Site-dependent effects of experimental hypo- and hyperthyroidism on resident macrophages in extraocular muscles of rats: a quantitative immunohistochemical study

Abstract

It has been suggested that the effects of dysthyroidism on resident immunocompetent cells of the extraocular muscles may play a role in the pathogenesis of Graves' ophthalmopathy. The distribution of such cells was therefore studied in extraocular muscles of rats that were made hyper- or hypothyroid by the oral administration of thyroxine or propylthiouracil respectively. Skeletal muscles were studied for comparison. The cell distributions were analysed in cryostat cross-sections subjected to a two-step immunoperoxidase method using well-characterized monoclonal antibodies against T cells, B cells, macrophages and MHC class II antigens. The extraocular muscles of control (euthyroid) rats contained numerous macrophages, fewer MHC-II positive cells and T cells and no B cells. Differences in the distribution of immunocompetent cells were found in control rats, between skeletal and extraocular muscles as well as within the various recti eye muscles. This particular tissue distribution resembles that previously reported for human extraocular and skeletal muscles. Quantitative analysis showed that experimental dysthyroidism only affected cell populations in the extraocular muscles. Significant effects on the number of macrophages were observed in the inferior rectus muscle of both hypo- and hyperthyroid rats, this was most pronounced in the orbital layer of the muscles. Both hyper- and hypothyroidism appear to affect local cell distributions in a tissue-specific manner. The presently observed site-dependent effects of dysthyroidism on local immunocompetent cell populations may have relevance for the differential involvement of muscular tissues in Graves' ophthalmopathy.

Macrophages and dendritic cells in normal and regenerating murine skeletal muscle

“…40 The use of one specific hindlimb muscle, the tibialis anterior, throughout the present study is unlikely to have biased results, as a recent investigation has shown that macrophage numbers were similar in both slow twitch (soleus) and fast twitch (extensor digitorum longus) muscle. 41 Presence of DC in Skeletal Muscle. The demonstration in the present study of irregularly shaped MHC class II + cells in the connective tissue of normal skeletal muscle is strong evidence that these cells are DC according to the generally accepted standards of immunomorphological criteria.…”

Evaluation of Immunological Mechanisms Mediating Thyroid-Associated Ophthalmopathy by Radionuclide Imaging Using the Somatostatin Analog111In-Octreotide

“…Radiochemical purity, i.e., the proportion of free radionuclide, was evaluated by thin layer chroma tography (12). [15][16][17][18][19]. Note the lack of tracer activity in the neck vessels (carotid, jugular veins), as well as in neck muscles.…”

“…The mechanisms leading to tracer uptake might depend on the primary state of hyperthyroidism. On experimental grounds it has been shown that a hyperthyroid state can induce an increased accumulation of immunocompetent cells along the retrobulbar muscle bundles (17). As a consequence, activated lymphocytes would have the ability to bind octreotide.…”