T-lymphocytes and B-lymphocytes both play important roles in the immune response. Explain how these two types of white blood cell work together when the body is infected by a pathogen for the first time, and describe what happens to some of the B-lymphocytes after the infection has been cleared.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
1. The pathogen presents unique antigens on its surface.
2. T‑lymphocytes recognise these antigens and become activated.
3. Activated T‑lymphocytes stimulate B‑lymphocytes.
4. B‑lymphocytes produce antibodies that are complementary to the antigen.
5. The antibodies bind to the pathogen, leading to its destruction or neutralisation, and some B‑lymphocytes become memory cells that remain after the infection has cleared.
2. T‑lymphocytes recognise these antigens and become activated.
3. Activated T‑lymphocytes stimulate B‑lymphocytes.
4. B‑lymphocytes produce antibodies that are complementary to the antigen.
5. The antibodies bind to the pathogen, leading to its destruction or neutralisation, and some B‑lymphocytes become memory cells that remain after the infection has cleared.
Examiner tips
- Use the exact sequence of events: pathogen → T‑cell activation → B‑cell stimulation → antibody production → pathogen neutralisation → memory B‑cells.
- Include the word "antigen" and "antibody" to show terminology.
- Mention that memory cells remain for faster response to re‑infection.
Common mistakes
- Mixing up the order of T‑cell and B‑cell activation.
- Failing to state that antibodies are specific to the antigen.
- Not mentioning that some B‑cells become memory cells.
Mark scheme (5 marks)
- The pathogen carries antigens on its surface / antigens are unique chemicals on the surface of the pathogen
- T-lymphocytes detect / respond to the foreign antigen and activate / stimulate B-lymphocytes
- B-lymphocytes produce antibodies specific to / complementary to that antigen
- Antibodies bind to / attach to the antigens on the pathogen, leading to destruction / neutralisation of the pathogen
- Some B-lymphocytes remain as memory cells / are retained after the infection, so the body can respond faster / produce antibodies more quickly if the same pathogen is encountered again
Key terms in this question
Related
- All Edexcel A-Level Biology A: Salters-Nuffield (9BN0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Immune response questions
- Explain how the immune system responds when a pathogen enters the body for the f…
- A person is infected with influenza virus for the first time. Some B-lymphocytes…
- A patient is given a blood transfusion using blood from a donor whose antigens d…
- Vaccines are used to protect individuals against communicable diseases. Explain …