Natural Killer Cells Quiz
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Questions and Answers

What happens to NK cells in the presence of intact MHC-I on the target cell?

  • They release perforin protein
  • They remain inactive (correct)
  • They become hyperactive
  • They start producing cytotoxic granules

    • What is the role of Major Histocompatibility Complex-I (MHC-I) on the cell surface?

  • Serving as an energy source for the cell
  • Serving as the identification card of the cell (correct)
  • Identifying foreign substances
  • Causing cell lysis

    • What is the main function of NK cells?

  • Producing antibodies
  • Detecting and destroying bacteria
  • Recognizing and eliminating virally infected cells and cancer cells (correct)
  • Breaking down food particles

    • How do NK cells destroy target cells?

    <p>Releasing cytotoxic granules with perforin protein and granzyme</p> Signup and view all the answers

    What is the main difference between NK cells and T cells in their activation process?

    <p>NK cells need prior activation by antigen presenting cells, while T cells do not.</p> Signup and view all the answers

    What is the function of perforin protein released by NK cells?

    <p>Forms pores in the plasma membrane of the target cell</p> Signup and view all the answers

    What is the main function of Natural Killer (NK) cells?

    <p>Detect and eliminate virally infected cells and cancer cells without prior activation by antigen presenting cells</p> Signup and view all the answers

    How do NK cells determine whether to destroy a target cell?

    <p>By checking for the presence of Major Histocompatibility Complex-I (MHC-I) molecules on the cell surface</p> Signup and view all the answers

    How do NK cells destroy target cells?

    <p>By releasing cytotoxic granules containing perforin and granzyme</p> Signup and view all the answers

    What is the role of perforin protein released by NK cells?

    <p>Form pores in the plasma membrane of the target cells</p> Signup and view all the answers

    What happens to NK cells in the presence of intact MHC-I on the target cell?

    <p>They remain inactive</p> Signup and view all the answers

    Why were Natural Killer (NK) cells named as such?

    <p>Due to their ability to detect and eliminate target cells without prior activation by antigen presenting cells</p> Signup and view all the answers

    Which of the following is NOT true about Natural Killer (NK) cells?

    <p>They remain inactive in the presence of intact Major Histocompatibility Complex-I (MHC-I) on the target cell</p> Signup and view all the answers

    What is the primary mode of action for NK cells in destroying target cells?

    <p>Releasing cytotoxic granules containing perforin and granzyme</p> Signup and view all the answers

    What is the main reason for naming these lymphocytes as Natural Killer (NK) cells?

    <p>They do not require prior activation by antigen presenting cells</p> Signup and view all the answers

    What is the specific role of perforin protein released by NK cells in destroying target cells?

    <p>Causing lysis of the target cell by forming pores in its plasma membrane</p> Signup and view all the answers

    What happens to NK cells in the presence of intact Major Histocompatibility Complex-I (MHC-I) on the target cell?

    <p>They remain inactive</p> Signup and view all the answers

    What role does Major Histocompatibility Complex-I (MHC-I) play in determining the action of NK cells?

    <p>It serves as an identification card of 'self' on the target cell</p> Signup and view all the answers

    Study Notes

    MHC-I and NK Cells

    • Intact MHC-I on target cells inhibits NK cell activation, preventing their destructive action.
    • Major Histocompatibility Complex-I (MHC-I) presents endogenous peptides to T cells and signals self-recognition to NK cells.

    Natural Killer (NK) Cells Function

    • Main function of NK cells is to identify and eliminate infected or cancerous cells without prior sensitization.
    • NK cells employ various mechanisms, including the release of cytotoxic granules, to induce apoptosis in target cells.

    Mechanisms of Destruction by NK Cells

    • NK cells destroy target cells primarily through the secretion of perforin and granzymes.
    • Perforin forms pores in the target cell membrane, allowing granzymes to enter and trigger apoptosis.

    Activation Process Comparison

    • NK cells are activated by the absence of MHC-I molecules, distinguishing them from T cells, which require specific antigen recognition through their T cell receptors.

    Perforin Protein Function

    • Perforin released by NK cells plays a critical role in forming pores in the membrane of target cells, facilitating the entry of granzymes.

    NK Cells' Decision-Making Process

    • NK cells evaluate target cells by balancing activating and inhibiting signals; intact MHC-I sends an inhibitory signal, while stress signals from damaged cells promote activation.

    Naming of Natural Killer (NK) Cells

    • Named 'Natural Killer' due to their inherent ability to destroy tumor and virus-infected cells without prior exposure or sensitization.

    Key Attributes of NK Cells

    • NK cells can rapidly respond to a wide range of threats, differentiating them from other lymphocytes such as T cells which require specific antigen encounter.
    • They do not require clonally expanded populations for activation, allowing for immediate immune response.

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    Description

    Test your knowledge about the characteristics and functions of natural killer cells, a type of lymphocyte involved in detecting and eliminating virally infected cells and cancer cells without the need for prior activation by antigen presenting cells.

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