Intra-ocular dendritic cells are increased in HLA-B27 associated acute anterior uveitis

Uveitis describes a heterogeneous group of inflammatory eye diseases characterized by infiltration of leukocytes into the uveal tissues. HLA-B27-associated uveitis is a common subtype of uveitis and a prototypical ocular autoimmune disease. Local immune mechanisms driving human uveitis are poorly characterized mainly due to the limited available biomaterial and subsequent technical limitations. Here, we provide the first high-resolution characterization of intraocular leukocytes in HLA-B27 positive and negative anterior uveitis and an infectious endophthalmitis control by combining single cell RNA-sequencing (scRNA-seq) with flow cytometry and low-input proteomics. Ocular cell infiltrates consisted primarily of lymphocytes in uveitis and of myeloid cells in infectious endophthalmitis. HLA-B27 positive uveitis exclusively featured an plasmacytoid and classical dendritic cells (cDC) infiltrate, and of plasma cells. Moreover, cDCs were central in predicted local cell-cell communication. The data suggests a unique pattern of ocular leukocyte infiltration in HLA-B27 positive uveitis with relevance of particular dendritic cells.