The vast majority of new human HLA class I alleles are formed by conversions between existing alleles of the same locus. A notable exception to this rule is HLA-B*4601 formed by replacement of residues 66-76 of the alpha 1 helix of B*1501 by the homologous segment of Cw*0102. This inter-locus recombination, which brings together characteristic elements of HLA-B and HLA-C structure, is shown here to influence function dramatically. Naturally processed peptides bound by B*4601 are distinct from those of its parental allotypes B*1501 and Cw*0102 and dominated by three high abundance peptides. Such increased peptide selectivity by B*4601 is unique among HLA-A,B,C allotypes. For other aspects of function, presence of the small segment of HLA-C-derived sequence in an otherwise HLA-B framework converts B*4601 to an HLA-C-like molecule. Alloreactive cytotoxic T lymphocytes (CTL), natural killer (NK) cells, and cellular glycosidases all recognize B*4601 as though it were an HLA-C allotype. These unusual properties are those of an allotype which has frequencies as high as 20% in south east Asian populations and is associated with predisposition to autoimmune diseases and nasopharyngeal carcinoma.
The inter-locus recombinant HLA-B*4601 has high selectivity in peptide binding and functions characteristic of HLA-C.
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L D Barber, L Percival, N M Valiante, L Chen, C Lee, J E Gumperz, J H Phillips, L L Lanier, J C Bigge, R B Parekh, P Parham; The inter-locus recombinant HLA-B*4601 has high selectivity in peptide binding and functions characteristic of HLA-C.. J Exp Med 1 August 1996; 184 (2): 735–740. doi: https://doi.org/10.1084/jem.184.2.735
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