Immunity System and Its Types | Biology Class 12

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Immune SystemZoology | Notes
Immunity System – Biology
For: Science Class 12

The organisms are surrounded by and environment that has numerous bacteria and other disease causing agents called aspathogens. The pathogens after entering the host secret chemicals called as antigens. The antigens stimulate the host body to secret pretentious chemical as antibodies. The antibodies react with antigens and make the host free from disease. This ability of the body is called immunity and the system involved during the process is called immune system. The immune system has ability to recognize, remember and destroy different antigens.

Antibodies are proteins found in the blood and are produced by lymphocytes. The immunity can be categorized into two types, inborn and acquired.

a) Inborn Immunity
It refers to the immunity present at the time of born. During development of embryo some antibodies from mother pass to fetus through placenta and give immunity for short time. These antibodies protect the child from different disease at childhood.

b) Acquired Immunity
The immunity which is acquired after birth by an individual in his life time is called acquired immunity. This is also called adaptive immunity. It is two types: active and passive immunity.

When the host is exposed to antigen and can produce antibodies own self, then the immunity is called active immunity which is also of two types, natural and artificial. If the body produces antibodies after suffering from disease then the immunity is called acquired active immunity. When vaccine is inject against certain antigen, the immune system of host produces antibodies and develops immunity, this kind of immunity is called acquired active artificial immunity.

When the host cell cannot produces antibodies against antigens, the antibodies from another animals are injected and immunity is developed. This kind of immunity is called acquired passive immunity. This immunity is only effective as long as antibodies remain in the body.

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