Pancreatic CD4+ and CD8+ T cells exhibited a striking degree of exhaustion in KC;iASPPΔ8/Δ8 mice, including increased expression of PD-1 and Tim-3 (Fig. S3C), indicative of an exhausted T cell response in KC;iASPPΔ8/Δ8 mice. This evidence concerns the gene PDCD1 and keratoconus.