Glycosylation of Sera Thyroglobulin

Antibody in Patients with

Thyroid Diseases

Department of Endocrinology,

Peking University First Hospital, Beijing 100034, China

Ying Gao, Lanlan Zhao, Mingming Liu, Youyuan Huang, Guizhi Lu, Yanming Gao, Xiaohui Guo

Backgrounds Thyroglobulin antibody (TgAb) is one of the major

autoantibodies in thyroid diseases. In papillary thyroid cancer (PTC) In autoimmune thyroid disease (AITD):

Hashimoto' thyroiditis (HT) and Graves' disease (GD)

Spencer CA, et al. J Clin Endocrinol Metab. 2011,96:3615-3627.Calder EA, et al. Clin Exp Immunol. 1973, 14: 153-8.

Backgrounds TgAb is predominantly of IgG class IgG is a glycoprotein with a sugar moiety

attached to each of the asparagin 297 residues in the CH2-domains of the two Fc-fragments.

Fuc ： fucoseGal ： galactoseNeu5AC: sialic acid

Torrigiani G, et al. Clin Exp Immunol. 1968,3:621-630.

Fc fragments

CH2 domains

Fab fragments

Shields RL, et al. J Biol Chem. 2002,277:26733-26740.Scallon BJ,et al. Mol Immunol. 2007,44:1524-1534.Kodar K et al. Glycoconj J. 2012,29:57-66.

Backgrounds The absence of core fucose residues in the Fc glycans

substantially increases the ADCC activity of IgG. Increased sialylation of Fc glycans results in decreased ADCC

activity. Alteration of IgG-Fc galactosylation have been described not

only in autoimmune diseases, but also in some malignancy diseases.

These glycoforms can differ in their efficacy of effector function activation as it influences binding of IgG molecules to Fc receptors and C1q .

Objective

The aim of our study was to investigate the

glycosylation of sera TgAb in patients with different

thyroid diseases including HT, GD, and PTC.

Materials and Methods

Sera samples were collected in Peking University First Hospital.

Eu: euthyroidism; sH: subclinical hypothyroidism; H: hypothyroidism

Thyroid function: Chemiluminescence immunoassays TgAb IgG: antigen specific ELISAs carbohydrate residues on sera TgAb: Lectin-ELISAs

The relative amount of fucose in each TgAb IgG was calculated as:

Comparisons were carried out by the Mann–Whitney test, ANOVA, Chi-Square test and Kruskal-Wallis H test.

x 100%the percentage of fucose positive control

the percentage of TgAb IgG positive control

Materials and Methods

a P < 0.05 vs. GD; b P < 0.05 vs. thyroid cancer group.

Table 1. Demographic data, thyroid functional status and TgAb IgG levels of the patients in different groups.

Groups HT (n=81) GD (n=16) Thyroid cancer (n=12)

Age (years) 50 (33-64) a 29 (23-41) 38 (29-61)

Gender (M/F) 5/76 0/16 2/10

TT3 (nmol/l) 1.51 (1.22-1.69)a, 5.81 (3.79-9.19) b 1.55 (1.28-1.66)

TT4 (nmol/l) 84.70 (61.70-102.80) a, b 220.60 (137.70- 262.10)b 102.75 (88.00-117.05)

TSH (mIU/l) 6.51 (4.12-22.81) a, b 0.01 (0.002-0.02) b 2.98 (1.09-4.81)

Positive percentage

of TgAb IgG (%)53.03±17.76 53.66±17.81 49.63±18.49

Results

Table2. Demographic data, thyroid functional status and TgAb IgG levels of the patients in HT subgroups.

a P < 0.05 vs. sH.; b P < 0.05 vs. H.

Groups Eu (n=26) sH (n=22) H (n=33)

Age (years) 43.35±16.34 49.36±14.20 48±13.56

Gender (M/F) 0/26 1/21 4/29

TT3 (nmol/l) 1.57 (1.44-1.63)a, b 1.75 (1.58-1.99) b 1.18 (0.99-1.41)

TT4 (nmol/l) 98.10 (83.43-107.35) b 93.50 (83.53-105.40) b 52.20 (30.80-68.60)

TSH (mIU/l) 2.87 (1.78-4.26) a, b 7.20 (6.10-11.55) b 38.38 (10.19-101.09)

Positive percentage

of TgAb IgG (%)44.93 (29.43-56.45) a, b 54.38 (44.67-68.77) 61.52 (40.24-72.37)

Results

Fig.1. Comparisons of the relative amount of carbohydrate residues on each sera TgAb from patients with different thyroid diseases.

Results

Fig.2. Comparisons of the relative amount of carbohydrate residues on each serum TgAb from Hashimoto’s thyroiditis patients with different thyroid functional status.

Results

Fig.3. The correlation between the relative amount of carbohydrate residues on each TgAb and TgAb IgG in all the patients (n = 109).

Results

The levels of fucosylation and sialylation on TgAb varied in different thyroid diseases.

We speculated that TgAb with lower content of core fucose and terminal sialic acid might have stronger ability to participate in ADCC in HT.

Terminal galactose content of IgG does not affect ADCC but complement dependent cytotoxicity (CDC).

Discussions

There were no significant differences in the levels of glycosylation on each TgAb among the three HT subgroups.

The levels of glycosylation on TgAb might not represent thyrocyte hyperplasia but merely reflect the capacity of inducing thyroid destruction

Discussions

The levels of glycosylation on each TgAb had a negative relationship with TgAb IgG levels

a consequence of elevated Ig synthesis by B cells.

the individuals with thyroid antibodies might be at high risk of developing thyroid failure.

Discussions

Vanderpump MP, et al. Clin Endocrinol (Oxf). 1995, 43:55-68.Parekh R, et al. J Autoimmun. 1989, 2:101-114.

1. Glycosylation of sera TgAb varied in the patients with different thyroid diseases.

2. The levels of glycosylation of TgAb might decrease with increasing TgAb levels.

Conclusions

Acknowledgements

Supported by Beijing Natural Science Foundation Beijing Nova Program Program for New Century Excellent Talents in University Sector funds of ministry of health (no. 201002002).

Thank you for your attention!!

Fig.1. The biotinylated lectins binding to Tg in different oxidation time with sodium periodate.

Fig.2. TgAb lgG binding to thyroglobulin with a serial dilution (diluted 1:12.5 - 1:800) in different oxidation time with sodium periodate.