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Questions and Answers
What is the main role of MHC class I molecules?
Which of the following cell types can function as Antigen Presenting Cells (APCs)?
How do T lymphocytes recognize antigens?
What is the primary function of dendritic cells in the immune response?
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What occurs after an antigen is processed by an Antigen Presenting Cell?
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During an immune response, macrophages significantly enhance which specific immune activity?
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What type of antigen do MHC class I molecules primarily present?
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What is a key feature of the specialized receptors in Antigen Presenting Cells?
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Why is it crucial for most tissues to express MHC class I molecules?
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Which types of pathogens are primarily managed by Cytotoxic T cell responses?
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What role do B cells play in relation to T cells?
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Which of the following describes intracellular antigens?
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What is the role of the transporter associated with antigen processing (TAP) system?
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How are extracellular antigens typically processed within a cell?
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What is a key difference between how intracellular and extracellular antigens are presented?
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Which mechanism is involved in transporting MHC molecules to the cell surface after the fusion of vesicles containing antigens?
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What characterizes extracellular antigens?
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In the presentation of antigens on MHC molecules, which structure contains pre-formed MHC 2 molecules?
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Which statement best describes the processing pathway of intracellular antigens?
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Which immune response type is primarily activated by MHC 1 molecules?
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Match the following types of MHC molecules with their primary T cell interactions:
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Match the following immune cells with their respective locations:
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Match the following antigen processing functions to the respective immune cells:
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Match the following pathogens with their primary immune targets:
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Match the following descriptions with the correct MHC molecule type:
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Match the cells to their roles in antigen presentation:
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Match the immune response activity with the respective immune components:
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Match the following characteristics with the correct type of antigen:
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Match the following immune processes with their descriptions:
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Match the following types of antigens with their characteristics:
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Match the following processes with their associated antigens:
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Match the following components with their functions:
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Match the following cells with their antigen-related functions:
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Match the following types of antigens to the pathogens they are associated with:
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Match the process with the correct step in antigen processing:
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Match the following terms with their descriptions:
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Match the following steps in the immune response with their roles:
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Match the following processes with their associated cellular structures:
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What is the primary function of Class 2 antigen-presenting cells?
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Which class of MHC molecules is associated with presenting antigens to Cytotoxic T cells?
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Which of the following antigen-presenting cells is known to take in surface immunoglobulin (Ig) and antigen?
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What characteristic distinguishes dendritic cells from other antigen-presenting cells?
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Which type of antigen-presenting cell is capable of phagocytosis?
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Match the MHC class with its primary function:
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Match the cell type with its phagocytic ability:
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Match the cell type with its MHC class:
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Match the antigen-presenting cell with its primary location for presenting antigens:
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Match the antigen-presenting cell with its function:
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Study Notes
T Cell Antigen Recognition
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T lymphocytes recognize antigens only when presented by MHC molecules on the surface of cells.
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MHC Class I and MHC Class II molecules are responsible for antigen presentation to T cells.
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MHC I presents processed antigen to Cytotoxic T cells.
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MHC II presents processed antigen to T Helper cells.
Antigen Presenting Cells (APCs)
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Three professional APCs exist: macrophages, dendritic cells, and B cells.
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APCs process antigens by breaking them down and presenting them on their MHC II molecules.
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APCs activate an immune response by presenting antigens to T Helper cells.
MHC Class 1: Intracellular Antigen Presentation
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All cells express MHC I molecules to present intracellular antigens, primarily from viral infections.
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MHC I molecules with bound antigen stimulate Cytotoxic T cells to destroy infected cells.
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This process facilitates the clearance of intracellular pathogens, especially viruses.
MHC Class 1: Cellular Functions
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Macrophages release cytokines which enhance phagocytosis.
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Dendritic cells bring antigens to lymph nodes, where T cell responses are mounted.
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Macrophages reside in the skin, nasopharynx, stomach, lungs, and intestines.
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B cells can present antigens to T cells, crucial for specific antibody responses.
Intracellular and Extracellular Antigen Processing
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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.
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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
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Intracellular antigens, often from viruses or intracellular parasites, are processed in the cytosol by the proteasome.
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These antigens are then transported to the endoplasmic reticulum by the transporter associated with antigen processing (TAP).
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Inside the endoplasmic reticulum, they associate with MHC I molecules and are transported to the cell surface.
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Extracellular antigens, typical of bacteria, parasites, and fungi, are internalized by receptor-mediated endocytosis.
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The resulting vesicles fuse with Golgi vesicles containing pre-formed MHC II molecules.
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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.