2.2 Natural Killer Cells
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Questions and Answers

What distinguishes Natural Killer (NK) cells from other immune cells like T cells or B cells?

  • They possess receptors generated through gene segment rearrangement.
  • They migrate to tissues only when an inflammatory reaction is not underway.
  • They originate from bone marrow and have a short lifespan. (correct)
  • They express CD56, CD16, and CD3 receptors.

Which receptors are responsible for cell trafficking in Natural Killer (NK) cells?

  • CD3 receptors
  • TCR and BCR
  • Antigen receptors
  • Chemokine receptors (correct)

How are Natural Killer (NK) cells identified in vitro?

  • By the lack of CD3 and expression of CD56, CD16. (correct)
  • By the expression of CD56, CD16, and CD3 receptors.
  • By the presence of TCR and BCR
  • By the expression of CD335 (NKp46) exclusively.

What is the role of Natural Killer (NK) cells in innate immunity?

<p>They play a role in target cell recognition and killing mechanisms. (B)</p> Signup and view all the answers

How are Natural Killer (NK) cells similar to large granular lymphocytes (LGL)?

<p>They resemble lymphocytes morphologically and contain granules. (C)</p> Signup and view all the answers

Which animals lack an exclusive marker for identifying Natural Killer (NK) cells?

<p>Pigs (B)</p> Signup and view all the answers

What is the role of inhibitory receptors on NK cells?

<p>Recognize MHC-I molecules expressed on normal cells (D)</p> Signup and view all the answers

Which mechanism involves the release of perforin from NK cells?

<p>Perforin-dependent mechanism (C)</p> Signup and view all the answers

What is the function of granzymes and protease in NK cell cytotoxicity?

<p>Induce apoptosis of target cells (B)</p> Signup and view all the answers

Which ligands do activating receptors on NK cells bind to?

<p>Ligands expressed on stressed, infected, or transformed cells (B)</p> Signup and view all the answers

What renders a cell vulnerable to destruction by NK cells?

<p>Reduction or lack of MHC-I expression (C)</p> Signup and view all the answers

Which mechanism involves binding of CD95L on NK cells to CD95 on target cells?

<p>CD95/CD95L (Fas/FasL) mechanism (A)</p> Signup and view all the answers

What is the role of the inhibitory signal in the context of NK cells?

<p>To preserve the target cell (C)</p> Signup and view all the answers

How do NK cells decide whether to kill a target cell?

<p>Based on the expression of stress molecules (A)</p> Signup and view all the answers

What happens when activating signals are blocked by inhibitory signals?

<p>The target cell is preserved (C)</p> Signup and view all the answers

What is the role of the activating signal in the context of NK cells?

<p>To kill the target cells (B)</p> Signup and view all the answers

What is the function of the inhibitory receptors in NK cells?

<p>To transmit the 'do not kill' signal (C)</p> Signup and view all the answers

What happens when the activating receptors sense changes on the target cell surface?

<p>The 'kill' signal is transmitted (C)</p> Signup and view all the answers

Which type of cells express NK1.1 and other KLR family receptors?

<p>Natural killer T cells (A)</p> Signup and view all the answers

Which type of cells are primarily responsible for lysing tumor cells spontaneously?

<p>Natural killer dendritic cells (A)</p> Signup and view all the answers

Which type of cells make up at least 0.5% to 1% of the peripheral blood mononuclear cells?

<p>Natural killer T cells (A)</p> Signup and view all the answers

Which type of cells primarily recognize glycolipid antigens on bacteria?

<p>Natural killer T cells (A)</p> Signup and view all the answers

Which type of cells express CD11c, a DC marker?

<p>Natural killer dendritic cells (C)</p> Signup and view all the answers

Which type of cells are activated by IL-15?

<p>Natural killer T cells (D)</p> Signup and view all the answers

What is the role of CD16 in NK cells?

<p>CD16 is a receptor that allows NK cells to bind to antibodies, leading to cellular cytotoxicity (A)</p> Signup and view all the answers

What are LAK cells?

<p>Lymphokine activated killer cells are NK cells treated with cytokines that have increased cytotoxic capacity (D)</p> Signup and view all the answers

Which of the following is NOT a cytokine that activates NK cells?

<p>IL-3 (B)</p> Signup and view all the answers

What is the primary function of NK cells?

<p>NK cells primarily exhibit cytotoxic activity against infected or abnormal cells (B)</p> Signup and view all the answers

What is a characteristic feature of antibody-dependent cellular cytotoxicity (ADCC) by NK cells?

<p>ADCC involves the binding of NK cells to antibodies through CD16 (B)</p> Signup and view all the answers

How do NK cells recognize target cells in the CD16 killing pathway?

<p>By recognizing antibodies bound to the infected cell (D)</p> Signup and view all the answers

What is the function of cytokines like IL-2 and IL-18 in regulating NK cell activity?

<p>Activating NK cells (B)</p> Signup and view all the answers

Which type of cells can NK cells be transformed into by treatment with certain cytokines?

<p>Lymphokine activated killer (LAK) cells (B)</p> Signup and view all the answers

In which type of therapy could lymphokine activated killer (LAK) cells be potentially used?

<p>Immunotherapy of tumors (B)</p> Signup and view all the answers

What is a consequence of an enhanced activity of NK cells in certain virus infections?

<p>Enhanced clearance of infected cells (C)</p> Signup and view all the answers

How do NK cells recognize abnormal cells?

<p>By the alteration of cell surface markers on stressed, infected, or transformed cells (A)</p> Signup and view all the answers

What happens when NK cells are activated in vitro with cytokines like IL-2 and IFNγ?

<p>They become Lymphokine Activated Killer (LAK) cells (B)</p> Signup and view all the answers

What is the regulatory role of ME in NK cell cytokine and chemokine production?

<p>Regulating the balance between activating and inhibitory receptors (A)</p> Signup and view all the answers

Which proteins are highly expressed on the surface of stressed cells?

<p>MICA, MICB, Rae-1, H60 (D)</p> Signup and view all the answers

What is the function of inhibitory receptors in regulating NK cell activation?

<p>Balancing signals from activating receptors (B)</p> Signup and view all the answers

Which receptors play a crucial role in balancing the activation of NK cells?

<p>Activating and inhibitory receptors (B)</p> Signup and view all the answers

What renders a cell susceptible to destruction by Natural Killer (NK) cells?

<p>Lack of MHC-I expression (D)</p> Signup and view all the answers

Which mechanism involves the release of granulysin, NK-lysin (granzymes), and fragmentin from cytotoxic granules?

<p>Perforin-dependent mechanism (C)</p> Signup and view all the answers

Which cell surface ligand interaction induces apoptosis of the target cell by the CD95/CD95L (Fas/FasL) mechanism?

<p>CD95 on NK cells with CD95 on target cells (D)</p> Signup and view all the answers

What is the primary outcome of perforin channels created by perforin released from NK cells?

<p>Passage of granulysin and granzymes into the target cell (A)</p> Signup and view all the answers

What is the function of activating receptors on NK cells in response to infected, stressed, or transformed cells?

<p>Lysis of abnormal cells (C)</p> Signup and view all the answers

Which molecule released from cytotoxic granules by NK cells specifically triggers the apoptosis of the target cell?

<p>NK-lysin (granzymes) (D)</p> Signup and view all the answers

What is the primary source of Natural Killer (NK) cells in the body?

<p>Bone marrow (A)</p> Signup and view all the answers

Which receptors are not found on Natural Killer (NK) cells?

<p>TCR (C)</p> Signup and view all the answers

Which of the following is not a common location for Natural Killer (NK) cells in the body?

<p>Lungs (D)</p> Signup and view all the answers

Which of the following is a characteristic of Natural Killer (NK) cells in morphology?

<p>Large granular lymphocytes (LGL) (D)</p> Signup and view all the answers

Which of the following is not a distinguishing feature of Natural Killer (NK) cells?

<p>Express CD4 (B)</p> Signup and view all the answers

Which of the following animals does not have an exclusive marker for identifying Natural Killer (NK) cells?

<p>Pigs (B)</p> Signup and view all the answers

Which type of cells link the T cell system and NK cells?

<p>NKT cells (B)</p> Signup and view all the answers

Which cells are responsible for producing large amounts of IFNγ upon stimulation through TLR9 (CpG)?

<p>NK DCs (B)</p> Signup and view all the answers

Which type of cells are activated by IL-15 and do not develop into memory cells?

<p>NKT cells (C)</p> Signup and view all the answers

Which type of cells are primarily involved in allergies, antitumor immunity, autoimmunity, and antimicrobial immunity?

<p>NKT cells (B)</p> Signup and view all the answers

Which type of cells express CD11c, a DC marker, and NK1.1, an NK cell marker?

<p>NK DCs (C)</p> Signup and view all the answers

Which type of cells spontaneously lyse tumor cells and can present antigen to naïve T cells?

<p>NK DCs (B)</p> Signup and view all the answers

Flashcards

What are NK cells?

Natural Killer (NK) cells are lymphocytes that are part of the innate immune system. They are distinct from T cells and B cells due to their origin, lifespan, and lack of specific antigen receptors.

Where do NK cells originate?

NK cells are derived from the bone marrow, unlike T cells which mature in the thymus and B cells which mature in the bone marrow.

What is the lifespan of NK cells?

Unlike T cells which have a long lifespan, NK cells have a relatively shorter lifespan, continuously being replenished from the bone marrow.

How do NK cells recognize their targets?

NK cells are equipped with receptors that bind to specific molecules expressed on stressed, infected, or tumor cells, allowing them to recognize and target these abnormal cells.

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Do NK cells have antigen-specific receptors?

NK cells, unlike T cells and B cells, do not have T cell receptors (TCR) or B cell receptors (BCR), which are specific for antigens.

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What are the components of NK cell cytotoxicity?

NK cells contain cytotoxic granules that hold proteins like perforin and granzymes, which are released upon activation, resulting in killing of target cells.

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What is perforin's role in NK cell killing?

Perforin is a protein released from NK cells that forms pores in the membrane of target cells, allowing granzymes to enter and induce apoptosis.

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What are granzymes and their function?

Granzymes are proteases that enter the target cell through perforin-formed pores and activate the apoptotic pathway, leading to programmed cell death.

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Describe the CD95/CD95L (Fas/FasL) mechanism.

NK cells can also induce apoptosis through a pathway involving CD95L, expressed on NK cells, and CD95 (Fas), present on the target cell. This mechanism relies on the interaction between these molecules.

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What is the function of inhibitory receptors on NK cells?

Inhibitory receptors on NK cells recognize MHC-I molecules expressed on normal cells, preventing them from attacking healthy cells. This mechanism ensures self-tolerance.

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What is the function of activating receptors on NK cells?

On the other hand, activating receptors on NK cells bind to certain ligands expressed on stressed, infected, or transformed cells. This triggers the killing cascade by NK cells.

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How do NK cells decide to kill or not?

NK cell activity is regulated by a delicate balance between activating and inhibitory signals. If activating signals outweigh inhibitory signals, NK cells will destroy the target cell.

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What influences NK cell activation?

One of the key factors determining NK cell activation is the expression of MHC-I molecules on the target cell. Reduced or absent MHC-I expression makes a cell susceptible to NK cell destruction.

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What are Natural Killer T (NKT) cells?

Natural Killer T cells (NKT cells) are a unique population of lymphocytes that express NK1.1 and other KLR family receptors. They bridge the gap between innate and adaptive immunity.

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What is the function of NKT cells?

NKT cells are primarily involved in recognizing glycolipid antigens presented by CD1d molecules on antigen-presenting cells. They are also known to produce cytokines, impacting both innate and adaptive immune responses.

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What are Natural Killer Dendritic (NKDC) cells?

Natural killer dendritic cells (NKDCs) are distinct from conventional DCs, expressing CD11c, a DC marker. They act as a link between innate and adaptive immunity, exhibiting both NK cell features and DC functions.

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What is the role of NKDCs in tumor immunity?

NKDCs are known for their ability to lyse tumor cells spontaneously. They are also crucial for activating T cell responses, further contributing to anti-tumor immunity.

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What are LAK cells?

Lymphokine activated killer (LAK) cells are NK cells that have been activated in vitro with cytokines like IL-2 and IFNγ. They exhibit enhanced cytotoxic activity, making them a promising therapeutic approach in cancer treatment.

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What is the potential therapeutic use of LAK cells?

LAK cells are a potential therapeutic strategy for treating cancer. They are used in immunotherapy due to their enhanced ability to target and kill tumor cells.

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What is antibody-dependent cellular cytotoxicity (ADCC)?

The process of antibody-dependent cellular cytotoxicity (ADCC) involves NK cells recognizing and binding to antibodies attached to target cells. This triggers the destruction of the target cell through cytotoxicity.

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What is the role of CD16 in ADCC?

NK cells express CD16, a receptor that binds to antibodies, enabling them to recognize antibody-coated cells. This is crucial for ADCC-mediated cytotoxicity.

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How do cytokines regulate NK cell activity?

NK cell activity is regulated by various cytokines, including IL-2 and IL-18, which act as activating signals, boosting their cytotoxic potential during immune responses.

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Can NK cells be transformed into LAK cells?

NK cells, when treated with certain cytokines like IL-2, undergo a transformation into LAK cells. This process enhances their cytotoxic capacity against tumor cells.

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What is the role of NK cells in viral infections?

NK cell activity can lead to enhanced clearance of infected cells during viral infections. This is due to their ability to recognize and eliminate virus-infected cells.

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What happens when NK cells are activated in vitro?

NK cells, like other immune cells, undergo activation upon recognition of specific signals. In vitro stimulation with cytokines like IL-2 and IFNγ transforms them into LAK cells.

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What is the role of ME in NK cell regulation?

The balance between activating and inhibitory receptors is regulated by molecules like ME, ensuring that NK cells only target abnormal cells while sparing healthy cells.

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Which proteins are expressed on stressed cells?

Stressed or abnormal cells often express specific molecules on their surface, including MICA, MICB, Rae-1, and H60, which are recognized by activating receptors on NK cells.

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