Antigen presentation to specific T cells by Ia molecules selectively altered by site-directed mutagenesis. 1989

S J Brett, and D McKean, and J York-Jolley, and J A Berzofsky
Molecular Immunogenetics and Vaccine Research Section, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.

A functional analysis of mutant class II molecules was conducted to identify regions important for antigen-specific T cell activation. Site-directed mutagenesis was used to construct a panel of mutant A beta k genes containing either single or multiple d allele substitutions in the beta 1 domain. The product of each of these genes was expressed with either the A alpha d or A alpha k polypeptide in the Ia-negative B cell lymphoma M12.C3. These mutant class II molecule-bearing cells were tested for their ability to present antigen to a panel of Ak-restricted T cell clones specific for various epitopes of myoglobin. Results from this analysis demonstrate that T helper clones recognized complex determinants interacting with multiple residues on the beta 1 domain and also requiring the haplotype-matched alpha 1 domain. This is in contrast to monoclonal antibodies that recognize a domain-specific, immunodominant region involving residues 40, 63, and 65-67. Every T helper clone was found to interact with a distinct pattern of residues, even among clones recognizing the same combination of peptide and major histocompatibility complex (MHC) molecule. The 3 for 1 residue substitution between k and d alleles at residues 65-67 was one of the most important, because it resulted in loss of ability to present antigen to 7 of 7 I-Ak-restricted T cell clones. These residues have been shown previously to comprise the immunodominant allo-specific serological determinants and to stimulate some alloreactive T cell clones. Substitution at residues 12 and 13 also abrogated antigen presentation to all the T cell clones, but this may be a consequence of a conformational change due to altered alpha beta chain pairing. Substitution at position 9, which is predicted to be located in the floor of the peptide-binding groove where it should not interact directly with the T cell receptor, enhanced presentation of the antigenic site 102-118 to some T cells and diminished it to others. This finding suggests a most interesting conclusion that the same antigenic site may bind in different conformations or orientations to the same MHC molecule, although an indirect effect on the conformation of the MHC molecule itself cannot be excluded. Substitutions at residues 85, 86 and 88 also abrogated the response of one T cell clone but not others specific for the same peptide with the same Ia molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

UI MeSH Term Description Entries
D008213 Lymphocyte Activation Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION. Blast Transformation,Blastogenesis,Lymphoblast Transformation,Lymphocyte Stimulation,Lymphocyte Transformation,Transformation, Blast,Transformation, Lymphoblast,Transformation, Lymphocyte,Activation, Lymphocyte,Stimulation, Lymphocyte
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D002999 Clone Cells A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed) Clones,Cell, Clone,Cells, Clone,Clone,Clone Cell
D005802 Genes, MHC Class II Genetic loci in the vertebrate major histocompatibility complex that encode polymorphic products which control the immune response to specific antigens. The genes are found in the HLA-D region in humans and include H-2M, I-A, and I-E loci in mice. Class II Genes,Genes, Class II,Genes, HLA Class II,MHC Class II Genes,Class II Gene,Gene, Class II
D006239 Haplotypes The genetic constitution of individuals with respect to one member of a pair of allelic genes, or sets of genes that are closely linked and tend to be inherited together such as those of the MAJOR HISTOCOMPATIBILITY COMPLEX. Haplotype
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D000938 Antigen-Presenting Cells A heterogeneous group of immunocompetent cells that mediate the cellular immune response by processing and presenting antigens to the T-cells. Traditional antigen-presenting cells include MACROPHAGES; DENDRITIC CELLS; LANGERHANS CELLS; and B-LYMPHOCYTES. FOLLICULAR DENDRITIC CELLS are not traditional antigen-presenting cells, but because they hold antigen on their cell surface in the form of IMMUNE COMPLEXES for B-cell recognition they are considered so by some authors. Accessory Cells, Immunologic,Antigen-Presenting Cell,Immunologic Accessory Cells,Accessory Cell, Immunologic,Cell, Immunologic Accessory,Cells, Immunologic Accessory,Immunologic Accessory Cell,Antigen Presenting Cell,Antigen Presenting Cells,Cell, Antigen-Presenting,Cells, Antigen-Presenting
D000949 Histocompatibility Antigens Class II Large, transmembrane, non-covalently linked glycoproteins (alpha and beta). Both chains can be polymorphic although there is more structural variation in the beta chains. The class II antigens in humans are called HLA-D ANTIGENS and are coded by a gene on chromosome 6. In mice, two genes named IA and IE on chromosome 17 code for the H-2 antigens. The antigens are found on B-lymphocytes, macrophages, epidermal cells, and sperm and are thought to mediate the competence of and cellular cooperation in the immune response. The term IA antigens used to refer only to the proteins encoded by the IA genes in the mouse, but is now used as a generic term for any class II histocompatibility antigen. Antigens, Immune Response,Class II Antigens,Class II Histocompatibility Antigen,Class II Major Histocompatibility Antigen,Ia Antigens,Ia-Like Antigen,Ia-Like Antigens,Immune Response Antigens,Immune-Associated Antigens,Immune-Response-Associated Antigens,MHC Class II Molecule,MHC II Peptide,Class II Antigen,Class II Histocompatibility Antigens,Class II MHC Proteins,Class II Major Histocompatibility Antigens,Class II Major Histocompatibility Molecules,I-A Antigen,I-A-Antigen,IA Antigen,MHC Class II Molecules,MHC II Peptides,MHC-II Molecules,Antigen, Class II,Antigen, I-A,Antigen, IA,Antigen, Ia-Like,Antigens, Class II,Antigens, Ia,Antigens, Ia-Like,Antigens, Immune-Associated,Antigens, Immune-Response-Associated,I A Antigen,II Peptide, MHC,Ia Like Antigen,Ia Like Antigens,Immune Associated Antigens,Immune Response Associated Antigens,MHC II Molecules,Molecules, MHC-II,Peptide, MHC II,Peptides, MHC II

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