Antibodies are Y-shaped chemicals made up of polypeptides and carbohydrates. Its structure is as follows.

1. Heavy and light chains: Each antibody has four polypeptide chains. Two light chains and two heavy chains. The two light chains are called L chains and the two heavy chains are H chains. L chains are two short. Its molecular weight is 20,000-25,000 daltons. It is composed of 220 amino acids. H chains are two large. Its molecular weight is 50,000-70,000 daltons. It is composed of 440 amino acids.
2. Disulfide Bonds: Each antibody has 3 disulfide bonds. There is one disulfide bond between the heavy chains and two disulfide bonds between the heavy and light chains. Antibodies look like the letter Y when joined by brackets.
3. Constant and variable regions: Each antibody has two regions. Fixed region and variable region. The posterior part of the antibody is called the constant or target region. The amino acids of the constant region are not changed.

The leading edge of the antibody is called the constant or variable region. The structure of this region changes to capture the antigen. It has a notch or paratop at its tip to catch germs. Antibodies bind to bacteria in a lock and key manner. In this case the key is the paratope and the lock is the antigen (bacteria).

This type of antibody is very low in the body. The human body contains 0.1% IgE. They are present in the membranes of the lungs, skin, mucous, mast cells and basophil cells and accelerate histamine secretion. They protect the body from allergies.

This type of antibody is less in the body. Human body contains 0.2% IgD. They remain on the surface of B-lymphocytes as monomers and stimulate B-lymphocytes to produce antibodies.

15% of the body’s total antibodies are IgA. It is found in the digestive system, reproductive system, respiratory system and breast milk.

This is the largest antibody. It exists as a pentamer in the blood. 5%-10% of the human body is IgM. They destroy bacteria by the process of agglutination and bacteriolysis. It accelerates the process of phagocytosis. They are effective against polysaccharide antigens. This is Dudhran. namely IgM1 and IgM2.

It is the smallest antibody. It is present in the blood, lymph and intestines. 75%-80% of the human body is IgG. IgG is the only antibody that can penetrate the placenta and enter the fetus. It inhibits bacteria and viruses in the process of opsonization. It also works in detoxification. It is of four types. Namely- IgG1, IgG2, IgG3 and IgG4.

Antibodies consist of five types of heavy chains. Antibodies are of 5 types based on heavy chain.

1. Immunoglobulin G (IgG): It is the smallest antibody. It is present in the blood, lymph and intestines. 75%-80% of the human body is IgG. IgG is the only antibody that can penetrate the placenta and enter the fetus. It inhibits bacteria and viruses in the process of opsonization. It also works in detoxification. It is of four types. Namely- IgG1, IgG2, IgG3 and IgG4.
2. Immunoglobulin M (IgM): This is the largest antibody. It exists as a pentamer in the blood. 5%-10% of the human body is IgM. They destroy bacteria by the process of agglutination and bacteriolysis. It accelerates the process of phagocytosis. They are effective against polysaccharide antigens. This is Dudhran. namely IgM1 and IgM2.
3. Immunoglobulin A (IgA): 15% of the body’s total antibodies are IgA. It is found in the digestive system, reproductive system, respiratory system and breast milk.
4. Immunoglobulin D (IgD): This type of antibody is less in the body. Human body contains 0.2% IgD. They remain on the surface of B-lymphocytes as monomers and stimulate B-lymphocytes to produce antibodies.
5. Immunoglobulin E (IgE): This type of antibody is very low in the body. The human body contains 0.1% IgE. They are present in the membranes of the lungs, skin, mucous, mast cells and basophil cells and accelerate histamine secretion. They protect the body from allergies.

1. It builds immunity against germs.
2. It stops the growth of microorganisms.
3. It inactivates the antigen.
4. It destroys the effectiveness of the toxin.
5. It cures diseases in animal body.
6. Their molecular weight is 1,50,000-9,00,000.

Antibodies are proteinaceous substances that neutralize antigens. Antibodies are chemically known as globulins or immunoglobulins. The human body can produce about 100 million (10 crore) antibodies. 85% of immunoglobulins are polypeptides and 15% are carbohydrates. Antibodies are produced from spleen, lymph glands, bone marrow, tonsils, thymus, appendix etc.

There are three types of antigens in human blood. Namely- A, B and Rh.

Antigens can be mainly divided into two categories based on location. namely-

1. Exogenous antigens: Antigens produced outside the body are called exogenous antigens.
2. Endogenous antigens: Antigens that are produced inside the organism are called endogenous antigens. For example, Forsmann antigen, cardiolipin antigen etc