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Questions and Answers
What is the main role of MHC class I molecules?
What is the main role of MHC class I molecules?
Which of the following cell types can function as Antigen Presenting Cells (APCs)?
Which of the following cell types can function as Antigen Presenting Cells (APCs)?
How do T lymphocytes recognize antigens?
How do T lymphocytes recognize antigens?
What is the primary function of dendritic cells in the immune response?
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?
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?
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?
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?
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?
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?
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?
What role do B cells play in relation to T cells?
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Which of the following describes intracellular antigens?
Which of the following describes intracellular antigens?
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What is the role of the transporter associated with antigen processing (TAP) system?
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?
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?
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?
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?
What characterizes extracellular antigens?
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In the presentation of antigens on MHC molecules, which structure contains pre-formed MHC 2 molecules?
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?
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?
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:
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:
Match the following immune cells with their respective locations:
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Match the following antigen processing functions to the respective immune cells:
Match the following antigen processing functions to the respective immune cells:
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Match the following pathogens with their primary immune targets:
Match the following pathogens with their primary immune targets:
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Match the following descriptions with the correct MHC molecule type:
Match the following descriptions with the correct MHC molecule type:
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Match the cells to their roles in antigen presentation:
Match the cells to their roles in antigen presentation:
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Match the immune response activity with the respective immune components:
Match the immune response activity with the respective immune components:
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Match the following characteristics with the correct type of antigen:
Match the following characteristics with the correct type of antigen:
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Match the following immune processes with their descriptions:
Match the following immune processes with their descriptions:
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Match the following types of antigens with their characteristics:
Match the following types of antigens with their characteristics:
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Match the following processes with their associated antigens:
Match the following processes with their associated antigens:
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Match the following components with their functions:
Match the following components with their functions:
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Match the following cells with their antigen-related functions:
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:
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:
Match the process with the correct step in antigen processing:
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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Match the following steps in the immune response with their roles:
Match the following steps in the immune response with their roles:
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Match the following processes with their associated cellular structures:
Match the following processes with their associated cellular structures:
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What is the primary function of Class 2 antigen-presenting cells?
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?
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?
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?
What characteristic distinguishes dendritic cells from other antigen-presenting cells?
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Which type of antigen-presenting cell is capable of phagocytosis?
Which type of antigen-presenting cell is capable of phagocytosis?
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Match the MHC class with its primary function:
Match the MHC class with its primary function:
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Match the cell type with its phagocytic ability:
Match the cell type with its phagocytic ability:
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Match the cell type with its MHC class:
Match the cell type with its MHC class:
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Match the antigen-presenting cell with its primary location for presenting antigens:
Match the antigen-presenting cell with its primary location for presenting antigens:
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Match the antigen-presenting cell with its function:
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.