Different regions of the N-terminal domains of HLA-DR1 influence recognition of individual peptide-DR1 complexes.
The contributions of individual amino acids in the polymorphic beta chain and the conserved alpha chain of HLA-DR1 to influenza HA-specific DR1-restricted and anti-DR1 allospecific T-cell recognition were analyzed. The genes encoding HLA-DR1 were subjected to site-directed mutagenesis in order to introduce single amino acid substitutions at 12 positions in the beta 1 domain and 11 positions in the alpha 1 domain. The beta 1-domain substitutions were all at polymorphic positions and introduced residues that are found in DR4 alleles. The amino acids introduced into the DR alpha 1 domain were based on the sequences of other human and mouse class II alpha chains. The responses of 12 DR1-restricted T-cell clones specific for two peptides of HA and seven anti-DR1 allospecific clones were studied. Substitutions at positions that point up from and into the peptide-binding site in the third variable region of the beta 1-domain alpha-helix caused substantial reduction in the responses of all of the clones. Substitutions at multiple positions in the beta 1-domain floor and in the alpha 1 domain influenced the anti-DR1 responses of the alloreactive and of the HA100-115-specific T-cell clones. In contrast, very few changes outside of the beta 1 domain third variable region affected the responses of the HA306-324-specific DR1-restricted T-cell clones. These results suggest that a surprisingly limited region of the HLA-DR1 molecule is critically involved in T-cell recognition of HA306-324 by DR1-restricted T cells. However, the susceptibility of the HA100-115-specific and the anti-DR1 allospecific T-cell clones to substitutions at multiple positions in both N-terminal domains shows that the response to DR1-HA306-324 is unusual and may reflect the promiscuity with which this peptide binds to HLA-DR molecules.
Tuosto
L
L
Department of Cell Biology, University of Rome, Italy.
Karr
R W
RW
Fu
X T
XT
Olson
R R
RR
Cundari
E
E
Piccolella
E
E
Lechler
R
R
Lombardi
G
G
D000595:Amino Acid Sequence; D002461:Cell Line, Transformed; D002999:Clone Cells; D000939:Epitopes / Q000276:immunology; D015798:HLA-DR1 Antigen / Q000737:chemistry* / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000276:immunology*
D000939:Epitopes; D015798:HLA-DR1 Antigen