15 Differences between antigen and antibody

An antigen is an agent present on the foreign cells, which the immune system recognizes.

It is an immunogenic portion present on the foreign cell or substance. These antigens are also present in cancer cells.

When the body recognizes them, it releases suitable antibodies that help to destroy those foreign or cancer cells.

To combat that antigen or foreign cell, our body’s immune system produces antibodies.

Differences between antigen and antibody
Antibody bound to an antigen

Differences between antigen and antibody

Sl.No Properties Antigen Antibody
1 Name Anti – Against
Gen – Generate/ formation
Anti – Against
Body-Against the body
2Other names Antigens are called Immunogens. Antibodies are also called immunoglobulins (Igs).
3Symbols The “Ag” symbol can represent the antigen. The antibody can be represented by the “Ab” symbol.
4Processing The antigen will be processed by the Macrophages, Dendritic cells, and B-cells are of
Antigen Processing cells (APC)
The Plasma and Memory B-cells will process the Antibody.
5 Composition Antigens are mostly made of proteins but also contain carbohydrates, lipids, or nucleic acids. Antibodies are made up of only proteins like glycoprotein, lipoprotein, etc.
6Key part in
An antigen contains the epitope region. It is the region that attaches to the antibodies.Antibody contains a paratope region. It is a variable region that specifically binds to an epitope.
7RoleThe antigen plays a role in causing disease or evoking an allergic reaction.Antibody plays a role in the nullification of pathogens or harmful substances. They
precipitate the antigenic substance, lyse it or and lead to phagocytosis
8SizeThe antigen Size varies from one to another; the greater the size of the molecule, the higher
is its antigenicity.
The size of immunoglobulin is
variable according to the type of antibody.
The structure of the antigen shows great complexity.The structure of all classes of immunoglobulins is Y-shaped.
10SpecificityThe specificity of the antigen depends upon its epitope.The specificity of the antibody depends on its paratope.
11ForeignnessAn antigen from the outside environment is highly antigenic. So it is a foreign substance to the body.Our body’s immune system produces the antibody.
12TypesAntigens are grouped into two divisions

1) Foreign Antigens:
These are also called Heteroantigens. These
antigens present in
bacteria, viruses, snake
venom, etc.

2) Self Antigens:

These are also called autoantigens; these antigens are present within the body and lead to autoimmune
Antibodies are divided into 5 different types.

1) Immunoglobulin G: Most important of all the antibodies. It is present in the bloodstream and other body fluids. The important function is it can cross the placenta.

2) Immunoglobulin A: It plays an important role in
neutralizing bacteria and viruses. It is widely present in respiratory secretions, saliva, tears, etc.

3) Immunoglobulin M: The function of the IgM is the same as IgG, but it cannot cross the placenta. It is the largest-sized antibody.

4) Immunoglobulin E: It is a secondary antibody. It helps to diagnose allergically-
reaction and diseases.

5) Immunoglobulin D: It is also a secondary antibody. They help in the activation of the B cell for the defense mechanism.
13PrevalenceThe antigens are found on bacteria, fungi, viruses, and all different types of cells and biological substances.The antibodies are produced only by the lymphocytes
14ImportanceThe antigens help to determine the type of microbe or substance entered into the
The antibodies are more
important to prevent diseases, kill pathogens, and overcome infections.
15FeaturesThere are three specific
features like being
1) Exogenous
2) Endogenous, and
3) Autoantigens.
1) Specificity.
2) Diversity.
3) Immunological memory.
4) Immune tolerance.
16FunctionsThe function of the antigens is to trigger the production of the
1) They activate the
complement system is to
destroy the pathogens.
2) Promotes the phagocytosis of foreign substances by neutrophils and macrophages

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