Genomes and Genes
THYROID PEROXIDASE AS AN AUTOANTIGEN
Principal Investigator: Basil Rapoport
Abstract: Thyroid peroxidase (TPO), a thyroid cell surface protein, is the major autoantigen in autoimmune thyroid disease in humans. Understanding the precise molecular interaction between autoantibodies and T cells with TPO is a necessary step towards understanding the basis of the autoimmune response to TPO. We plan the following specific studies:- 1. TPO AUTOANTIBODY EPITOPES Polyclonal TPO autoantibodies in patients' sera are primarily directed to a restricted immunodominant region (IDR). We propose to identify many, if not all, TPO amino acid residues that comprise these epitopes using complementary approaches which, together, can help to complete the many pieces in the puzzle:- (i) Epitopic footprinting and identification of protected residues. Amino acids adjacent to these sentinel residues will then be identified by mutagenesis guided by the known three-dimensional structure of myeloperoxidase; (ii) X-ray diffraction crystals of TPO-TPO autoantibody complexes. 2. MOLECULAR CLONING OF NEW TPO AUTOANTIBODIES Human monoclonal autoantibodies are key reagents for defining B and T cell epitopes, as well as studying TPO processing and presentation to T cells. Autoantibodies cloned thus far are almost exclusively to the IDR. Important members of the TPO autoantibody repertoire remaining to be cloned include:- (i) Autoantibodies to the unique C-terminal region of the TPO molecule ectodomain with EGF-like and Sushi domains (amino acids 742-848); (ii) autoantibodies with dual thyroglobulin and TPO specificity ("TG-PO"). Important questions to be answered by these studies include:- (i) Are autoantibodies to the C-terminus the main component of serum autoantibodies with epitopes outside the IDR? (ii) Are some non-IDR TPO autoantibodies functionally important by inhibiting TPO enzymatic activity? 3. NATURALLY PROCESSED AND PRESENTED HUMAN T CELL EPITOPES FOR TPO Identification of TPO T cell epitopes is an important goal for understanding the autoimmune response to TPO. Identification of naturally processed peptide epitopes (NPPE) is preferable to testing T cell responsiveness with panels of synthetic peptides. We, therefore propose to extract TPO peptides from MHC molecules in APC and identify directly their amino acid sequence. We will use two different models:- (i) Human Epstein-Barr virus transformed human B cells that can capture, internalize and process TPO; (ii) Mouse fibroblasts co-expressing both human TPO and MHC class II molecules, whose injection induces TPO antibodies with the same epitopes as human autoantibodies. These studies will help answer the following questions:- (i) Which TPO T cell epitopes are most likely to be of pathophysiological importance? (ii) Does similarity between NPPE generated in different systems contribute to epitopic restriction of TPO autoantibodies? (iii) Conversely, do human autoantibodies influence the spectrum of NPPE generated from TPO.
Funding Period: 1985-07-01 - 2007-01-31
more information: NIH RePORT
- Antibodies to thyroid peroxidase arise spontaneously with age in NOD.H-2h4 mice and appear after thyroglobulin antibodiesChun Rong Chen
Thyroid Autoimmune Disease Unit, Cedars Sinai Research Institute and University of California, Los Angeles School of Medicine, Los Angeles, California 90048, USA
Endocrinology 151:4583-93. 2010..These findings demonstrate a novel aspect of murine and human thyroid autoimmunity, namely breaking B cell self-tolerance occurs first for Tg and subsequently for TPO...
- Dissociation between iodide-induced thyroiditis and antibody-mediated hyperthyroidism in NOD.H-2h4 miceSandra M McLachlan
Autoimmune Disease Unit, Cedars Sinai Research Institute and University of California Los Angeles School of Medicine, Los Angeles, California 90048, USA
Endocrinology 146:294-300. 2005..The fact that inducing an immune response to the TSHR had no effect on thyroiditis raises the possibility that the TSHR may not be the target involved in the variable thyroiditis component in some humans with Graves' disease...
- Human autoantibodies modulate the T cell epitope repertoire but fail to unmask a pathogenic cryptic epitopeSonia Quaratino
Cancer Sciences Division, Southampton General Hospital, University of Southampton, Tremona Road, Southampton SO16 6YD, United Kingdom
J Immunol 174:557-63. 2005..However, our results further stress the biological significance of the immunodominant cryptic epitope we have defined and its potential importance in the evolution of autoimmunity...
- Interactions between the mannose receptor and thyroid autoantigensG D Chazenbalk
Autoimmune Disease Unit, Cedars Sinai Research Institute and UCLA School of Medicine, Los Angeles, CA 90048, USA
Clin Exp Immunol 139:216-24. 2005....
- Insight into Graves' hyperthyroidism from animal modelsSandra M McLachlan
Autoimmune Disease Unit, Cedars Sinai Medical Center, University of California Los Angeles School of Medicine, CA 90048, USA
Endocr Rev 26:800-32. 2005..Finally, developing immunospecific forms of therapy for Graves' disease will require painstaking dissection of immune recognition and responses to the TSHR...
- Relationship between thyroid peroxidase T cell epitope restriction and antibody recognition of the autoantibody immunodominant region in human leukocyte antigen DR3 transgenic miceJin Guo
Autoimmune Disease Unit, Cedars Sinai Medical Center, 8700 Beverly Boulevard, Suite B 131, Los Angeles, California 90048, USA
Endocrinology 146:4961-7. 2005..These data suggest a relationship between major histocompatibility complex class II molecules and the development of antibodies to the IDR, a feature of human thyroid autoimmunity...
- Antibodies focused on the human autoantibody immunodominant region are induced by B lymphocytes that constitutively express thyroid peroxidase diverted to the major histocompatibility complex II pathwayJin Guo
Autoimmune Disease Unit, Cedars Sinai Research Institute and UCLA School of Medicine, Los Angeles, California
Thyroid 16:343-9. 2006..However, these antibodies are of low titer that is itself associated with this epitopic bias...
- Thyroid peroxidase as an autoantigenSandra M McLachlan
Autoimmune Disease Unit, Cedars Sinai Medical Center and UCLA Medical School, Los Angeles, California, USA
Thyroid 17:939-48. 2007..Overall, some TPO-specific T cells and the majority of autoantibodies in humans develop in response to TPO presented by thyroid cells, rather than to TPO released by damaged thyrocytes...