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High frequency of thymic ectopy in thyroids from autoimmune prone nonobese diabetic female mice
M C Many1, H A Drexhage, J F Denef
1Laboratory of Histology, Louvain Medical School, Brussels, Belgium.
Background:
The female nonobese diabetic (NOD) mouse, a well known experimental model to study autoimmune type 1 diabetes, also spontaneously develops thyroiditis. In this study, we report an abnormally high frequency of thymic ectopy in thyroids from NOD mice.
Experimental Design:
Thyroids and thymuses from NOD mice and from control mice of different strains were processed for light and electron microscopy and for immunohistochemistry.
Results:
Ectopic thymic tissue was observed in the thyroids of 80% of female NOD mice, whereas it was not found in control age-paired female mice from various other strains. The thymic tissue was present beneath the capsule as a large and unique fragment consisting of both a cortical dark one and a medullary light region. Thymic ectopies, as the thymus itself, contained thymocytes expressing both L3T4 and Lyt2 antigens, specific respectively for T helper and T suppressor/cytotoxic cells. Cortical and medullary epithelial cells were also easily identified by electron microscopy and by immunohistochemical staining using ER-TR4 and ER-TR5 monoclonal antibodies.
Conclusions:
Our observation could be an indication for a relation between abnormal thymus development and autoimmune disorder such as thyroiditis.