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* Division of Gastroenterology, Infectiology and Rheumatology, Charité Berlin, Campus Benjamin Franklin,
Institute for Chemistry/Crystallography, Free University Berlin, and
Deutsches Rheumaforschungszentrum Berlin, Berlin, Germany;
Medical Research Council Human Immunology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, United Kingdom;
¶ Institute for Anthropology and Human Genetics, Ludwig-Maximillians-Universität Munich, Munich, Germany; and
|| Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute and Department of Neurology, Harvard Medical School, Boston, MA 02115
Crystallographic studies have suggested that the cysteine at position 67 (Cys67) in the B pocket of the MHC molecule HLA-B*2705 is of importance for peptide binding, and biophysical studies have documented altered thermodynamic stability of the molecule when Cys67 was mutated to serine (Ser67). In this study, we used HLA-B27.Cys67 and HLA-B27.Ser67 tetramers with defined T cell epitopes to determine the contribution of this polymorphic, solvent-inaccessible MHC residue to T cell recognition. We generated these HLA-B27 tetramers using immunodominant viral peptides with high binding affinity to HLA-B27 and cartilage-derived peptides with lower affinity. We demonstrate that the yield of refolding of HLA-B27.Ser67 molecules was higher than for HLA-B27.Cys67 molecules and strongly dependent on the affinity of the peptide. T cell recognition did not differ between HLA-B27.Cys67 and HLA.B27.Ser67 tetramers for the viral peptides that were investigated. However, an aggrecan peptide-specific T cell line derived from an HLA-B27 transgenic BALB/c mouse bound significantly stronger to the HLA-B27.Cys67 tetramer than to the HLA-B27.Ser67 tetramer. Modeling studies of the molecular structure suggest the loss of a SH ...
hydrogen bond with the Cys
Ser substitution in the HLA-B27 H chain which reduces the stability of the HLA-B27/peptide complex. These results demonstrate that a solvent-inaccessible residue in the B pocket of HLA-B27 can affect TCR binding in a peptide-dependent fashion.
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