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The HLA-DRB1 (MHC Class II) family of genes codes for human leukocyte antigen membrane proteins of the DR family, and are involved in presentation of antigens to T cells. The results of an examination of the locus suggests a recent origin of multiple alleles. Findings implicate HLA-DRB1 lineages 8 and 11-14 as human-specific via multiple analyses, while some analyses indicate that 3, 15 and 16 are HLS and others do not. Lineages 1, 4 and 7, meanwhile, appear to be shared among multiple species. It is thought that this rapid appearance of new alleles is mediated by gene conversions and related events.