Serum PD-1 regulation and PD-1 expression of CD4+Foxp3+ regulatory T cells in patients in thyroid eye disease associated with immunosuppression treatment.

Purpose: Thyroid eye disease (TED) primarily occurs in hyperthyroid patients, sometimes resulting in poor visual prognosis. Although other autoimmune diseases have been reported to be associated with serum programmed cell death 1 (PD-1), the relationship with TED remains unknown. This study investigated the relationship between TED and immune checkpoint molecules.

Methods: Serum immune checkpoint molecules were measured in TED and control patient blood samples. In TED patients, blood samples were compared before and 6 months after steroid pulse treatment. Cytometry analysis was additionally performed in TED and control patients to compare the expression of (PD-1) of T cells.

Results: Serum concentrations of PD-1 in TED and control patients were 163.49 ± 79.01 (pg/mL) and 123.58 ± 46.61 (pg/mL) (P = 0.03). Serum PD-L1 concentration in TED was 157.89 ± 55.34 (pg/mL), while 152.58 ± 22.70 (pg/mL) in control patients (P = 0.92). For flow cytometry analysis, the mean fluorescence intensity (MFI) ratio of PD-1 in Foxp3high CD45RA- of the CD4+ T cells and CD127-CD25high of the CD4+ T cells were higher in TED versus control patients (P = 0.04, P = 0.02). There was also a higher percentage of PD-1 expressions on CD4+ T cells and Foxp3high CD45- T cells in TED patients versus that for control patients (P < 0.001, P = 0.003).

Conclusions: PD-1 expression of CD4+Foxp3+ regulatory T cells appear to be associated with TED pathogenesis before and after treatment. Regulatory T cells expressed PD-1 have possibilities of clinical activity and autoimmune pathology of TED.