Diseases and Immunity (2.30-2.35)

  • Pathogen: a disease causing organism
    • Each pathogen has a uniquely shaped ‘marker’ on the surface of their membranes- antigens
  • Transmissible disease: disease in which the pathogen can be passed from one host to another
    • Can be transmitted through direct contact (eg. blood/body fluids) or indirect contact (eg. contaminated food/air)

Mechanical Barriers:

  1. Skin- When you cut or graze your skin it immediately begins to heal itself
  2. Nose hairs- Stop pathogens from getting past them further up the nose preventing them from entering the lungs.

Chemical Barriers:

  1. Mucus- produced throughout the body and traps pathogens and can be released (through coughing, blowing your nose, swallowing)
  2. Hydrochloric Acid- Kills pathogens that have been caught in mucus in the airways and then swallowed or have been consumed in food or water

Cells:

  1. Phagocytosis- Englufes and digests pathogen

    

   

  1. Sensitive cell membrane detecs chemicals produced by pathogen
  2. Engulfes pathogen
  3. Releases digestive enzymes on pathogen
  4. Digested and excreted
    1. Antibodies- Clumps pathogens together and releases chemicals to destroy pathogens

   All cells have antigens on their surface

Antigens and Antibodies
  • Lymphocytes detect the antigens on the surfaces of cells and recognise any that are foreign
  • Antibodies are then made in a complementary shape to pathogen antigens which then attach to antigens and cause aggulitination
  • Chemicals are released to signal to phagocytes to destroy the pathogen
  • Lymphocytes that have made antibodies for a specific pathogen will make ‘memory cells’ that retain the instructions for making those specific antibodies for that type of pathogen
    • If a pathogen reinfects the body antibodies can be made very quickly and the pathogens can be destroyed before they can multiply and cause illness (immunity)

 

Passive immunity:

  • Short-term defense against a pathogen by antibodies transferred from one individual to another (rather than making their own)
    • Mother to infant through breast milk
    • Injected antibodies

Active immunity:

  • Making antibodies and developing memory cells for future response to infection
    • The body is infected with a pathogen and the lymphocytes go through the process of making antibodies specific to that pathogen (and producing memory cells)
  • Vaccination

Protection against specific diseases and boost the body’s defence against infection from pathogens

  1. A harmless variant on a certain antigen is introduced to the body (injected)
  2. Immune response is triggered and activate lymphocytes produce antibodies and memory cells to fight against the antigen variant
  3. When real pathogen makes its way inside the body, there are antibodies/memory cells which can rapidly fight against it

 

 

Methods to control the spread of disease:

  1. Personal hygiene
  2. Food hygiene
  3. Waste disposal
  4. Sewage treatment

Autoimmune disease

  • Body attacks own body cells; recognises own body cells as foreign
  • A lymphocyte targets specific body cells and makes antibodies against them, destroying them
  • Example Type 1 Diabetes- Causes people to be unable to regulate their blood glucose levels since they are unable to make their own insulin
  • Due to the immune system targeting and destroying the pancreatic cells, leading to dangerously high blood glucose levels