The immune system

• Phagocytosis

  1. White blood cells (phagocytes) engulf and digest invading pathogens

  2. Phagocyte changes shape to surround pathogen

  3. Phagocyte releases enzymes to digest pathogen
• Antigens

  Unique markers on the surface of pathogens
• Lymphocytes

  White blood cells that can identify antigens
• Antibody production

  1. Lymphocytes produce antibodies

  2. Antibodies bind to pathogen antigens and mark them for destruction

  3. Most lymphocytes die off after pathogens are killed, but memory cells remain

  4. Memory cells rapidly produce more antibodies if pathogen reappears
• Immune

  When a person's memory cells can rapidly produce antibodies to kill a pathogen before symptoms appear
• Toxins

  Poisons produced by bacteria that cause harm to body cells
• Antitoxins

  Substances that neutralise toxins released by invading bacteria