3.5 - Immune System and Defences

• What is an antigen?

  A molecule that triggers an immune response
• What is an antibody?

  A protein produced by white blood cells that binds to specific antigens to break them down.
• What act as barriers to reduce the entry of pathogens in humans?

  Skin

  Hairs in the nose

  Enzymes in tears
• The cells that line the trachea, bronchi and bronchioles have tiny hair-like projections that waft the mucus and pathogens away from the lungs. What are these structures called?

  Cilia
• Stages of phagocytosis:

  1. Phagocytosis is carried out by s special type of white blood cell called a phagocyte.
  2. The first step is for the phagocyte to track down and bind to a pathogen.
  3. The phagocytes membrane then surrounds the pathogen, engulfing it.
  4. Enzymes in the phagocyte break down the pathogen in order to destroy it.
• What do antitoxins do?

  Bind and neutralise the toxins produced by bacteria