Textbook Question
Small molecules that must combine with large proteins to become immunogenic are called:
a. Complete antigens
b. Kinins
c. Antigenic determinants
d. Haptens
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21. The Immune System
Antigens
Problem 21
Textbook Question
How does a cytotoxic T cell destroy another cell displaying antigens bound to class I MHC proteins?
Verified step by step guidance1
Understand the role of cytotoxic T cells: Cytotoxic T cells (also known as CD8+ T cells) are specialized immune cells that target and destroy infected or abnormal cells displaying antigens bound to class I MHC (Major Histocompatibility Complex) proteins. Class I MHC proteins are present on all nucleated cells and present intracellular antigens, such as those from viruses or cancerous mutations.
Recognize the interaction between the cytotoxic T cell and the target cell: The cytotoxic T cell uses its T-cell receptor (TCR) to specifically bind to the antigen-MHC class I complex on the surface of the target cell. This recognition is highly specific and ensures that only cells displaying the correct antigen are targeted.
Describe the activation of the cytotoxic T cell: Once the cytotoxic T cell binds to the antigen-MHC class I complex, it becomes activated. This activation is further supported by co-stimulatory signals and cytokines released by helper T cells or other immune cells.
Explain the release of cytotoxic molecules: After activation, the cytotoxic T cell releases perforins and granzymes. Perforins create pores in the membrane of the target cell, allowing granzymes to enter the cell. Granzymes are enzymes that trigger apoptosis (programmed cell death) in the target cell by activating caspases, which dismantle the cell's internal structures.
Summarize the result of the cytotoxic T cell's action: The target cell undergoes apoptosis, effectively eliminating the infected or abnormal cell. This process helps maintain the integrity of the organism by removing cells that could harm the body, such as virus-infected cells or cancerous cells.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cytotoxic T Cells
Cytotoxic T cells, also known as CD8+ T cells, are a type of immune cell that play a crucial role in the adaptive immune response. They recognize and kill infected or cancerous cells by identifying specific antigens presented on the surface of these cells. Upon activation, they proliferate and differentiate into effector cells that can directly induce apoptosis in target cells.
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MHC Class I Molecules
Major Histocompatibility Complex (MHC) Class I molecules are proteins found on the surface of nearly all nucleated cells. They present endogenous antigens, typically derived from proteins synthesized within the cell, to cytotoxic T cells. The interaction between MHC Class I and the T cell receptor (TCR) is essential for T cell activation and subsequent immune response.
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Apoptosis
Apoptosis is a form of programmed cell death that is a critical mechanism for maintaining cellular homeostasis and eliminating damaged or infected cells. Cytotoxic T cells induce apoptosis in target cells through the release of perforin and granzymes, which create pores in the target cell membrane and trigger the apoptotic pathway, leading to cell death without causing inflammation.
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