Difference Between Antigen and Antibody (original) (raw)

Last Updated : 18 Dec, 2025

The primary distinction between an antigen and an antibody is that an antigen is a substance that may trigger an immune response in the body. In contrast, an antibody is a globulin protein that is produced in response to a specific antigen. An antigen must bind to an antibody or T-cell receptor to generate an immune response.

**Antigen

Antigens are typically bacteria or viruses, but they can also be foreign substances that endanger your health. This type of battle is known as an immunological response****.**

Features of an antigen are given below:

Antigens, also known as immunogens, are substances or toxins in your blood that stimulate your immune system to fight them.
The presence of antigens activates your body's disease-fighting white blood cells, known as **lymphocytes.
Due to the presence of antigens, white blood cells produce antibodies that fight against the antigens.
For example, when a common cold virus enters the body, it induces the body to produce **antibodies to prevent illness.

**Antibody

Immunoglobulin (Ig) is also known as an Antibody (Ab). Plasma cells produce these large Y-shaped blood proteins. They bind to foreign particles and infiltrate them.

Features of an antibody are given below:

Antigens are foreign pathogens that enter the body and can elicit a response from our immune system, either by grouping with a larger molecule or by binding with antibodies for a specific immune reaction.
As a result, antigens stimulate the system's ability to generate antibodies.
Antibodies can be found in both the bloodstream and the lymphatic system.
The binding of antibodies to their particular antigens neutralises the antigen and initiates an immunological response.
This binding can immobilise infections in circulation.
It also leads to complement reactions, which lyse the pathogen.

**Antigen vs Antibody

Antigen	Antibody
An antigen is an outside substance that stimulates the formation of antibodies by inducing an immune response.	An antibody is a glycoprotein that is formed in reaction to and in response to a specific antigen.
They are also known as immunogens since they act against the immune system.	As they are immune system globulin proteins, they are also known as immunoglobulins.
It is responsible for illnesses and allergic reactions.	It safeguards the immune system by lysis, phagocytosis, and precipitation of an antigenic substance.
Proteins and carbohydrates are the most common; however, lipids and nucleic acids can also act as antigens when combined with proteins or carbs.	They are merely proteins.
They include specialised areas known as epitopes that interact with antibodies.	They have specialised areas known as paratopes that interact with antigen epitopes.
It originates from outside the body.	It originates within the body.
Endogenous, exogenous, and autoantigens are types of antigens	IgG, IgM, IgA, IgD and IgE types of antibody
It is denoted by Ag	It is denoted Ab