Immunity is a process or ability of an organism to detect the intrusion of foreign materials or substances and products of cells,and the ability to metabolise cells to remove these particular foreign materials with great speed and effectiveness. On the other side when we talk of immune response, it is the production of antibodies in response to the presence of an antigen.
Immunity can be described as passive or active in which both types may be acquired naturally or artificially. The process of providing immunity artificially is called immunisation.
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What is natural active immunity?
This is a kind f immunity which is obtained as a result of an infection. Due to the presence of an infection in an organism the body manufacture, it own antibodies when exposed to an infectious agent. This is naturally accomplished because of the presence of memory cells which are produced during the first exposure to an infection, and are able to stimulate the production of massive amounts of antibody when expose to the same antigen again.
Not that natural active immunity is no very effective but generally persists for a long time or even for the entire life time.
What is artificial active immunity?
This is archived by injecting a small amount of antigen, called vaccine into the body of an individual. The process is all vaccination. IF a whole organism is used then it first made safe by being killed or attenuated. The antigen introduced into the organism body stimulates the production of antibodies against the antigen.
In passive immunity, antibodies from one individual are passed onto another individual which gives immediate protection. they are classified as natural or artificial immunity.
Natural passive immunity
Passive may be gained naturally for example, antibodies from mother can cross the placenta and enter the fetus, by so doing providing protection for the baby until the child own immunity is fully functional.
Passive immunity may also be provided by colostrum, the first secretion of the mammary glands.
Artificial passive immunity
Here antibodies which have been formed from one individual are extracted and then injected into the blood of another individual which may or may not be of the same species. They are applicable for immediate protection if a person is exposed to a particular disease. For example, specific antibodies used for combating tetanus and diphtheria used to be cultured in horses and injected into humans.