Cell recognition & immunity

• What happens if a pathogen gets past the body's barriers?

  The immune system responds with white blood cells
• What are the two types of responses from white blood cells?

  Specific and nonspecific responses
• What type of white blood cells are phagocytes?

  They are nonspecific responders
• What is another name for phagocytes?

  Macrophages
• What do phagocytes do during phagocytosis?

  Engulf and destroy pathogens
• How do phagocytes recognize pathogens?

  By binding to chemicals or antigens
• What happens to a phagocyte after it engulfs a pathogen?

  It forms a vesicle called a phagosome
• What is the role of lysosomes in phagocytosis?

  They fuse with phagosomes to release enzymes
• What enzyme do lysosomes release to destroy pathogens?

  Lysozyme
• What does lysozyme do to pathogens?

  It hydrolyzes and destroys them
• What happens to the soluble products after a pathogen is destroyed?

  They are absorbed and recycled by phagocytes
• What is an antigen presenting cell?

  A phagocyte that displays antigens on its surface
• How do phagocytes respond to different foreign particles?

  They respond the same regardless of the particle
• What is the significance of phagocytosis in the immune response?

  It is a nonspecific mechanism to eliminate pathogens
• Where can phagocytes be found in the body?

  In blood and tissues
• What attracts phagocytes to pathogens?

  Chemicals or debris released by pathogens
• How does the process of phagocytosis contribute to the immune system?

  It helps eliminate pathogens and present antigens
• What are the steps involved in phagocytosis?

  1. Phagocyte detects chemicals from pathogens.
  2. Phagocyte binds to the pathogen via receptors.
  3. Phagocyte engulfs the pathogen, forming a phagosome.
  4. Lysosome fuses with the phagosome.
  5. Lysozyme is released to destroy the pathogen.
  6. Soluble products are absorbed and recycled.
  7. Antigens are presented on the cell surface.
• What are the key features of phagocytes in the immune response?

  • Nonspecific response to pathogens
  • Engulf and destroy foreign particles
  • Present antigens to activate other immune cells
  • Found in blood and tissues
• What type of lymphocytes are involved in the cell mediated response?

  T lymphocytes
• Why are T cells called T cells?

  They mature in the thymus
• What is the specific immune response?

  Response to an exact antigen
• What are antigen presenting cells abbreviated as?

  APC
• What do antigen presenting cells do?

  Present non-self antigens on their surface
• What types of cells can be antigen presenting cells?

  Infected body cells, macrophages, and cancer cells
• Why is the response called cell mediated?

  It involves T cells responding to antigens
• What happens after a pathogen is engulfed by phagocytosis?

  Antigens are placed on the surface of APCs
• What do helper T cells do when they bind to antigens?

  They activate and start dividing by mitosis
• What is the result of helper T cells dividing by mitosis?

  Large numbers of helper T cells are produced
• What can some of the helper T cells differentiate into?

  B cells, memory cells, or cytotoxic T cells
• What do cytotoxic T cells do?

  Destroy abnormal or infected cells
• What protein do cytotoxic T cells release?

  Perforin
• What is the function of perforin?

  Creates pores in infected cell membranes
• What happens to infected cells when perforin is released?

  They die due to pore formation
• Why do you have a sore throat during a cold?

  Cytotoxic T cells destroy infected throat cells
• What is the summary of the cell-mediated response?

  • Involves T lymphocytes responding to antigens
  • Antigen presenting cells include phagocytes and abnormal cells
  • Helper T cells divide and stimulate B cells or become memory cells
  • Cytotoxic T cells kill infected cells using perforin
• What is the role of memory cells in the immune response?

  Store memory of specific antigens
• What triggers the B cell mediated response?

  Activation by helper T cells
• What is the process of phagocytosis?

  Engulfing and destroying pathogens
• What is the role of macrophages in the immune response?

  Engulf pathogens and present antigens