What Are Antibodies? - Definition, Function & Types

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  • 0:00 What are Antibodies?
  • 0:25 Function
  • 0:55 How Antibodies Fight Antigens
  • 1:45 Immunizations
  • 2:40 Types of Antibodies
  • 4:35 Lesson Summary
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Lesson Transcript
Kelly Robson

Kelly has taught High School Science and Applied Communications. She holds an Education Specialist Degree in Ed. Leadership.

Expert Contributor
Maria Airth

Maria has a Doctorate of Education and over 20 years of experience teaching psychology and math related courses at the university level.

Antibodies play a key role in the immune system. They begin the process of getting rid of the invaders that may cause harm or infection. This lesson covers how antibodies work and the different kinds of antibodies.

What Are Antibodies?

Antibodies, also known as immunoglobulins, are Y-shaped proteins that are produced by the immune system to help stop intruders from harming the body. When an intruder enters the body, the immune system springs into action. These invaders, which are called antigens, can be viruses, bacteria, or other chemicals. When an antigen is found in the body, the immune system will create antibodies to mark the antigen for the body to destroy.


The antibodies act sort of like the immune system's scouts. They find antigens, stick to them, and identify for the immune system the exact type of antigen so that it can be destroyed. Each antibody is made for one and only one antigen, and it's fitted with special receptors that will only bind to that antigen. For instance, a specific antibody is created to help destroy the chickenpox virus. Only that particular antibody will attack a chickenpox virus.

How Antibodies Fight Antigens

So what happens when an antigen tries to enter the body? When it does, the immune system is triggered. Chemical signals are sent to alert all the different parts of the immune system into action.

First, the virus is met by a type of cell called B cells. The B cells are responsible for creating antibodies to match the antigen. Remember, each type of antibody matches to only one antigen. After the B cells have created their antibodies, the antibodies stick to the virus, marking it for the next round of attack. T cells are then ordered to attack the antigen that the antibodies have marked for it.

After the antigen has been destroyed, the cleanup crew comes along. A wave of phagocytes, large cells that can consume foreign matter, eats the remains of the infection.


After an infection is defeated, the antibodies still remain in the body. They are left there to wait in case that particular antigen returns. For example, after a person gets chickenpox, the antibody that was created by the immune system to get rid of the chickenpox will remain in the body. The next time the chickenpox virus tries to invade the patient, the antibody will be ready. It will instantly attach to the virus, calling the T cells and phagocytes much quicker, and stopping the infection much earlier.

Immunizations take advantage of the fact that antibodies remain in the body after an infection is eradicated. Most immunizations consist of a weak or diluted form of an antigen - not enough of the antigen to make the patient sick, but just enough to trigger the creation of antibodies. This way, the body can instantly attack any form of the infection it encounters, stopping the infections before they begin.

Types Of Antibodies

In total, there are five types of antibodies. Each type is found in a different part of the body and has a different set of duties. Each one of them is referred to by a letter following the abbreviation Ig for immunoglobulin.

The most common antibody we have is the IgG antibody. IgG is found in all of the body's fluids. It makes up about 75-80% of all of our antibodies. These antibodies help to fight off bacteria and viruses. To go with the flow of the fluids, IgG antibodies are the smallest antibodies in size.

The biggest in size are the IgM group, found in the lymphatic and circulatory systems. The IgMs are the first responders, the first type of antibodies to confront invaders to these two systems.

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Additional Activities

Comic Relief Activity

Students will create a humorous comic strip summarizing what they have learned about antibodies.


  • Transcripts of the video lesson
  • Art supplies: art paper, markers, colored pencils etc.


  • Conduct a discussion in which you lead your students to consider what it might be like to be an antibody. Use anthropomorphic language to encourage your students to really think about what they have learned from the perspective of an antibody. For example:
    • So, do you think the little antibody guy is just hanging out all the time waiting to be called to a fight, or can you picture him or her marching around the body totally on guard 24/7?
  • After your students have warmed to the idea of viewing the body from the antibodies' perspective, instruct them to create a comic strip, or book, that teaches the reader all about what antibodies are and how they work. The comic must:
    • Be from the perspective of the antibody.
    • Include all the information given in the lesson.
      • Including all the definitions and all five of the types of antibodies.
    • Be creative (not just an academic repeat of the lesson).
  • Allow your students to use external material to research more information about antibodies if they desire.
  • Consider building in time in your instruction schedule to allow students to share their comic strips with you or each other.

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