Patients with a fast progression profile in geographic atrophy have increased CD200 expression on circulating monocytes.

Importance Geographic atrophy (GA) is a progressing atrophy of the neuroretina with no treatment option. Background Age-related malfunction of retinal microglia amplifies response towards age-related tissue stress in age-related macular degeneration. Here, we investigated monocyte CD200 expression - the circulating middleman negotiating retinal microglial activity - in a poorly understood subtype of age-related macular degeneration. Design Prospective case-control study. Participants Forty-six patients with GA and 26 healthy controls were included. Methods All participants were subjected to a structured interview and detailed retinal examination. Controls were recruited from patient's spouses accompanying them in the clinic to match the groups best possibly. Participants had no history of immune disorders or cancer, and did not receive any immune-modulating medication. Patients did not have any history or sign of choroidal neovascularization in either eye. Fresh drawn blood was stained with monoclonal antibodies and prepared for flow cytometry to evaluate CD200 expression in monocytes and their functional subsets. Main Outcome Measures The percentage of CD200+ monocytes in patients and controls. Results We found that monocytes were more CD200 positive in patients with GA compared to healthy age-matched controls. Then, we explored the potential relationship between CD200 expression and important fundus autofluorescence patterns that predict disease progression. Patients with a high risk of progression (patients with high degree of hyperautofluorescence) had distinctly increased CD200 expression compared to other patients with GA. Conclusions and Relevance Our data reveals that abnormal monocytic CD200 expression is present in GA, and in particular among those identified as fast progressors.