Disease and the immune response

Disease
1. A disease causing organism is called a pathogen.
  1. Pathogens need to enter the body to cause disease.
    1. Different entrances into the body
      1. SKIN
        If the skin is damaged, pathogens on the surface can enter your blood stream.
        Blood clots at the area of damage to prevent pathogens from entering, but some may get in before the clot forms
      2. Gas exchange system
        Pthogens that enter will be trapped in mucus which lines the lung epithelium
        Cells also have cillia that beat to move the mucus up to the larynx, where it is removed
        SOme pathogens are still able to reach the alveoli where they can invade and cause damage
      3. Digestive system
        if you ingest pathogens, most will be killed by the acidic conditions of the stomach
        Some may survive and pass into the intestines where they can invade cells and cause damage
2. How pathogens cause disease
  1. By the production of toxins
  2. Cell damage
    1. Can rupture them to increase nutrients inside them
    2. breaking down nutrients inside the cell for their own use. Eventually kills cell
    3. replicating inside cells, and bursting them when they're released
The immune response
1. Phagocytosis
  1. Phagocyte recognises antigens on pathogen
  2. Cytoplasm engulfs pathogen by phagocytosis
  3. Lysosome fuses with it. Lysosomal enzymes break down the pathogen
  4. phagocytes then present the pathogen's antigens on its surface to activate other cells
2. T-cells
  1. Phagocytes activate the T-cells
    1. Some release substances to activate B-cells
    2. Some attack antigens on a pathogen and kill the cell
3. B-cells
  1. T-cells activate B-cells, which divide into plasma cells
  2. When an antibody on a B-cell meets a complimentary shaped antigens, it binds to it
  3. Plasma cells make more antibodies to the specific antigen on the pathogen
4. Antibodies
  1. Coat the pathogen to make it easier for a Phagocyte to engulf it
  2. Also coat it to prevent the pathogen from entering host cells
  3. Also binds to and neutralises toxins made by the pathogen
  4. Protein structure of antibodies
    1. Specifity of antibody depends on it variable regions
      1. Each antibody has a different shaped variable region thats complimentary to one specific antigen
      2. Constant regions are the same in all antibodies
      3. Has a quarternary structure of 4 polypeptides chains arranged together
  5. Antigen and antibodies from an antigen antibody complex
5. Cellular Response
  1. Consists of the T-cells and the cells they react with (phagocytes)
6. Humoral response
  1. Consists of B-cells and the production of antibodies
Primary and Secondary Immune response
1. Antigens
  1. Antigens on the surface of pathogens activate the primary response
  2. When infected a 2nd time, they activate the secondary immune response
  3. Some pathogens can change their surface antigens, which is called ANTIGENIC VARIATION
    1. Memory cells won't recognise the different antigen, so the immune system carries out the primary response from scratch
2. Primary
  1. Slower. B-cells aren't numerous enough to make enough antibodies
  2. eventually, the body will produce enough, but in the meantime, the person will get symptoms
  3. After being exposed to the antigen, both T- and B-cells produce memory cells

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Disease and the immune response

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	Created by poppyekoronka almost 11 years ago