Abstract
Purpose :
The pathogenic lymphocytes in human uveitis has been inferred based on abundance within an ocular or pathological sample. Here, we evaluated lymphocyte clonal expansion to provide a stronger link between putative antigen-specific responses and pathophysiology in uveitis.
Methods :
We performed single cell RNA-sequencing (scRNAseq) to obtain an unbiased gene expression survey of aqueous and blood immune cells in 4 subjects with chronic granulomatous uveitis. This analysis allowed quantification, cell type identification, and transcriptional profiling of individual lymphocytes within the inflamed eye as compared to cells in circulation, along with T cell receptor and B cell receptor sequencing to determine clonotype distribution.
Results :
The majority of aqueous immune cells were T cells with a ratio of CD4:CD8 T cells of approximately 2:1 for all four patients. Despite this consistent proportion of ocular T cells across individuals, each subject contained highly expanded lymphocyte clonotypes from different lineages, e.g. CD4 T cells, CD8 T cells, or B cells, where 1-3 clonotypes accounted for ~25-33% of all sequenced cells in that lineage. While CD8 T cells demonstrated similar transcriptional programming in the eye across all patients, ocular CD4 T cell responses were individualized, further defining each subjects’ inflammatory process.
Conclusions :
While previous reports have suggested the most abundant cell type is central to disease pathogenesis, the current data suggest that lower frequency lymphocyte populations, such as CD8 T cells or B cells, display antigen-specific responses that drive granulomatous uveitis. Furthermore, extensive clonal expansion was seen in a different lymphocyte lineage for each individual, suggesting a distinct antigen-specific response in each patient. Further investigation of these expanded lymphocyte clones and the corresponding CD4 T cell response may identify personalized therapeutic targets.
This is a 2020 ARVO Annual Meeting abstract.