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Immunology - Coggle Diagram

- - - - The mutant form of prion protein can cause normal prion proteins to change shape.
        
        This causes damage so the nervous system and eventual death.
- - - - Increases the risk of faecal-oral transmission of a wide range of pathogens.
- - - - This weakens the cell walls, meaning that the bacteria swell and burst
      - Lysozyme is present in tears, helping to protect the surface of the eyes,
  - - - Skin & mucous membranes
      - Antimicrobial proteins & lysozymes
      - Inflammation
        
        Inflammation is a response to injury or infection where the area becomes hot, red and swollen as a result of increased blood flow
        
        Mast cells respond to tissue damage (caused by injury or infection) by secreting histamine.
        
        This cell-signalling compound stimulates a range of responses including:
        
        Increased blood flow in capillaries
        
        capillaries begin to leak more, allowing fluid to enter the tissues resulting in swelling, phagocytes leave the blood and enter the tissues where they can engulf foreign material
        
        Histamine also stimulates cells to release cytokines, including interleukins that lead to more inflammation.
        
        Cytokines also lead to the promotion of phagocytosis
      - Phagocytosis
        
        Chemicals released by pathogens into the blood attract phagocytes.
        
        Receptors on the surface of phagocytes bind to antigens that are present on the surface of most pathogens
        
        this leads to the phagocyte engulfing and digesting the pathogen
        
        Some types of phagocyte known as macrophages do not completely digest the pathogen.
        
        Instead, antigens from the partially digested pathogen are processed and then appear on the plasma membrane of the macrophage
        
        These are known as antigen-presenting cells
        
        They 'present' the antigens to lymphocytes (T cells)
        
        The process of antigen presentation initiates the immune response. This is the slower, more specific and more effective stage of defence against infection
    - - Antibody-mediated
      - Cell-mediated
  - - - T helper cells have a type of cell-surface receptor known as CD4.
        
        There are many different shapes of CD4 receptor corresponding to the millions of antigen shapes
        
        When a TH cell encounters an APC (antigen presenting cell), the CD4 receptors on the TH cell may be complimentary to the antigen i.e. the shapes match. If so the following event happens:
        
        The TH cell binds, via its CD4 receptor, to the APC
        
        This activates the TH cell
        
        The activated TH cells divide by mitosis to form a clone of active TH cells and memory cells
        
        Activated TH cells are then able to activate TW and B cells
    - - Tc cells have cell-surface receptors known as TCRs.
        
        There are many different shapes of TCR, complementary to different antigens.
      - If a Tc cell encounters an APC with complementary antigens the following series of events occurs:
        
        The Tc cell becomes activated. This process also involves TH cells.
        
        Once activated, the Tc cells will divide by mitosis to form a clone of activated Tc cells and memory cells.
        
        The Tc cells will bind to the surface of other infected cells and destroy them.
        
        This prevents pathogens such as viruses replicating inside the infected cells
  - - - The antigen binds to the BCR
        
        B cell takes in the BCR and antigen
        
        The B cell takes in the BCR and antigen
        
        The B cell processes the antigen and so becomes an APC
        
        At this stage, activated TH cells become involved.
        
        Any activated TH cells with complementary CD4 receptors will then bind to the antigens on the APC
        
        The TH cell then secretes cytokines
        
        1 more item...
- - - - skin-to-skin contact
      - contaminated surfaces
    - - Can result in transmission of blood-borne pathogen
    - - Can lead to STIs
  - - - Occurs when infected food or water are ingested
      - Faecal -oral transmission is the result of poor hygiene and is a significant cause of food-poisoning
      - Infected blood on in animate obscures such as clothing or bedding
    - - An organism that transfers the pathogen from host to host