Glycan Signatures on Neutrophils in an Equine Model for Autoimmune Uveitis.

Glycosylation of surface proteins is a crucial post-translational modification that reflects the activation status of neutrophils, the predominant leukocyte subset in humans and horses. Neutrophils have emerged as active contributors to diseases mediated by the adaptive immune system, such as equine recurrent uveitis (ERU), a sight-threatening disease in horses and a unique model for studying the pathogenesis of autoimmune uveitis in humans. Since changes in surface glycosylation can impact neutrophil function, we were interested in the surface glycosylation landscape on neutrophils from healthy horses and the potential changes in surface glyco-signatures in ERU. Using 35 different plant lectins, we outlined a profile of surface-exposed glycan moieties on equine neutrophils and detected significantly increased O-glycosylation in a diseased state through Jacalin (JAC) binding via flow cytometry. Subsequent molecular weight comparison of JAC pull-down assay data and neutrophil proteomics indicated the surface proteins Integrin beta-2 and CUB domain-containing protein 1 as potential anchors for increased O-glycan levels in ERU. These findings give novel insights into neutrophil surface glycosylation in health and disease and propose O-glycosylation as a possible biomarker for autoimmune uveitis.