Killer Cell Immunoglobulin-Like Receptor (KIR) Genes in the Basque Population: Association Study of KIR Gene Contents With Type 1 Diabetes Mellitus

Killer cell immunoglobulin-like receptors (KIR) form a group of regulatory molecules that specifically recognize HLA class I molecules, modulating cytolytic activity of natural killer cells. The number of KIR genes can vary between individuals, significant allelic variations have been described, and KIR genes are organized in a complex and heterogeneous family. In the present study we have performed KIR genotype analysis in the Basque general population. Additionally, we have tested the possible association between KIR gene content (in combination with its HLA ligand) and type 1 diabetes mellitus (T1DM). KIR genotyping was performed using a commercial sequence-specific primer amplification genotyping kit and amino acid position 80 of HLA-C was genotyped by specific amplification and direct sequencing. Haplotypes and genotypes were deduced based on previous studies, and frequencies were compared between disease and control groups. All KIR genes tested were present in Basques and several of these genes (KIR2DS5, KIR3DS1, and KIR2DL2) displayed significant differences from corresponding genes in other Caucasoid populations. In general, Basques present an increase in activating KIR gene frequency and, consequently, the proportion of B haplotypes is higher. Three novel haplotypes were identified in the Basque population. Overall, our results confirm the particular genetic characteristics of the Basque population. No association between KIR gene content and susceptibility to T1DM was observed.