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 (2016) TSH Receptor Cleavage Into Subunits and Shedding of the A-Subunit; A Molecular and Clinical Perspective. Endocr Rev 37:114-34|
|Rapoport, Basil; Banuelos, Bianca; Aliesky, Holly A et al. (2016) Critical Differences between Induced and Spontaneous Mouse Models of Graves' Disease with Implications for Antigen-Specific Immunotherapy in Humans. J Immunol 197:4560-4568|
|Rapoport, Basil; Aliesky, Holly A; Banuelos, Bianca et al. (2015) A unique mouse strain that develops spontaneous, iodine-accelerated, pathogenic antibodies to the human thyrotrophin receptor. J Immunol 194:4154-61|
|Pelletier, A-N; Aliesky, H A; Banuelos, B et al. (2015) Evidence that MHC I-E dampens thyroid autoantibodies and prevents spreading to a second thyroid autoantigen in I-A(k) NOD mice. Genes Immun 16:268-74|
|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|
|Aliesky, Holly; Courtney, Cynthia L; Rapoport, Basil et al. (2013) Thyroid autoantibodies are rare in nonhuman great apes and hypothyroidism cannot be attributed to thyroid autoimmunity. Endocrinology 154:4896-907|
|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|
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