The alpha 1/alpha 2 domains of class I HLA molecules confer resistance to natural killing.
The expression of transfected HLA class I Ag has previously been shown to protect human target cells from NK-mediated conjugation and cytolysis. In this same system, transfected H-2 class I Ag fail to impart resistance to NK. In this study, we have mapped the portion of the HLA class I molecule involved in this protective effect by exploiting this HLA/H-2 dichotomy. Hybrid class I genes were produced by exon-shuffling between the HLA-B7 and H-2Dp genes, and transfected into the class I Ag-deficient B-lymphoblastoid cell line (B-LCL) C1R. Only those transfectants expressing class I Ag containing the alpha 1 and alpha 2 domains of the HLA molecule are protected from NK, suggesting the "protective epitope" is located within these domains. Since a glycosylation difference exists between HLA and H-2 class I Ag within these domains (i.e., at amino acid residue 176), the role of carbohydrate in the class I protective effect was examined. HLA-B7 mutant genes encoding proteins which either lack the normal carbohydrate addition site at amino acid residue 86 (B7M86-) or possess an additional site at residue 176 (B7M176+) were transfected into C1R. Transfectants expressing either mutant HLA-B7 Ag were protected from NK. Thus, carbohydrate is probably not integral to a class I "protective epitope." The potential for allelic variation in the ability of HLA class I Ag to protect C1R target cells from NK was examined in HLA-A2, A3, B7, and Bw58 transfectants. Although no significant variation exists among the HLA-A3, B7, and Bw58 alleles, HLA-A2 appears unable to protect. Comparison of amino acid sequences suggests a restricted number of residues which may be relevant to the protective effect.
Storkus
W J
WJ
Department of Microbiology and Immunology, Duke University Medical Center, Durham, NC 27710.
Alexander
J
J
Payne
J A
JA
Cresswell
P
P
Dawson
J R
JR
D000595:Amino Acid Sequence; D002236:Carbohydrate Conformation; D015923:Complement C1r / Q000235:genetics / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D015789:HLA-A2 Antigen / Q000235:genetics / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate; D007694:Killer Cells, Natural / Q000276:immunology*; D008297:Male; D008969:Molecular Sequence Data; D010449:Peptide Mapping
D000939:Epitopes; D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D015923:Complement C1r