title: HLA-Bw22: a family of molecules with identity to HLA-B7 in the alpha 1-helix.
abstract: Various HLA-B molecules exhibit serologic cross-reactions with HLA-B7, including HLA-B27, B40, Bw42, and Bw22. Of this group, primary structures for the three serologic subdivisions of HLA-Bw22, HLA-Bw54, Bw55, and Bw56, have yet to be determined. Here, we describe the nucleotide sequences of five distinctive HLA-Bw22 alleles isolated from cells of different ethnic origins typed either for Bw54, Bw55, or Bw56. Heterogeneity in molecules typed as Bw55 and Bw56 was defined. The five HLA-Bw22 alleles form a closely related family that appears to have evolved by a series of simple gene conversion events, all of which alter the antigen recognition site of the encoded proteins. Of note, HLA-Bw54 is the product of a gene conversion between HLA-B and C alleles. All the Bw22 alleles encode an alpha 1-helix identical in amino acid sequence to that of HLA-B7 and Bw42, a feature almost certainly responsible for the serologic cross-reactivity of these molecules. Shared substitutions in the alpha 1-helix can also explain the cross-reactivity of Bw22 and B7 with B27. Patterns of amino acid substitution in the alpha 2-domain of Bw22 heavy chains correlate with certain antibody and T cell cross-reactivities, thereby implicating particular amino acids in their target epitopes.
authors.affiliation: Department of Cell Biology, and Microbiology and Immunology, Stanford University, CA 94305.
authors.forename: W H
authors.initials: WH
authors.lastname: Hildebrand
authors.forename: J A
authors.initials: JA
authors.lastname: Madrigal
authors.forename: A M
authors.initials: AM
authors.lastname: Little
authors.forename: P
authors.initials: P
authors.lastname: Parham
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001665:Binding Sites; D005075:Biological Evolution; D003429:Cross Reactions; D015235:HLA-B Antigens / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D015793:HLA-B7 Antigen / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D011487:Protein Conformation
chemical_list: D015235:HLA-B Antigens; C105903:HLA-B22 antigen; D015793:HLA-B7 Antigen