1. Supplemental Fig. 1. Gating strategy to define Treg and iNKT cell subsets. (A) Representative scatter plots showing: the lymphocyte gate (R1), CD4+ cells (R2), CD4+ cells with CD25 and FoxP3 co-expression (R3). The boxed areas for Foxp3 were gated on the top part of the near linear correlation with CD25, as it represent the cells with higher CD25 expression and stronger suppressive capacity. (B) CD3+ cells expressing Vα24 and Vβ11 TCR chains (R3) in cells acquired from one mL of blood.

2. Supplemental Fig. 2. Representative suppression assay. (A) Stimulated PBMCs were cultured alone (ratio Treg:responder of 0:1) or with Treg at various ratios (1:1, 1:2 and 1:4). CFSE dilution graphs from a representative assay showed Treg suppressive capacity up to 1:4 ratio. The corresponding Proliferation index (PI) was calculated using the ModFit LT for Win32 software. (B) Suppression assay with co-culture with Treg or non-labelled PBMC. Representative data on graphs are presented as the mean± SEM.

3. Supplemental Fig. 3. Correlation between frequency of peripheral Treg and free thyroxine level in Graves’ disease patients before RAI therapy. Each data of the proportion of CD4 + CD25 hi FoxP3 + Treg cells over the total peripheral CD4 + T cells is paired with the same patient’s free thyroxine value (F T4) in G patients (n = 26) sorting out those taking antithyroid medication (black circle, G- ATD, n = 11) or not (white circle, G-no ATD, n = 15) ns: not significant.

4. Supplemental Fig. 4. Proportion variation in frequency of peripheral Treg before and after radioiodine therapy in patients with Graves’ disease. Each data of the proportion variation of CD4 + CD25 hi FoxP3 + Treg cells over the total peripheral CD4 + T cells in 5 patients with hypothyroidism after RAI therapy (Low T4) and in 10 patients without hypothyrodism (Normal/High T4) are shown. All data are presented as the variation of the proportion using the formula: [Number of cells from (Sample post RAI/Sample pre RAI)]-1, and presented on graphs as the mean ± SD. ns: not significant.