Interactions between the amino-terminal domains of MHC class II molecules have a profound effect on serologic and T cell recognition: an analysis using recombinant HLA-DR/H-2E molecules.
A series of transfected L cell lines were generated expressing the products of wild-type or recombinant HLA-DR1/H-2Ek beta-chain-encoding genes paired to DR alpha or E alpha. The recombinant genes were created by reciprocal exchange of the gene segments encoding the amino (NH2)-terminal and carboxy (COOH)-terminal halves of the beta 1 domain and the beta 2 domain. The majority of the serologic determinants, predicted from the genetic composition of the class II dimers, were expressed indicating that no gross conformational changes were induced by the creation of the interspecies recombinant molecules. Subtle conformational variation was detected by the anti-H-2Eb,k,s mAb Y17. Epitope expression was dependent on the presence of the E alpha-chain and NH2-terminal sequence from the beta 1 domain of H-2Ek. Substitution of DR1 sequence in either region led to loss of recognition by Y17. This pattern of reactivity maps the Y17 epitope either to the E alpha-chain or to an exposed sequence on the fourth strand of the beta sheet of the beta 1 domain. If the Y17 epitope is located on the E alpha-chain this raises the interesting possibility that the conformation of this chain, which is invariant by sequence, may vary according to the beta-chain with which it is coexpressed. The ability of the recombinant class II dimers to present Ag to the pigeon cytochrome c-specific, H-2Ek-restricted T cell hybridoma 2B4 was assessed. Transfected L cells expressing E beta k paired to E alpha or DR alpha presented Ag with equal efficiency, and the beta 2 domain of H-2Ek could be substituted with the equivalent region from DR1 without any loss of response. Wild-type DR1 failed to function as a restriction element, however, substitution of the COOH-terminal portion of the beta 1 domain with the equivalent sequence from H-2Ek was sufficient to produce a partial recovery of Ag recognition. Cells expressing a recombinant beta 1 domain comprising the COOH-terminal sequence from H-2Ek and the NH2-terminal sequence from DR1 presented Ag when paired to DR alpha but failed to do so when paired to E alpha. This indicates that a subtle conformational disturbance caused by mismatching of the NH2-terminal region of the beta-chain and the alpha-chain can have pronounced effects on T cell recognition.(ABSTRACT TRUNCATED AT 400 WORDS)
Barber
L D
LD
Department of Immunology, Royal Postgraduate Medical School, Hammersmith Hospital, London, England.
Lechler
R I
RI
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000939:Epitopes / Q000032:analysis; D006183:H-2 Antigens / Q000276:immunology*; D006684:HLA-DR Antigens / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000276:immunology; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000276:immunology*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D006183:H-2 Antigens; D006684:HLA-DR Antigens; D011994:Recombinant Proteins