Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Poultry Science

Advisor/Mentor

Erf, Gisela

Committee Member/Reader

Alrubaye, Adnan

Committee Member/Second Reader

Orlowski, Sara

Abstract

The Obese strain (OS) of chickens spontaneously develops autoimmune thyroiditis and is a well-established biomedical model for Hashimoto’s thyroiditis in humans. Both conditions are characterized by the infiltration of the thyroid glands with mononuclear cells resulting in destruction of the thyroid tissue and impairment of the thyroid’s endocrinological functions. Past studies have described mononuclear cell infiltration in thyroids of the OS chickens, but the time-course, cell composition, and relative amounts of the various mononuclear cells infiltrating the thyroids has not been well defined. In this project, the mononuclear cell infiltrate was characterized phenotypically and quantitatively in OS chickens over the first six weeks of life using specific markers to identify various mononuclear cell populations. Frozen and stored thyroid glands that were previously collected from OS chickens at 1, 4, 7, 14, 21, 28, 35, and 42 days of age (n = 4 to 5 birds/age) were used in this study. Frozen thyroid sections (8 μm thick) were used in an indirect immunochemical staining procedure to identify macrophages, B cells, T cells, T helper cells, cytotoxic T cells, γδ T cells, and MHC II expressing cells using monoclonal antibodies to chicken KUL-01, Bu-1, CD3, CD4, CD8, γδ T cell receptor, and MHC II cell surface molecules, respectively. Stained sections were evaluated by microscopy at 40x magnification, and the percentage area of the thyroid tissue occupied by various cell types determined. Thyroid infiltration was first observed at 7 days and was near completion in most samples from 3 weeks onwards. Macrophages were the first cells to infiltrate, but T cells dominated the response at later time-points. Early in the response, ratios of T cells to B cells, and T helper to cytotoxic T cells were similar (near 1), but both increased above 2 with advanced infiltration. MHC II expression reached very high levels by 14 days and remained at nearly 100% thereafter, reflecting the intensive inflammatory activity of the autoimmune response. This study provided new insights regarding the participating immune cells and the chronological order of their infiltration into thyroid glands, laying the foundation for further study into mechanisms involved in onset, progression, and autoimmune activities in Hashimoto’s thyroiditis in the OS chicken model.

Keywords

Hashimoto's thyroiditis; Obese strain chicken; mononuclear leukocytes; immunohistochemistry; thyroid infiltration

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