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Flashcards

Week 8

Dolu Falowo Foundations 3 English 36 cards

Cards in this deck (36)

  1. 1What happens in T cell re-circulation?-Naive T cells enter the lymph nodes
    -T cells are activated by antigen presenting by dendritic cells in the periphery and lymph node
    -Given survival signals to proliferate and differentiate
  2. 2What is needed for naive T helper cell activation?Signal 1: signal through a functioning TCR
    Signal 2: moderation of the signal through CD28 on T cells and CD80/86 on APCs
    Signal 3: cytokine production eg. IL-4, IL-12
  3. 3What do CD4 T helper cells do?-Help B cells make antibody
    -Enhance and maintain responses of CD8 cytotoxic T cells
    -Regulate macrophages
    -Organise immune responses
    -Regulate/suppress immune responses
    -Mediators of immunologic memory
  4. 4What drives CD4+ T cell differentiation?-Molecular environment of the dendritic/T cell interaction
    -Type of T cell made depends on cytokines released by dendritic cell
  5. 5Differentiation of CD4+ Th1 cells What do CD4+ cells differentiate in the presence of? (to form Th1 cells) What do CD4+ Th1 cells secrete? What transcription factor is needed?IL-12
    IFN gamma (acts as a positive feedback loop for further differentiation into Th1)
    T-bet
  6. 6CD4+ Th1 cells activate macrophages to kill intracellular bacteria via IFN gamma What increases this response?-MHC expression
    -co-stimulatory molecule expression
    -NO production
    -Phagolysosome maturation
    -TNF alpha production
  7. 7What is Th1 also associated with?-AI conditions
    -Inflammatory disease
    -Deficiencies can result in reactivation of latent infections eg. TB
  8. 8Differentiation of CD4+ Th2 cells What do CD4+ cells differentiate in the presence of? (to form Th2 cells) What do CD4+ Th2 cells secrete? What do Th2 cells promote resistance to?IL-4
    IL-4, IL-5, IL-13
    Resistance to large extracellular helminth parasites (ie. large worms!)
  9. 9What does IL-4 from Th2 cells promote? What cells are activated by Th2 cells?Promotes B cell class switching to IgE
    Eosinophils, mast cells and plasma cells
  10. 10Differentiation of CD4+ Th17 cells What do CD4+ cells differentiate in the presence of? (to form Th17 cells) What do CD4+ Th17 cells secrete? What transcription factor is needed?Stimulated by IL-1 beta, IL-6, IL-21 and maintained by IL-23
    Il-17
    ROR(gamma)T
  11. 11What do Th17 cells protect against? How?Fungal infection and some bacteria
    Increases neutrophil recruitment and controls epithelial barrier function
  12. 12Differentiation of CD4+ TFH cells What do CD4+ cells differentiate in the presence of? (to form TFH cells) What do CD4+ TFH cells express? What transcription factor is needed?IL-21
    Express chemokine receptor CXCR5
    Bcl-6
  13. 13What are TFH cells used for?-Germinal centre formation
    -Affinity maturation
    -Development of high-affinity antibodies and memory B cells
  14. 14Differentiation of CD4+ Treg cells What do CD4+ cells differentiate in the presence of? (to form Treg cells) What transcription factor is needed?TGF beta and retinoic acid
    FoxP3
  15. 15What is the function of Treg cells?Restrict other immune responses:
    -suppress T cell proliferation
    -control peripheral autoimmunity
  16. 16What are the 2 ways CD8+ cytotoxic T cells target intracellular pathogens?-Granules contain perforin and granzymes which cause apoptosis. They migrate towards the T/infected cell contact point
    -Fas ligand on T cell binds to Fas expressed on target cell (once infected) triggering apoptosis
  17. 17What are CD8+ cytotoxic T cells stimualted by?-Dendritic cells acting as APCs
    -CD4+ helper cell-activated APC
    -High concentrations of IL-2 produced by helper T cells
  18. 18What are examples of the host's innate anti-microbial killing mechanisms?-Acidification
    -Toxic superoxides
    -Toxic nitric oxide
    -Antimicrobial peptides such as defensins and cationic proteins
    -Lyzozyme
    -Lactoferrin (binds to iron)
    -Vitamin B12 binding proteins
  19. 19Describe the stages of phagocytosis1) Pathogen is endocytosed
    2) Early phagosome matures into a late phagosome. pH inside falls
    3) Lysosome fuses with a phagosome to form a phagolysosome
    4) Microbe is digested
    5) Priteins are either loaded onto MHCs or degraded into harmless non-peptides and released out of the cell
  20. 20What are key examples of cytoplasmic intracellular organisms?Viruses
    Listeria
  21. 21What are key examples of vesicular intracellular organisms?Mycobacterium derivatives
    Salmonella
  22. 22How does M.tuberculosis interfere with the phagocytosis mechanism?Restricts phagosome maturation early on since the bacteria is sensitive to a low pH
  23. 23How do pathogens such as Shigella and Listeria interfere with the phagocytosis mechanism?Escapes from the phagosome into the cytosol. Even is the phagosome matures, it doesn't matter since the pathogen is not inside
  24. 24How do bacteria interfere with host production of superoxide?-Bacterial produces superoxide dismutase which converts superoxides into hydrogen peroxide
    -Catalase converts breakdown of hydrogen peroxide to water
  25. 25What is the result of no Th1 cells?No bacterial clearance
  26. 26Th1 cells activate macrophages. What does this result in?-More superoxides and NO
    -Phago/lysosome fusion
    -More MHC expression
    -Enhanced cytokine production
  27. 27What type of intracellular pathogens do CD4 and CD8 cells target?CD4: Vesicular pathogens
    CD8: Cytosolic pathogens
  28. 28What are the clinical symptoms of TB?-Breathlessness
    -Chest pains
    -Loss of appetite
    -Haemoptysis
    -Tiredness
    -Persistant cough
    -Weight loss
    -Night sweats
  29. 29What is a Ghon focusGranuloma formed as a result of TB. Indicative of latent TB
  30. 30What is the purpose of granulomas?-Result of a chronic inflammatory infection
    -Attempt by immune system to isolate and wall of a chronic irritant/infection
  31. 31Describe the structure of granulomas-Lymphocytes (CD4/8 T cells) are around and within the macrophage mass
    -Central area of cell necrosis (caseation)
    -If infection is contained, layer of fibroblasts and collagen forms around the granuloma
  32. 32Granuloma's can grow and erode into...-air pocket (eg. bronchial tree)
    -blood vessel
    -another granuloma
    Indicates control of infection has failed
  33. 33What 3 innate killing mechanisms do M.tb inhibit?-Reactive oxygen radical generation
    -Reactive nitrogen radical generation
    -Phagosome fusion with lysosomes
  34. 34How is M.tb able to block phagosome-lysosome fusion?-Cell wall is unusually thick with glycolipids and is covered in a waxy coat
  35. 35Describe the process of T cell priming1) Immature dendritic cells (DC) are infected or take up antigens via PRR/PAMP interactions
    2) Activated dendritic cells express MHC I/II to T cells
    3) To enhance T cell response, co-stimulatory molecules CD80/86/40 are released
    4) DCs releast IL-12/18 for T cell differentiation into Th1/Tc effector cells
    5) Both Th1/Tc effector cells release IFN(gamma)
  36. 36Patients with genetic defects in IL-12/18 and IFN(gamma) suffer from...Recurrent infections with intracellular pathogens eg. mycobacterium

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Effector functions of T cells Immunity to intracellular pathogens
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Dolu Falowo
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