Defence Mechanisms

• How does the immune system recognise self and non-self cells?

  Each cell has specific molecules on its surface that identify it. These molecules are usually proteins.
• What is the benefit of identifying molecules being proteins?

  Proteins have highly unique tertiary structures.
• What are some examples of physical defences?

  1. Skin
  2. Mucus
  3. Tears
• If the physical defences are breached, the next line of defence is...

  Phagocytes
• What can white blood cells identify?

  1. Pathogens
  2. Cells from other organisms of the same species.
  3. Abnormal body cells e.g. cancer
  4. Toxins
• What are antigens?

  Molecules that generate an immune response by lymphocytes when detected in the body.
• How does antigen variability occur?

  1. A pathogen's DNA can frequently mutate.
  2. If a mutation occurs in the gene coding for the antigen, the shape of the antigen may change.
  3. Previous immunity is no longer effective as the memory cells remember only the old shape of the antigen.
• What are the two types of immune response?

  1. Specific
  2. Non-specific
• What response are phagocytes responsible for?

  Non-specific response- same for all pathogens
• What response are lymphocytes responsible for?

  Specific response- particular to the pathogen.
• What is a pathogen?

  A microorganism that causes disease.