Major Histocompatibility (MHC)
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Questions and Answers

What is the main role of MHC class I molecules?

  • Presenting antigens to Cytotoxic T cells (correct)
  • Presenting antigens to T Helper cells
  • Transporting antigens to lymph nodes
  • Digesting pathogens for immune response

    • Which of the following cell types can function as Antigen Presenting Cells (APCs)?

  • Macrophages (correct)
  • Eosinophils
  • Neutrophils
  • Natural Killer cells

    • How do T lymphocytes recognize antigens?

  • Through presentation on the surface of cells via receptors (correct)
  • By direct interaction with floating antigens
  • By detecting changes in body temperature
  • Through contact with all immune cells

    • What is the primary function of dendritic cells in the immune response?

    <p>To transport antigens to lymph nodes</p> Signup and view all the answers

    What occurs after an antigen is processed by an Antigen Presenting Cell?

    <p>It is presented on the cell surface with MHC molecules.</p> Signup and view all the answers

    During an immune response, macrophages significantly enhance which specific immune activity?

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

    What type of antigen do MHC class I molecules primarily present?

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

    What is a key feature of the specialized receptors in Antigen Presenting Cells?

    <p>They specifically present antigens in conjunction with MHC molecules.</p> Signup and view all the answers

    Why is it crucial for most tissues to express MHC class I molecules?

    <p>To mount a T cell response against intracellular infections</p> Signup and view all the answers

    Which types of pathogens are primarily managed by Cytotoxic T cell responses?

    <p>Intracellular pathogens, especially viruses</p> Signup and view all the answers

    What role do B cells play in relation to T cells?

    <p>They present antigens to T cells for antibody responses.</p> Signup and view all the answers

    Which of the following describes intracellular antigens?

    <p>They are processed in the cytosol by the proteasome.</p> Signup and view all the answers

    What is the role of the transporter associated with antigen processing (TAP) system?

    <p>To bring processed antigens into the endoplasmic reticulum.</p> Signup and view all the answers

    How are extracellular antigens typically processed within a cell?

    <p>They undergo receptor-mediated endocytosis.</p> Signup and view all the answers

    What is a key difference between how intracellular and extracellular antigens are presented?

    <p>Intracellular antigens are presented on MHC 1, while extracellular antigens utilize MHC 2.</p> Signup and view all the answers

    Which mechanism is involved in transporting MHC molecules to the cell surface after the fusion of vesicles containing antigens?

    <p>Transport vesicle movement.</p> Signup and view all the answers

    What characterizes extracellular antigens?

    <p>They come from bacteria, parasites, and fungi that do not replicate inside cells.</p> Signup and view all the answers

    In the presentation of antigens on MHC molecules, which structure contains pre-formed MHC 2 molecules?

    <p>Golgi complex.</p> Signup and view all the answers

    Which statement best describes the processing pathway of intracellular antigens?

    <p>They are processed by the proteasome before interacting with MHC molecules.</p> Signup and view all the answers

    Which immune response type is primarily activated by MHC 1 molecules?

    <p>Cell-mediated response.</p> Signup and view all the answers

    Match the following types of MHC molecules with their primary T cell interactions:

    <p>MHC class I = Antigen Presenting Cells MHC class II = Macrophages</p> Signup and view all the answers

    Match the following immune cells with their respective locations:

    <p>Macrophages = Skin and mucosal surfaces Dendritic cells = Regional draining lymph nodes B cells = Bone marrow T cells = Peripheral blood</p> Signup and view all the answers

    Match the following antigen processing functions to the respective immune cells:

    <p>Macrophages = Phagocytosis and cytokine release Dendritic cells = Antigen transport to lymph nodes B cells = Antigen recognition and antibody production Cytotoxic T cells = Destruction of infected cells</p> Signup and view all the answers

    Match the following pathogens with their primary immune targets:

    <p>Viruses = MHC class I molecules Bacteria = Antigen Presenting Cells Fungi = Cytotoxic T cells Parasites = T Helper cells</p> Signup and view all the answers

    Match the following descriptions with the correct MHC molecule type:

    <p>MHC class I = Found on almost all nucleated cells MHC class II = Found on professional APCs</p> Signup and view all the answers

    Match the cells to their roles in antigen presentation:

    <p>Macrophages = Enhance phagocytosis Dendritic cells = Activate T cell responses B cells = Produce antibodies Cytotoxic T cells = Kill infected cells</p> Signup and view all the answers

    Match the immune response activity with the respective immune components:

    <p>Cytotoxic T cells = Targeting infected cells T Helper cells = Activation of other immune cells Antigen Presenting Cells = Antigen processing and presentation Cytokines = Regulation of immune responses</p> Signup and view all the answers

    Match the following characteristics with the correct type of antigen:

    <p>Intracellular antigens = Present in virus-infected cells Extracellular antigens = Found in body fluids Peptides = Result from antigen digestion Carbohydrates = Often a component of bacterial structure</p> Signup and view all the answers

    Match the following immune processes with their descriptions:

    <p>Antigen uptake = Digestion into smaller fragments MHC transport = Bringing antigen-MHC complex to cell surface T cell activation = Recognition of MHC-antigen complex Cytokine release = Enhances immune response efficiency</p> Signup and view all the answers

    Match the following types of antigens with their characteristics:

    <p>Intracellular Antigens = Presented by MHC class I molecules Extracellular Antigens = Brought into cells by receptor-mediated endocytosis</p> Signup and view all the answers

    Match the following processes with their associated antigens:

    <p>Proteasome processing = Intracellular antigens Endocytosis = Extracellular antigens MHC class I presentation = Intracellular antigens MHC class II presentation = Extracellular antigens</p> Signup and view all the answers

    Match the following components with their functions:

    <p>TAP system = Transports peptides to the endoplasmic reticulum Golgi complex = Contains pre-formed MHC class II molecules Transport vesicle = Moves MHC molecules to the cell surface Vesicle fusion = Combines antigen-containing and MHC-containing vesicles</p> Signup and view all the answers

    Match the following cells with their antigen-related functions:

    <p>B cells = Produce antibodies upon T cell activation Dendritic cells = Primarily activate T cells Macrophages = Enhance immune responses</p> Signup and view all the answers

    Match the following types of antigens to the pathogens they are associated with:

    <p>Intracellular antigens = Certain intracellular bacteria Extracellular antigens = Non-replicating pathogens</p> Signup and view all the answers

    Match the process with the correct step in antigen processing:

    <p>Vesicle fusion with Golgi = For extracellular antigens Cytosolic processing = For intracellular antigens TAP transport = Delivers peptides to MHC class I Endocytosis mechanism = For bringing extracellular antigens in</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>MHC class I molecules = Present intracellular antigens MHC class II molecules = Present extracellular antigens Transport vesicles = Deliver antigens to the cell surface Proteasome = Processes intracellular proteins for antigen presentation</p> Signup and view all the answers

    Match the following steps in the immune response with their roles:

    <p>Antigen presentation = T cell activation Antibody production = B cell response Intracellular antigen processing = Involves the proteasome Extracellular antigen processing = Involves receptor-mediated endocytosis</p> Signup and view all the answers

    Match the following processes with their associated cellular structures:

    <p>Endoplasmic reticulum = Where MHC class I molecules bind peptides Golgi apparatus = Packages MHC class II molecules Cytosol = Site of intracellular antigen processing Cell surface = Location for the display of processed antigens</p> Signup and view all the answers

    What is the primary function of Class 2 antigen-presenting cells?

    <p>Stimulate phagocytosis and present antigen to T Helper</p> Signup and view all the answers

    Which class of MHC molecules is associated with presenting antigens to Cytotoxic T cells?

    <p>Class 1 MHC molecules</p> Signup and view all the answers

    Which of the following antigen-presenting cells is known to take in surface immunoglobulin (Ig) and antigen?

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

    What characteristic distinguishes dendritic cells from other antigen-presenting cells?

    <p>They bring and present antigens to T Helper cells in lymph nodes.</p> Signup and view all the answers

    Which type of antigen-presenting cell is capable of phagocytosis?

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

    Match the MHC class with its primary function:

    <p>Class 1 = Stimulates Cytotoxic T cell immune response Class 2 = Stimulates antibody secretion by B cell line</p> Signup and view all the answers

    Match the cell type with its phagocytic ability:

    <p>All = No Macrophage = Yes Dendritic = Yes, in tissues B cell = Yes, takes in surface Ig and antigen</p> Signup and view all the answers

    Match the cell type with its MHC class:

    <p>Macrophage = Class 2 Dendritic = Class 2 B cell = Class 2 All = Class 1</p> Signup and view all the answers

    Match the antigen-presenting cell with its primary location for presenting antigens:

    <p>Dendritic = Lymph nodes Macrophage = Primary infection site B cell = Lymph nodes All = Throughout the body</p> Signup and view all the answers

    Match the antigen-presenting cell with its function:

    <p>Macrophage = Stimulates phagocytosis and presents antigen Dendritic = Brings antigen to T Helper B cell = Stimulates antibody secretion All = Stimulates Cytotoxic T cell immune response</p> Signup and view all the answers

    Study Notes

    T Cell Antigen Recognition

    • T lymphocytes recognize antigens only when presented by MHC molecules on the surface of cells.

    • MHC Class I and MHC Class II molecules are responsible for antigen presentation to T cells.

    • MHC I presents processed antigen to Cytotoxic T cells.

    • MHC II presents processed antigen to T Helper cells.

    Antigen Presenting Cells (APCs)

    • Three professional APCs exist: macrophages, dendritic cells, and B cells.

    • APCs process antigens by breaking them down and presenting them on their MHC II molecules.

    • APCs activate an immune response by presenting antigens to T Helper cells.

    MHC Class 1: Intracellular Antigen Presentation

    • All cells express MHC I molecules to present intracellular antigens, primarily from viral infections.

    • MHC I molecules with bound antigen stimulate Cytotoxic T cells to destroy infected cells.

    • This process facilitates the clearance of intracellular pathogens, especially viruses.

    MHC Class 1: Cellular Functions

    • Macrophages release cytokines which enhance phagocytosis.

    • Dendritic cells bring antigens to lymph nodes, where T cell responses are mounted.

    • Macrophages reside in the skin, nasopharynx, stomach, lungs, and intestines.

    • B cells can present antigens to T cells, crucial for specific antibody responses.

    Intracellular and Extracellular Antigen Processing

    • Intracellular antigens, typically from viruses and intracellular bacteria, are processed in the cytosol by the proteasome, transported to the endoplasmic reticulum via TAP, and then presented through MHC I.

    • Extracellular antigens are engulfed by endocytosis, fuse with Golgi vesicles containing MHC II, and are ultimately presented by MHC II on the cell surface.

    T Cell Recognition

    • T lymphocytes do not recognize free-floating antigens or antigens on pathogen surfaces.
    • T cells specifically recognize antigens presented on the surface of cells by Major Histocompatibility Complex (MHC) molecules.

    MHC Molecules

    • MHC class I and MHC class II molecules are involved in antigen presentation.
    • Both MHC classes process antigens and transport them to the cell surface.
    • MHC class I presents antigens to cytotoxic T cells.
    • MHC class II presents antigens to T helper cells.

    Antigen Presenting Cells (APCs)

    • Macrophages, dendritic cells, and B cells are professional APCs.
    • APCs possess MHC class II receptors and present antigens to T helper cells, initiating an immune response.
    • APCs engulf antigens and process them by breaking them down into smaller fragments.
    • These fragments are then presented on the cell surface bound to MHC molecules.
    • The combination of MHC and antigen fragment is recognized by the T cell receptor.
    • Several cell types express MHC I to present intracellular antigens.
    • This facilitates recognition by cytotoxic T cells, leading to the destruction of infected cells.
    • MHC I expression is crucial for combating intracellular pathogens, especially viruses.

    APC Functions

    • Macrophages stimulate T cells to release cytokines that enhance phagocytosis.
    • Dendritic cells phagocytose pathogens and transport antigens to lymph nodes.
    • Lymph nodes are crucial sites for T cell responses against pathogens in interstitial tissues.
    • B cells can present antigens to T cells, contributing to antibody responses.

    Intracellular vs. Extracellular Antigens

    • Intracellular antigens, often from viruses or intracellular parasites, are processed in the cytosol by the proteasome.

    • These antigens are then transported to the endoplasmic reticulum by the transporter associated with antigen processing (TAP).

    • Inside the endoplasmic reticulum, they associate with MHC I molecules and are transported to the cell surface.

    • Extracellular antigens, typical of bacteria, parasites, and fungi, are internalized by receptor-mediated endocytosis.

    • The resulting vesicles fuse with Golgi vesicles containing pre-formed MHC II molecules.

    • This fusion leads to the association of antigen and MHC II, followed by transport to the cell surface.

    Antigen-Presenting Cells (APCs)

    • APCs present antigens to T cells to trigger an immune response.
    • APCs express MHC molecules on their surface.
    • MHC class I is expressed by all cells and presents antigens to cytotoxic T cells.
    • MHC class II is expressed by macrophages, dendritic cells, and B cells.
    • Macrophages are phagocytic and engulf pathogens.
    • They present antigens to T helper cells at the site of infection.
    • Dendritic cells are phagocytic in tissues and migrate to lymph nodes to present antigens to T helper cells.
    • B cells can internalize antigens via their surface immunoglobulin receptors and present them to T helper cells to trigger antibody secretion.

    Antigen-presenting Cells - MHC Class One

    • All cells present MHC class one molecules
    • MHC class one does not engage in phagocytosis
    • Presents antigen to cytotoxic T cells
    • Triggers cytotoxic T cell responses

    Antigen-presenting Cells - MHC Class Two

    • MHC class two molecules are expressed on macrophages, dendritic cells, and B cells
    • Macrophages engulf and destroy pathogens through phagocytosis
    • Macrophages present antigens to T helper cells at the site of infection
    • Dendritic cells phagocytose in tissues
    • Dendritic cells then migrate to lymph nodes and present antigen to T helper cells
    • B cells present antigen to T helper cells
    • B cells internalize antigens via surface immunoglobulin
    • B cells undergo differentiation and promote antibody secretion

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    Description

    This quiz covers the fundamentals of T cell antigen recognition and the role of MHC molecules in immune responses. It explores how MHC Class I and Class II present antigens to Cytotoxic and T Helper cells, and the function of Antigen Presenting Cells in activating an immune response. Test your knowledge on these vital immunological concepts.

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