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27 Cards in this Set
- Front
- Back
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How do T cells "see" antigens?
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Via the T cell receptor (TcR)
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What type of molecule is TcR?
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a signal transducing membrane protein
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What protein is co-expressed with TcR?
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CD3
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The two main tyes of TcRs account for all the receptors on what percentage of T cells?
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90-95%
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What molecule is used to present or display peptides to T cells?
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MHC molecules
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What is the process by which peptides are generated from larger polypeptides (for presentation)?
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Antigen processing
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What is necessary for T cells to function?
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contact with other cells
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What is the MHC?
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a cluster of closely linked genes on Chr. 6 that encode immune proteins
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What is the function of the proteins encoded by the MHC?
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control T cell mediated immune responses, determine the fate of transplanted tissue, encodes human leukocyte antigens (HLA)
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Which classes of MHC molecules bind peptides and present them to T cells?
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class I and II
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How is the peptide oriented in the MHC molecule?
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it sits within the groove
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How are peptides bound to MHC molecules?
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via anchor residues
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What does the T cell receptor "see"?
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BOTH the peptide and the MHC molecule
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Is it true that expression of MHC molecules differs between tissues and cell types?
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yes
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Describe the genetics of MHC genes.
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They are co-dominant and inherited as haplotypes
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What do polymorphisms in MHC molecules determine?
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which peptides the MHC can bind
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TcRs only recoginize specific combinations of what two molecules (MHC restriction)?
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specific MHCs with specific peptides
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How do class I and II antigen processing and presentation pathways differ?
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the sites where peptides originate
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How do macrophages take up antigen?
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phagocytosis
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In CD8 T cells, where is peptide bound to class I MHC?
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in the ER
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Where do T cell precursors go after they leave the bone marrow?
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to the thymus
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Where do Mature T cells go after they leave the thymus?
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to Secondary lymphoid tissues (Lymph node, Spleen, GALT)
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What does the term "double-negative" refer to?
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A "pro T-cell" that isnt not expressing CD4 or CD8 characteristics
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What happens if T cells do not exhibity positive selection in the thymus?
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they die via Apoptosis
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What happens if selection occurs on a class I MHC molecule?
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then the cell is committed to the CD8+ subset (cytotoxic T lymphocyte)
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What happens if selection occurs on a class II MHC molecule?
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then the cell is committed to the CD4+ subset (T helper lymphocyte, Th1 or Th2)
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What does negative selection protect against?
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it stops the formation of T cells that react against "self" peptides
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