1 / 17

Immunity and Vaccinations

Immunity and Vaccinations. If you survive an infection with a pathogen e.g. Vibrio cholerae you usually acquire permanent immunity against that organism.

sloan
Télécharger la présentation

Immunity and Vaccinations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Immunity and Vaccinations

  2. If you survive an infection with a pathogen e.g. Vibrio cholerae you usually acquire permanent immunity against that organism. During primary response one B cell is activated by a specific antigen that has a complementary shape to that of the immunoglobulin on the cell surface of the B cell. Natural Active immunity

  3. The B cell divides many times to form a clone of cells which can produce identical antibodies against the antigen. Some of the B cells resulting from mitosis become memory cells.

  4. If person is exposed to same antigen again, the secondary response takes place. The memory cells formed in the primary response divide to form a large population of B cells. Second Exposure

  5. Each one of these can produce clones that can make antibodies to destroy the antigen or disease agent The secondary response is faster and greater than the primary response because it starts with a large number of memory cells rather than one B cell

  6. This can reinforce natural immunity e.g. vaccination. Vaccination was first used by Edward Jenner – http://www.bbc.co.uk/history/historic_figures/jenner_edward.shtml Artificial active immunity

  7. Involve using weakened pathogens – called attenuation. It can be natural (as in cowpox) or it may be carried out artificially by - How vaccinations work

  8. Culturing the pathogen repeatedly in high or low temps, or without oxygen, until suitable mutants occur (e.g. the Sabin poliomyelitis vaccine) Using viruses or bacteria that have been killed so that they still trigger the immune response but cannot induce the disease e.g. the Salk poliomyelitis vaccine Use inactivated toxins called toxoids that are harmless but trigger the same type of immune response e.g. diphtheria and tetanus vaccines.

  9. Herd Immunity • Ideally vaccinations for highly contagious diseases should be given to a large number of people at the same time. This gives a general immunity to the population called herd immunity. • Vaccinations are not equally effective on all people – in fact some people will not respond at all. They may have inherited a defective immune system or their defences may already have been weakened by disease or malnutrition. • How does herd immunity offer these people some protection?

  10. Some diseases are difficult to vaccinate against e.g. the influenza virus because they mutate regularly and change their surface antigens. Our immune systems can recognise small changes (known as antigenic drift) but not large changes (antigenic shift) such as the one that caused Hong Kong ‘flu in 1997 http://www.sciencefriday.com/pages/1997/Dec/hour1_121997.html Antigenic variation

  11. The way the influenza virus evades attack is called Antigenic Variation Antigenic concealment – this is where pathogens avoid the immune system in another way. E.g. Vibrio cholerae lives on the wall of the intestine bathed in intestinal juices. How does this mean it avoids the immune system?

  12. The vibrio cholerae bacterium also undergoes considerable antigenic variation This is why it spreads so rapidly and is very virulent

  13. Active immunity, whether natural or artificial is not immediate. During the delay between infection and full immune response, some disease causing agents, such as the toxins from Clostridium tetani can kill. A person infected with a life-threatening disease such as tetanus may be given ready-made antibodies against the toxin. This is called passive immunity. Passive immunity

  14. This occurs when a fetus is still in the uterus. Maternal antibodies cross the placenta into fetal blood. They may protect the baby for example against measles, during the first few months after birth. Infants also acquire some passive immunity from the antibodies in colostrum (the first milk produced by a lactating mother). Passive immunity is only temporary – Why? Natural Passive Immunity

  15. Now answer the following • Which type of immunity involves the body making its own antibodies in response to an antigen? • Why are influenza vaccines sometime not effective? • Why is the secondary response to an infection quicker than the primary response? • Explain why passive immunity is only temporary.

  16. The antibodies are eventually broken down by the spleen and liver • There is no immunological memory because the baby did not make the antibodies for itself.

More Related