Pos1441 ocular and Peripheral Blood Immune Phenotypes Suggest Transmigration of Cd16+ Monocytes to an Important Effector Site in Behçet’s Disease

Abstract

BackgroundCellular immunity of Behçet’s Disease (BD) remains poorly understood. Previous work has provided clues pointing to most innate and adaptive immune cell types in BD, but strong signals from non-immunogenetic studies are rare and often inconclusive.ObjectivesHere we aimed to identify BD/HD discriminant single immune cell profiles in semi-biased and targeted approaches and determine their significance at a BD relevant effector site.MethodsWe utilized multi-parametric flow cytometry to dissect cellular phenotypes in PBMC of untreated BD patients (n=27) and HD (n=22) consisting predominantly of active ocular and major vascular BD subjects. Data were subjected to supervised machine learning (CITRUS) and results verified with targeted gating. We also analyzed anterior chamber (AC) fluid cells and autologous PBMC from BD uveitis subjects with scRNA seq.ResultsCITRUS identified CD16+, CD14low, CD4low, CD3-, CD19- cells as a BD/HD distinguishing cellular expression pattern at an FDR of >0.05. Targeted gating confirmed highly significant differences with large effect sizes in PBMC of BD vs HD for “non-classical” (CD14lowCD16hi) and “intermediate” (CD14+CD16+) monocytes at decreased frequencies compared to peripheral blood. “Classical” (CD14++CD16-) monocytes were more abundant in BD PBMC than in HD. CD16+ dendritic cells (DC) were significantly decreased in BD PBMC. CD14+ cells showed high abundance in the AC during BD uveitis and co-expressed CD16 far more frequently than CD14+ cells in autologous peripheral blood.ConclusionSignificantly lower frequencies of CD16+ monocyte and DC subsets in PBMC of untreated active BD vs HD strongly point to their importance in BD. The high abundance of CD14+ cells with CD16 co-expression in the eye during uveitis relative to their frequency in autologous peripheral blood, suggests their transmigration or post-migrational interconversion within the eye during BD uveitis rather than a stochastic process.REFERENCES:NIL.Acknowledgements:NIL.Disclosure of InterestsYesim Ozguler: None declared, Ziyan Lin: None declared, Gulen Hatemi: None declared, Ann Cavers: None declared, Johannes Nowatzky Grant/research support from: NIH-NEI R01EY031383 (Nowatzky), NIH-NEI R01EY033495 (Nowatzky)