“The capacity to recognize the foreign material in the body and mobilize cells and cell products to remove this foreign material with greater speed and effectiveness is called Immunity. There are two types of immunity which are Active and Passive immunity” Basically, the immune system is the body’s defense against different infectious organisms and other invaders.
There are three mechanisms in animals to define the body against foreign invaders. These are:
- Physical barriers: like skin and mucous members
- Immune system
Types of Immunity in the Immune system:
There are two major types of Immunity i.e., adaptive immunity and innate immunity. Adaptive immunity can be divided further into two types which are natural immunity and artificial immunity. natural immunity consists of passive (maternal) and Active(infection) immunity while artificial has passive (Antibody Transfer) and active (immunization).
Active immunity can be induced in the human body in two different ways:
- by natural exposure to a pathogen
- by vaccination
“The use of vaccines or antigens, which stimulates the production of antibodies in the body and makes the person immune against the disease or infection, is called active immunity.” Most of the vaccines consist of non-virulent, mutant strains of the virus. There are two types of active immunity:
- Artificially induced active immunity: Active immunity is achieved by artificially introducing antigens into the body. So it is called artificially active immunity.
- Naturally induced active immunity or autoimmune response: Sometimes the person is infected by an antigen and becomes ill. In most cases, he survives and developed immunity against these diseases. It is called natural-induced immunity or autoimmune response.
“The injection of antibody in the form of antisera for making a person immune against a diseased is called passive immunity.” Antigen antibodies complex is formed within the body. This complex is destroyed by the phagocytes. So the patient is saved from complications and sometimes from death.
During the infection, the cell is not given time for the production of a sufficient level of antibodies, and antibodies are injected artificially. The passive immunity response is immediate. It is not long-lasting. After some time, the antibodies are used in the level of antibodies is decreased. The antibodies are not left in the body.
The methods of passive immunization are used to combat active infections like tetanus, infectious hepatitis, rabies, snake bite venom, etc. antitoxin produced passive immunity in the snack bite venom. So the antitoxin serum is called antivenom serum.
What is the Immune system composed of?
The immune system is composed of lymphocytes and antibodies.
There are two types of lymphocytes.
They recognize the antigen and combat with them. The antigen may be any foreign object like microorganisms, or foreign tissue in case of tissue transplant. So T lymphocytes show cell-mediated response.
They recognize the antigen and form a plasma cell cone. These plasma cell cones synthesize and liberate antibodies into the blood plasma and tissue fluid. These antibodies attract the surface of the bacteria and speed up phagocytosis. Sometimes, the microorganisms produce toxins. The antibodies produced antitoxin and neutralize these toxins. This is called the humoral immune response.
The people are vaccinated against the antigen of specific diseases like polio, Smallpox, Measles, and Mumps. So the persons produced the antibodies against the antigen and become immune to the infection of this specific disease in the future.
The antibodies are a special type of protein called immunoglobulin. The vertebrates produce antibodies in response to the antigens. The antigen or immunogen is a foreign substance (often protein) that stimulates the synthesis of antibody formation.
The antibodies immobilize the antigen. It ultimately causes the destruction of antigens. The antibodies are specific. These destroy the only antigen which stimulates the formation of that antigen. Antibodies are synthesized in B- lymphocytes. Then these are secreted into the lymph and blood. These circulate freely in the lymph and blood.
Structure of antibody:
An antibody molecule consists of four polypeptide chains: two identical light chains and two identical heavy chains. These chains are linked by disulfide (S-S). Each chain of the antibody has two parts.
- Variable amino acid sequences (V): These sequences determine which antigen will bind with the particular antibody.
- Constant amino acid sequences (C): These chains are the same in all the antibodies in one class.
Sometimes they are multiple copies of the antigenic molecule on the foreign cell, surface. So large antigen-antibody complexes are formed.