Flashcards in Immunity, vaccination, Mabs + autoimmune diseases (Chapter 11) Deck (64)
What is active immunity?
Immunity gained after an antigen (e.g. pathogen) has entered the body, an immune response has occurred and ABs have been produced by plasma cells
What is natural active immunity?
Immunity gained by being infected i.e. when lymphocytes are activated by antigens on the surface of pathogens that have entered the body, therefore memory cells have been produced
What is artificial active immunity?
Vaccination - when an immune response is activated artificially either by injecting antigens into the body or taking them by mouth
How does the immune response which leads to active or natural active immunity differ?
The immune responses are similar, and the effect of long term immunity is the same
What is passive immunity?
Immunity gained without an immune response ∴ B and T cells have not been activated and plasma cells have not produced any ABs (ABs are provided externally)
What is artificial passive immunity?
When ABs/antitoxins are injected normally in the case of a disease which can be fatal before the body's natural primary response can take place
What happens if someone is infected with tetanus?
They are given an injection of ABs against the tetanus toxin (antitoxins) which have been collected from blood donors who have recently been vaccinated against tetanus
Although antitoxins provide immediate protection, why is the protection only temporary?
The ABs are not produced by the body's own B cells and are ∴ regarded as foreign and so removed from circulation by phagocytes
Why do antitoxins provide artificial passive immunity?
Because the ABs have not entered the body by a natural process but have come from another person who has encountered the antigen
What is natural passive immunity?
When ABs pass from mother to child across the placenta or in breast milk
Why are infants not entirely unprotected against pathogens, even though their immune system is less effective?
ABs from the mother cross the placenta during pregnancy and remain in the infant for several months e.g. ABs to protect from measles last 4 or more months in the infant's blood
What is an example of natural passive immunity?
Colostrum (thick, yellowish fluid produced by a mother's breasts for the first 4/5 days of birth) contains an AB called IgA which acts in the gut to prevent growth of bacteria/viruses and also circulates in the blood
What is natural immunity?
Immunity gained by being infected (active) or by receiving ABs from the mother across the placenta or in breast milk (passive)
What is a vaccine?
A preparation containing antigens which is used to stimulate an immune response artificially
What is active immunity?
Immunity gained either by vaccination (active) or by injecting ABs (passive)
What might a vaccine contain?
1) a live/dead/attenuated (harmless) organism
2) a harmless form of a toxin (toxoid)
3) a preparation of surface antigens
How are some vaccinations made?
By genetic engineering
How are vaccinations given?
1) by injection into a vein/muscle
2) taken orally
What is vaccination?
Giving a vaccine containing antigens for a disease, either by injection/by mouth (artificial active immunity)
Why does vaccination try to mimic a natural infection e.g. by using live microorganisms?
- Immunity derived from a natural infection is often extremely good at providing protection, bc the immune system has met living organisms which persist inside the body for some time, so the immune system has time to develop an effective response
- The microorganisms reproduce (quite slowly) so that the immune system is continually presented with a large dose of antigens
What is herd vaccination?
Vaccinating all or most of the people in a population
Why are vaccines that do not mimic an infection less effective?
They are made from dead bacteria/viruses that do not replicate in the body
What happens in a vaccine is less effective?
Booster injections are needed to stimulate secondary responses that give enhanced protection
What are the 4 problems with vaccines?
1) Poor response to vaccine
2) Live virus + herd immunity
3) Antigenic variation
4) Antigenic concealment
Why do some people not respond (very well) to vaccines and what is the effect of this?
1) Some people have a defective immune system meaning that they do not develop the necessary B and T cell clones
2) Malnutrition, especially protein-energy malnutrition because they do not have enough protein to make ABs or clones of lymphocytes
- Effect: these people are at a high risk of developing infectious diseases and transmitting them to people with no immunity
Why might a live virus vaccination be a problem and why is herd immunity a solution to this problem?
- People vaccinated with a live virus may pass it out in their faeces during the primary response and infect others
- ∴ better to vaccinate a large no. of people at the same time to give herd immunity, or to ensure that all children are vaccinated within a few months of birth
- Herd immunity interrupts transmission in a population, o that those who are susceptible never encounter the infectious agents concerned
Why is antigenic variation a problem with vaccination?
When major changes in antigen structure (antigenic shift) occur, memory cells will no longer recognise the virus ∴ the protective immunity given by vaccination against a previous strain is ineffective against the new one
Why are there not yet any effective vaccines against diseases caused by protoctists e.g. malaria?
- Protoctists are eukaryotes with many more genes than bacteria and viruses have, ∴ they can have many hundred/thousands of antigens on their cell surface
How many life cycle stages does plasmodium pass through while in a human host?