Killer cell immunoglobulin-like receptor genes in Latvian patients with type 1 diabetes mellitus and healthy controls.

T1DM is very common in Sweden and is positively associated with HLA class II genes. Approximately 89% of the newly diagnosed patients carry the high-risk HLA DR4-DQ8 and DR3-DQ2. The remaining 11% develop T1DM without them. This can be due to involvement of other genes and environmental factors. Natural killer (NK) cells of the innate immune system are important in antiviral and antitumor immunity. They are implicated in the etiology of autoimmune T1DM. Human NK cells express killer cell immunoglobulin-like receptors (KIR) that belong to the polymorphic multigene family in chromosome 19q3.4. They modulate NK cell response by interacting with HLA class I. In addition, polymorphic MICA in HLA class I interacts with non-polymorphic NKG2D receptor on NK cells. We have studied, in addition to HLA-DR and -DQ, genes of the innate immune system MICA and KIR in Latvian patients (n = 98) with T1DM and controls (n = 100). They were genotyped using standard PCR-based typing methods. MICA allele 5 is positively associated with T1DM. KIR2DL2 and KIR2DS2 were both positively associated. Combined association of MICA4 and KIR2DL2 gave an odds ration (OR) of 26.7. However, the combined risk of KIR2DL2 and HLA class II genes, HLADR3 (OR = 73.4), DR4 (OR = 66.8), and DR3 and DR4 (OR = 88.3), was higher. The maximum risk was when KIR2DL2, MICA5, and DR3/DR4 were in combination. In conclusion, our results suggest that a balance between innate and acquired immunity is important, and an imbalance coud lead to T1DM.