Questions and Answers
What is the primary function of the thymus in T cell development?
What is the outcome for thymocytes that express a non-functional TCR?
What is the primary site of positive selection for self-MHC in the thymus?
What is the role of thymic medullary epithelial cells (TMECs) in T cell development?
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What is the outcome for thymocytes that have high affinity for self-MHC?
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What is the function of CD4 and CD8 accessory molecules in T cell development?
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What is the significance of TCR gene rearrangement in T cell development?
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What is the purpose of thymic education in T cell development?
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What role do CD4 T cells primarily perform in the immune response?
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Which mechanism contributes most significantly to the diversity of T Cell Receptors (TCRs)?
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What is the primary function of antigen presenting cells in the immune system?
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How does immune tolerance relate to autoimmune conditions?
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What best describes the process involved in establishing immune tolerance?
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Which type of T cell is primarily responsible for the direct killing of infected cells?
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What impact does TCR diversity have on the recognition of pathogens?
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What characterizes the adaptive immune response to foreign pathogens?
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Study Notes
Immune Tolerance and Immune Recognition
- Self/non-self recognition is crucial for the immune system to distinguish between the body's own cells and foreign pathogens.
Main Cellular Players in the Immune Response
- Adaptive immune response involves B cells, CD4 T cells, and CD8 T cells.
- B cells produce antibodies.
- CD4 T cells provide help, while CD8 T cells kill infected cells.
- Antigen-presenting cells, such as dendritic cells (DC) and macrophages, present antigens and kill pathogens.
TCR Diversity and Self-Reactivity
- T-cell receptor (TCR) diversity is generated by gene rearrangement and is estimated to be around 4.5 x 10^9.
- Random TCR diversity makes self-reactivity possible, where CD8+ T cells can kill virus-infected cells or endocrine cells.
Establishing Immune Tolerance
- Immune tolerance prevents autoreactivity while permitting appropriate anti-pathogen responses.
- T cells develop in the thymus, which is seeded by bone marrow-derived precursors and contains organized zones with specialized cell types.
- Thymic education involves T cells acquiring the "tools of the trade," including expression of a functional TCR and CD4 or CD8 receptors.
Thymic Selection
- Positive selection for self-MHC occurs in the thymic cortex, where thymocytes with affinity for MHCII or MHCI express CD4 or CD8, respectively.
- Negative selection eliminates high-affinity self-reactive T cells in the thymic medulla, where thymic medullary epithelial cells (TMECs) express tissue-restricted antigens and induce activation-induced death in T cells with high-affinity receptors.
Immune Tolerance and Autoimmunity
- Immunodeficiency occurs when there is a lack of immune tolerance, while autoimmunity results from a failure of immune tolerance.
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Description
Understand the importance of self/non-self recognition and outline the processes involved in establishing immune tolerance and immune recognition.
