Questions and Answers
What type of immune response do T cells mediate?
Which type of T cell is cytotoxic and kills cells directly?
Which type of T cell activates macrophages and allows uptake of pathogens by phagocytosis?
Which type of T cell mediates anti-parasitic response and allergic reactions?
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What do CD8+ T cells bind to?
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On which type of cell are MHC Class I proteins expressed?
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What do MHC Class II proteins display?
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Which cells recognize soluble or extracellular pathogens?
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Study Notes
T Lymphocytes
- Cell mediated arm of the adaptive immune response
- Two main populations: CD4+ and CD8+
CD4+ T Cells
- Helper T cells (Th1, Th2, TFH)
- Activate macrophages and allow uptake of pathogens by phagocytosis
- Stimulate production of ROS and NOS
- Mediate destruction of pathogens ingested by macrophages
- Th2 cells: mediate anti-parasitic response, allergic reactions, and activate B cells
CD8+ T Cells
- Cytotoxic T cells (Tc/CTL)
- Cytotoxic and kill cells directly
- Respond to pathogens in the cytosol of target cells
- Prevent the spread of infection by inducing programmed cell death (apoptosis)
T Cell Receptors (TCR)
- Bind to Major Histocompatibility Complex (MHC) proteins
- Two classes of MHC proteins: Class I and II
- MHC proteins bind to peptide fragments from self- and non-self proteins
- Displayed on the cell surface and recognized by T cells
MHC Class I Proteins
- Expressed by all nucleated body cells
- Bind to peptide fragments from cytosolic proteins
- Recognized by CD8+ T cells (Tc)
MHC Class II Proteins
- Expressed by selected immune cells (macrophages, dendritic cells, activated B cells)
- Bind to peptide fragments from vesicular proteins
- Recognized by CD4+ T cells (Th1/Th2/TFH)
T Cell Recognition
- Recognize intracellular pathogens, either infecting a cell directly or taken up by a cell (e.g. macrophage)
- In contrast, B cells recognize soluble/extracellular pathogens
- Together, B and T cells recognize pathogens in all cellular locations
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Description
Explore the cell-mediated arm of the adaptive immune response, including CD4+ and CD8+ T-lymphocytes, their functions and populations such as helper T cells and cytotoxic T cells.
