Thyroid associated ophthalmopathy: evidence for CD4 cd T cells; de novo differentiation of RFD7 macrophages, but not of RFD1 dendritic cells; and loss of cd and ab T cell receptor expression

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; ab and cd 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 cd T cells, while ab 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 cd T cells in TAO. Successful treatment apparently downregulates orbital monocyte recruitment and effects functional T cell knockout.