Immunity

• Immune Response

  The way in which an organism protects itself against pathogens.
• Natural immunity

  • Is present at birth.
  • First line of defence against pathogens
  • Non-specific (able to destroy different pathogens )
• Acquired Immunity

  • Developed through exposure to pathogens.
  • Activated when pathogens penetrate the “first line of defence”.
  • Leukocytes destroy the pathogens and prevent re-infection.
• Immune response in plants

  • Plants are also affected by pathogens
  • Plants only have natural immunity.
  • When infected, the natural immune response is activated and chemical compounds(e.g. salicylic acid) is released.
  • These compounds move through the phloem to uninfected cells and are then stimulated to produce chemical defences.
• Natural Immunity in Animals

  • e.g. coughing, sneezing, nasal congestion(mucus)
  • The body’s first line of defence is the external barrier, the skin.
  • If pathogens penetrate the first line, inflammation and fevers are the 2nd line.
  • Fever - High temperatures inhibit pathogen growth as they thrive in lower temperatures.
  • Inflammation - blood vessels dilate, increasing blood flow. Leukocytes reach the area faster to fight the infection.
• Acquired Immunity

  Immunity developed after exposure to pathogens
• Lymphocytes

  A type of white blood cell involved in acquired immunity
• Pathogens that have penetrated the body tissues are actively destroyed and the body stores memory of the response
• Leukocytes

  Recognise pathogens as foreign cells and are then neutralised
• 1. Lymphocytes

  • Attach to specific antigens of pathogens
  • Multiply and produce antibodies
  • Mark pathogens for ingestion by phagocytes
  • Clump pathogens together which inactivates them
• 1. Lymphocytes

  • Destroy the body’s cells that are infected by a virus
  • Secrete chemicals to destroy virus-infected cells
• Antibodies can’t reach viruses as they “hide” in host cells
• Memory cells

  • B- and T-Lymphocytes that remain in the blood
  • Enable a faster immune response upon re-infection
• Phagocytes

  Large leukocytes that can change shape and engulf pathogens by phagocytosis
• Immunisation

  The administration of a vaccine to develop immunity to a disease.
• Vaccines

  • The vaccine stimulates the immune system to produce antibodies to develop a memory of the response.
  • The person is now immune
  • No vaccine for Malaria or HIV.
  • e.g. Smallpox eradication.
• Antibiotics

  • Chemical substances that destroy bacteria(not viruses)
  • Most are obtained from moulds.
  • Most are semi-synthetic as natural antibiotics are modified to have different effects on different bacteria.

  Antibiotics kill b:

  • Weakening the cell wall, causing the pathogen to burst.
  • Damaging the cell membrane, causing the pathogen cell contents to leak out.
  • Inhibiting pathogen metabolism( no protein synthesis = death)
• Antibiotic Resistance

  • Bacteria develop resistance to antibiotics as part of evolution.
  • Through mutation, bacteria develop resistance to antibiotics.

  Resistance develops due to

  1. Bacteria rapidly reproduces
  2. Mutation that provides protection against antibiotics.
  3. The mutated bacteria survives the antibiotics & multiplies.
  4. The new resistant bacteria is formed.
• Immunocompetence

  The ability to produce antibodies
• Vector

  Organism that transfers pathogens from one organism to another.