A novel hypothesis for the etiology of Graves' disease: TSAb may be thyroid stimulating animal IgG-like hormone and TBAb may be the precursor of TSAb

Possible participation of colloid antigen 2 and abhormone (IgG with hormone activity) for the etiology of Graves' disease

The theory that antibody (Ab) directed against the TSH receptor (TSHR) (TSHRAb) is the causal factor of Graves' disease seems unlikely. Corticosteroids have not had a curative effect on the hyperthyroidism of Graves' disease despite their effectiveness for other autoimmune diseases. Two kinds of TSHRAb, thyroid-stimulating Ab (TSAb) and thyroid-blocking Ab (TBAb), are known as causal factors of hyperthyroidism and hypothyroidism, respectively. Previously, we reported that TSAb may be thyroid stimulating animal IgG-like hormone and TBAb may be the precursor of TSAb. In this paper we suggested that TBAb (precursor) converts to TSAb (active form) via the action of the protease, colloid antigen 2 (CA2). We speculate that the conversion of TBAb to TSAb is controlled by two factors: the protease and an anti-protease Ab. When anti-protease Ab levels are high, the patient exhibits hypothyroidism due to the increase in TBAb levels caused by neutralization of the protease. When anti-protease Ab levels are negative, the patient's hypothyroidism disappeared by the negative serum TBAb due to increased protease. An immunoglobulin G (IgG) with enzyme activity is known as an abzyme, which may be an undeveloped form. IgG with hormone activity may be likewise called an abhormone, which could also be an undeveloped form. The tumor marker CEA is a known member of the IgG supergene family. Many ancestral versions of proteins may have been produced as an IgG form. Possible participation of colloid antigen 2 and abhormone for the etiology of Graves' disease is suggested.

An improved method for the establishment of a model of Graves' disease in BALB/c mice

The present study aimed to develop a stable Graves' disease (GD) model in BALB/c mice by immunization and electroporation (EP). A total of 90 mice were divided into experimental (n=50), control (n=20) and blank (n=20) groups. The recombinant plasmid pcDNA3.1/thyroid-stimulating hormone (TSH) receptor 268 was constructed and injected into the bilateral gastrocnemius of experimental group mice at weeks 1, 4, 7 and 10. Equal volumes of saline were injected into the control and blank groups at the same time. The experimental and control groups were subjected to EP at the same time and location to enhance immunization. The levels of total serum thyroxine (T₄) and serum TSH were examined by radioimmunoassay and immunoradiometric assay, respectively. The levels of serum thyrotropin receptor N-terminal (TRAb N) and C-terminal (TRAb C) antibodies were assessed by ELISA. Whole body pertechnetate (99mTcO₄-) imaging was performed. Mouse weight and thyroid morphology and pathology were analyzed. The GD BALB/c mouse model was successfully established, with a positive rate of 79.17% (38/48). T₄ levels increased from baseline levels of 12.05±4.23 to 52.51±23.58 ng/ml by week 12 (P<0.0001). TSH levels decreased from baseline levels of 5.53±2.78 to 1.43±0.89 µIU/ml by week 12 (P<0.0001). TRAb N antibody levels increased from baseline levels of 0.006±0.002 to 0.278±0.106 mIU/ml by week 12 (P<0.0001). TRAb C antibody levels increased from baseline levels of 11.111±2.808 to 46.701±26.436 arbitrary units/ml by week 12 (P<0.0001). At week 21, TSH levels remained reduced compared with pre-immunization levels (P<0.0001). Although T₄, and TRAb N and C levels decreased, they remained increased compared with preimmunization levels (P<0.0001, P<0.0001, P=0.001). There were no significant alterations in antibody levels between the control and blank groups. Following four immunizations, the uptake of 99mTcO₄- by the thyroid was significantly increased in the experimental group. The mean weight of the experimental mice was significantly reduced compared with the control and blank groups (all P<0.0001). Furthermore, the thyroid glands of the immunized mice were enlarged and exhibited lymphocyte infiltration, fewer colloid nodules and an increased height of epithelial cells. In conclusion, by injecting recombinant plasmid pcDNA3.1/TSHR268 and EP, a GD mouse model was successfully established.