The endocrine system of animals uses hormones to regulate virtually every internal function of their bodies while the immune system defends the body against attack from the outside. Steroid hormones, in particular, are important regulators of growth and reproduction, but some steroid hormones, such as testosterone, depress immune function. In contrast, estrogens generally stimulate immune function. Because females often transfer steroid hormones and immune molecules to their offspring, immune function of offspring may be enhanced or impaired by these maternal contributions. This project will use the egg-laying red-eared slider turtle to test the hypothesis that elevating estrogens during embryonic development is a way that females can manipulate the developing immune system of their offspring. Because female turtles provide no post-laying parental care, they can only manipulate their developing offspring by providing resources, such as estrogens and antibodies, to the egg yolk. Eggs will be exposed to (i) elevated levels of estrogen (17ß-estradiol), (ii) to a chemical that blocks estrogen production, or (iii) to a combination of both 17ß-estradiol and the estrogen-production blocker. It is predicted that if estrogens enhance immune function, animals from 17ß-estradiol treated eggs will have higher immune responsiveness than controls and eggs treated with the estrogen blocker. The hypothesis that adult female turtles treated with estrogen will have improved immune responsiveness compared with controls will also be tested. This research will clarify the potential effects of estrogen exposure during both early development and in the adult. Such information is needed because many environmental contaminants mimic the effects of estrogens. Only by experimentally manipulating estrogen exposure can the effects of estrogen-mimicking environmental contaminants on natural populations of animals be identified. In addition, this project will provide research training to a number of undergraduate and graduate students in both field and laboratory-based methods. .
