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Questions and Answers
What is the primary location where T cell precursors complete their maturation?
What is the primary location where T cell precursors complete their maturation?
Which process allows T cells to recognize self-MHC during their development?
Which process allows T cells to recognize self-MHC during their development?
What happens to thymocytes that do not recognize an MHC molecule within 3-4 days of initial expression?
What happens to thymocytes that do not recognize an MHC molecule within 3-4 days of initial expression?
Which cells mediate positive selection in the thymus?
Which cells mediate positive selection in the thymus?
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What is the outcome for CD4LOW CD8HIGH thymocytes that recognize MHC class I molecules?
What is the outcome for CD4LOW CD8HIGH thymocytes that recognize MHC class I molecules?
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What is a characteristic of thymocytes that survive both positive and negative selection?
What is a characteristic of thymocytes that survive both positive and negative selection?
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In which part of the thymus does negative selection primarily take place?
In which part of the thymus does negative selection primarily take place?
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Which cell types play a role in negative selection of thymocytes?
Which cell types play a role in negative selection of thymocytes?
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What primarily influences the survival or death of thymocytes during selection?
What primarily influences the survival or death of thymocytes during selection?
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What is the role of co-receptor downregulation during T cell development?
What is the role of co-receptor downregulation during T cell development?
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What role does IL-2 play in T cell activation?
What role does IL-2 play in T cell activation?
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Which process ensures that T cells recognize self-MHC molecules during their development?
Which process ensures that T cells recognize self-MHC molecules during their development?
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What determines the type of effector T cell that a T cell will become?
What determines the type of effector T cell that a T cell will become?
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During T cell activation, what is the significance of the co-stimulatory signal B7:CD28?
During T cell activation, what is the significance of the co-stimulatory signal B7:CD28?
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What is the primary role of T cells in immune defense?
What is the primary role of T cells in immune defense?
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What is the significance of cell adhesion molecules (CAMs) in T cell activation?
What is the significance of cell adhesion molecules (CAMs) in T cell activation?
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What characterizes the transition of naive T cells to effector T cells?
What characterizes the transition of naive T cells to effector T cells?
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What is the first step in T cell activation?
What is the first step in T cell activation?
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Which T cell subset is primarily associated with helping other immune cells?
Which T cell subset is primarily associated with helping other immune cells?
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What physiological process occurs during T cell activation following antigen recognition?
What physiological process occurs during T cell activation following antigen recognition?
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Flashcards
Positive Selection
Positive Selection
The stage of T cell development where immature T cells learn to recognize and bind to self-MHC molecules, a crucial step for immune system function.
Negative Selection
Negative Selection
A process in T cell development where immature T cells that bind too strongly to self-MHC-peptide complexes are eliminated, preventing autoimmune reactions.
T Cell Activation
T Cell Activation
The process by which T cells become mature and capable of recognizing and responding to specific antigens presented by antigen-presenting cells (APCs).
Antigen-Presenting Cells (APCs)
Antigen-Presenting Cells (APCs)
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MHC Class I
MHC Class I
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MHC Class II
MHC Class II
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CD8+ T Cell (Cytotoxic T Cell)
CD8+ T Cell (Cytotoxic T Cell)
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CD4+ T Cell (Helper T Cell)
CD4+ T Cell (Helper T Cell)
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Cytokines
Cytokines
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Naive T Cell
Naive T Cell
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T cell monitoring of APCs
T cell monitoring of APCs
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T cell development
T cell development
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T cell activation & differentiation
T cell activation & differentiation
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Positive and Negative selection of T cells
Positive and Negative selection of T cells
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B7:CD28 co-stimulation
B7:CD28 co-stimulation
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T cell clonal expansion
T cell clonal expansion
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IL-2's role in T cell activation
IL-2's role in T cell activation
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Effect of cytokines on T cell differentiation
Effect of cytokines on T cell differentiation
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T cell mediated immunity
T cell mediated immunity
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T cell circulation & antigen seeking
T cell circulation & antigen seeking
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Study Notes
T Cell Development and Activation
- T cells develop from hematopoietic stem cells in the bone marrow, but complete maturation in the thymus.
- The thymus is divided into lobules with a cortex and medulla.
- Development stages are identified by the presence/absence of cell-surface markers (TCR, CD3, CD4, CD8).
- T-cell precursors proliferate extensively in the thymus, and most die there.
- T cells differentiate into two lineages: γ:δ and α:β.
- α:β T cells further distinguish into CD4+ and CD8+ T cells.
- T cells that recognize self-MHC (positive selection) and are self-tolerant (negative selection) are generated.
Learning Objectives
- Describe the stages of T cell development from hematopoietic stem cells in the bone marrow to mature T cells.
- Recognize positive and negative selection in T cell development.
- Describe the process of T cell activation.
- Understand T cell-mediated immune responses.
Positive Selection
- Occurs in the thymic cortex.
- Mediated by thymic cortical epithelial cells expressing MHC class I and II proteins.
- Thymocytes that do not recognize MHC molecules within 3-4 days of α:β expression die.
- Successful recognition by cortical epithelial cells results in a survival signal.
Co-receptor Selection
- Recognition of an MHC molecule by one co-receptor results in downregulation of the other co-receptor gene.
- CD4lowCD8high cells survive if they recognize MHC class I molecules.
- CD4highCD8low cells survive if they recognize MHC class II molecules.
- Co-receptor recognition by epithelial cells triggers a maturation signal.
Negative Selection
- Occurs in the thymic cortex and medulla.
- Mediated by cortical epithelial cells, macrophages, and dendritic cells.
- Thymocytes that strongly recognize self-peptide:MHC complexes die.
- Different binding affinities to MHC-peptide drive survival or death (positive/negative selection).
- Self-peptides are derived from thymic and ubiquitous blood proteins.
- T cells that successfully complete positive, co-receptor, and negative selection are single positive, self-tolerant, naïve T cells.
T Cell Activation
- Antigen recognition occurs on antigen-presenting cells (APCs) by MHC-peptide complexes.
- Co-stimulatory signals are delivered (e.g., B7:CD28).
- T cells enter the cell cycle (G1) for proliferation, known as clonal expansion.
- Interleukin-2 (IL-2) mediates proliferation and differentiation into effector cells.
- Cytokines expressed by APCs determine the effector T cell type.
T Cell-Mediated Immunity
- Naive T cells circulate between blood and lymphoid tissues.
- Activation occurs via antigen co-stimulation and recognition of MHC-peptide complexes on APCs.
- Cell adhesion molecules (CAMs) mediate the process.
- T cells monitor MHC-peptide complexes within lymphoid tissue.
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Description
Explore the intricate process of T cell development, including their origin in the bone marrow and maturation in the thymus. This quiz covers the stages of differentiation, positive and negative selection, and the mechanisms behind T cell activation and immune responses. Test your knowledge on these essential components of the immune system.
