Abstract

Aim: To characterise periorbital immune cells (stages, kinetics) in active and inactive thyroid associated ophthalmopathy (A-TAO; I-TAO).

Methods: In orbital tissue cryosections of patients with A-TAO (n = 15), I-TAO (n = 11), and healthy controls (n = 14), adipose and fibrovascular areas were evaluated for MHC II⁺ cells, CD45⁺ total leukocytes, myeloid cells (CD33⁺ monocytes; CD14⁺ macrophages; mature RFD7⁺ macrophages; RFD1⁺ dendritic cells (DCs)), and lymphoid cells (CD4⁺ T cells; αβ and γδ T cells; CD20⁺ B cells). Results are expressed as medians and 5% confidence intervals.

Results: In fibrovascular septae, a surge of CD33⁺ immigrants clearly correlating with disease activity generated significantly increased (p<0.05) percentages of CD14⁺ and RFD7⁺ macrophages. Intriguingly, CD4⁺ cells were mostly γδ T cells, while αβ T helper cells were much less frequent. Successful treatment rendering TAO inactive apparently downregulates monocyte influx, macrophage differentiation, and T cell receptor expression. Similar trends were recorded for adipose tissue. Interestingly, RFD1⁺ DCs were completely absent from all conditions examined.

Conclusion: A-TAO coincides with periorbital monocyte infiltration and de novo differentiation of macrophages, but not DCs. The authors discuss a novel potential role for inflammatory CD4⁺ γδ T cells in TAO. Successful treatment apparently downregulates orbital monocyte recruitment and effects functional T cell knockout.