Simulation · Biology · Class 12
Active and passive immunity: fast but fading, or slow with memory
From the lesson Active and passive immunity in Human Health and Disease. Change the values and watch what happens.
Active and passive immunity: fast but fading, or slow with memoryBiology · Class 12
The idea behind it
NCERT §7.2.3, §7.2.4
- Active immunity: the host is exposed to antigens (living or dead microbes or other proteins) and makes its own antibodies. It is slow and takes time to reach full effect.
- Active immunity follows either deliberate immunisation or natural infection.
- Passive immunity: ready-made antibodies are given directly to protect the body.
- Colostrum, the yellowish fluid a mother secretes in the first days of lactation, is rich in IgA antibodies that protect the infant; the foetus also receives antibodies across the placenta. Both are passive immunity.
- Vaccination rests on immune memory. A vaccine (antigenic proteins of a pathogen, or the pathogen inactivated or weakened) makes the body produce antibodies that neutralise the real pathogen later, and memory B and T cells that recognise it quickly and flood it with antibodies.
- When a quick response is needed against a deadly microbe, as in tetanus, preformed antibodies or an antitoxin (antibodies against the toxin) are injected. The snakebite injection likewise carries preformed antibodies against the venom. This is passive immunisation.
- Recombinant DNA technology makes a pathogen's antigenic polypeptides in bacteria or yeast, allowing large-scale production of vaccines, for example the hepatitis B vaccine made from yeast.