10. Disease and immunity

• Pathogen: a disease causing organism

  • transmissible disease may be transmitted through: direct contact, blood and bodily fluids
  • non direct: contaminated surface (food, animals, air)
• Transmissible disease: a disease in which the pathogen can be passed from one host to another
• Body defences:

  • Mechanical barriers: skin and hairs in nose
  • Chemical barriers: mucus and stomach acid
  • Cells: phagocytosis and antibody production by white blood cells ( can be enhanced by vaccination)
• Ways of controlling the spread of diseases:

  • a clean water supply
  • hygienic food preparation
  • good personal hygiene
  • waste disposal
  • sewage treatment
• Pathogens/antibody:

  • each pathogen have antigens onto its surface, have specific shape
  • specific antibodies have complementary shape which fit specific antigens
  • antibodies lock onto the antigens for direct destruction, or marking of pathogens for destruction by phagocytes
  • helper B cells creates antibodies
• Active immunity - defence against a pathogen by antibody production in the body

  • gained after infection by a pathogen/ vaccination
• Vaccination:

  • weakened pathogens or their antigens are put into the body
  • the antigens stimulate an immune response by lymphocytes which produces antibodies
  • memory cells are produced that give long-term immunity
  • having a population vaccinated against a particular disease helps to achieve herd immunity
• Passive immunity - short-term defence against a pathogen by antibodies acquired from another individuals (e.g mother to infant)

  • memory cells are NOT created
  • can help a baby's immune system since they are not well developed
  • some disease are caused by the immune system targeting and destroying body cells (Type 1 diabetes)
• Ways of controlling spread of disease:

  • a clean water supply - prevent getting water borne diseases
  • hygienic food preparation - avoid eating contaminated food
  • good personal hygiene - bacteria/viruses wouldn't have a suitable environment for them to grow
  • waste disposal
  • sewage treatment