Mapping of an epitope defined by a human hybridoma antibody (TrD3): a new HLA-B supertype associated with a subset of HLA-Bw6.
The new human-human hybridoma TrD3 secretes a cytotoxic IgM mAb, which reacted with 28 of a panel of 56 HLA-typed lymphoblastoid cells. All 28 TrD3+ cells expressed the HLA-B supertype Bw6, whereas 10 Bw6+ cells were not recognized by the mAb. None of the 17 Bw4 homozygous cells were positive with TrD3. Thus, TrD3 divided the Bw6+ HLA-B specificities of the cell lines into two subgroups, namely, Bw6+TrD3+ and Bw6+TrD3-, and therefore defines a new HLA-B supertype. TrD3 reacted strongly with some B8+ cell lines and weakly or not at all with others, suggesting a new split of HLA-B8. Compared with cell lines, TrD3 reacted more weakly with freshly isolated T cells from blood. The Bw6-specific rat mAb SFR8-B6 partially blocked the binding of 125I-labeled TrD3 to a Bw6+ cell line. By using cell lines transfected with hybrid genes between HLA-B7 (Bw6+) and HLA-B27 (Bw6-) as targets in flow cytometry, critical residues for the TrD3 epitope could be mapped to the amino acid region 24-62 of the HLA class-I alpha 1 domain. Comparison of deduced amino acid sequences of TrD3-positive and -negative cells indicated that a tryptophane residue at position 95 destroyed the TrD3 epitope, and that one or more of the residues in positions 24, 45, and 46 may be critical, suggesting that it is a discontinuous epitope. It is notable that none of these residues are located on alpha-helixes.(ABSTRACT TRUNCATED AT 250 WORDS)
Kolstad
A
A
Department of Immunology, University of Tromsø School of Medicine, Norway.
Toubert
A
A
Weyl
D
D
Jun
G
G
Hannestad
K
K
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology*; D002461:Cell Line, Transformed; D000939:Epitopes / Q000235:genetics* / Q000276:immunology; D015235:HLA-B Antigens / Q000235:genetics / Q000276:immunology*; D004854:Herpesvirus 4, Human; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D008969:Molecular Sequence Data; D011487:Protein Conformation; D016415:Sequence Alignment
D000911:Antibodies, Monoclonal; D000939:Epitopes; D015235:HLA-B Antigens; C038652:HLA-Bw6 antigen; D007075:Immunoglobulin M