Purpose: To assess correlations between orbital immune cell subsets and the clinical activity in thyroid eye disease (TED).

Methods: The orbital samples from 12 healthy controls and 29 TED patients (active group, n=12; inactive group, n=17) were analyzed. Total lymphocytes, CD3+T cells, CD4+T cells, CD8+ T cells, CD3+CD4+CD8+ T cells (double-positive (DPT) T-cells), CD3+CD4-CD8-T cells (double negative (DNT) T-cells), B cells, natural killer (NK) cells and NKT cells were counted on flow cytometry. Correlations between the number of orbital immune cells and clinical activity score (CAS) were analyzed.

Results: Age was greater in active than inactive TED patients, and in inactive TED patients than in controls (all p<0.05). TED duration was shorter in active than inactive patients (all p<0.05). FT3 and TSH levels were higher in controls than in active TED patients (p<0.05). There was no significant difference in TRAb level between active and inactive patients. There were no significant differences in smoking status, gender or FT4 level between the 3 groups (all p > 0.05).

The numbers of orbital total lymphocytes, CD3+ T cells, CD4+ T cells, CD8+ T cells, DNT cells, NK cells, NKT cells and CD4+/CD8+ T cells in active TED patients were significantly higher than in inactive patients and controls (all p<0.05). After adjusting for age and TED duration, the number of CD3+ T cells, CD4+ T cells, CD8+ T cells, NK cells and NKT cells were independent predictors of TED activity (p=0.03, OR=1.19; p=0.04, OR=1.69; p=0.03, OR=1.48; p=0.04, OR=2.08; p=0.03, OR=2.89, respectively).

Conclusions: Numerous immunoinflammatory cells were observed in the orbits of both active and inactive TED patients and in controls, but expression was highest in active TED patients. CD4+ T cell, CD8+ T cell, NK cell, and NKT cell counts were independent factors for the CAS in TED.