immune system exam questions

• Describe how HIV is replicated.

  • Attachment proteins attach to receptors on helper T cell
  • RNA enters cell;
  • Reverse transcriptase converts RNA to DNA;
  • Viral protein produced;
  • Virus assembled and released from cell
• ADCs are molecules made of a monoclonal antibody linked to a cancer drug.

  Figure 1 shows how an ADC enters and kills a tumour cell.

  The process of entering the cell and the breakdown of the antibody to

  release the drug is very similar to phagocytosis.

  *Use your knowledge of phagocytosis to describe how an ADC enters and kills the tumour cell.

  • cell engulfs the antibody
  • lysosomes fuse with vesicle (containing ADC)
  • lysosomes breakdown ADC to release the drug

  
• Define the term "antigen".

  Answer:A molecule, usually a protein, that triggers an immune response when recognized as foreign by the body
• Name one type of white blood cell involved in the immune response.

  ✅ Answer:Lymphocyte or Phagocyte
• What is phagocytosis?

  ✅ Answer:The process by which phagocytes engulf and digest pathogens
• Describe the role of lysosomes in phagocytosis.

  ✅ Answer:Lysosomes contain digestive enzymes that break down the pathogen inside the phagocyte
• What is the role of antigen-presenting cells in immunity?

  ✅ Answer:They display antigens from pathogens on their surface to activate T cells
• Explain how B cells respond to an antigen.

  ✅ Answer:B cells divide by mitosis and differentiate into plasma cells, which produce antibodies
• What is the function of memory cells?

  ✅ Answer:Memory cells provide long-term immunity by producing a faster secondary immune response if the same antigen is encountered again
• Describe the difference between active and passive immunity.

  ✅ Answer:

  • Active immunity involves the production of antibodies by the immune system after exposure to an antigen. (1 mark)
  • Passive immunity involves receiving antibodies from another source (e.g., maternal antibodies or an injection). (1 mark)
• How do vaccines work?

  ✅ Answer:Vaccines contain antigens that stimulate the immune system to produce memory cells without causing disease. (2 marks)
• What is the role of T helper cells in the immune response?

  ✅ Answer:T helper cells release cytokines that activate B cells and phagocytes.
• Explain why a person may develop flu again even after having it before.

  ✅ Answer:The flu virus mutates frequently, changing its antigens, so memory cells may not recognize the new strain
• What is an autoimmune disease?

  ✅ Answer:A condition where the immune system mistakenly attacks the body’s own cells
• Give an example of an autoimmune disease.

  ✅ Answer:Type 1 diabetes, rheumatoid arthritis, or multiple sclerosis
• How do monoclonal antibodies work in treating cancer?

  ✅ Answer:They bind to specific antigens on cancer cells to mark them for destruction by the immune system
• What is the role of the HIV virus in causing AIDS?

  ✅ Answer:HIV infects and destroys T helper cells, weakening the immune system and leading to AIDS.
• Why do antibiotics not work against viruses?

  ✅ Answer:Viruses do not have cell walls, ribosomes, or metabolic processes that antibiotics target.
• What is herd immunity?

  ✅ Answer:When a high percentage of a population is vaccinated, reducing the spread of disease and protecting those who are unvaccinated.
• What is the role of plasma cells in the immune response?

  ✅ Answer:Plasma cells produce and release large quantities of specific antibodies.
• Explain how the structure of an antibody is related to its function.

  ✅ Answer:Antibodies have a specific variable region that binds to a complementary antigen and a constant region that allows interaction with immune cells
• What is the difference between the primary and secondary immune response?

  ✅ Answer:The primary response is slower and weaker, as it takes time to activate B cells and produce antibodies. (1 mark)The secondary response is faster and stronger due to memory cells.
• • Why does antigen variability make it difficult to develop vaccines? (2 marks)
  • Antigen variability leads to changes in the shape of antigens on pathogens. (1)
  • Memory cells from a previous infection may not recognize the new antigens, preventing an effective immune response. (1)
• • Explain how antigenic variability can cause repeated infections of the same disease. (3 marks)
  • Pathogens mutate, altering their surface antigens. (1)
  • Memory cells from a previous infection no longer recognize the altered antigen. (1)
  • The immune system must undergo a new primary response each time, delaying antibody production. (1)
• • Why do influenza vaccines need to be updated every year? (2 marks)
  • The influenza virus undergoes frequent antigenic variation. (1)
  • New vaccines must be developed to match the new antigen shapes. (1)
• • Describe the process of phagocytosis. (4 marks)
  • A phagocyte recognizes the foreign antigen on a pathogen. (1)
  • The phagocyte engulfs the pathogen and forms a phagosome. (1)
  • Lysosomes fuse with the phagosome and release digestive enzymes. (1)
  • The pathogen is broken down and destroyed. (1)
• • What is the role of lysozymes in destroying pathogens? (2 marks)
  • Lysozymes contain hydrolytic enzymes. (1)
  • These enzymes break down bacterial cell walls, killing the pathogen. (1)
• • What is the role of antigen-presenting cells in the immune response? (3 marks)
  • After phagocytosis, antigen-presenting cells (APCs) display foreign antigens on their surface. (1)
  • This helps activate specific T helper cells. (1)
  • The activated T cells then stimulate other immune responses. (1)
• • Describe how T helper cells activate other immune cells. (4 marks)
  • T helper cells bind to antigen-presenting cells and become activated. (1)
  • They release cytokines. (1)
  • These cytokines stimulate B cells to divide and produce antibodies. (1)
  • They also activate cytotoxic T cells to destroy infected cells. (1)
• • Describe the role of B cells in immunity. (4 marks)
  • B cells recognize and bind to specific antigens. (1)
  • They undergo clonal selection, dividing into plasma cells. (1)
  • Plasma cells produce monoclonal antibodies. (1)
  • Some B cells become memory cells for long-term immunity. (1)
• • How does an antigen-antibody complex lead to pathogen destruction? (2 marks)
  • Antibodies cause agglutination of pathogens, making them easier for phagocytes to engulf. (1)
  • The complex marks the pathogen for destruction by immune cells. (1)
• • Explain how vaccination leads to immunity. (4 marks)
  • A vaccine contains weakened or dead pathogens with antigens. (1)
  • The immune system produces a primary immune response. (1)
  • Memory cells are formed. (1)
  • On re-exposure, a faster and stronger secondary response occurs. (1)
• • What is herd immunity and why is it important? (3 marks)
  • Herd immunity occurs when a large proportion of a population is vaccinated. (1)
  • This reduces disease spread. (1)
  • Protects those who cannot be vaccinated (e.g., newborns, immunocompromised individuals). (1)
• • Describe the structure of HIV. (3 marks)
  • HIV has an outer lipid envelope with glycoproteins. (1)
  • It contains RNA and reverse transcriptase enzyme. (1)
  • It also has a protein capsid surrounding the genetic material. (1)
• • Explain how HIV causes the symptoms of AIDS. (4 marks)
  • HIV infects and destroys T helper cells. (1)
  • This weakens the immune response. (1)
  • Fewer B cells and cytotoxic T cells are activated. (1)
  • The person becomes vulnerable to opportunistic infections. (1)
• • What is the purpose of the ELISA test? (2 marks)
  • The ELISA test detects specific antigens or antibodies in a sample. (1)
  • It is used in disease diagnosis (e.g., HIV, pregnancy tests). (1)
• • Describe the steps of a direct ELISA test. (4 marks)
  • A monoclonal antibody is attached to a well plate. (1)
  • The sample is added; if the antigen is present, it binds to the antibody. (1)
  • A second enzyme-linked antibody is added. (1)
  • A color change indicates a positive result. (1)
• • Explain how indirect ELISA differs from direct ELISA. (3 marks)
  • Indirect ELISA detects antibodies rather than antigens. (1)
  • The antigen is coated on the plate instead. (1)
  • A second antibody with an enzyme binds to the first antibody, causing a color change. (1)
• 1. What is the role of monoclonal antibodies in cancer treatment? (3 marks)

  • Monoclonal antibodies bind specifically to cancer cell antigens. (1)
  • A therapeutic drug is attached to the antibody. (1)
  • The drug is delivered directly to cancer cells, reducing damage to healthy cells. (1)
• Explain how a pregnancy test strip detects the presence of (hCG) in urine. (4 marks)

  Answer:

  • Urine containing hCG moves along the test strip by capillary action.
  • hCG binds to mobile antibodies with a colored bead attached (e.g., gold or dye).
  • The hCG-antibody complex binds to immobilized antibodies in the test region, forming a visible line.
  • A second line appears in the control region to confirm the test is working properly.