B5 - Cell recognition and the immune system

Question 1

Some white blood cells are phagocytic. Describe how these phagocytic white blood cells destroy bacteria.

Answer 1

1. Phagocyte recognises foreign antigens of bacterial cell
2. Engulf/ ingest bacteria
3. Bacteria is in a vesicle called phagosome
4. Lysosome fuses with phagosome and enzyme Lysozyme is released into phagolysosome
5. Bacteria is digested/ hydrolysed

Question 2

When vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how.

Answer 2

1. Vaccine contains antigen from pathogen
2. Macrophage presents antigen on its surface
3. T cell with complementary receptor protein binds to antigen
4. T cell stimulates B cell
5. Complementary antibody on its surface
6. B cell secretes large amounts of antibody
7. B cell divides to from clone all secreting the same antibody

Question 3

Describe the difference between active and passive immunity.

Answer 3

1. Active involves memory cells, passive does not
2. Active involves production of antibodies by plasma cells, passive involves antibody introduced externally to body (vaccination)
3. Active is long term, because antibody is produced in response to an antigen
4. Passive is short term, because antibody is broken down
5. Active takes time to develop, passive is fast acting

Question 4

Bacterial meningitis is a potentially fatal disease affecting the membranes around the brain. Neisseria meningitis (Nm) is a leading cause of bacterial meningitis. In the Uk, children are vaccinated against the disease. describe how vaccinations can lead to protection against bacterial meningitis.

Answer 4

1. Antigen on surface of Nm binds to surface protein on a B cell
2. B cell divides by mitosis to produce clone
3. This division is stimulated by cytokines/ T cells
4. B cells/ plasma cells release antibodies
5. B cells become memory cells
6. Memory cells produce plasma/ antibodies faster in the case of secondary infections