16 Questions
What is the characteristic of thymic education in the thymus?
T cells acquire 'tools of the trade' and ability to use them safely
What is the result of cells with non-functional TCR during thymic education?
They die due to lack of functional TCR
What is the primary function of thymic medullary epithelial cells (TMECs) during negative selection?
To express a variety of tissue-restricted antigens
What is the outcome of T cells with high affinity for self-antigens during negative selection?
They are eliminated due to high affinity for self-antigens
What is the characteristic of T cells that express CD4?
They recognize MHCII
What is the process by which T cells acquire the ability to recognize self-MHC?
Positive selection for self-MHC
What is the role of the thymic cortex in T cell development?
It is the site of thymic education
What is the outcome of T cells that fail to undergo positive selection?
They die due to lack of functional TCR
What is the primary function of CD4 T cells in the immune response?
Providing help to other immune cells
What is the outcome of ineffective immune tolerance?
Autoimmunity and immunodeficiency
What is the estimated number of possible TCR diversities generated by random events?
4.5x10^9
Which of the following cells is responsible for antigen presentation?
Dendritic cell
What is the consequence of random TCR diversity?
Self-reactivity
What is the function of CD8 T cells?
Killing infected cells
What is the primary mechanism of generating TCR diversity?
Gene rearrangement
What is the importance of self/non-self recognition?
To prevent autoreactivity
Study Notes
Thymus Development and Function
- Thymus develops from seeded bone marrow-derived precursors
- Comprises multiple lobules with organized zones and specialized cell types
- Essential for thymic education, where T cells acquire necessary tools for immune function
Thymic Education
- T cells express functional TCR and accessory molecules (CD4 or CD8)
- TCR genes are rearranged, and cells with non-functional TCR undergo apoptosis
- Thymocytes learn to use TCR and CD4/CD8 safely, within the laws of MHC restriction
Positive Selection for Self-MHC
- Thymocytes with affinity for self-MHC (MHC II or MHC I) are positively selected
- Thymocytes without affinity for self-MHC undergo apoptosis
Negative Selection for Self-Reactive T Cells
- Thymocytes with high affinity for self-antigens are eliminated to prevent autoimmunity
- Low/moderate affinity thymocytes are allowed to mature, ensuring immune tolerance
- Thymic medullary epithelial cells (TMECs) express tissue-restricted antigens, promoting immune tolerance
Importance of Self/Non-Self Recognition
- Immune tolerance prevents autoreactivity while permitting appropriate anti-pathogen responses
- Immune recognition ensures the adaptive immune response to foreign pathogens
Immune Tolerance and Immune Recognition
- Key players in immune response include adaptive T cells, B cells, antigen-presenting cells, and innate immune cells
- TCR diversity is generated by random gene rearrangement events, allowing for recognition of unseen pathogens
- Random TCR diversity makes self-reactivity possible, highlighting the importance of immune tolerance
This quiz covers the development and function of the thymus, including the cortex and medulla, and the role of T cells and their education.
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