When a person is infected by influenza for the first time, white blood cells respond to destroy the pathogen. Describe the roles of lymphocytes and phagocytes in this immune response, and explain how the body responds more quickly if the same pathogen enters the body a second time.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
Lymphocytes recognise specific antigens on the influenza virus and secrete antibodies that are complementary to those antigens, binding the virus and neutralising it.
Phagocytes, such as macrophages and neutrophils, engulf the virus or infected cells and digest them through phagocytosis.
After the first infection, some lymphocytes become memory cells.
When the same virus enters again, these memory cells rapidly proliferate and immediately produce large amounts of the specific antibodies.
The quicker antibody response neutralises the virus before it can cause noticeable symptoms.
Phagocytes, such as macrophages and neutrophils, engulf the virus or infected cells and digest them through phagocytosis.
After the first infection, some lymphocytes become memory cells.
When the same virus enters again, these memory cells rapidly proliferate and immediately produce large amounts of the specific antibodies.
The quicker antibody response neutralises the virus before it can cause noticeable symptoms.
Examiner tips
- Use the word "lymphocytes" and "phagocytes" early. Mention antibody specificity. Explain memory cells and rapid response. Keep answer to 5 points, one per mark.
Common mistakes
- Confusing macrophages with lymphocytes. Saying antibodies are produced by phagocytes. Omitting the memory cell step or the rapid response on reinfection.
Mark scheme (5 marks)
- Lymphocytes detect antigens on the surface of the pathogen and release/produce antibodies
- Antibodies are specific / complementary to the antigen on the influenza pathogen and bind to it to neutralise it
- Phagocytes engulf / ingest and digest the pathogen (phagocytosis)
- After the first infection, memory cells remain in the body
- On second exposure, memory cells rapidly divide and produce the correct antibodies more quickly, destroying the pathogen before symptoms appear
Key terms in this question
Related
- All Eduqas A-Level Biology revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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