vaccines

Question 1

1. Describe how a vaccine can lead to protection against specific bacteria.

Answer 1

Antigen on surface of bacterium binds to surface receptor on a specific B cell. Activated B cell divides by mitosis to produce clones; Division stimulated by specific T helper cells; B plasma cells release antibodies; Some B cells become memory cells; upon re-exposure to the pathogen-memory cells produce plasma cells and therefore antibodies faster and in greater volumes.

Question 2

2. Why is it better to have a variety of antigens from the same pathogen in a vaccine?

Answer 2

Contains a greater range of antigens; Each antigen causes its own immune response and so the production of a range of specific antibodies directed against different antigens on the same pathogen.

Question 3

3. Describe how a vaccine leads to the production of antibodies against a disease-causing organism.

Answer 3

Vaccine contains antigen from pathogen; Phagocyte presents antigen on its surface; T cell with complementary receptor protein binds to antigen; T helper cell stimulates specific B cell; With complementary antibody on its surface; B cell divides to form cloned plasma cells all producing and secreting same antibody; B cell secretes large amounts of antibody;

Question 4

4. Give an example of natural and artificial active immunity and an example of natural and artificial passive immunity.

Answer 4

Passive immunity: Natural -antibodies given to a foetus by the mother (through the placenta) or passed to baby in breast milk Artificial- Injected with antibodies Active immunity: Natural- exposure to a pathogen followed by an immune response Artificial- Vaccination

Question 5

5. Compare and contrast active and passive immunity

Answer 5

Active involves memory cells, passive does not; Active involves production of antibody by plasma cells and memory cells; Passive involves antibody introduced into body from an outside source; Active is long term, because antibody produced in response to antigen; Passive short term, because given antibody is broken down; Active can take time to develop and work, passive is fast acting

Question 6

6. What is vaccination?

Answer 6

Injection of antigens; Antigen from attenuated microorganism or dead microorganisms; Stimulates the formation of memory cells;

Question 7

7. What is meant by herd immunity

Answer 7

When unvaccinated individuals in a population are protected because most of the population is vaccinated so the spread of the pathogen is much reduced.