Phagocytes and lymphocytes are both present in samples of blood.

a. Describe how the structure of a phagocyte differs from the structure of a lymphocyte.

T-lymphocytes are involved in immune responses to pathogens that invade the body. Immune responses involve the following:

• Antigen presentation
• Clonal selection
• Clonal expansion.

Certain groups of T-lymphocytes are activated when the body is infected with the measles virus.

b. Using the information above, describe what happens to T-lymphocytes during an immune response to measles.

c. State how the response of B-lymphocytes during an immune response is different to the response of T-lymphocytes.