Question 21 What role do Natural Killer (NK) cells play in the immune response?
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You are studying the role of Natural Killer cells in the innate immune response by setting up an assay in which you infect epithelial cells with a non-cytopathic virus (i.e. does not kill cells) and then add normal or modified NK cells to the culture and observe the effect on the epithelial cells. Match the following conditions with what is likely to occur in your assay. Normal NK Cells and Virus Infected Epithelial Cells Normal NK cells and epithelial cells with MHC Class I gene deleted. NK cells in which the genes KIR-2DL, Kir-3DL and CD94/NKG2A are deleted. NK cells in which KIR-2DS, Kir-3DS and CD94/NKG2C gene are deleted A. Kill Infected Cells B. Kill infected and uninfected cells C. No effect on normal nor infected cells
Shaiju T.
NK cells have multiple activating and inhibitory receptors. Activating receptors send signals that help "switch on" the NK cell. Inhibitory receptors act as a check on NK cell killing. NK cells constantly 'patrol' tissues contacting other cells; signals from activating and inhibitory receptors determine whether NK cells kill the other cells they are in contact with or leave them alone. NK cells and cytotoxic T-cells are both part of the anti-viral responses. Cytotoxic T-cells target virally infected cells for killing by recognizing viral specific antigens displayed by the infected cell. NK cells target virally infected cells using their multiple activating and inhibitory receptors as described above. What would the advantage of how NK cells target virally infected cells (activating & inhibitory receptors) vs. T-cells (antigen specific)? Make sure you're explaining your thought process.
Madhur L.
Killing of virus-infected cells is carried out by cytotoxic T cells (CTLs) and natural killer (NK) cells. Which of the following statements about these cells below are correct? A. CTLs express on their surface a unique T cell receptor that recognizes specific viral peptides bound to MHC class I molecules presented on the surface of infected cells. B. NK cells recognize viral peptides in the context of MHC class I molecules presented on the surface of infected cells. C. NK cells have 1) activating NK receptors that sense stress-induced molecules on the surface of infected cells, and 2) inhibitory MHC class I receptors that detect the presence of MHC class I molecules and normally inhibit NK cell activity, but when MHC class I molecules are absent on the surface of virus-infected cells due to viral interference, no longer inhibit, thereby permitting NK cell killing of the infected cell to proceed. D. CTLs recognize viral peptides presented in the context of MHC class I molecules with their CD8 receptor that also senses activating, stress-induced molecules on the infected cell's surface. E. CTLs effect their cytotoxic response by creating perforin channels and injecting granzymes into the cytoplasm and/or through engaging death receptors, e.g. Fas, which altogether trigger the extrinsic pathway of apoptosis. Answer choices: 1. C, D, E 2. B, C, D 3. A, C, E 4. A, B, C
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