HLA-E monoclonal antibodies recognize shared peptide sequences on classical HLA class Ia: relevance to human natural HLA antibodies.
The non-classical HLA-Ib molecule, HLA-E share several peptide sequence similarities with the heavy chains of classical HLA class Ia (-B and -C) molecules. Therefore, the antibodies to HLA-E, that recognize shared sequences, may bind to HLA-Ia alleles. This hypothesis is tested by examining the affinity of HLA-E monoclonal antibodies (HLA-E-MAbs) to HLA-Ia molecules and by inhibiting the antibody binding to both HLA-E and HLA-Ia with the shared peptide sequence(s). Single recombinant HLA molecule-coated beads are used for antibody binding. The antibody binding is evaluated by measuring mean fluorescence index [MFI] with Luminex multiplex flow-cytometric technology. The peptide-inhibition experiments are carried out with synthetic shared peptides, most prevalent to HLA-E and HLA-Ia alleles. The number of HLA-Ia alleles recognized by the HLA-E-MAbs varies with the density of the antigen (quantity of antigen-coated beads) and dilution of MAb. Binding of HLA-E-MAbs to beta2 microglobulin (beta(2)m)-free HLA-Ia antigens confirms the location of the epitopes on the heavy chain (HC) of the antigens. Strikingly, the nature of alleles of HLA-Ia recognized by different HLA-E-MAbs is identical. The binding of HLA-E-MAbs to the HLA-Ia is inhibited dosimetrically by the adjacent peptides, (115)QFAYDGKDY(123) and (137)DTAAQI(142), but not by (126)LNEDLRSWTA(135), another closer shared peptide sequence. The inhibitory peptide sequences in HLA-E are at the alpha2-helix terminal facing beta(2)m. The HLA-Ia alleles recognized by HLA-E-MAb (e.g., MEM-E/02) are similar to those recognized by the natural anti-HLA antibodies found in the sera of healthy non-alloimmunized males. This study postulates that some, if not all, of the natural HLA-Ia antibodies seen in healthy males could be anti-HLA-E antibodies cross-reacting with HLA-Ia alleles.
Ravindranath
Mepur H
MH
Terasaki Foundation Laboratory, Los Angeles, CA 90064, USA. glycoimmune@terasakilab.org
Taniguchi
Michiko
M
Chen
Chien-wei
CW
Ozawa
Miyuki
M
Kaneku
Hugo
H
El-Awar
Nadim
N
Cai
Junchao
J
Terasaki
Paul I
PI
D000483:Alleles; D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000276:immunology*; D000918:Antibody Specificity / Q000235:genetics / Q000276:immunology*; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D006680:HLA Antigens / Q000235:genetics / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology*; D006801:Humans; D051379:Mice; D010455:Peptides / Q000235:genetics / Q000276:immunology*; D017433:Protein Structure, Secondary / Q000235:genetics; D001613:beta 2-Microglobulin / Q000235:genetics / Q000276:immunology; D000097625:HLA-E Antigens
D000911:Antibodies, Monoclonal; D000939:Epitopes; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D010455:Peptides; D001613:beta 2-Microglobulin; D000097625:HLA-E Antigens