Topic 5: Cell Recognition & Immune system

• What type of white blood cells carry out phagocytosis?

  Phagocytes
• What are the two types of phagocytes?

  Macrophages and neutrophils
• What is the role of macrophages?

  They are large phagocytic cells
• How do neutrophils differ from macrophages?

  Neutrophils are smaller phagocytic cells
• What are the steps of phagocytosis?

  1. Phagocytes recognize antigens on pathogens.
  2. Phagocyte engulfs the pathogen.
  3. Pathogen trapped in a phagosome.
  4. Lysosomes fuse with phagosome.
  5. Pathogen digested and products absorbed.
• What is a phagosome?

  A vacuole containing the engulfed pathogen
• What do lysosomes release during phagocytosis?

  Lysozymes
• What is the outcome of the digestion of a pathogen by phagocytes?

  Pathogen is destroyed and products absorbed
• What does it mean that phagocytosis is a non-specific response?

  It is the same for all pathogens
• What type of cell displays antigens after phagocytosis?

  Antigen-presenting cell
• What triggers the specific immune response?

  Antigen-presenting cells displaying antigens
• What are lymphocytes involved in?

  Specific immune response
• How do lymphocytes differ from phagocytes?

  Lymphocytes attack specific antigens
• Where do B lymphocytes mature?

  Bone marrow
• What is the function of B lymphocytes?

  They secrete antibodies into the blood
• Where do T lymphocytes mature?

  Thymus
• What is the role of T lymphocytes?

  They attack pathogens or infected cells
• What are antibodies?

  Proteins secreted in response to antigens
• What shape do antibodies have?

  Y-shaped molecule
• How many binding sites do antibodies have?

  Two binding sites
• What forms when an antibody binds to an antigen?

  Antigen-antibody complex
• What is the primary response in the immune system?

  First detection of an antigen
• What happens during the secondary response?

  Faster and larger response to the same antigen
• What are the steps of the cellular response involving T lymphocytes?

  1. T-helper cells recognize antigens on pathogens.
  2. T-cells undergo mitotic divisions.
  3. T-helper cells assist B-cells in producing antibodies.
  4. Cytotoxic T-cells destroy infected body cells.
• What is the role of plasma cells in the humoral response?

  They secrete antibodies
• What is agglutination in the context of antibodies?

  Formation of a lattice-like structure
• How do antibodies immobilize pathogens during agglutination?

  By binding to antigens on different pathogens
• What is the effect of agglutination on pathogens?

  It makes them easier for phagocytes to destroy
• What happens to pathogens during phagocytosis after agglutination?

  They are engulfed and destroyed by phagocytes
• What are the physical barriers to infection?

  Skin, stomach acid, gut and skin flora
• What is the role of skin in the immune response?

  It acts as a tough physical barrier
• How does stomach acid contribute to immunity?

  It kills bacteria through hydrochloric acid
• What is the function of gut and skin flora?

  They compete with pathogens for resources
• What are antigens?

  Proteins on the surface of cells
• How do antigens help the immune system?

  They identify cells as self or non-self
• What are the non-specific immune responses to infection?

  • Inflammation
  • Lysozyme action
  • Interferon
  • Phagocytosis
• What happens during inflammation?

  Histamines cause vasodilation and increased blood flow
• What is the role of lysozyme in the immune response?

  It kills bacteria by damaging their cell wall
• How do interferons function in the immune response?

  They prevent viruses from spreading to cells
• What is phagocytosis?

  White blood cells engulf and destroy pathogens