Mechanisms of CD4+ T tolerance to a corneal epithelial neoantigen

Tissue-specific peripheral tolerance mechanisms are essential to prevent autoimmunity. The cornea is immune privileged, and anterior chamber-associated immune deviation (ACAID) governs its inner surface. However, the mechanisms that apply to corneal epithelial (outer surface) antigens remain unknown. Using an inducible, cornea-restricted neoantigen mouse model, we found that the cornea relies on inducible regulatory T cells (Tregs) rather than ignorance or ACAID for its epithelial antigens. Although the cornea is both avascular and alymphatic, its epithelial antigens are still efficiently presented by ocular surface-derived antigen-presenting cells to T cells in draining lymph nodes under homeostatic conditions, leading to conventional antigen-specific Treg expansion without ocular pathology. This tolerance was not absolute: systemic immunization redirected antigen-specific responses toward pathogenic effector T cells that disrupted epithelial barrier function. These findings identify Treg induction as a dominant mechanism of corneal epithelial immune homeostasis and demonstrate that inflammatory priming can render a tolerated corneal antigen into an autoimmune target, providing mechanistic insight into dry eye pathogenesis.

This study shows that immune tolerance to corneal epithelial neoantigens relies not on immune privilege but on peripherally induced regulatory T cells in the draining lymph nodes that can be subverted by innate activation, shedding light on ocular surface disease pathophysiology.