IDO1 and diabetes mellitus: To explore whether the expression of these immune-inhibitory ligands is a general feature of pancreatic inflammation or whether it is specific for CPI-DM, we stained pancreatic tissue from patients with autoimmune and chronic pancreatitis (Supplemental Figure 1A) and also found PD-L1 (Supplemental Figure 1B) and IDO1 (Supplemental Figure 1C) expression in β cells in these inflammatory conditions.