In T1D, IA-2 autoantibody levels positively correlated with EOMES+, CD161–EOMES+, and CD8–EOMES+ NK cells, and negatively – with CD3–CD8+ NK lymphocytes, CD8+CD38–, CD56brightCD8+CD38– NK cell populations, as well as with EOMES-negative NK populations expressing CD8, CD161, or NKG2A, and with perforin potential of CD16+ NK cells. This evidence concerns the gene KLRC1 and type 1 diabetes mellitus.