The Essential Role of Circulating Thyroglobulin in Maintaining Dominance of Natural Regulatory T Cell Function to Prevent Autoimmune Thyroiditis

Nanoparticles Bearing TSH Receptor Protein and a Tolerogenic Molecule Do Not Induce Immune Tolerance but Exacerbate Thyroid Autoimmunity in hTSHR/NOD.H2h4 Mice

Transgenic NOD.H2h4 mice that express the human (h) TSHR A-subunit in the thyroid gland spontaneously develop pathogenic TSHR autoantibodies resembling those in patients with Graves disease. Nanoparticles coupled to recombinant hTSHR A-subunit protein and a tolerogenic molecule (ligand for the endogenous aryl-hydrocarbon receptor; ITE) were injected i.p. four times at weekly intervals into hTSHR/NOD.H2h4 mice with the goal of blocking TSHR Ab development. Unexpectedly, in transgenic mice, injecting TSHR A-subunit-ITE nanoparticles (not ITE-nanoparticles or buffer) accelerated and enhanced the development of pathogenic TSHR Abs measured by inhibition of TSH binding to the TSHR. Nonpathogenic TSHR Abs (ELISA) were enhanced in transgenics and induced in wild-type littermates. Serendipitously, these findings have important implications for disease pathogenesis: development of Graves TSHR Abs is limited by the availability of A-subunit protein, which is shed from membrane bound TSHR, expressed at low levels in the thyroid. The enhanced TSHR Ab response following injected TSHR A-subunit protein-nanoparticles is reminiscent of the transient increase in pathogenic TSHR Abs following the release of thyroid autoantigens after radio-iodine therapy in Graves patients. However, in the hTSHR/NOD.H2h4 model, enhancement is specific for TSHR Abs, with Abs to thyroglobulin and thyroid peroxidase remaining unchanged. In conclusion, despite the inclusion of a tolerogenic molecule, injected nanoparticles coated with TSHR A-subunit protein enhanced and accelerated development of pathogenic TSHR Abs in hTSHR/NOD. NOD.H2h4 These findings emphasize the need for sufficient TSHR A-subunit protein to activate the immune system and the generation of stimulatory TSHR Abs in genetically predisposed individuals.

Elevated thyroglobulin level is associated with dysfunction of regulatory T cells in patients with thyroid nodules

OBJECTIVE

Thyroid nodules are usually accompanied by elevated thyroglobulin (Tg) level and autoimmune thyroid diseases (AITDs). However, the relationship between Tg and AITDs is not fully understood. Dysfunction of regulatory T cells (Tregs) plays an important role in the development of AITDs. We aimed to evaluate the effects of Tg on the function of Tregs in patients with thyroid nodules.

METHODS

Tg levels and the functions of Tregs in peripheral blood and thyroid tissues of patients with thyroid nodules from Nanjing First Hospital were evaluated. The effects of Tg on the function of Tregs from healthy donors were also assessed in vitro. The function of Tregs was defined as an inhibitory effect of Tregs on the effector T cell (CD4+ CD25- T cell) proliferation rate.

RESULTS

The level of Tg in peripheral blood correlated negatively with the inhibitory function of Tregs (R = 0.398, P = 0.03), and Tregs function declined significantly in the high Tg group (Tg >77 μg/L) compared with the normal Tg group (11.4 ± 3.9% vs 27.5 ± 3.5%, P < 0.05). Compared with peripheral blood, the function of Tregs in thyroid declined significantly (P < 0.01), but the proportion of FOXP3+ Tregs in thyroid increased (P < 0.01). High concentration of Tg (100 μg/mL) inhibited the function of Tregs and downregulated FOXP3, TGF-β and IL-10 mRNA expression in Tregs in vitro.

CONCLUSIONS

Elevated Tg level could impair the function of Tregs, which might increase the risk of AITDs in patient with thyroid nodules.

Association between thyroglobulin polymorphisms and autoimmune thyroid disease: a systematic review and meta-analysis of case-control studies

Emerging evidence revealed that thyroglobulin (TG) contributes to the development of autoimmune disease, and the relationship between TG and autoimmune thyroid disease (AITD) is still controversial. The aim of this study was to quantify the association between rs2076740, rs853326, rs180223, and rs2069550 TG polymorphisms and risk of AITD using a meta-analysis approach. We identified all studies that assessed the association between TG polymorphisms and AITD from PubMed, Embase, and Web of Science databases. A total of 3013 cases and 1812 controls from ten case-control studies were included. There was no significant associations found between rs2069550, rs180223, and rs853326 polymorphisms and AITD risk. The association between the rs2076740 polymorphism and AITD risk was significant in the codominant model (P = 0.005), suggesting the CC rs2076740 genotype might be a protective factor for AITD. Sensitivity analysis by removing one or two study changed the results in dominant rs2076740 and rs853326 and rs2069550 allele models (P = 0.016, 0.024, 0.027). Latitude and ethnicity significantly affected the association between rs2076740 and rs2069550 polymorphisms and AITD, indicating their protective effects in allele or dominant model (P = 0.012, 0.012, 0.012, 0.009, 0.009). The association between rs2076740, rs2069550, and rs853326 polymorphisms and AITD risk is significantly affected by study characteristics.

Thyroid Autoantibodies Display both "Original Antigenic Sin" and Epitope Spreading

Evidence for original antigenic sin in spontaneous thyroid autoimmunity is revealed by autoantibody interactions with immunodominant regions on thyroid autoantigens, thyroglobulin (Tg), thyroid peroxidase (TPO), and the thyrotropin receptor (TSHR) A-subunit. In contrast, antibodies induced by immunization of rabbits or mice recognize diverse epitopes. Recognition of immunodominant regions persists despite fluctuations in autoantibody levels following treatment or over time. The enhancement of spontaneously arising pathogenic TSHR antibodies in transgenic human thyrotropin receptor/NOD.H2^h4 mice by injecting a non-pathogenic form of TSHR A-subunit protein also provides evidence for original antigenic sin. From other studies, antigen presentation by B cells, not dendritic cells, is likely responsible for original antigenic sin. Recognition of restricted epitopes on the large glycosylated thyroid autoantigens (60-kDa A-subunit, 100-kDa TPO, and 600-kDa Tg) facilitates exploring the amino acid locations in the immunodominant regions. Epitope spreading has also been revealed by autoantibodies in thyroid autoimmunity. In humans, and in mice that spontaneously develop autoimmunity to all three thyroid autoantigens, autoantibodies develop first to Tg and later to TPO and the TSHR A-subunit. The pattern of intermolecular epitope spreading is related in part to the thyroidal content of Tg, TPO and TSHR A-subunit and to the molecular sizes of these proteins. Importantly, the epitope spreading pattern provides a rationale for future antigen-specific manipulation to block the development of all thyroid autoantibodies by inducing tolerance to Tg, first in the autoantigen cascade. Because of its abundance, Tg may be the autoantigen of choice to explore antigen-specific treatment, preventing the development of pathogenic TSHR antibodies.

Cellular and Molecular Mechanisms of Autoimmunity and Lupus Nephritis

Autoimmunity involves immune responses directed against self, which are a result of defective self/foreign distinction of the immune system, leading to proliferation of self-reactive lymphocytes, and is characterized by systemic, as well as tissue-specific, inflammation. Numerous mechanisms operate to ensure the immune tolerance to self-antigens. However, monogenetic defects or genetic variants that weaken immune tolerance render susceptibility to the loss of immune tolerance, which is further triggered by environmental factors. In this review, we discuss the phenomenon of immune tolerance, genetic and environmental factors that influence the immune tolerance, factors that induce autoimmunity such as epigenetic and transcription factors, neutrophil extracellular trap formation, extracellular vesicles, ion channels, and lipid mediators, as well as costimulatory or coinhibitory molecules that contribute to an autoimmune response. Further, we discuss the cellular and molecular mechanisms of autoimmune tissue injury and inflammation during systemic lupus erythematosus and lupus nephritis.

TGF-β1 along with other platelet contents augments Treg cells to suppress anti-FVIII immune responses in hemophilia A mice

Platelets are a rich source of many cytokines and chemokines including transforming growth factor β 1 (TGF-β1). TGF-β1 is required to convert conventional CD4⁺ T (Tconv) cells into induced regulatory T (iTreg) cells that express the transcription factor Foxp3. Whether platelet contents will affect Treg cell properties has not been explored. In this study, we show that unfractionated platelet lysates (pltLys) containing TGF-β1 efficiently induced Foxp3 expression in Tconv cells. The common Treg cell surface phenotype and in vitro suppressive activity of unfractionated pltLys-iTreg cells were similar to those of iTreg cells generated using purified TGF-β1 (purTGFβ-iTreg) cells. However, there were substantial differences in gene expression between pltLys-iTreg and purTGFβ-iTreg cells, especially in granzyme B, interferon γ, and interleukin-2 (a 30.99-, 29.18-, and 17.94-fold difference, respectively) as determined by gene microarray analysis. In line with these gene signatures, we found that pltLys-iTreg cells improved cell recovery after transfer and immune suppressive function compared with purTGFβ-iTreg cells in factor VIII (FVIII)-deficient (F8^null, hemophilia A model) mice after recombinant human FVIII (rhF8) infusion. Acute antibody-mediated platelet destruction in F8^null mice followed by rhF8 infusion increased the number of Treg cells and suppressed the antibody response to rhF8. Consistent with these data, ex vivo proliferation of F8-specific Treg cells from platelet-depleted animals increased when restimulated with rhF8. Together, our data suggest that pltLys-iTreg cells may have advantages in emerging clinical applications and that platelet contents impact the properties of iTreg cells induced by TGF-β1.