What is meant by the term ‘passive immunity’?
Immunity that is achieved as a result of antibodies being introduced directly into the body
Why is passive immunity NOT long lasting?
- as no B-cells are involved in the production of antibodies and therefore no memory cells are formed. When the antibodies are broken down they can not be replaced again.
What is meant by the term ‘active immunity’?
Immunity that is a result of the immune system being stimulated to produce antibodies. It requires direct contact with the pathogen or it’s antigens.
What are the 2 types of active immunity?
artificial and natural
How do vaccines work?
- By injecting small amounts of a pathogen or it’s antigen into a body.
- this stimulates an (slight) immune response
- this results in the production of memory cells
- if the person were to come into contact with the pathogen, the memory cells would be able to activate a rapid immune response, preventing illness
What are 5 features that make a successful vaccination programme?
- there must be sufficient quantities available in or order to vaccinate large populations (considered economically)
- there must be appropriate means to produce, transport and store large quantities of the vaccine
- it should have minimal side effects so enough people are willing to be vaccinated
- there must be a suitable way to distribute the vaccination, with well-trained administrators
- it must be possible to vaccinate the majority of the vulnerable population
What is meant by the term ‘herd immunity’?
Herd immunity refers to a population being protected from a pathogen, because the vast majority of people in it are vaccinated against that disease
How does herd immunity work?
- based on the idea that pathogens spread through close contact
- if most of the population is immune to the disease/vaccinated, then it is unlikely than a susceptible person will come into contact with the pathogen and catch the disease
- this means unvaccinated people are also protected
Why is herd immunity important?
As it is not possible to vaccinate 100% of the population. Young children and babies have not got fully developed immune systems so can it be vaccinated. Also, people with some illnesses will not be able to have. a vaccination due to an impaired immune system
Why might a vaccination not be effective in eliminating a disease?
- the vaccine may not be effective on some people (those with defective immune systems)
- antigenic variability
- too many varieties of a pathogen (e.g common cold)
- some pathogens conceal/hide themselves from the immune system
How does antigenic variability limit the effectiveness of vaccinations?
- if a pathogen has a lot of antigenic variability, then the immune system may not be able to recognise the and respond to the pathogen This occurs as a result of mutations
How is a pathogen able to hide itself from the body’s immune system?
Hiding inside self-cells or in places out of reach (e.g the small intestine)
What are some ethical considerations of vaccines?
- The use of animals in their development
- The risk of side effects (vs the risk of disease)
- Who should test vaccines?
- Should it be compulsory?
- Individual health risks vs advantage for population
Describe how a vaccination leads to the production of antibodies
- Vaccine contains antigen from pathogen
- Phagocyte presents antigen on cell-surface membrane
- T-cell with complementary receptor binds to antigen
- T-cell stimulate B-cell (with the complementary antibody)
- B-cell secretes a large amount of antibodies and clones itself, all clones produce the same antibody
Why does a high mutation rate make it difficult to develop a vaccine ?
- antigenic variability
- vaccine contains one specific antigen
- the antibodies (that are stimulate by the vaccine) are not complementary to the changed antigen
Explain the antibody concentration before a vaccine, after the 1st and after the 2nd dose
- before: no antibodies produced as patients have not yet encountered the antigen
- 1st dose: clonal expansion of B cells into plasma cells, which release antibodies
- 2nd dose: memory cells produce more antibodies / produce antibodies more quickly;
How do vaccines prevent against disease?
- Vaccines contain antigens Memory cells made On second exposure memory cells produce antibodies
- Rapidly produce antibodies / produces more antibodies
- Antibodies destroy pathogens;
What do memory cells do when they come into contact with antigens?
differentiate to form plasma cells
Why would determining the genome of viruses allow for a vaccine to be developed?
- identify the proteome
- therefore identify antigens (and their shape)
