Cell recognition and the immune system

• What is an antigen?

  Foreign molecule that stimulates immune response
• How does the immune system identify cells?

  By specific molecules on cell surfaces
• What types of cells can the immune system identify?

  Pathogens, abnormal cells, toxins, and transplanted cells
• What is the process of phagocytosis of pathogens?

  1. Phagocyte attracted by chemicals
  2. Engulfs pathogen with cell membrane
  3. Pathogen contained in phagosome
  4. Lysosome fuses with phagosome
  5. Lysozymes digest the pathogen

  
• What happens after phagocytosis in the immune response?

  Antigens are presented on phagocyte surface

  
• How do T lymphocytes respond to foreign antigens?

  They recognize antigens on antigen-presenting cells
• What do specific helper T cells do upon activation?

  They stimulate cytotoxic T cells and B cells
• What is the response of B lymphocytes to a foreign antigen?

  1. Clonal selection occurs
  2. B lymphocyte binds to antigen
  3. Stimulated by helper T cells
  4. Divides to form clones
  5. Some become plasma cells, others memory cells

  
• What are antibodies?

  Quaternary structure proteins secreted by B lymphocytes
• How do antibodies lead to pathogen destruction?

  By forming antigen-antibody complexes
• What is the difference between primary and secondary immune responses?

  Primary is slower; secondary is faster and stronger

  
• What is a vaccine?

  Injection of antigens from weakened pathogens
• How do vaccines provide protection against disease?

  1. B lymphocyte binds to antigen
  2. T helper cell stimulates B cell
  3. B lymphocyte divides to form clones
  4. Some become plasma cells, others memory cells
  5. Memory cells respond faster on re-exposure
• What is herd immunity?

  Large proportion of population vaccinated
• What are the differences between active and passive immunity?

  Active Immunity:

  • Exposure to antigen
  • Memory cells involved
  • Slower to develop

  
  

  Passive Immunity:

  • No exposure to antigen
  • No memory cells
  • Faster acting
• How does antigen variability affect immunity?

  Changes in antigens can lead to loss of immunity
• What is the structure of a HIV particle?

  • Lipid envelope
  • Capsid containing RNA
  • HIV attachment proteins

  
• Describe the replication process of HIV in helper T cells.

  1. HIV attaches to T cell receptors
  2. Lipid envelope fuses with membrane
  3. Capsid releases RNA and reverse transcriptase
  4. Viral RNA converted to DNA
  5. Viral DNA integrates into T cell DNA
  6. New HIV proteins produced
  7. Virus particles released

  
• How does HIV cause AIDS symptoms?

  By infecting and killing helper T cells
• Why are antibiotics ineffective against viruses?

  Viruses lack structures antibiotics target
• What is a monoclonal antibody?

  Antibody from cloned B lymphocytes
• How are monoclonal antibodies used in medical treatments?

  • Specific binding to target cells
  • Therapeutic drug attached
  • Forms antigen-antibody complex to deliver drug
• How are monoclonal antibodies used in medical diagnosis?

  • Specific binding to target antigens
  • Dye or marker attached
  • Forms antigen-antibody complex for detection
• What is the process of the ELISA test to detect antigens?

  1. Attach sample to well
  2. Add complementary monoclonal antibodies
  3. Wash to remove unbound antibodies
  4. Add substrate for color change

  
• What is the process of the ELISA test to detect antibodies?

  1. Attach specific antigens to well
  2. Add sample with potential antibodies
  3. Wash and add complementary antibodies
  4. Add substrate for color change

  
• What is the purpose of a control well in the ELISA test?

  To ensure only enzyme causes color change
• What are some ethical issues associated with vaccines and monoclonal antibodies?

  • Animal testing concerns
  • Potential harm in clinical trials
  • Risk of vaccine misuse
  • Side effects of drugs
• What points should be considered when evaluating vaccine methodology?

  • Sample size and diversity
  • Use of control groups
  • Duration of study
  • Double-blind trials
• What points should be considered when evaluating evidence for vaccines?

  • Observed side effects and frequency
  • Statistical significance of results
  • Standard deviation analysis
  • Cost-effectiveness of dosage