Understanding population-wide haplotype frequencies of human leukocyte antigen (HLA) alleles in linkage disequilibrium is important for hematopoietic stem cell transplantation☆

matched sibling donor, the search for a matched unrelated inkage disequilibrium (LD) refers to the non-random assoiation of alleles at different gene loci. Alleles that always andomly sort independent of others at surrounding foci are aid to be in linkage equilibrium. For two alleles, say A and , the probability of an individual having one haplotype AB is function of the population frequency of A (pA) and B (pB). f these two alleles are in complete linkage equilibrium and o are independently sorted, the true population frequency of he haplotype AB would equal the product of pA and pB. So AB − (pA × pB) = 0. When allele A and allele B do not independently sort, or re linked together despite being on different loci, the true opulation frequency of the haplotype AB exceeds the prodct of their individual frequencies. So pAB − (pA × pB) > 0. The alue of this difference represents the co-efficient of linkage isequilibrium. The higher this positive value, the stronger the inkage between these alleles, i.e. the higher the LD. Of course, the coefficient of LD calculation gets more comlicated the more alleles being studied in defining haplotypes f interest in various diseases. In particular, the major hisocompatibility system has a significant number of genes xhibiting strong linkage disequilibrium.1 This has an imporant bearing on ideal donor identification for hematopoietic tem cell transplantation (HSCT) as it is related to risk of graft