Antigen vs Antibody- Definition and 12 Major Differences

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Differences between antigen and antibody

Antibodies are produced by the immune system in response to antigens (material perceived as foreign). The antibody response to a particular antigen is highly specific and often involves a physical association between the two molecules. This association is governed by biochemical and molecular forces. The reaction between antigens (Ags) and antibodies (Abs) involves complementary binding sites on the Ab and on the Ag molecules. Some of the differences between antigen and antibody are as follows:

Differences between antigen and antibody

Some of the differences are:

S.N.	Characteristics	Antigen	Antibody
1	Molecule Type	Usually, proteins may also be polysaccharides, lipids or nucleic acids.	Proteins
2	Definition	These are substances that provoke an immune response.	These are Glycoproteins that are secreted by immune cells (plasma cells) in response to a foreign substance (antigen).
3	Effect	Cause disease or allergic reactions.	Protect the system by lysis of antigenic material.
4	Origin	Within the body or externally.	Within the body.
5	Parts	Highly variable with different structural conformations and is usually composed of different epitopes.	Composed of three main parts: -Two light chains -Two heavy chains -Four polypeptides
6	Prevalence	Exists in all types of cells; mostly found in viruses, bacteria, and fungi.	Only present in some types of cells.
7	Synonyms	Immunogens	Immunoglobulins
8	Specific binding site	Epitope	Paratope
9	Complexity	Medium; exists due to random mutations in the cell’s gene.	Very High; Complex chemical that bonds to a very specific Antigen.
10	Source	Usually from a foreign substance (viruses, and bacterial and fungal toxins).	Naturally produced by the body (B lymphocytes or B cells).
11	Kinds	There are three basic kinds of antigens (Exogenous, Endogenous, and Autoantigens)	There are five basic kinds of antibodies (IgG, IgM, IgA, IgE, and IgD).
12	Examples	Exogenous antigens: bacteria, viruses, fungi, etc. Endogenous antigens: Blood group antigens, HLA (Histocompatibility Leukocyte antigens), etc. Autoantigens: Nucleoproteins, Nucleic acids, etc.	Breast milk, tears, saliva, sweat, and mucus.