The human body has various defense mechanisms to protect itself from infection.
The table below lists several cells, structures, and molecules involved in the human immune response.
| Letter | Cell, structure, or molecule |
|---|---|
| P | neutrophils |
| Q | lysozyme |
| R | antibodies |
| S | memory B-cells |
| T | sebum |
| U | hydrochloric acid |
| V | macrophages |
| W | mast cells |
(i) Which letter or letters indicate chemical secretions that act as primary defenses to prevent the entry of or destroy pathogens? (ii) Which letter or letters indicate cells capable of performing phagocytosis? (iii) Which letter or letters indicate proteins that specifically bind to antigens on pathogens to neutralise them or mark them for destruction?
During an immune response, cells release various molecules to coordinate the defense. State the role of each of the following:
A traveller is given a yellow fever vaccination (containing a live-attenuated, weakened yellow fever virus) before visiting a tropical region. (i) Which type of immunity is functioning when the traveller is given this vaccination? Select from: natural active, natural passive, artificial active, or artificial passive. (ii) Explain your answer to part (i).
