Graves'disease, a common disorder, has an unusual etiology: the immune system targets one molecule, the thyrotropin receptor (TSHR), autoantibodies mediate disease, and the target organ is stimulated not destroyed. The TSHR is unusual because it undergoes intramolecular cleavage into an A-subunit linked by disulfide bonds to a transmembrane B-subunit. Shed A-subunits drive immunity leading to thyroid stimulating antibodies and hyperthyroidism. Immunization using an adenovirus (Ad) engineered to express the A-subunit is an effective approach to induce thyroid stimulating antibodies and hyperthyroidism in mice. Our goal is to use this Graves'disease model to provide insight into the following important issues: 1. Tolerance to the TSHR. We generated transgenic mice with the human TSHR A-subunit targeted to the thyroid. These mice are unresponsive, or "tolerant", to A-subunit-Ad immunization. Tolerance is a complex process that may involve the Autoimmune Regulator (Aire) protein and/or regulatory T cells (Treg). The role of Aire can be studied in Aire knockout mice;Treg can be depleted by pretreatment with specific antibodies. To investigate tolerance to the TSHR, we will cross our A-subunit transgenics to Aire deficient mice and study the outcome of A-subunit-Ad immunization in untreated or Treg depleted mice. 2. TSHR-associated thyroid inflammation: A-subunit-Ad immunization of some A-subunit transgenics depleted of Treg induces thyroid lymphocytic infiltrates, hypothyroidism and murine thyroglobulin and thyroid peroxidase antibodies. Mice without infiltrates lack these antibodies. Moreover, TSHR autoantibody and T cell epitopes are highly restricted. We will further characterize immune responses to the TSHR and other thyroid autoantigens in mice with thyroid infiltrates. These studies will provide insight into the relationship between thyroiditis, auto antibodies and TSHR T cell epitopes in mice and possibly also into the pathogenesis of human thyroid autoimmunity. 3. Induced tolerance to prevent or treat experimental Graves'disease. Dendritic cells (DC) are potent antigen-presenting cells. In the "mature" state, DC initiate immunity but immature DC induce antigen-specific tolerance. We will target the TSHR A-subunit to these cells using antibodies to a DC-specific marker (DEC205) and test the abilityof these antibody:A-subunit complexes to blunt responses to A-subunit-Ad immunization. These studies will demonstrate the feasibility of antigen-specific immune tolerance and, if successful, could be adapted for use in humans to more intractable aspects of Graves'disease, namely ophthalmopathy and dermopathy.
Graves'hyperthyroidism, a common disease in humans, is caused by an abnormal immune response to a "self" protein in the thyroid gland called the thyrotropin receptor. We will use a mouse model of Graves'disease to provide insight into the factors involved in the breakdown in "self tolerance" to self proteins that lead to the abnormal autoimmune response to the thyrotropin receptor. Moreover, we will test the efficacy of an approach to block autoimmune responses to the thyrotropin receptor in order to prevent or treat Graves'disease, initially in mice and ultimately in humans.
|Rapoport, Basil; McLachlan, Sandra M (2014) Graves' hyperthyroidism is antibody-mediated but is predominantly a Th1-type cytokine disease. J Clin Endocrinol Metab 99:4060-1|
|McLachlan, Sandra M; Rapoport, Basil (2014) Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity. Endocr Rev 35:59-105|
|McLachlan, Sandra M; Hamidi, Sepehr; Aliesky, Holly et al. (2014) Sex, genetics, and the control of thyroxine and thyrotropin in mice. Thyroid 24:1080-7|
|McLachlan, Sandra M (2013) Prescience of a surgeon in 1980. Thyroid 23:773-4|
|McLachlan, Sandra M; Rapoport, Basil (2013) Thyrotropin-blocking autoantibodies and thyroid-stimulating autoantibodies: potential mechanisms involved in the pendulum swinging from hypothyroidism to hyperthyroidism or vice versa. Thyroid 23:14-24|
|Chen, Chun-Rong; Salazar, Larry M; McLachlan, Sandra M et al. (2012) Novel information on the epitope of an inverse agonist monoclonal antibody provides insight into the structure of the TSH receptor. PLoS One 7:e31973|
|McLachlan, Sandra M; Lu, Lu; Aliesky, Holly A et al. (2011) Distinct genetic signatures for variability in total and free serum thyroxine levels in four sets of recombinant inbred mice. Endocrinology 152:1172-9|
|Hamidi, Sepehr; Chen, Chun-Rong; Mizutori-Sasai, Yumiko et al. (2011) Relationship between thyrotropin receptor hinge region proteolytic posttranslational modification and receptor physiological function. Mol Endocrinol 25:184-94|
|McLachlan, Sandra M; Aliesky, Holly A; Chen, Chun-Rong et al. (2011) Exceptional hyperthyroidism and a role for both major histocompatibility class I and class II genes in a murine model of Graves' disease. PLoS One 6:e21378|
|Chen, Chun-Rong; Aliesky, Holly A; Rapoport, Basil et al. (2011) An attempt to induce "Graves' disease of the gonads" by immunizing mice with the luteinizing hormone receptor provides insight into breaking tolerance to self-antigens. Thyroid 21:773-81|
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