A NOVEL HLA-A-ASTERISK-8001 ALLELE IDENTIFIED IN AN AFRICAN-AMERICAN POPULATION

HLA polymorphism varies among different racial origins. Certain antige ns are restricted to a particular ethnic group, suggesting that geneti c events might have generated further unique polymorphism following ra cial diversification. In this study, we have identified and characteri zed a novel HLA-A allele, officially designated A8001. The class I mo lecule, HLA-AXBG, encoded by this allele could not be defined by commo nly available HLA antisera. We have identified two alloantisera that a ppear to be monospecific for this new antigen. The observed frequency of AXBG antigen specificity is 2% in African Americans among the total of 254 tested, but it has not been found in 305 Caucasians tested. IE F and cDNA sequencing analyses on multiple individuals revealed that A XBG antigen defined by the two antisera are encoded by an identical HL A-A8001 allele and it has a number of unique amino acid residues that have not been observed among other HLA-A alleles but are known to occ ur in certain human nonclassic class I genes and nonhuman primate clas s I genes. The ability to identify the new HLA-AXBG antigen will impro ve the precision of HLA-A typing in black populations and enable us to match a patient with a donor for this otherwise undefined antigen in transplantation.