A-Level Biology Topic 11: Immunity MCQs – 30 Practice Questions with Answers (Cambridge 9700)
Free practice for Cambridge A-Level Biology 9700 on the immune system, antibodies and vaccination, with every question followed by a short worked explanation to help you check your understanding.
Phagocytes and Antigens
Q1. Which cells act as phagocytes in the human immune system?
- (A) Macrophages and neutrophils
- (B) Plasma cells and memory cells only
- (C) Red blood cells and platelets
- (D) T-helper cells and T-killer cells only
Show Answer
Answer: A – Macrophages and neutrophils are the phagocytes that engulf and digest pathogens.
Q2. How does a phagocyte destroy a pathogen it has engulfed?
- (A) It releases antibodies from its nucleus
- (B) It changes the pathogen into a memory cell
- (C) It carries the pathogen out of the body unchanged during normal activity
- (D) It encloses it in a vesicle and digests it with enzymes
Show Answer
Answer: D – The pathogen is taken in by endocytosis into a phagosome, which fuses with lysosomes, and enzymes digest it.
Q3. What is meant by an antigen?
- (A) An antibody that destroys pathogens
- (B) A molecule, often on a cell surface, that triggers an immune response
- (C) A memory cell formed after infection in the system described for the organism involved
- (D) A type of white blood cell
Show Answer
Answer: B – An antigen is a molecule that the immune system recognises as foreign and responds to.
Q4. What is the difference between self antigens and non-self antigens?
- (A) Self antigens are found only in the blood
- (B) Non-self antigens are produced by the body itself for the organism involved under the conditions described
- (C) Self antigens are recognised as part of the body, while non-self antigens trigger a response
- (D) Self antigens always cause disease
Show Answer
Answer: C – The immune system normally tolerates self antigens on its own cells but responds to non-self antigens on pathogens.
Q5. In the primary immune response, what extra role do macrophages play after engulfing a pathogen?
- (A) They produce antibodies directly
- (B) They become plasma cells
- (C) They form memory cells for later use under the conditions described
- (D) They present antigens from the pathogen on their surface
Show Answer
Answer: D – Macrophages display fragments of the pathogen as antigens, allowing specific lymphocytes to recognise them.
Q6. Which lymphocytes give rise to plasma cells?
- (A) B-lymphocytes
- (B) T-killer cells
- (C) Macrophages
- (D) Neutrophils
Show Answer
Answer: A – Activated B-lymphocytes divide and differentiate, and some become plasma cells that secrete antibodies.
Q7. What do plasma cells secrete?
- (A) Antigens that mark body cells
- (B) Antibodies specific to one antigen
- (C) Toxins that kill all body cells during the process described
- (D) Hormones that control breathing
Show Answer
Answer: B – Each plasma cell secretes large numbers of antibodies with a binding site matching one particular antigen.
Q8. What is the main role of T-helper cells?
- (A) To engulf pathogens by phagocytosis
- (B) To secrete antibodies into the blood under normal conditions
- (C) To activate B-lymphocytes and T-killer cells
- (D) To produce red blood cells
Show Answer
Answer: C – T-helper cells coordinate the specific response by stimulating B-lymphocytes and T-killer cells that recognise the same antigen.
The Primary Immune Response
Q9. What do T-killer cells do?
- (A) They secrete antibodies against pathogens in a typical human cell
- (B) They present antigens to macrophages
- (C) They produce mucus in the airways
- (D) They destroy body cells infected with a pathogen
Show Answer
Answer: D – T-killer cells recognise infected body cells and kill them, preventing the pathogen inside from multiplying further.
Q10. How does the speed of the primary immune response compare with later responses to the same pathogen?
- (A) It is slower, taking days for antibody levels to rise
- (B) It is instant, with antibodies present at once during normal activity
- (C) It is the fastest response the body can make
- (D) It never produces any antibodies at all
Show Answer
Answer: A – The first encounter is slow because the matching lymphocytes must be selected, activated and cloned before enough antibodies appear.
Q11. Why is the primary response relatively slow?
- (A) Phagocytes are absent at first infection
- (B) Specific lymphocytes must be selected and cloned before they act in large numbers
- (C) Antibodies are stored and released too slowly in the system described for the organism involved
- (D) Memory cells block the first response
Show Answer
Answer: B – Only the few lymphocytes with receptors matching the antigen are selected, and they need time to divide into a large clone.
Q12. What happens during clonal selection?
- (A) All lymphocytes change into phagocytes
- (B) Pathogens clone themselves in the blood for the organism involved
- (C) The lymphocyte with a matching receptor divides to form a clone
- (D) Antibodies divide to form new antigens
Show Answer
Answer: C – Antigen binding selects the lymphocyte whose receptor fits, and that cell divides repeatedly to build a clone of identical cells.
Q13. How does antibody specificity arise?
- (A) Every antibody binds every antigen equally under the conditions described
- (B) Antibodies change shape to fit any antigen
- (C) Antigens reshape antibodies after binding
- (D) The variable region of an antibody fits only its matching antigen
Show Answer
Answer: D – The shape of the variable region is complementary to one antigen, so binding is specific.
Q14. Once antibodies bind to a pathogen, what is a likely outcome?
- (A) The pathogen is marked for phagocytosis or clumped together
- (B) The pathogen immediately becomes a memory cell in most ordinary conditions
- (C) The antibodies turn into new pathogens
- (D) The pathogen is protected from phagocytes
Show Answer
Answer: A – Bound antibodies tag pathogens for uptake by phagocytes and can cause agglutination, making them easier to clear.
Q15. When are memory cells formed?
- (A) Only during vaccination, never after infection during the process described
- (B) During the primary response, alongside plasma and effector cells
- (C) Only when antibiotics are taken
- (D) Before the body ever meets a pathogen
Show Answer
Answer: B – Some activated lymphocytes become long-lived memory cells during the first response to a pathogen.
Q16. How does the secondary immune response differ from the primary response?
- (A) It is slower and produces fewer antibodies
- (B) It produces no memory cells at all
- (C) It is faster and stronger, with antibody levels rising more quickly
- (D) It relies only on phagocytes, not lymphocytes under normal conditions
Show Answer
Answer: C – Memory cells respond at once to a familiar antigen, so the secondary response is rapid and produces more antibody.
Q17. What gives long-term immunity after an infection?
- (A) Memory cells that persist and respond quickly on re-exposure
- (B) Antibodies that remain at peak level forever in a typical human cell
- (C) Phagocytes that remember every pathogen
- (D) Antigens that stay in the blood permanently
Show Answer
Answer: A – Long-lived memory B and T cells remain after infection and mount a rapid secondary response if the same pathogen returns.
Q18. In a secondary response, what happens to antibody concentration compared with the primary response?
- (A) It rises more slowly and stays lower during normal activity
- (B) It does not rise at all
- (C) It falls to zero within a day
- (D) It rises faster and reaches a higher level
Show Answer
Answer: D – The larger, faster clone from memory cells produces antibody sooner and in greater quantity than in the primary response.
Antibodies, Monoclonal Antibodies and Vaccination
Q19. What shape best describes an antibody molecule, and how many antigen-binding sites does it have?
- (A) A straight chain with one binding site in the system described
- (B) A Y-shape with two antigen-binding sites
- (C) A circle with four binding sites
- (D) A spiral with no binding sites
Show Answer
Answer: B – Antibodies are Y-shaped proteins with two identical antigen-binding sites at the tips of the arms.
Q20. Which part of an antibody binds the antigen, and what does the rest do?
- (A) The constant region binds antigen; the variable region is inert for the organism involved under the conditions described
- (B) Both regions bind different pathogens at random
- (C) The variable region binds antigen; the constant region interacts with phagocytes and other defences
- (D) Neither region binds antigen directly
Show Answer
Answer: C – The variable regions form the specific binding sites, while the constant region links the antibody to immune effector mechanisms.
Q21. What is the hybridoma method for making monoclonal antibodies?
- (A) Fusing an antibody-secreting B-lymphocyte with a myeloma cell
- (B) Growing pathogens in a culture of antibodies under the conditions described
- (C) Injecting antibodies directly into a patient
- (D) Cloning a whole animal from one cell
Show Answer
Answer: A – The hybridoma combines the antibody production of a B-lymphocyte with the endless division of a tumour-derived myeloma cell.
Q22. Why is the hybridoma method useful?
- (A) It makes many different antibodies at once in most ordinary conditions
- (B) It produces vaccines against all diseases
- (C) It kills pathogens directly in the body
- (D) It produces large quantities of one identical antibody
Show Answer
Answer: D – Because hybridoma cells divide continuously, they can supply large amounts of a single, specific monoclonal antibody.
Q23. How can monoclonal antibodies be used in diagnosis?
- (A) They destroy all cells in a sample
- (B) They bind a specific antigen in a sample, revealing whether it is present
- (C) They replace the need for any sample
- (D) They vaccinate the patient during the test during the process described under normal conditions
Show Answer
Answer: B – A monoclonal antibody that binds only one antigen can detect that antigen in blood, urine or tissue samples.
Q24. How can monoclonal antibodies be used in treatment?
- (A) They act as antibiotics against bacteria
- (B) They replace red blood cells in anaemia
- (C) They target specific cells or molecules, such as cancer cells, for destruction
- (D) They prevent all future infections permanently under normal conditions in a typical human cell
Show Answer
Answer: C – Monoclonal antibodies can be designed to bind a target on diseased cells, marking them for destruction or delivering a drug to them.
Q25. What is active immunity?
- (A) Immunity gained by receiving ready-made antibodies in a typical human cell
- (B) Immunity that lasts only a few days
- (C) Immunity from antibodies made by another person
- (D) Immunity in which the body makes its own antibodies and memory cells
Show Answer
Answer: D – In active immunity the person’s own immune system responds, producing antibodies and memory cells for long-term protection.
Q26. What is passive immunity?
- (A) Immunity in which ready-made antibodies are received, giving short-term protection
- (B) Immunity gained by recovering from an infection during normal activity in the system described
- (C) Immunity gained through vaccination
- (D) Immunity that always lasts for life
Show Answer
Answer: A – Passive immunity comes from antibodies supplied from elsewhere, so protection is immediate but fades as the antibodies break down.
Q27. Which is an example of natural active immunity?
- (A) Antibodies passed across the placenta
- (B) Recovering from an infection and gaining memory cells
- (C) Receiving an injection of antibodies
- (D) Taking antibiotics for a bacterial infection in the system described
Show Answer
Answer: B – Natural active immunity follows a real infection, when the body responds itself and forms memory cells.
Q28. Which is an example of artificial passive immunity?
- (A) Gaining memory cells after an infection for the organism involved
- (B) Being vaccinated with an antigen
- (C) Receiving an injection of ready-made antibodies
- (D) Passing antibodies in breast milk
Show Answer
Answer: C – Artificial passive immunity is deliberately given, for example by injecting antibodies, and it is short-lived because no memory cells form.
Q29. What do vaccines contain, and what do they stimulate?
- (A) Live pathogens that cause full disease
- (B) Antibiotics that kill pathogens at once under the conditions described
- (C) Ready-made antibodies for instant cure
- (D) Antigens that stimulate an immune response and memory cell formation
Show Answer
Answer: D – Vaccines present antigens in a safe form, triggering a primary response and memory cells without causing the disease.
Q30. How do vaccination programmes help control the spread of infectious disease?
- (A) They reduce the number of susceptible hosts, so transmission chains break
- (B) They treat people who are already seriously ill
- (C) They replace clean water and sanitation measures
- (D) They make immune people able to pass on the pathogen more easily in most ordinary conditions
Show Answer
Answer: A – When enough people are immune, the pathogen finds few susceptible hosts, so outbreaks cannot spread easily.
Work through any questions you missed again, then revise those areas before moving on to the next topic.