Interactions of HLA‐B*4801 with peptide and CD8

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Abstract
Functional properties of the B*4801 allotype were investigated using HLA class I‐deficient 221 cells transfected with B*4801 cDNA. From pool sequence analysis of endogenously bound peptides, B*4801 was shown to select for nonamer peptides having glutamine or lysine at position 2 and leucine at the carboxyl‐terminus. In an in vitro cell‐cell binding assay, B*4801 binds CD8α homodimers weakly due to the presence of a threonine residue at position 245 in the α3 domain. A mutant B*4801 molecule in which alanine replaces threonine 245, binds CD8α homodimers at levels comparable to those of other HLA class I allotypes. Despite the low affinity of B*4801 for CD8α, alloreactive T‐cells that recognize B*4801 molecules expressed by the 221 transfectant are inhibited by anti‐CD8 monoclonal antibodies. Analysis of 25 B*48‐expressing individuals from various populations showed threonine 245 was encoded by every B*48 allele.