Antigenicity of HLA-A2 and HLA-B7. Loss and gain of serologic determinants induced by site-specific mutagenesis at residues 62 to 80.
The contribution of the hypervariable region spanning amino acid residues 62 to 80 to the serologic determinants of HLA-A2 and HLA-B7 has been examined by site-directed mutagenesis. Three HLA-A2 mutants, having changes as in HLA-B7 at positions 62, 76, and at the complete 65-to-80 segment, respectively, were obtained and expressed on class I HLA-deficient human cells upon transfection. The reactivity of 19 monoclonal antibodies (mAbs) against both broad public and allospecific determinants on HLA-A2 and HLA-B7 was analyzed. The results indicate that: (1) the change at residue 62 abrogated recognition of the corresponding HLA-A2 mutant by mAb MA2.1 (anti-A2 + B17); (2) the change at residue 76 did not effect any of the determinants analyzed, although its side chain is easily accessible at the surface of the molecule; (3) the replacement of the whole 65-to-80 segment in HLA-A2 by that from HLA-B7 abrogated recognition by MA2.1 and by 108-2C5, a mAb recognizing a public determinant from the HLA-A locus. Such replacement led to gaining the determinants recognized by mAbs GS145.2 (anti-B7 + B27) and SFR8-B6 (anti-Bw6); and (4) the HLA-A2-reactive mAbs whose reactivity was known to be abrogated by changes in alpha 2 were unaffected by the changes introduced in alpha 1, underlining the frequent segregation of serologic determinants on class I antigens to single domains.
Doménech
N
N
Department of Immunology, Fundación Jiménez Díaz, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Santos-Aguado
J
J
López de Castro
J A
JA
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000939:Epitopes / Q000032:analysis*; D015789:HLA-A2 Antigen / Q000235:genetics / Q000276:immunology*; D015793:HLA-B7 Antigen / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D014162:Transfection
D000911:Antibodies, Monoclonal; D000939:Epitopes; D015789:HLA-A2 Antigen; D015793:HLA-B7 Antigen