Phagocytosis

• What is phagocytosis?

  Engulfing large particles by cells
• What is the difference between specific and non-specific defence mechanisms?

  Non-specific is immediate; specific is slower
• Why is there a time lag between infection and immune response?

  Clonal selection of specific lymphocytes takes time
• Why might donor tissues from a genetically similar relative be less likely to be rejected?

  Similar tissues share more surface proteins
• What are the first lines of defence against disease?

  • Physical barriers (e.g., skin)
  • Chemical barriers (e.g., mucus)
  • White blood cells if barriers fail
• What are the two types of white blood cells?

  Phagocytes and lymphocytes
• What do phagocytes do?

  Ingest and destroy pathogens
• How do phagocytes respond to pathogens?

  They move towards chemical signals from pathogens
• What happens when a pathogen is engulfed by a phagocyte?

  A vesicle called a phagosome is formed
• What do lysosomes do during phagocytosis?

  Fuse with phagosomes and release enzymes
• What are lysozymes?

  Enzymes that break down pathogens' cell walls
• How does the breakdown of pathogens by lysozymes compare to digestion?

  Similar to digestion of food in intestines
• What happens to soluble products of pathogen breakdown?

  They are absorbed into the phagocyte's cytoplasm