Type 1 diabetes (T1D) is a T cell-mediated autoimmune disease in which pancreatic beta cells are selectively destroyed. Although autoimmune diseases are driven by inappropriate adaptive immunity, innate immunity may play a role in the development of T1D. To study the potential involvement of innate immunity in the pathogenesis of autoimmune disease, we investigated associations of the genes for 14 different killer Ig-like receptors (KIRs), the well-characterized receptors in natural killer cells, with Korean T1D patients. Genetic association analyses revealed that some of the KIR genes were associated with T1D. KIR2DL5 and 2DS2 genes were present at significantly low frequency in Korean T1D patients (P < 10(-4)). We did not detect any influence of ligand distribution on KIR association. With the haplotype assignments, 53% of the KIR haplotypes in the control are of type A. Compared with the control (P < 10(-3)) and autoantibody-negative patients (P < 10(-2)), the group A haplotype predominates in Korean patients with T1D. The KIR gene is associated with T1D and distribution differences between T1D and controls were not influenced by the HLA genes (DR-DQ-A-C). T1D, at least in Koreans, is associated with KIR genes, especially in the group A KIR haplotypes. There is a close relationship between innate and adaptive immunity.