The substance which reacts with antibodies and stimulates the immune system of our body is an antigen. There are many types of antigens. An antigen test is necessary for the detection of a particular antigen like the Penicilloyl polylysine test. (Skin test used to determine whether a patient is allergic to penicillin)
Types of antigens
There are mainly four types of antigens.
- Endogenous Antigen: It synthesized in the body due to some diseases.
- Exogenous Antigen: These antigens entered the body from external sources.
- Hepten: It is a molecule that is not immunogenic itself, but it can react with the specific antibody.
- Auto Antigens: Some time immune system considers the body cell as a foreign object. So it starts synthesizing antibody against own body parts.
Antigen vs epitope
The antigen is a molecule that stimulates immune response and reacts with antibodies.
While epitope is a small portion of amino acid on the surface of the antigen. It is also called a determinant.
what is the difference between antigen and Immunogen?
Antigens (Ag) are molecules with react with the antibody (IgA, IgM, IgE, IgG, IgD), while immunogens are the molecules that produce an immune response.
What is Hapten?
It is a small molecule that is nonimmunogenic by itself but it can react with antibodies. Nonimmunogenicity is due to its body composition. It can not bind with MHC protein due to a lack of polypeptide in its structure.
Univalent also the reason for its non-immunity itself.
What are the examples of Hapten?
Following are the haptens.
- Penicillin molecule
- High molecular weight nucleic acid
- Catechol
what is the difference between Hapten and epitopes (Determinants)
Epitopes or determinants are the small groups of chemicals on the antigen surface. It reacts with antibodies. A number of epitopes are varied from antigen to antigen.
One epitope consists of about five amino acid.
What is the difference between antigen and antibody?
Antigen and antibody are two different terms of immunology. The main difference between antigen and antibody is that antigen is a substance that stimulates the immune system of our body. The antibody is the globulin protein synthesis in the body, which is synthesis by the response to a particular antigen.
To understand an immune system, let us take an example, “A” is an antigen (Ag). This antigen bind to T-cell receptor cells in the body. In response to this Ag “A” body with synthesis antibody (ab) “A”. This Ab “A” will protect the body against that antigen “A”. Immunogen is a short term for immunoglobulin.
What is the Structure of an antibody molecule?
An Antibody is consisting of four chains. In these four chains, two chains are heavy chains and the other two chains are called light chains. These chains join with each other by joining chains. This combination of light and heavy chains gives a Y-shape to the molecule of antibody.
what are the source of Antibodies
Antibodies are synthesis by the plasma cells or B.cell in the body. Each antibody(Ab) is specific to a particular Ig. As explained in the above examples.
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