vaccines Flashcards
Describe how a vaccine can lead to protection against specific bacteria.
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.
Why is it better to have a variety of antigens from the same pathogen in a vaccine?
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.
Describe how a vaccine leads to the production of antibodies against a disease-causing organism.
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;
Give an example of natural and artificial active immunity and an example of natural and artificial passive immunity.
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
Compare and contrast active and passive immunity.
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.
What is vaccination?
Injection of antigens; Antigen from attenuated microorganism or dead microorganisms; Stimulates the formation of memory cells;
What is meant by herd immunity?
When unvaccinated individuals in a population are protected because most of the population is vaccinated so the spread of the pathogen is much reduced.
