Killer Immunoglobulin-Like Receptors (KIRs) Genotypes in a Belgian Population.

KIRs (Killer cell Immunoglobulin-like Receptors) are expressed on NK (Natural Killer) cells and a subpopulation of T lymphocytes namely memory CD8+ T cells. The distribution of KIR genes varies among individuals and populations. These genes are encoded on chromosome 19 (19q13.4). Till now 17 KIR genes and pseudogenes have been identified. KIRs recognise groups of HLA class I alleles. NK activity is partially controlled through the interaction between KIRs and their HLA ligands. Several studies report that KIRs may affect the outcome of Hematopoietic Stem-Cell Transplantations.

We performed KIR typing of 17 genes and pseudogenes in 100 healthy Belgian unrelated individuals in “West-Vlaanderen” from Caucasoid origin using a PCR-SSP method. Three genes (KIR3DL3, 2DL4 and 3DL2), named frame-work genes, and the pseudogene 3DP1 were found in all individuals. KIR2DL1 and 2DP1 genes were present in a frequency of 99%. In addition, KIR3DL1 and 2DS4 genes represented a frequency of 97. The KIR2DL3 was found in 90% and the frequencies of other genes varied between 56% and 24%. The individual KIR gene content ranged from 8 to 17 genes. A total of 19 KIR locus profiles was observed. The most common KIR locus profile (32%) consisted of a combination of genes characterising A haplotypes (KIR2DL1 and 2DL3) without the presence of genes characteristic of B haplotypes (KIR2DL2 and 2DS2). The second most common KIR locus profile, accounting for 20% contained a combination of genes characteristics for both A and B haplotypes. The allele KIR2DS4*003 was found in 89% and KIR2DS4*00101/00102/002 only in 41%. KIR3DP1*00301/00302 was present in all individuals and KIR3DP1*001/002 only in 35%.

Our results show that frequencies of most KIR loci in our Belgian population were comparable to literature data of other Caucasian populations. Only KIR2DS1 was lower (27% vs 47.7% with a p-value of 0.0002).

In the future, KIR typing of donor and patient before a Hematopoietic Stem-cell Transplantation may be necessary, due to the diversity in KIR genotypes.