Biochemistry of Protein Structure
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Questions and Answers

What is the structure of MHC class I antigens?

  • A single light chain
  • A pair of non-identical heavy chains (α and β) (correct)
  • A single heavy chain
  • A pair of identical heavy chains

    • How many amino acids long are the peptides that can be tightly bound to a groove in MHC class I antigens?

  • Ten
  • Eleven
  • Twelve
  • Nine (correct)

    • What is the function of the groove produced by the pairing of the two extracellular domains of the α chain?

  • To bind to the plasma membrane
  • To bind to peptides (correct)
  • To bind to the T cell receptor
  • To bind to β2m

    • What determines the affinity of individual peptide binding to MHC class I antigens?

    <p>The nature and shape of the groove</p> Signup and view all the answers

    Which of the following is NOT a characteristic of MHC class I antigens?

    <p>They have two heavy chains</p> Signup and view all the answers

    What is the name of the molecule that pairs with the α chain to form the groove in MHC class I antigens?

    <p>β2m</p> Signup and view all the answers

    What technique was used to determine the detailed structure of MHC class II antigens?

    <p>X-ray crystallography</p> Signup and view all the answers

    Which chromosome contains the genes that code for MHC class I and class II antigens?

    <p>Chromosome 6</p> Signup and view all the answers

    What is the function of TAP in the context of MHC Class I molecules?

    <p>To transport peptides into the endoplasmic reticulum</p> Signup and view all the answers

    How do MHC Class I molecules interact with viral peptide antigens?

    <p>Through the binding of viral peptide to the groove of the MHC Class I molecule</p> Signup and view all the answers

    What is the function of the invariant chain in MHC Class II molecules?

    <p>To protect the MHC Class II molecule from binding to antigen</p> Signup and view all the answers

    What is the approximate number of amino acids in each domain of the immunoglobulin molecule?

    <p>110</p> Signup and view all the answers

    What is the purpose of the disulphide bond between two cysteine residues in the immunoglobulin chain?

    <p>To hold the domains together in a loop</p> Signup and view all the answers

    Where do MHC Class I molecules bind to viral peptide antigens?

    <p>In the endoplasmic reticulum</p> Signup and view all the answers

    What determines the isotype of the immunoglobulin?

    <p>The heavy chain</p> Signup and view all the answers

    What is the role of the vesicle in the context of MHC Class II molecules?

    <p>To fuse with the endosome to allow antigen processing</p> Signup and view all the answers

    Where is the carbohydrate side chain found in MHC class I antigens?

    <p>Between the α and β chains</p> Signup and view all the answers

    What is the term used to describe the recognition of peptide and MHC molecule by T cells?

    <p>MHC restriction</p> Signup and view all the answers

    What is the function of β2-microglobulin in MHC class I antigens?

    <p>To form a complex with the α chain</p> Signup and view all the answers

    What is the importance of MHC restriction in the immune response?

    <p>It restricts the ability of T cells to recognize antigens</p> Signup and view all the answers

    What is the name of the Nobel Prize winners who discovered MHC restriction?

    <p>Peter Doherty and Rolf Zinkernagel</p> Signup and view all the answers

    How many groups are MHC class I antigens subdivided into?

    <p>Three</p> Signup and view all the answers

    What are the three groups of variable class II antigens in humans?

    <p>HLA-DP, HLA-DQ, HLA-DR</p> Signup and view all the answers

    What induces the expression of class II molecules on certain cells?

    <p>Interferon-γ</p> Signup and view all the answers

    What is the location of the carbohydrate side chain in MHC class I antigens?

    <p>Between the α and β chains</p> Signup and view all the answers

    What is the name of the molecule that pairs with the α chain in MHC class I antigens?

    <p>β2-microglobulin</p> Signup and view all the answers

    Which of the following cell types expresses MHC class I molecules?

    <p>Most nucleated cells</p> Signup and view all the answers

    What is the term used to describe the recognition of peptide and MHC molecule by T cells?

    <p>MHC restriction</p> Signup and view all the answers

    How many groups are MHC class I antigens subdivided into?

    <p>3</p> Signup and view all the answers

    What is the importance of MHC restriction in the immune response?

    <p>It restricts the ability of T cells to recognize antigen</p> Signup and view all the answers

    What is the name of the Nobel Prize winners who discovered MHC restriction?

    <p>Peter Doherty and Rolf Zinkernagel</p> Signup and view all the answers

    What induces the expression of class II molecules on certain cells?

    <p>Interferon-γ</p> Signup and view all the answers

    What is the structural feature of MHC class I antigens that allows it to bind to peptides?

    <p>A groove formed by the pairing of the two extracellular domains of the α chain</p> Signup and view all the answers

    What is the component that pairs with the α chain to form the groove in MHC class I antigens?

    <p>β2-microglobulin</p> Signup and view all the answers

    How many amino acids long are the peptides that can be tightly bound to a groove in MHC class I antigens?

    <p>8-11 amino acids</p> Signup and view all the answers

    What determines the affinity of individual peptide binding to MHC class I antigens?

    <p>The nature and shape of the groove</p> Signup and view all the answers

    What is the name of the molecule that helps to form the groove in MHC class I antigens?

    <p>β2-microglobulin</p> Signup and view all the answers

    What is the function of the groove in MHC class I antigens?

    <p>To bind to the peptide antigen</p> Signup and view all the answers

    What is the characteristic of the peptides that can be tightly bound to a groove in MHC class I antigens?

    <p>They are 8-11 amino acids long</p> Signup and view all the answers

    What is the function of MHC class I antigens?

    <p>To present peptide antigens to T cells</p> Signup and view all the answers

    What is the purpose of the TAP in the context of MHC Class I molecules?

    <p>To transport viral peptides from the endoplasmic reticulum to the cytosol</p> Signup and view all the answers

    Where are MHC Class I molecules loaded with viral peptides?

    <p>In the endoplasmic reticulum</p> Signup and view all the answers

    What is the function of the MHC class I molecule?

    <p>To present viral peptides to CD8+ T cells</p> Signup and view all the answers

    What is the result of the interaction between MHC Class I molecules and viral peptides?

    <p>Activation of CD8+ T cells</p> Signup and view all the answers

    Where are the genes that code for MHC class I molecules located?

    <p>On chromosome 6</p> Signup and view all the answers

    What is the role of the endoplasmic reticulum in the context of MHC class I molecules?

    <p>To load MHC class I molecules with viral peptides</p> Signup and view all the answers

    What is the function of β2-microglobulin in the context of MHC class I molecules?

    <p>To stabilize the MHC class I molecule</p> Signup and view all the answers

    What is the result of the binding of viral peptides to MHC class I molecules?

    <p>Presentation of viral peptides to CD8+ T cells</p> Signup and view all the answers

    How many chains do MHC class II antigens have?

    <p>Two heavy chains (α and β)</p> Signup and view all the answers

    Where are the genes that code for MHC class II antigens located?

    <p>Chromosome 6</p> Signup and view all the answers

    How was the detailed structure of MHC class II antigens determined?

    <p>X-ray crystallography</p> Signup and view all the answers

    What is the characteristic of the structure of MHC class II antigens?

    <p>A folded structure</p> Signup and view all the answers

    What is the name of the molecule that pairs with the α chain to form the groove in MHC class I antigens?

    <p>β2-microglobulin</p> Signup and view all the answers

    How many amino acids long can peptides be that are tightly bound to a groove in MHC class I antigens?

    <p>Nine amino acids</p> Signup and view all the answers

    What determines the affinity of individual peptide binding to MHC class I antigens?

    <p>The shape of the groove</p> Signup and view all the answers

    What is the name of the region of chromosome 6 where MHC class I and II genes are located?

    <p>MHC region</p> Signup and view all the answers

    Which cells are restricted to express MHC class II molecules?

    <p>Dendritic cells, B lymphocytes, activated T cells, macrophages, and some epithelial cells</p> Signup and view all the answers

    What is the name of the loci that are known for the three groups of variable class II antigens in humans?

    <p>HLA-DP, HLA-DQ, HLA-DR</p> Signup and view all the answers

    Under what condition can other cells be induced to express class II molecules?

    <p>During inflammation</p> Signup and view all the answers

    What is the function of MHC class II molecules in the immune response?

    <p>To present antigens to CD4+ T cells</p> Signup and view all the answers

    What is the characteristic of cells that express MHC class II molecules?

    <p>They are able to present antigens to CD4+ T cells</p> Signup and view all the answers

    What is the result of the interaction between MHC class II molecules and antigens?

    <p>Activation of CD4+ T cells</p> Signup and view all the answers

    What is the role of MHC class II molecules in the immune response?

    <p>To present antigens to CD4+ T cells</p> Signup and view all the answers

    What is the role of the invariant chain in the context of MHC Class II molecules?

    <p>To protect the MHC class II molecule from binding to antigen in the groove</p> Signup and view all the answers

    What is the significance of MHC class II molecules in the immune response?

    <p>They are involved in the presentation of antigens to CD4+ T cells</p> Signup and view all the answers

    Where are MHC Class II molecules loaded with antigen?

    <p>Endosome</p> Signup and view all the answers

    What is the structure of the domains in MHC Class II molecules?

    <p>A loop held together by a disulphide bond between two cysteine residues</p> Signup and view all the answers

    What is the function of the vesicle in the context of MHC Class II molecules?

    <p>To fuse with the endosome to deliver antigen to MHC class II molecules</p> Signup and view all the answers

    How do MHC Class II molecules interact with antigen?

    <p>By binding to the antigen in the groove</p> Signup and view all the answers

    What is the characteristic of the antigen that can be bound to MHC Class II molecules?

    <p>It is a processed exogenous antigen</p> Signup and view all the answers

    Where are the genes that code for MHC Class II molecules located?

    <p>On an autosome</p> Signup and view all the answers

    What is the function of MHC Class II molecules?

    <p>To present exogenous antigen to T cells</p> Signup and view all the answers

    What type of T cells recognize antigens presented by MHC class II molecules?

    <p>CD4+</p> Signup and view all the answers

    What is the function of β2-microglobulin in MHC class I antigens?

    <p>To associate with the α chain</p> Signup and view all the answers

    What prevents MHC class II molecules from binding to peptides in the endoplasmic reticulum?

    <p>Invariant chain</p> Signup and view all the answers

    What is the function of MHC class I molecules?

    <p>To present endogenous antigens to CD8+ T cells</p> Signup and view all the answers

    What determines the differences between individual MHC class I antigens?

    <p>Variations in the α chain</p> Signup and view all the answers

    What is the structure of the immunoglobulin molecule?

    <p>Two heavy chains and two light chains</p> Signup and view all the answers

    What is the role of antigen-presenting cells (APCs) in the context of MHC class I antigens?

    <p>To present antigens to T cells</p> Signup and view all the answers

    What is the purpose of the peptide binding groove in MHC class I antigens?

    <p>To present antigens to T cells</p> Signup and view all the answers

    Where are the genes that code for MHC class II antigens located?

    <p>Chromosome 6</p> Signup and view all the answers

    What type of antigens are processed by the lysosomal route and presented by MHC class II antigens?

    <p>Exogenous antigens</p> Signup and view all the answers

    What type of bonding is used to determine the detailed structure of MHC class I antigens?

    <p>X-ray crystallography</p> Signup and view all the answers

    What is the role of β2-microglobulin in MHC class I molecules?

    <p>To pair with the α chain to form the groove</p> Signup and view all the answers

    What is the location of the genes that code for MHC class I antigens?

    <p>Chromosome 6</p> Signup and view all the answers

    What is the function of TCRs and BCRs?

    <p>To recognize and bind to antigens</p> Signup and view all the answers

    What is the function of the α chain in MHC class I antigens?

    <p>To form the peptide binding groove</p> Signup and view all the answers

    Why do T cells specific for a particular peptide and a particular MHC allele not respond if the same peptide were to be presented by a different MHC molecule?

    <p>Because the MHC molecule is not recognized by the T cell</p> Signup and view all the answers

    What is the result of the activation of dendritic cells by binding to detection receptors?

    <p>Inflammation and activation of the adaptive system</p> Signup and view all the answers

    What is the function of adjuvants in vaccines?

    <p>To enhance the immune response to a separate antigen</p> Signup and view all the answers

    What are the patterns recognized by phagocytic cells?

    <p>Lipoproteins and charged molecules or peptides</p> Signup and view all the answers

    What is the characteristic of an antigenic molecule?

    <p>It can have several antigenic determinants</p> Signup and view all the answers

    What determines the species differences in the immune response?

    <p>Genetic factors of the recipient animal</p> Signup and view all the answers

    What is the result of the interaction between antigens and the adaptive immune system?

    <p>Inflammation and activation of the adaptive system</p> Signup and view all the answers

    What is the role of phagocytic cells in the immune response?

    <p>To recognize and eliminate pathogens</p> Signup and view all the answers

    What is the characteristic of antigens that interact with components of the adaptive immune system?

    <p>They can bind to T-cell recognition receptors</p> Signup and view all the answers

    What is the main function of MHC molecules in the context of antigen recognition by T cells?

    <p>To facilitate the interaction between T cells and antigen-presenting cells</p> Signup and view all the answers

    What is the term used to describe the recognition of peptide and MHC molecule by T cells?

    <p>MHC restriction</p> Signup and view all the answers

    Which of the following MHC molecules is responsible for presenting antigens to CD4+ T cells?

    <p>MHC class II</p> Signup and view all the answers

    What is the location of the genes that code for MHC class I and class II molecules?

    <p>Chromosome 6</p> Signup and view all the answers

    What is the significance of MHC restriction in the immune response?

    <p>It facilitates the interaction between T cells and antigen-presenting cells</p> Signup and view all the answers

    Which of the following T cells does not respond to antigen presentation by MHC molecules?

    <p>B cells</p> Signup and view all the answers

    What is the role of MHC molecules in the context of antigen presentation?

    <p>To process and present antigens to T cells</p> Signup and view all the answers

    Which of the following MHC molecules is responsible for presenting antigens to CD8+ T cells?

    <p>MHC class I</p> Signup and view all the answers

    What is the main consequence of MHC restriction in the immune response?

    <p>Restriction of the ability of T cells to recognize antigen</p> Signup and view all the answers

    Which of the following cell types is restricted to expressing MHC class II molecules?

    <p>Dendritic cells, B lymphocytes, macrophages, and some epithelial cells</p> Signup and view all the answers

    What is the role of interferon-γ in the expression of MHC class II molecules?

    <p>It induces the expression of MHC class II molecules on certain cells</p> Signup and view all the answers

    What is the term used to describe the dual recognition of peptide and MHC molecule by T cells?

    <p>MHC restriction</p> Signup and view all the answers

    What is the importance of MHC restriction in the immune response?

    <p>It restricts the ability of T cells to recognize antigen</p> Signup and view all the answers

    What is the name of the Nobel Prize winners who discovered MHC restriction?

    <p>Peter Doherty and Rolf Zinkernagel</p> Signup and view all the answers

    What is the result of the interaction between MHC class I molecules and viral peptides?

    <p>Recognition of viral peptides by CD8+ T cells</p> Signup and view all the answers

    What is the characteristic of the MHC class II molecules that allows them to bind to peptides?

    <p>The presence of a peptide-binding groove</p> Signup and view all the answers

    What is the role of the β2m molecule in MHC class I antigens?

    <p>It pairs with the α chain to form the groove</p> Signup and view all the answers

    What is the characteristic of the peptides that can be tightly bound to a groove in MHC class I antigens?

    <p>They are 9-11 amino acids long</p> Signup and view all the answers

    What determines the affinity of individual peptide binding to MHC class I antigens?

    <p>The nature and shape of the groove</p> Signup and view all the answers

    How do MHC class I and class II antigens differ in terms of their chain structure?

    <p>MHC class I has one heavy chain, while MHC class II has two</p> Signup and view all the answers

    What is the significance of MHC restriction in the immune response?

    <p>It enables the recognition of foreign antigens by T-cells</p> Signup and view all the answers

    What is the function of the groove produced by the pairing of the two extracellular domains of the α chain?

    <p>It binds to viral peptides</p> Signup and view all the answers

    What is the name of the technique used to determine the detailed structure of MHC class II antigens?

    <p>X-ray crystallography</p> Signup and view all the answers

    Where are the genes that code for MHC class I and class II antigens located?

    <p>Chromosome 6</p> Signup and view all the answers

    Study Notes

    MHC Class I Antigens

    • MHC class I antigens are composed of a heavy chain (α) and a light chain (β2-microglobulin)
    • The heavy chain is divided into three domains: α1, α2, and α3
    • The peptide-binding groove is formed by the pairing of the α1 and α2 domains
    • The β2-microglobulin chain is paired with the α chain
    • The affinity of peptide binding depends on the nature and shape of the groove

    MHC Class II Antigens

    • MHC class II antigens have two heavy chains: α and β
    • Both chains are coded for by genes in the MHC region of chromosome 6
    • The detailed structure of MHC class II antigens was determined by X-ray crystallography
    • Each chain is made up of domains of about 110 amino acids held together in a loop by a disulphide bond between two cysteine residues

    MHC Restriction

    • MHC restriction is the process of dual recognition of peptide and MHC molecule
    • The MHC molecule restricts the ability of the T cell to recognize antigen
    • MHC restriction was recognized by the award of the Nobel Prize in Medicine to Peter Doherty and Rolf Zinkernagel

    Class I and Class II Antigen Expression

    • Most nucleated cells express class I molecules
    • Expression of class II molecules is restricted to a few cell types: dendritic cells, B lymphocytes, activated T cells, macrophages, inflamed vascular endothelium, and some epithelial cells
    • Other cells can be induced to express class II molecules under the influence of interferon (IFN)-γ released during inflammation

    Antigen Presentation

    • Antigens in different intracellular compartments can be captured and presented to CD4+ or CD8+ T cells via different mechanisms
    • There are different forms of MHC molecule, including HLA-DP, HLA-DQ, and HLA-DR in humans

    MHC Class I Antigens

    • MHC class I antigens consist of a heavy chain (α) and a light chain (β2m)
    • The heavy chain is made up of three domains (α1, α2, and α3) with a similar structure and amino acid sequence
    • The peptide-binding groove is formed by the pairing of the two extracellular domains (α1 and α2) of the α chain
    • The affinity of individual peptide binding depends on the nature and shape of the groove

    MHC Class II Antigens

    • MHC class II antigens have two heavy chains (α and β) coded for by genes in the MHC region of chromosome 6
    • Each chain is made up of domains of about 110 amino acids held together in a loop by a disulphide bond between two cysteine residues
    • The heavy chains determine the isotype of the immunoglobulin
    • MHC class II antigens have a folded structure with a peptide-binding groove between the α and β chains

    MHC Restriction

    • MHC restriction is the process of dual recognition of peptide and MHC molecule by T cells
    • The MHC molecule restricts the ability of the T cell to recognize antigen
    • MHC restriction is important in the immune response and was recognized by the Nobel Prize in Medicine

    Expression of MHC Molecules

    • Most nucleated cells express class I molecules
    • Expression of class II molecules is restricted to a few cell types: dendritic cells, B lymphocytes, activated T cells, macrophages, inflamed vascular endothelium, and some epithelial cells
    • Other cells can be induced to express class II molecules under the influence of interferon (IFN)-γ released during inflammation

    HLA Loci

    • In humans, there are three groups of variable class II antigens: HLA-DP, HLA-DQ, and HLA-DR

    MHC Class I Antigens

    • MHC class I antigens have a groove produced by the pairing of the two extracellular domains (α1 and α2) of the α chain.
    • A peptide of 9 amino acids can be tightly bound to this groove.
    • The affinity of individual peptide binding depends on the nature and shape of the groove.

    MHC Class II Antigens

    • MHC class II antigens have two heavy chains, α and β, both coded for by genes in the MHC region of chromosome 6.
    • The detailed structure of MHC class II antigens has a folded structure similar to class I antigens with the peptide-binding groove found between the α and β chains.
    • Expression of class II molecules is restricted to a few cell types: dendritic cells, B lymphocytes, activated T cells, macrophages, inflamed vascular endothelium, and some epithelial cells.

    MHC Restriction

    • MHC restriction refers to the process of dual recognition of peptide and MHC molecule, restricting the ability of the T cell to recognize antigen.
    • This process was recognized by the award of the Nobel Prize in Medicine to Peter Doherty and Rolf Zinkernagel.

    Immunoglobulin Structure

    • Immunoglobulin molecules have a basic structure consisting of two heavy chains and two light chains.
    • Each chain is made up of domains of about 110 amino acids held together in a loop by a disulphide bond between two cysteine residues in the chain.
    • The heavy chains determine the isotype of the immunoglobulin.

    Antigen Presentation

    • Antigens in different intracellular compartments can be captured and presented to CD4+ or CD8+ T cells through different mechanisms.
    • This process involves the complexing of viral antigen with MHC class I molecules in the endoplasmic reticulum and the complexing of processed exogenous antigen with MHC class II molecules in the endosome.

    Antigen Presentation

    • Exogenous antigens are processed by the lysosomal route and presented by MHC class II antigens to CD4+ T cells.
    • MHC class II molecules are synthesized and stored in the endoplasmic reticulum until they are ready to be transported to the cell surface.
    • In the endoplasmic reticulum, class II molecules are prevented from binding to peptides in the lumen by a protein known as MHC class II-associated invariant chain.

    MHC Class I and II Molecules

    • MHC class I molecules present endogenous/viral antigens to CD8+ T cells.
    • MHC class II molecules present exogenous antigens to CD4+ T cells.
    • MHC class I molecules are made up of an α heavy chain, controlled by a gene in the relevant MHC locus, associated with a smaller chain called β2-microglobulin, controlled by a gene on chromosome 12.

    T-Cells and B-Cells

    • T cells specific for a particular peptide and a particular MHC allele will not respond if the same peptide were to be presented by a different MHC molecule or as a different peptide.
    • B cells have surface-bound immunoglobulin molecules that can be secreted as soluble molecules, with predetermined specificity for epitopes, and are extremely diverse.

    Immunoglobulin Molecule Structure

    • The basic structure of the immunoglobulin molecule has a four-chain structure: two identical heavy (H) chains (mol. wt. 50 kDa) and two identical light (L) chains (mol. wt. 25 kDa).

    Adjuvants and Immune Response

    • Adjuvants are substances that improve an immune response to a separate, often rather weak, antigen.
    • Genetic factors, such as species differences and individual differences, can affect the immune response.
    • Activation of dendritic cells by binding to detection receptors leads to inflammation and subsequently activates the adaptive system.

    MHC Molecules

    • MHC molecules have a peptide-binding groove, similar to class I antigens, and are composed of α and β chains.
    • The β2-microglobulin (β2m) is a carbohydrate side chain found between the α and β chains.

    MHC Restriction

    • MHC restriction is the process of dual recognition of peptide and MHC molecule, restricting the ability of T cells to recognize antigens.
    • This concept was recognized by the award of the Nobel Prize in Medicine to Peter Doherty and Rolf Zinkernagel.

    MHC Class I Antigens

    • MHC class I antigens are subdivided into three groups: A, B, and C, each controlled by a different gene locus.
    • MHC class I antigens are expressed by most nucleated cells.

    MHC Class II Antigens

    • MHC class II antigens are expressed by a few cell types, including dendritic cells, B lymphocytes, activated T cells, macrophages, and inflamed vascular endothelium.
    • MHC class II antigens can be induced to express in other cells under the influence of interferon (IFN)-γ released during inflammation.
    • There are three groups of variable class II antigens: HLA-DP, HLA-DQ, and HLA-DR.

    Antigen Presentation

    • Antigens in different intracellular compartments can be captured and presented to CD4+ or CD8+ T cells through different mechanisms.
    • MHC class II antigens have two heavy chains, α and β, both coded for by genes in the MHC region of chromosome 6.

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    Description

    This quiz covers the biochemistry of protein structure, including the binding of amino acids to a groove produced by beta 2 microglobulin (β2m).

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