Further diversity at HLA-A and -B loci identified in Afro-Caribbean potential bone marrow donors.

Two novel HLA-A and three novel HLA-B alleles were identified within a group of Afro-Caribbean individuals who were recruited as potential donors for the Anthony Nolan Bone Marrow Trust Register. HLA typing was performed on DNA extracted from peripheral blood mononuclear cells using sequence-specific oligonucleotide (SSO) probes for HLA-A and -B loci. Eight individuals analysed exhibited hybridisation patterns for which a type could not be assigned. DNA from these individuals was further typed by two methodologies: direct sequencing of PCR products and reference strand conformation analysis (RSCA). The direct sequencing results allowed the identification of new alleles but did not allow confirmation of the cis/trans orientation of the new sequence motifs identified. RSCA analysis confirmed the results obtained by SSO and direct sequencing and in addition confirmed the cis/trans orientation of the new sequences. One individual possesses a new A*30 allele--A*3008 and two individuals possess an identical new A*74 allele--A*7404. The three novel HLA-B alleles were identified in three individuals: B*0812, B*1554 and B*4503 respectively. For the remaining two samples, A*2612 was identified. At present Caucasoid individuals, and therefore Caucasoid phenotypes, are predominantly represented on the various different volunteer bone marrow donor registries. The examples presented here highlight the potential for identification of further polymorphisms within the HLA system as more individuals from the much-needed ethnic minorities are recruited onto bone marrow donor registers.