Allelism in the HLA class I multigene family.

Recent data on the structure of functional HLA class I genes shows that, at least at the HLA-A locus, the allelic genes are more related to each other than to HLA genes from other loci. This "A-ness" is discernible at the protein sequence level but much more evident when nucleotide sequences are compared; the homology is particularly striking in the 3' non-coding region. Genes coding for the same HLA specificity in different genetic backgrounds show no obvious difference, although in one case the 3' flanking regions are clearly different; the restriction maps around the HLA-A3 and HLA-AW24 genes are also compared to see whether the chromosomal environments of these two genes are recognizably similar.