Decreased Frequencies of Peripheral Blood CD4+CD25+CD127-Foxp3+ in Patients with Graves' Disease and Graves' Orbitopathy: Enhancing Effect of Insulin Growth Factor-1 on Treg Cells

Graves' orbitopathy (GO) is characterized by orbital T cell infiltration. We evaluated the regulatory T (Treg) cell fractions induced with IGF-1 in Graves' disease (GD) with and without GO. Peripheral blood mononuclear cells (PBMCs) were obtained from 13 patients with GD without eye manifestations; 10 patients with active GO; and 12 patients with nodular goiter (NG). All the patients from GD, GO, and NG were subclinical hyperthyroid. We analyzed the expression of Treg cell markers (CD4, CD25, CD127^-, Foxp3) on T cells and their ability to respond to IGF-1 stimulation. In patients with GD without GO, we found lowered percentages of CD4⁺ Foxp3⁺ cells, as compared to nodular goiter 1.77 vs. 5.42% (p=0.0276). Similarly, significantly reduced frequencies of CD4⁺CD25⁺CD127^-Foxp3⁺ and CD4⁺CD25⁺CD127^- cells were observed in GD patients as compared to nodular goiter patients with hyperthyreosis, (0.7 vs. 1.48%) (p=0.0071) and (14.5 vs. 37.2%) (p=0.0051), respectively. In GO with active GO, only the percentage of CD4⁺CD25⁺CD127^- cells was found to be decreased versus nodular goiter (9.35 vs. 37.2) (p=0.0275). Stimulation of PBMC derived from GO patients with IGF-1 resulted in significant increase of frequency of both CD4⁺ Foxp3⁺ and CD4⁺CD25⁺CD127^- Foxp3 cells. Decreased frequencies of peripheral blood CD4⁺CD25⁺CD127^-Foxp3⁺ in patients with GD and GO could be an useful marker of autoimmune process and perhaps a possible target for future therapies. This is the first study demonstrating Treg-enhancing effects of IGF-1. Thus IGF-1 can be accounted for modulating Treg cell-related action in GO.