New HLA-DPB1 alleles generated by interallelic gene conversion detected by analysis of sperm.

The rate at which allelic diversity at the HLA loci evolves has been the subject of considerable controversy. The patchwork pattern of sequence polymorphism within the second exon of the HLA class II loci, particularly in the DPB1 locus, may have been generated by segmental exchange (gene conversion). We have analysed the frequency of variant DPB1 sequences that have been created by interallelic gene conversion in the germline by screening pools of sperm using PCR amplification and oligonucleotide probe typing. Our results indicate that about 1/10,000 sperm represents a new DPB1 sequence generated by short tracts of segmental exchange (gene conversion) within the second exon, suggesting that interallelic gene conversion may have an important role in generating the extensive allelic diversity at the HLA loci.