A person recovered from a disease caused by a pathogen with surface antigen P.
Six months later, researchers collected lymphocytes from the person's blood. They added equal numbers of the lymphocytes to two cultures. One culture contained antigen P. The other contained antigen Q from a strain of the pathogen with a changed surface antigen. All other conditions were the same.
| Antigen in culture | Number of lymphocytes at the start | Number of lymphocytes after 48 hours | Antibody concentration after 72 hours in µg cm⁻³ |
|---|---|---|---|
| P | 1.0 × 10⁵ | 7.8 × 10⁵ | 96 |
| Q | 1.0 × 10⁵ | 1.4 × 10⁵ | 12 |
Explain the results and predict how infection with the strain carrying antigen Q could affect the person.
87 exam-style questions on Edexcel GCSE Biology 5.3 Immune system and medicines, covering 5.3.1 The specific immune system, 5.3.2 Response to immunisation, 5.3.3 Advantages and disadvantages of immunisation, 5.3.4 Antibiotics and bacterial infections, 5.3.5 Aseptic techniques in culturing, 5.3.6 Cross-sectional areas of cultures, 5.3.7 Stages of developing new medicines, and 5.3.8 Production of monoclonal antibodies. Each one has a worked solution and a mark scheme showing where the marks go.