol early in embryogenesis. The goal of this study was to determine the effects of one-time yolk injections of estradiol at day 4 of incubation on the development of the bursa and spleen as indices of treatment effects on the immune system. Follicle size and numbers in hatchling bursas were significantly reduced at 50 and 500 microg/egg, respectively. Additionally, distorted plicae and thicker epithelial layers surrounding the plicae were observed in day-old chicks at the same treatment levels. Adult bursas from birds embryonically exposed to estrogen were significantly larger than controls, suggesting an inhibition of natural bursal regression. Although estradiol altered the development of the bursa, the spleen appeared to be unaffected. The observed effects of estradiol on the development of the bursa indicate that this lymphoid organ may be a target for developmental disruption by estrogenic endocrine disrupting chemicals, though long-term consequences of embryonic exposure on immune function remain unknown.