Podcast
Questions and Answers
During T-cell development, what is the primary purpose of negative selection in the thymus?
During T-cell development, what is the primary purpose of negative selection in the thymus?
- To induce the expression of AIRE protein, which is essential for T-cell activation.
- To eliminate T-cells that strongly bind to self-antigens, preventing autoimmune reactions. (correct)
- To promote the survival of T-cells with high affinity for self-antigens, thus enhancing autoimmunity.
- To ensure T-cells can effectively bind to foreign antigens presented on MHC I and MHC II.
Which of the following represents the correct sequence of events in T-cell development, starting from the lymphoid progenitor cell?
Which of the following represents the correct sequence of events in T-cell development, starting from the lymphoid progenitor cell?
- Precursor T-cell → Naive T-cell pre-selection → Positive selection → Negative selection (correct)
- Positive selection → Negative selection → Naive T-cell pre-selection → Precursor T-cell
- Negative selection → Positive selection → Precursor T-cell → Naive T-cell post-selection
- Naive T-cell pre-selection → Precursor T-cell → Negative selection → Positive selection
AIRE protein plays a critical role in which of the following processes during T-cell development?
AIRE protein plays a critical role in which of the following processes during T-cell development?
- Promoting the differentiation of precursor T-cells into CD4+ and CD8+ T-cells.
- Facilitating the rearrangement of T-cell receptor (TCR) genes in the thymus.
- Presenting self-antigens to T-cells in the thymus to induce negative selection. (correct)
- Enhancing the positive selection of T-cells with moderate affinity for MHC molecules.
A developing T-cell in the thymus expresses both CD4 and CD8 co-receptors. If this T-cell successfully interacts with MHC class II molecules, which of the following outcomes is most likely?
A developing T-cell in the thymus expresses both CD4 and CD8 co-receptors. If this T-cell successfully interacts with MHC class II molecules, which of the following outcomes is most likely?
Which of the following events would most likely occur if a developing T-cell in the thymus fails to bind to either MHC class I or MHC class II molecules during positive selection?
Which of the following events would most likely occur if a developing T-cell in the thymus fails to bind to either MHC class I or MHC class II molecules during positive selection?
What is the role of RAG1 and RAG2 enzymes in T-cell development within the thymus?
What is the role of RAG1 and RAG2 enzymes in T-cell development within the thymus?
During positive selection, T-cells must interact with MHC molecules with a certain affinity to survive. Which of the following best describes the ideal affinity?
During positive selection, T-cells must interact with MHC molecules with a certain affinity to survive. Which of the following best describes the ideal affinity?
If a T-cell strongly binds to self-antigens during negative selection, what is the most likely outcome?
If a T-cell strongly binds to self-antigens during negative selection, what is the most likely outcome?
What is the ultimate fate of a T-cell that successfully passes both positive and negative selection in the thymus?
What is the ultimate fate of a T-cell that successfully passes both positive and negative selection in the thymus?
How does the location of positive and negative selection differ within the thymus, and why is this important for T-cell development?
How does the location of positive and negative selection differ within the thymus, and why is this important for T-cell development?
Which of the following distinguishes the function of CD4+ T-helper cells from CD8+ cytotoxic T-cells after T-cell post selection?
Which of the following distinguishes the function of CD4+ T-helper cells from CD8+ cytotoxic T-cells after T-cell post selection?
How would a defect in the AIRE gene most likely affect T-cell development and the overall immune system?
How would a defect in the AIRE gene most likely affect T-cell development and the overall immune system?
What is the main difference between T-cell pre-selection and T-cell post-selection?
What is the main difference between T-cell pre-selection and T-cell post-selection?
Which of the following best explains why T-cell development occurs primarily in the thymus rather than in another immune organ?
Which of the following best explains why T-cell development occurs primarily in the thymus rather than in another immune organ?
What is a key difference between the T-cell receptor (TCR) of a naive T-cell and that of an effector T-cell?
What is a key difference between the T-cell receptor (TCR) of a naive T-cell and that of an effector T-cell?
In T-cell development, what would happen if a T-cell that recognizes a ubiquitous self-antigen presented on MHC II molecules in the thymus escapes negative selection?
In T-cell development, what would happen if a T-cell that recognizes a ubiquitous self-antigen presented on MHC II molecules in the thymus escapes negative selection?
Which of the following best explains the role of co-stimulatory molecules during T-cell activation after the T-cell has left the thymus?
Which of the following best explains the role of co-stimulatory molecules during T-cell activation after the T-cell has left the thymus?
How do T-regulatory cells (Tregs) contribute to maintaining immune homeostasis after T cell post selection?
How do T-regulatory cells (Tregs) contribute to maintaining immune homeostasis after T cell post selection?
During T-cell development, what is the significance of having distinct stages of selection (positive and negative) mediated by different cell types (e.g., cortical vs. medullary thymic epithelial cells)?
During T-cell development, what is the significance of having distinct stages of selection (positive and negative) mediated by different cell types (e.g., cortical vs. medullary thymic epithelial cells)?
How does the process of T-cell development contribute to the establishment of central tolerance?
How does the process of T-cell development contribute to the establishment of central tolerance?
Flashcards
Lymphoid Progenitor Cells
Lymphoid Progenitor Cells
Cells that originate from the bone marrow and are the origin of T-cells.
Precursor T-cell
Precursor T-cell
An immature T-cell that migrates from the bone marrow to the thymus.
Naïve T-cell Pre-selection
Naïve T-cell Pre-selection
The process where T-cells are created using RAG1 and RAG2.
Positive Selection
Positive Selection
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Negative Selection
Negative Selection
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AIRE protein
AIRE protein
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Naïve T-cell Post-selection (T-helper)
Naïve T-cell Post-selection (T-helper)
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Naïve T-cell Post-selection (Cytotoxic)
Naïve T-cell Post-selection (Cytotoxic)
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Study Notes
- T-cell Development
Lymphoid Progenitor Cells:
- Originate from the bone marrow
Precursor T-cell:
- Leave bone marrow and migrate to the thymus
- Initially, they are CD4-/CD8- (negative for both CD4 and CD8)
Naïve T-cell Pre-selection:
- T-cell receptor (TCR) is created using RAG1 and RAG2 recombinase enzymes
- Double positive T-cells develop, CD4+/CD8+
Positive Selection:
- Takes place in the cortex
- CD8+ binds with MHC I, resulting in a cytotoxic T-cell
- CD4+ binds with MHC II, resulting in a T-helper cell
- If binding is not adequate, the T-cell undergoes apoptosis
Negative Selection:
- Takes place in the thymic medulla
- Self-antigens are presented on MHC I and MHC II receptors
- If there is strong binding to self-peptides, the naïve T-cell undergoes apoptosis
- Exception: T-regulatory cells are a small percentage and don't undergo apoptosis but recognize self antigens
- AIRE protein (Autoimmune regulator protein) is involved
Naïve T-cell Post-selection (Immunocompetent):
- CD4+/CD8- T-cells with a TCR become T-helper cells
- CD4-/CD8+ T-cells with a TCR become Cytotoxic T-cells
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