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49 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 is TcR co-expressed with
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CD3
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What form of antigen does Ig recognize
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macromolecules and small chemical. Conformational and linear epitopes
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What forrms of antigens does TcR recognize
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Peptides displayed by molecules on APC's. linear epitopes
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Describe the diversity of Ig
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Each clone has a unique specificity. Potential for 10^9 distinct specificities
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Describe the diversity of TcR
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Each clone has a unique specificity. Potential for 10^11 distinct specificities
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What is antigen recognition mediated by in Ig
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Variable regions of heavy and light chains of membrane Ig
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What is antigen recognition mediated by in TcR
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Variable regions of alpha and beta chains
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What are the two classes of TcR and which is most common
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alpha-beta (most common) and gamma-delta (5-10 percent)
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What is antigen processing
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the process by which peptides are generated from larger polypeptides
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What is the MHC and what does it do
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a cluster of closely linked genes on Chr. 6 that encode proteins that control T cell mediated immune responses and determine the fate of transplanted tissues
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What key molecules are encoded in the MHC
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HLA molecules (Human leukocyte antigens
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Describe the structure of MHC class I molecules
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Alpha 1 and 2 variable regions and alpha 3 and beta 2 microglobulin on the constant region
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Describe the structure of MHC class II molecules
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alpha 1 and beta 1 variable regions and alpha 2 and beta 2 constant regions
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What does MHC class I bind to
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CD8 in concert with the TCR
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what does MHC class II bind to
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CD4 in concert with the TCR
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What do MHC class I and II molecules do?
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bind peptides and present them to the T cells
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What is MHC stand for
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Major histocompatibility complex
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Describe the structure of an MHC molecule
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The MHC is a binding pocket for peptide presentation and a polymorphic residue which binds the T cell receptor
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What are the three isotypes of MHC class I molecules that we have know about
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HLA – a, HLA – b, and HLA – c
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What are the three ISA types of MHC class to molecules to know about
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HLA – DP, HLA – DQ, HLA – DR
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How to HLA molecules differ
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The cell types there expressed on, the peptide display, their peptide generation pathways, and the T-cell they talk to
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What types of cells do MHC class I will molecules live on
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Nearly every cell in the body except for erythrocytes
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What types of cells do MHC class to molecules live on
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Antigen presenting cells i.e. B cells, macrophages, dendritic cells
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Describe the genetics and heritability of MHC genes
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they are codominant and inherited as haplotypes
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What determines the peptides that bind to MHC molecules
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Polymorphism
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In the absence of disease what do MHC molecules display
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Normal peptides found in the body
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What is MHC restriction
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It means that they T cell is restricted to seeing one particular peptide on one particular MHC molecule that encodes for. For example a T cell that is designed to bind to and HLA –a MHC molecule and peptide X will not see that same peptide X if it is bound to and HLA – b molecule
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How does MHC class I into antigen processing and presentation pathways differ
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They differ in the sites were peptides originate
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Where would MHC class II peptides originate from
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And extracellular origin
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Where would MHC class I molecules originate from
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And intracellular origin
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how would a macrophage take in an antigen
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Phagocytosis
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How would a B cell take up an antigen
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It would be taken up by a surface immunoglobulin and routed to endosomal compartments
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How to dendritic cell take-up antigen
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endocytosis
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What is the MHC class I pathway designed to do
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To get a pathogenic peptide seen by a CD8 positive T cell
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With his MHC heterozygosity due to the progression of AIDS and HIV positive individuals
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It delays the onset
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On a typical hepatocyte how many class I molecules would you find
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6
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Describe the development of a T cell
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They are made in the bone marrow and a T cell precursor will travel up the bone marrow into the thymus to mature. It will then travel to the secondary lymphoid tissues
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What kind of T cell precursor enters the thymus and what does that mean
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A double negative it expresses neither CD4 or CD8
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Where it is TCR rearrangement occur
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The cortex of the thymus
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After rearrangement what kind of committed alpha-beta T cell occurs
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A double positive
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If an immature T cell weekly recognizes a class II molecule what does it become and what is this called
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A mature CD4 positive T cell and positive selection
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If an immature T cell weekly recognizes a class I MHC molecule what is a become and what is this called
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A mature CD8 positive T cell and positive selection
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If there is no recognition of an MHC molecule what is is called and what happens
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Failure of positive selection and apoptosis
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There is strong recognition of either class I or class II MHC molecules what is this called and what happens
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Negative selection and apoptosis
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What happens after positive selection
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Be mature single positive naïve T cell migrates to the thymic medulla and then to the periphery
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how many thymocytes dies either by failure of positive selection or negative selection
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95%
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What are the four steps of thymic selection of T cells
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TcR rearranges, Positive selection on DP celles in concert with cortical epithelial cells, negative selection of DP cells in concert with dendritic cells, mature self tolerant, self MHC restricted single positive T cells
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does positive negative or failure of positive selection happened first
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Positive
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