Difference Between Antigen and Antibody

Antigen and antibodies play a vital role in illness and disease. While one tries to wreak havoc on the body, the other helps protect health.

Antigen brings in sickness and antibodies are produced to protect the body against the antigen.

What is an Antigen?

Antigens are the molecules that are capable of stimulating an immune response in the body. They are toxins present in the blood that trigger the body to fight against them.

They can be anything like bacteria, viruses, or any other substance from outside the body that threatens health.

The presence of antigen rouses illness-fighting white blood cells known as lymphocytes in the body. These cells make antibodies that fight against the antigens.

Antigens are of two types:

  1. Heteroantigens: These are substances that are foreign to the body and are made from bacteria, protozoa, virus, snake venom, allergen, and certain proteins.
  2. Autoantigens: These are the antigens that are made by the body to fight its own cells. These are found during an autoimmune illness.

What is an Antibody?

Antibodies, also known as immunoglobins, are Y-shaped proteins that are produced by the B cells of the immune system of the body.

B cells help in fighting illness by eliminating viruses and toxins outside the cell. This is done by making a specific antibody for a single type of antigen. These tailored antibodies attack the antigen, block them and keep them away from healthy cells. These antibodies kill the antigen, thereby, stopping the infection.

The types of antibodies include:

  • IgG: These are the most abundant type of antibodies that detoxify harmful substances in the body and provide long-term protection.
  • IgM: These antibodies made by B cells in response to antigens
  • IgA: These antibodies collect antigens and remove them from the body in the mucus and other body fluids.
  • IgE: These antibodies trigger allergies and protect the body against parasites. They are present in small amounts in the skin, lungs, and mucosal membranes.
  • IgD: These antibodies bind with B cells and signal the release of IgM antibodies.

Role of Antigen and Antibody in Vaccination

Vaccines work by imitating antigens that trigger infection, but do not cause any harm to the body. As the infection mimicked by the vaccine enters the body, the body is already aware of how to protect itself.

Traditional Vaccine

These vaccines include weakened or inactive parts of antigens from viral infections like flu. The inactive antigens trigger B cells to release targeted antibodies to fight a specific infection.

The newer vaccines contain blueprints for making antigens instead of using actual antigen components and are equally effective.

As the vaccine is introduced, the B-cells respond as if the naturally occurring component has attacked the body. The antibodies created by the body stay dormant until an infection is contracted and they are called to action.

During an infection attack, the antibodies are quickly reproduced to destroy the antigen.

Antigens and Antibodies in COVID-19 Testing

According to the FDA, there are 3 types of testing for COVID-19.

  1. Molecular Testing: It tests genetic material from the virus in the body. The swab is taken from the nose and throat of a person. A negative result means there is no COVID-19 infection. Sometimes low levels of the virus also give a negative test result.
  2. Antigen Test: This test measures virus antigen proteins. The material is collected from the nose or throat in a swab. Most of the rapid testing of COVID is the antigen test. It may diagnose COVID-19 but not be able to rule out an active infection. Even if the antigen test is negative, molecular testing may be required to confirm the presence of COVID-19 infection.
  3. Antibody Test: This test is done to test the antibodies of a particular infection in the blood. The sample is collected by drawing blood from the arm or finger. Depending on the measure of antibodies, this test can determine whether the body has COVID-19 antibodies. It may not be a reliable way to tell if the body has a current infection or not.

Antigens trigger the immune system for an antibody response. Specific antibodies detect specific antigens and fight against the target antigen.

This distinct function of antigens and antibodies is used to create tests and vaccines that can help detect and fight illness and diseases.

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:March 24, 2021

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