The immune responseEdexcel A-Level Biology B: Mind map

Exam questions on The immune response

1. A patient has a cut that becomes infected with bacteria. Within a few hours the area is swollen and red, and large numbers of phagocytes are seen in the tissue. Many of the first phagocytes to arrive die at the site and form pus, while other phagocytes remain active for longer.
   Explain how a phagocyte destroys a bacterium after engulfing it.2 marks
2. Researchers infect a mouse with a virus. A few days later they find that a small number of B cells, each with surface antibodies that bind to a viral protein, have divided many times to form a large number of identical cells. Some of these cells are secreting large amounts of antibody into the blood.
   Explain why only a small number of B cells divided in response to the viral protein.2 marks
3. A virus enters the liver cells of a patient and replicates inside them. Fragments of viral protein are displayed on the surface membranes of the infected cells. The patient's blood contains antibodies against the virus, but the virus inside the liver cells is still not cleared until other cells of the immune system respond.
   Describe how T helper cells are activated in the cell-mediated response and how they activate T killer cells.3 marks