Lecture 25- NK cells
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Questions and Answers

Which receptor on NK cells primarily facilitates antibody-dependent cell-mediated cytotoxicity (ADCC)?

  • CD16 (correct)
  • CD56
  • FcgRIIIA (correct)
  • NCAM

What is the typical life span of mature NK cells in the absence of activation?

  • 6-12 months
  • 1-3 days
  • 7-10 days (correct)
  • 2-4 weeks

Which of the following mechanisms is NOT a method by which NK cells can induce cytolysis?

  • Cytotoxic cytokines
  • Antibody-Dependent Cell-mediated Cytotoxicity (ADCC)
  • Natural cytotoxicity
  • Inhibition by MHC molecules (correct)

How do NK cells influence the immune response in the context of pregnancy?

<p>By promoting fetal tolerance (A)</p> Signup and view all the answers

What is the primary cytokine released by NK cells that helps regulate the activity of T and B cells?

<p>Interferon-gamma (A)</p> Signup and view all the answers

Which type of receptors on NK cells are primarily responsible for their activation?

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

Which is a characteristic feature differentiating NK cells from B and T cells?

<p>Lack of TCRs or BCRs expression (A)</p> Signup and view all the answers

What is the primary functional role of NK cells during an immune response?

<p>Directly killing virally-infected or tumor cells (A)</p> Signup and view all the answers

What primarily determines the intensity of the NK cell response?

<p>The combination of engaged inhibitory and activatory receptors. (D)</p> Signup and view all the answers

What is meant by the term 'missing self' in the context of NK cell function?

<p>The downregulation of MHC class I expression on abnormal cells. (D)</p> Signup and view all the answers

Which of the following cytokines is NOT mentioned as a priming cytokine for NK cells?

<p>Tumor Necrosis Factor (TNF) (A)</p> Signup and view all the answers

What characterizes a host cell displaying 'induced self'?

<p>Normal levels of self MHC and elevated activating ligands. (C)</p> Signup and view all the answers

Which receptor class exclusively contains activating receptors?

<p>Natural cytotoxicity receptor (NCR). (B)</p> Signup and view all the answers

How do activating receptors signal within NK cells?

<p>By utilizing associated signaling units with ITAMs. (B)</p> Signup and view all the answers

What is the primary role of NK cells in pregnancy?

<p>To modulate the maternal immune response to tolerate the fetus. (B)</p> Signup and view all the answers

NK cell-mediated ADCC involves which of the following processes?

<p>Utilization of antibodies bound to target cells to enhance cytotoxicity. (D)</p> Signup and view all the answers

What is the role of NK cells in pregnancy?

<p>They secrete cytokines that promote new blood vessel formation. (A)</p> Signup and view all the answers

Which receptor is involved in triggering ADCC by NK cells?

<p>FcgRIIIA (CD16) (C)</p> Signup and view all the answers

Which combination of cytokines is primarily produced by NK cells to influence innate immunity?

<p>IFN-g, TNF, IL-1 (C)</p> Signup and view all the answers

What effect does IFN-g produced by NK cells have on TH cell development?

<p>Enhances TH1 cell development via inhibitory effects on TH2. (B)</p> Signup and view all the answers

How do activating receptors on NK cells contribute to their function upon stimulation?

<p>They cause NK cells to secrete growth factors and chemokines. (B)</p> Signup and view all the answers

What triggers the initial priming of NK cells?

<p>Cytokines produced by phagocytes and innate leukocytes. (D)</p> Signup and view all the answers

The engagement of which receptor activates NK cells to release their cytotoxic granules?

<p>FcgRIIIA (CD16) (D)</p> Signup and view all the answers

What is the primary function of NK cells in the context of ADCC?

<p>Binding to antibodies and lysing target cells. (C)</p> Signup and view all the answers

What distinguishes natural killer (NK) cells from NKT and T cells?

<p>They lack TCRs or BCRs expression. (D)</p> Signup and view all the answers

Which statement accurately describes the tissue distribution of NK cells?

<p>NK cells are present in high frequency in the spleen and liver. (C)</p> Signup and view all the answers

How do NK cells primarily recognize target cells without being MHC restricted?

<p>By using a broad recognition of antigens independent of pMHC complexes. (C)</p> Signup and view all the answers

Which of the following is NOT a known function of NK cells?

<p>Production of antibodies. (D)</p> Signup and view all the answers

In what way do NK cells contribute to the process of immune tolerance?

<p>By remaining dormant and not responding to self-antigen. (A)</p> Signup and view all the answers

What primarily determines whether NK cells will activate against a target cell?

<p>The ratio of activating to inhibitory receptor engagement (B)</p> Signup and view all the answers

Which of the following correctly describes a scenario in which a host cell may be killed by NK cells due to 'induced self'?

<p>The host cell expresses high levels of activating ligands while normal levels of MHC class I are present (A)</p> Signup and view all the answers

What is a key outcome of priming NK cells with cytokines such as IL-12 or IL-15?

<p>Upregulation of activating and inhibitory receptors (C)</p> Signup and view all the answers

Which type of receptors signal through ITAMs in NK cells?

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

Which factor does NOT typically contribute to the intensity of the NK cell response?

<p>The age of the organism (B)</p> Signup and view all the answers

What characterizes the intracellular domains of activating versus inhibitory NK cell receptors?

<p>Inhibitory receptors contain ITIMs while activating receptors contain ITAMs (D)</p> Signup and view all the answers

What is primarily responsible for the 'missing self' mechanism that activates NK cells?

<p>Downregulation of MHC class I expression on abnormal cells (D)</p> Signup and view all the answers

Which characteristic distinguishes activated NK cells from activated T and B cells?

<p>Activated NK cells can function within hours of infection. (B)</p> Signup and view all the answers

What mechanisms allow NK cells to differentiate between healthy and abnormal cells?

<p>The balance of activating and inhibitory signals from surface receptors. (C)</p> Signup and view all the answers

Which statement accurately describes the nature of 'experienced NK cells'?

<p>They can proliferate upon re-exposure to the same pathogen. (C)</p> Signup and view all the answers

What role do innate immune cytokines play in NK cell activity?

<p>They stimulate NK activity during the early stages of viral infections. (C)</p> Signup and view all the answers

How do NK cells contribute to the immune response against viruses?

<p>They provide immediate defense while CTLs are activated. (A)</p> Signup and view all the answers

Which statement best describes the granules found in activated NK cells?

<p>They are preformed and ready to induce apoptosis in target cells. (B)</p> Signup and view all the answers

What is a significant factor contributing to the mortality of patients with a complete absence of NK cells?

<p>Enhanced susceptibility to viral infections. (C)</p> Signup and view all the answers

Which of the following best describes the concept of 'missing self' as it relates to NK cells?

<p>NK cells identify and target cells lacking MHC class I molecules. (D)</p> Signup and view all the answers

Flashcards

NK Cell Activation

NK cells are activated when they recognize signals from infected or stressed cells.

NK Cell Inhibition

Healthy cells display MHC molecules, which signal NK cells not to kill them.

NK ADCC

Antibodies bind to target cells. NK cells with receptors for those antibodies destroy the target.

NK Cytokines

NK cells release signalling molecules called cytokines that affect immune response.

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NK Cell Tolerance

NK cells typically do not attack healthy cells, meaning they tolerate self-cells.

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NK Cell Function

Kill infected or cancerous cells and produce cytokines that coordinate the immune response.

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NK Cell Location

NK cells are found in the spleen, liver, blood, and other tissues where they patrol and protect.

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NK Cell & Adaptive Immunity Bridge

NK cells connect innate and adaptive immunity by quickly responding to threats and influencing other immune cells.

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Natural Cytotoxicity

NK cell killing of abnormal host cells, triggered by reduced MHC class I expression (missing self) or elevated activating ligands (induced self).

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MHC Class I

A major histocompatibility complex protein class that is normally expressed on healthy host cells.

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Missing Self

Abnormal host cells that have downregulated MHC class I expression, triggering NK cell activation

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Induced Self

Abnormal host cells that express abnormally high levels of activating ligands while having normal levels of MHC class I.

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NK cell Activation

NK cell activation is enhanced by "priming" through cytokines, like IFNα, IFNβ, IL-12, or IL-15.

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Activating Ligands

Ligands that activate receptors on the NK cells.

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Activating Receptors

NK cell receptors that trigger the killing program when activated.

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Inhibitory Receptors

NK cell receptors that prevent the killing of healthy cells.

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NK cell function in pregnancy

Instead of causing cell death, some NK cells interact with placental cells to secrete cytokines, promoting new blood vessel formation for a successful pregnancy.

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NK cell receptors

NK cells have receptors that bind to specific molecules on other cells.

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Antibody-dependent cell-mediated cytotoxicity (ADCC)

NK cells can kill target cells coated with antibodies.

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FcgRIIIA (CD16)

A receptor on NK cells that recognizes antibodies bound to target cells, triggering ADCC.

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Cytokine secretion by NK cells

NK cells release cytokines in response to infection or stimulation to influence immune responses.

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IFN-γ production by NK cells

NK cells produce IFN-γ, which activates macrophages and influences T-cell development.

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NK cell activation

NK cell activation occurs via receptor engagement or antibody stimulation, leading to cytokine and chemokine production.

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TNF-mediated cytotoxicity

Tumor Necrosis Factor (TNF) is a cytokine released by NK cells which can be involved in killing target cells.

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NK Cell Function

NK cells kill infected or cancerous cells and release cytokines to direct the immune response.

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NK Cell Activation

NK cells are triggered when they detect abnormal cells lacking normal MHC class I or having high activating ligands.

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NK Cell Inhibition

Healthy cells display MHC class I proteins, preventing NK cells from attacking them.

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NK Cell ADCC

Antibodies attached to target cells trigger NK cell killing.

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NK Cytokine Release

Activated NK cells release cytokines, influencing other immune cells.

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NK Cell Response Time

NK cells respond rapidly to infections, peaking within hours or a few days

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NK Cell Memory

Some surviving NK cells develop characteristics of memory lymphocytes, enhancing their response on re-exposure to the same pathogen.

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NK Cell Activation

NK cell activation is stimulated by cytokines (like IFN-α, IFN-β, IL-12) produced during initial viral infections.

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NK Cell Cytotoxicity

NK cells kill infected and cancerous cells via pre-formed granules containing perforin and granzymes that induce apoptosis.

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Activating NK Receptors

NK cell receptors that trigger the killing response when bound to ligands on target cells (infected, cancerous or stressed).

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Inhibitory NK Receptors

NK receptors that prevent killing of healthy cells by recognizing MHC class I molecules on normal cells.

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Missing Self

A signal triggering NK cell activation, caused by reduced MHC class I molecules on infected/cancerous cells, perceived by NK cells as 'missing self'.

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Cytokine Secretion

NK cells release cytokines such as IFN-γ, that enhance the immune response.

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Natural Cytotoxicity

NK cell killing of abnormal cells, triggered by reduced MHC class I expression (missing self) or high activating ligands (induced self).

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Missing Self

Abnormal cells lacking normal MHC class I expression, triggering NK cell attack.

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Induced Self

Abnormal cells with elevated activating ligands, despite normal MHC class I levels, triggering NK cell killing.

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NK Cell Activation

NK cell activation is triggered by cytokines such as IFNα, IFNβ, IL-12, and IL-15.

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MHC Class I

A major histocompatibility complex protein that is normally expressed on healthy cells, signaling to avoid NK cell attack.

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Activating/Inhibitory Receptors

NK cells use both activating and inhibitory receptors to distinguish between healthy and abnormal cells and then decide whether to kill it.

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Priming Cytokines

Cytokines that enhance NK cell ability to kill abnormal cells by increasing the number/strength of both activating and inhibiting receptors.

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