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Regulatory T-Cells, Cytotoxic T-Cells, Macrophages and Intraepithelial Lymphocytes – Cell-Mediated Immunity

by Peter Delves, PhD
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    So those are different types of helper T-cells. What about the regulatory T-cells? Well these suppress immune responses. In fact, they’d probably be better called suppressor T-cells rather than regulatory T-cells. And they act in a number of different ways. One of the ways in which they function is by releasing immunosuppressive cytokines such as interleukin-10 and transforming growth factor beta (β). And these cytokines can down-regulate the activity of eosinophils, basophils, mast cells, helper T-cells and cytotoxic T-cells. So really, suppressing a very broad range of immune responses. There is a second way in which regulatory T-cells can suppress immune responses, and that’s a cell contact-dependant mechanism whereby molecules on the surface of the regulatory T-cell interact with molecules on the surface of the cell that is going to be suppressed. And cell surface CTLA-4 and LAG-3, are functional in down-regulating the activity of dendritic cells. What about cytotoxic T-cells? Well, as their name suggests, they can kill; cytotoxic cell killing. They can kill infected cells and also tumor cells. They can also secrete cytokines; in fact virtually all cells in the body can secrete cytokines. And cytotoxic T-cells have been divided into different subpopulations, just like the helper T-cells have. So, we can identify Tc1 cells that secrete gamma interferon, just like Th1 cells secrete gamma interferon, Tc2 cells that secrete IL-4 and so forth just like Th2 cells do. So there are also subpopulations of cyctoxic T-cells. The killing of an infected cell by cytotoxic T-cell depends upon peptides from the pathogen being presented by MHC Class I to the T-cell receptor on the surface of the cytotoxic T-cell. This will lead to the activation of the cytotoxic T-cell. And there are two ways in which the killing process can function. First of all, infected cells have...

    About the Lecture

    The lecture Regulatory T-Cells, Cytotoxic T-Cells, Macrophages and Intraepithelial Lymphocytes – Cell-Mediated Immunity by Peter Delves, PhD is from the course Humoral Immunity and Cell-Mediated Immunity. It contains the following chapters:

    • Regulatory T-Cells
    • Cytotoxic T-Cells
    • Removal of Killed Cells by Macrophages
    • Intraepithelial Lymphocytes

    Included Quiz Questions

    1. CD8αα
    2. CD8αβ
    3. CD8ββ
    4. CD4αα
    5. CD4αβ
    1. Dendritic cells
    2. Mast cells
    3. Eosinophils
    4. Basophils
    5. Helper T cells
    1. Cytotoxic T cell mediated apoptosis is dependent on Fas and FasL interaction
    2. Cytotoxic T cells would downregulate the production of FasL and upregulate the release of Granzymes
    3. Cytotoxic T cells would increase the amount of Granzymes released into order to create a concentration gradient that will bring them into the tumor cell
    4. Caspase activation would increase
    5. Cell death could only be mediated by phagocytosis- apoptosis would be impossible
    1. A healthy cell has internal phosphatidylserine, external phosphatidylserine signals to macrophages to phagocytose the cell
    2. Internal phosphatidylserine makes a cell more likely to be phagocytosed by macorphages
    3. External phosphatidylserine signal to Dendritic cells that an antigenic cell has been engulfed
    4. Treg cells recognize external phosphatidylserine and down regulate release to cytokines, which leads to an enhanced immune response
    5. Macrophages will not engulf a cell with external phosphatidylserine

    Author of lecture Regulatory T-Cells, Cytotoxic T-Cells, Macrophages and Intraepithelial Lymphocytes – Cell-Mediated Immunity

     Peter Delves, PhD

    Peter Delves, PhD


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