Fig. 3

A model of fibrocytes in the pathogenesis of thyroid-associated orbitopathy (TAO). Fibroblasts are uniformly CD34⁻ in healthy humans and CD34⁺ in TAO patients. Fibrocytes appear to infiltrate the orbit in TAO and transition into CD34⁺ orbital fibroblasts, which express much higher levels of thyroglobulin (Tg) and thyroid-stimulating hormone receptor (TSHR), and mediate orbital inflammation and remodeling. Bovine thyroid-stimulating hormone (bTSH) and M22 are TSHR inhibitors. HLA-DR human leukocyte antigen D-related, IGF-1R insulin-like growth factor-1 receptor, IL interleukin, MCP-1 monocyte chemotactic protein 1, mTOR mammalian target of rapamycin, TCR T-cell receptor, TNF tumor necrosis factor