Antigen-specific CD8+ T cells reactive to the islet-associated autoantigen glucose-6-phosphatase catalytic subunit-related protein (IGRP), found in both NOD mice and humans with T1D, were measured using MHC class I (H-2Kd) IGRP tetramer staining (see Methods; Supplemental Figure 5A). Here, G6PC2 is linked to type 1 diabetes mellitus.