Identification of the novel allele HLA-B*0809 in a Caucasian individual: estimation of allogeneic potential between B*08 variants

The identification of the new allele HLA-B*0809, which was found in a Cauca sian individual, is described. In the sequence analysis the new allele diff ers from B*0801 by six nucleotides located in exon 3. As the structure is i dentical to a variety of other HLA-B alleles, it is likely that the new all ele originated by gene conversion, At the protein level, the new allele has two amino acid differences compared to B*0801. Comparing the residues of t he a, and cc, domains of the B*08 variants to each other, a high degree of polymorphism was found. Three alleles differ from B*0801 by only one amino acid residue whereas the other comparisons revealed at least two disparitie s. B*0809 differs from the other B*08 variants by at least two amino acid r esidues, suggesting that mismatching may provoke alloreactivity and thus im pair clinical outcome of bone marrow transplantation. Among the B*08 allele s with a single amino acid difference, the mismatch combinations B*0801 vs. B*0805 and B*0801 vs. B*0807 appear to be the most compatible based on str uctural data.