Position 71 in the α helix of the DRβ domain is predicted to influence peptide binding and plays a central role in allorecognition

Abstract

Despite all the structural and functional data that have been accumulated regarding major histocompatibility complex (MHC) class II molecules during recent years, the relative contribution of putative T cell receptor (TcR)-contacting residues and peptide-binding MHC polymorphisms to MHC-restricted and allospecific T cell responses remains a point of contention. Some authors emphasize the importance of direct interaction between the allospecific TcR and polymorphic MHC residues whereas other emphasize the role of naturally processed MHC-bound peptides. We have previously described a new HLA-DRB1 allele: DR BON (DRB1*0103). This gene differs from DRB1*0101 by six base pairs clustered in the third variable region of the second exon leading to three amino acid changes at positions 67, 70 and 71 of the beta chain of the HLA-DR molecule. To define the respective role of these residues in allorecognition, we have performed site-directed mutagenesis on the DRB1*0103 allele to create six mutants which are intermediary between the DR BON and the DR1 alleles. These mutant cDNA were expressed in mouse fibroblasts and the transfectants with the highest expression of class II molecules were used as stimulators for a panel of ten anti-DR BON and five anti-DR1 alloreactive T cell clones. We demonstrate that the residue at the peptide-binding position 71 is of paramount importance in the alloresponse of these clones. In addition some clones were sensitive to amino acid substitution at the TcR-contacting position 70, while substitution at position 67 affects very few clones. The dominance of residue 71 was also observed with an influenza hemagglutinin-specific HLA-DR BON-restricted T cell line.

Sequence Variability Analysis of Human Class I and Class II MHC Molecules: Functional and Structural Correlates of Amino Acid Polymorphisms

“…58 Indeed, polymorphisms in the TCR contact sites of the MHC have been reported to lead to alloreacitivity for both class I 59 and class II allogeneic MHC. 60 However, alloresponse is often directed against allogeneic MHC molecules displaying amino acid sequencing differences only in the buried portion of the MHC binding groove, which is inaccessible to the TCR. 57,61 To account for these observations, a second model for alloreactivity has been proposed, driven by the specific peptide presented by the allogeneic MHC molecules.…”

Role of polymorphic residues of human leucocyte antigen‐DR molecules on the binding of human immunodeficiency virus peptides

“…9,10 We have previously constructed intermediate HLA-DR molecules by either single or double substitution of the amino acids on the DR103 molecule by those of the DR1 molecule at positions 67, 70 and 71. 7 These mutated molecules were used to test selected HIV peptides in binding experiments and in stimulation of specific T-cell responses.…”

“…8 Residues 71 and probably 67 are part of a polymorphic peptide-binding pocket, while residue 70 may influence contacts with the TCR. 5,7 Binding of 96 peptides derived from HIV proteins (p18, p25, nef, gp120 and gp41) to DR1 and DR103 molecules was performed to define the role of polymorphic human leucocyte antigen (HLA)-DR residues in interaction specificity. Peptides that bind to most class II molecules (promiscuous peptides), form potentially important T cell epitopes for the design of putative peptidebased HIV vaccines.…”

“…4 This region is known to be important for peptide-specific and alloreactive T-cell responses. [5][6][7] Recently, the three-dimensional structure of the DR1 molecule complexed with the influenza haemagglutinin peptide HA306-318 was resolved. 8 Residues 71 and probably 67 are part of a polymorphic peptide-binding pocket, while residue 70 may influence contacts with the TCR.…”

“…7 Hybridoma cells secreting a monoclonal antibody (mAb) L243 reactive with a monomorphic DR epitope were obtained from the American Type Culture Collection (ATCC #HB55). Antibodies were purified using protein A Sepharose CL-4B (Pharmacia Biotech SA, St Quentin Yvelines, France).…”