Immunity And Vaccines Flashcards
What is active immunity?
The immune system produces its own antibodies after being stimulated by an antigen
1. Natural - when individuals become infected with a disease under normal circumstances, body produces its own antibodies
2. Artificial - inducing an immune response eg vaccines
What is passive immunity?
Introduction of antibodies into individuals from an outside source. Immune system does not produce any antibodies of its own.
1. Natural - antibodies from mother passed through placenta of breast milk
2. Artificial- injected with antibodies eg tetanus
What are the differences between active and passive?
What is vaccination?
Deliberate exposure to harmless antigenic material to activate the immune system response and antibodies and memory B cells which provides immunity
What is herd immunity?
Vaccines protect individuals that have them and because they reduce the occurrence of the disease, those not vaccinated are also less likely to catch the disease.
Why can it be difficult to eradicate a disease even with successful vaccinations?
• vaccinations fails to induce immunity in certain individuals
• pathogen may mutate so its antigens change (antigenic variation) therefore vaccine no longer effective
• there may be many varieties of a particular pathogen so it would be impossible to develop a vaccine that is effective against them all
• individuals may have objections to vaccinations for religious ethical or medical reasons
What are the ethical issues with vaccines?
• vaccines are tested on animals
• testing on humans can be risky, who should take part in trials?
• vaccines have side effects that may cause long term harm
• to be fully effective the whole population should be vaccinated
How does a vaccine work?
1) small amounts of dead antigens are introduced either by mouth or injection
2) exposure to these antigens activates B cells to undergo Clonal selection and expansion
3) B cells differentiate into plasma B cells that secrete antibodies and memory B cells
4) when exposed to the same antigen the memory B cells recognise it and divide into plasma cells which secrete more antibodies, quickly
How do antibiotics work?
Antibiotics work by preventing the bacteria from making a normal cell well
Eg penicillin works by inhibiting enzymes required for the synthesis and assembly of the peptide cross linkages in bacteria cell wall, this weakens the walls making them unable to withstand pressure so as water enters by osmosis the cell bursts and the bacteria die.
