Distribution of HLA-A, B and DR genes and haplotypes in the Irish population.

The distribution of HLA phenotypes, genes and haplotypes in the normal population is of considerable importance in, for example, disease susceptibility studies, platelet transfusion support and transplantation. HLA population genetics studies have been carried out on numerous population samples, however, no major studies have been performed on Irish Caucasoids. We have analysed the HLA-A, B and DR phenotypes of 1,910 healthy unrelated Irish blood donors recruited onto the Irish Bone Marrow Donor Panel. HLA typing was performed by a combination of serology, the polymerase chain reaction with sequence-specific primers and reverse hybridisation. We calculated Hardy-Weinberg fit, phenotype and gene frequencies and two- and three-locus haplotype frequencies, linkage disequilibrium (LD) values and their significance levels and relative LD values. Compared to many other European populations, the Irish show a high frequency of HLA-A1, B7, B8 and DR2 and a reduced frequency of HLA-A9, A30, B15 and DR4. Two- and three-locus haplotypes and the combinations of alleles in positive LD were all typical of northern European populations. However, the Irish have especially high frequencies of the common HLA-A1/B8, A2/B44, A3/B7, HLA-B8/DR3, B7/DR2, B44/DR4 and B44/DR7 haplotypes, while the frequency of other relatively common haplotypes, e.g. HLA-A2/B15, is reduced. These frequencies are of particular value for estimating the likelihood of finding bone marrow donors in patients' extended families and unrelated donor panels.