Date of Award

6-2007

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Judith Shillcock

Committee Member

Sandra Adams

Committee Member

Bonnie Lustigman

Abstract

Experimental Autoimmune Thyroiditis (EAT) could not be induced in young, immature Sprague-Dawley rats (150-200g). EAT was successfully induced in the same group of animals when they weighed 400g. The animals developed the disease every time. Sexual immaturity or immaturity of the immune system may be responsible for these results (Fernandez, 2006). It has been proven that pharmacologic doses of testosterone have shown immunosuppressive effects on the severity of EAT in the PVG/c strain of rats (Ahmed et al, 1982). In this current thesis research, it appears that normal physiologic levels of testosterone have no effect on the development and severity of EAT in Sprague-Dawley rats. At 150-200g., Sprague-Dawley rats were castrated or sham-operated and at 400g. the animals were injected with a bovine thyroglobulin (5.5mgBTg/ per 100g body weight) emulsified in Complete Freud’s Adjuvant (CFA), and saline. Animals were sacrificed two weeks after the second injection and the thyroids were examined using the SEM. All of the animals, both sham-operated and castrated, showed moderate destruction of the thyroid tissue. Destruction of the thyroid follicles, reduction in the number of follicles, and the replacement of normal thyroid follicular tissue with non-functional connective tissue was observed in both castrated and sham-operated animals. However there was one exception, one castrated animal displayed both normal and diseased tissue. There are two possible explanations for these results, first, this may indicate that EAT is a progressive disease. Secondly, because the animals are outbred, this particular animal may have had a slower response to the foreign thyroglobulin. Yu et al (2001) reported that during cellular-mediated responses, CD-4 and CD-8 cells were the first cells to infiltrate the area, and then produced interleukins and cytokines to activate B-cells and macrophages. Sexual maturity plays no role in the induction and severity of EAT in Sprague-Dawley rats, which means that the state of immune system must be the reason why the young, immature animals did not develop the disease.

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