title: Breaking tolerance in transgenic mice expressing the human TSH receptor A-subunit: thyroiditis, epitope spreading and adjuvant as a 'double edged sword'.
abstract: Transgenic mice with the human thyrotropin-receptor (TSHR) A-subunit targeted to the thyroid are tolerant of the transgene. In transgenics that express low A-subunit levels (Lo-expressors), regulatory T cell (Treg) depletion using anti-CD25 before immunization with adenovirus encoding the A-subunit (A-sub-Ad) breaks tolerance, inducing extensive thyroid lymphocytic infiltration, thyroid damage and antibody spreading to other thyroid proteins. In contrast, no thyroiditis develops in Hi-expressor transgenics or wild-type mice. Our present goal was to determine if thyroiditis could be induced in Hi-expressor transgenics using a more potent immunization protocol: Treg depletion, priming with Complete Freund's Adjuvant (CFA) + A-subunit protein and further Treg depletions before two boosts with A-sub-Ad. As controls, anti-CD25 treated Hi- and Lo-expressors and wild-type mice were primed with CFA+ mouse thyroglobulin (Tg) or CFA alone before A-sub-Ad boosting. Thyroiditis developed after CFA+A-subunit protein or Tg and A-sub-Ad boosting in Lo-expressor transgenics but Hi- expressors (and wild-type mice) were resistant to thyroiditis induction. Importantly, in Lo-expressors, thyroiditis was associated with the development of antibodies to the mouse TSHR downstream of the A-subunit. Unexpectedly, we observed that the effect of bacterial products on the immune system is a "double-edged sword". On the one hand, priming with CFA (mycobacteria emulsified in oil) plus A-subunit protein broke tolerance to the A-subunit in Hi-expressor transgenics leading to high TSHR antibody levels. On the other hand, prior treatment with CFA in the absence of A-subunit protein inhibited responses to subsequent immunization with A-sub-Ad. Consequently, adjuvant activity arising in vivo after bacterial infections combined with a protein autoantigen can break self-tolerance but in the absence of the autoantigen, adjuvant activity can inhibit the induction of immunity to autoantigens (like the TSHR) displaying strong self-tolerance.
authors.affiliation: Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, California, United States of America. mclachlans@cshs.org
authors.forename: Sandra M
authors.initials: SM
authors.lastname: McLachlan
authors.forename: Holly A
authors.initials: HA
authors.lastname: Aliesky
authors.forename: Chun-Rong
authors.initials: CR
authors.lastname: Chen
authors.forename: Gao
authors.initials: G
authors.lastname: Chong
authors.forename: Basil
authors.initials: B
authors.lastname: Rapoport
mesh_terms: D000276:Adjuvants, Immunologic / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D000939:Epitopes / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology; D007453:Iodide Peroxidase / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D021122:Protein Subunits / Q000737:chemistry / Q000276:immunology*; D011989:Receptors, Thyrotropin / Q000737:chemistry / Q000276:immunology*; D013966:Thyroiditis / Q000097:blood / Q000276:immunology*; D013974:Thyroxine / Q000097:blood
chemical_list: D000276:Adjuvants, Immunologic; D000906:Antibodies; D000939:Epitopes; D007074:Immunoglobulin G; D010455:Peptides; D021122:Protein Subunits; D011989:Receptors, Thyrotropin; D007453:Iodide Peroxidase; D013974:Thyroxine