Difference between antigen and antibody

Antibody and antigen are part and parcel of the human body. Antigen exposure is a compulsory element for the production of antibodies. The person having antibodies is much capable of resisting germs and diseases.

Antibody VS Antigen

The antigen is indeed the foreign particles that come to the human body. The entry of antigen into the body leads to the formation of antibodies. Exposure to antigen leads to the triggering of the immune response. This triggering leads to the production of specific protein molecules that play a defensive role in the body. 

These particular protein molecules produced in response to antigen exposure. It is known as an antibody; Antigen is an unknown substance for our immune system. It can be any substance such as virus, food, chemicals, bacteria, and others. 

Binding Sites

There are specific binding sites for the antibody and antigen. It is the structure of these that lets them bind at these peculiar sites. The antibody is Y in appearance as antigen is an unknown substance entered into the body to be of any shape. The binding site for antigen is epitope, while for the antibody, the specific binding site is paratope.


Antibodies are substances that originate in the human body. Therefore, Its origin is within the human body, while the origin of antigen varies from it. The antigen origin can be internal or external. 

Molecule Type

Hence, The molecule type for the antibody is protein, while antigen can be of various molecule types. The molecule type for antigen can be nucleic acid, protein, lipid, or polysaccharide. 

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An antibody is distributed throughout the body as it locate in the blood. There are five significant types of antibodies. These include

  • IgG
  • IgD
  • IgE
  • IgM
  • IgA

IgE is the antibody that is involved in allergy, while the function of IgD is unknown. IgA is the antibody that is responsible for forming dimers after secretion. It expresses in the mucosal tissues. IgM is the antibody that enhances transiently and is produced on antigen invasion. However, IgG is the antibody that reflects neutralization activities and the highest opsonization. It further has four categories that include IgG4, IgG3, IgG2, and IgG1. There are no particular or predefined types for antigens.

Antigen and Antibody Test

The antibody test is the one that helps in the detection of antibodies present in the serum or blood. It is indicative of the infection prevailing in the human body. However, When a body has an infection, it can determine using an antibody test.  The antibody test, having had a high level of antibodies in it, reflects infection. However, the antigen test is papular as the diagnostic test to determine a peculiar viral antigen of the body.

Cost of Tests

The antibody test is the one that demands the use of clinical equipment. However, It requires extensive knowledge and takes time for its execution and results. However, in the case of antigen tests, the outcomes are pretty quick and faster. These diagnose infectious diseases and are relatively cheaper as compared to antibody tests.

Also read: Difference between smoke and sanity testing

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