Immunity is the ability of the body to fight infection and preserve itself from self-destruction. It can be INNATE and ACQUIRED.
Innate immunity is the natural barriers to the infection like our skin defense mechanism, lymph nodes, tonsils, spleen and other barriers that trap the infecting organism.
Acquired immunity comes through the antibodies which fight the infection causing organism. It is of two kinds: ACTIVE and PASSIVE.
Active Immunity and how is it generated?
Active Immunity is natural production of antibodies in one’s own body. These antibodies can be produced as a result of exposure to the disease causing organism and getting sick. After recovery from the illness these antibodies circulate in the blood giving protection.
Another way of generating antibodies actively is by vaccination. In vaccination the antigen of the disease causing organism is injected into the body of the recipient. This antigen is not capable of causing the disease in the body but it triggers the formation of the antibodies which provide protection against the disease causing organism.
In Active immunity there is a time lag between exposure to the organism and development of immunity but it is long lasting. There is immunological memory which has a booster effect. Also the side effects are less.
Passive Immunity and how is it generated?
Passive immunity preformed antibodies are transferred into the body to provide protection and fight against the disease causing organism. This can be done by the mother when the baby is inside the mother’s womb. The antibodies are transferred across the placenta to the fetus by the mother. After birth preformed antibodies can be injected into the body inform of immunoglobulin infusion to fight the disease causing organism.
In passive immunity the protection is immediate but the effect is very short lasting. Serious life threatening reactions can occur after injection of immunoglobulins.