1) How are NK cells similar/different to CTL and TH cells (especially in terms o

Question

1) How are NK cells similar/different to CTL and TH cells (especially in terms of their development)?

2) How are NK cells involved in the overall immune response to a viral infections; also, what cytokine(s) promote their development and appearance at a site of viral infection?

3) What are the general classes of receptors on these cells, and what influences whether they activate or inhibit the cell?

4) What on the target cell may induce NK cell activation, what may inhibit it? Also, how can viral infections influence this process?

5) Be able to compare/contrast T-cells with T-cells—especially in terms of their development, localization (where are they found), and what they respond to.

Explanation / Answer

Natural killer cells or NK cells are a type of cytotoxic lymphocyte critical to the innate immune system. The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to viral-infected cells, acting at around 3 days after infection, and respond to tumor formation.  A cytotoxic T-cells is a, T-cell with the glycoprotein CD8 on its surface that has come into contact with an antigen, the T-cell also receives a second signal from either helper T-cells. This activates the T-cells to form cytotoxic T-cells that uses vesicles with cytotoxins to kill "enemy cells". Cytokines play a crucial role in NK cell activation. As these are stress molecules released by cells upon viral infection, they serve to signal to the NK cell the presence of viral pathogens in the affected area. Cytokines involved in NK activation include IL-12, IL-15, IL-18, IL-2, and CCL5. NK cells are activated in response to interferons or macrophage-derived cytokines. They serve to contain viral infections while the adaptive immune response generates antigen-specific cytotoxic T cells that can clear the infection. NK cells work to control viral infections by secreting IFN and TNF. IFN activates macrophages for phagocytosis and lysis, and TNF acts to promote direct NK tumor cell killing. Patients deficient in NK cells prove to be highly susceptible to early phases of herpes virus infection. Many viruses infect humans and most are controlled satisfactorily by the immune system with limited damage to host tissues. Some viruses, however, do cause overt damage to the host, either in isolated cases or as a reaction that commonly occurs after infection. The outcome is influenced by properties of the infecting virus, the circumstances of infection and multiple factors controlled by the host. Natural killer (NK) cells, as part of the innate immune system, play a key role in host defense against viral infections. Recent advances have indicated that NK cell activation and function are regulated by the interplay between inhibitory and activating signals. Thus, a better understanding of mechanisms responsible for NK cell activation and function in the control of viral infections will help develop NK cell-based therapies. NK Cell-Activating Receptors- The ‘missing self’ hypothesis predicted the mechanism whereby NK cells destroy virus-infected cells that have a downregulated expression of MHC class I. However, in many circumstances, NK cells can efficiently eliminate virus-infected cells that maintain expression of the inhibitory MHC class I. Recent advances have indicated that NK cell activation and function are regulated by the interplay between the inhibitory and activating receptors . NK Cell Inhibitory Receptors- These include lectin-like heterodimers such as CD94-NKG2A , KIRs found in humans or lectin-like Ly49 homodimers found in mice . These inhibitory receptors survey MHC class I molecules and seem to protect healthy cells from inappropriate NK cell-mediated killing.

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.