Antibody Vs Antigen: Comparisons & Differences

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Getting sick is no fun, and it can take a toll on our busy schedules, especially if all it seems we can do is sleep. When we are sick, while it may seem like we have no energy, our bodies are actually hard at work. When a harmful bacterium or virus enters our body, our immune systems are busy fighting every one of them. Our bodies are experts at making a secret weapon that can take down any intruder. In this article we take a comprehensive look at antibody vs antigen and how our bodies fight to keep healthy.

What Are Antibodies And Antigens?

They may sound similar, but antibodies and antigens play opposite roles in our overall health. While antigens are part of the viruses and bacteria that make us sick, antibodies are the proteins that our immune system makes to fight off these harmful germs. While it's typically antibody vs antigen, the two "antis" have both differences and similarities, and modern science has even allowed us to use antigens in vaccines to help build our antibodies against certain dangerous viruses and bacteria.


In a nutshell, antibodies are proteins our bodies make in response to dangerous and foreign microorganisms that sneak into our bloodstreams or other bodily fluids. Once a foreign substance is identified, an appropriate antibody is created by our immune systems that will bind to that foreign substance to destroy it or tag it so that other members of our immune system will fight it off. They are produced by a specific white blood cell called B-lymphocytes or B-cells.

Antibodies have a distinct Y shape, and the tips of the Y are calledparatope, and each paratope recognizes specific epitopes on the antigen, and this is where they bind to the antigen, and help the body discard them. Antibodies are vital to our immune system, and there are five different antibodies that help keep us healthy.

Antibody Classes

Immunoglobulin G is the most important antibody, as this type circulates through blood and other bodily fluids to protect the body from harmful bacteria, viruses, and other microorganisms. We find immunoglobulin A in saliva, tears, mucus, and other respiratory secretions, and in the urinary tract. This antibody neutralizes harmful bacteria that tries to enter the body. Immunoglobulin M is very similar to the G, but this is a very large antibody, so large that it cannot pass through the membranes of cells.

The last two types of antibodies are immunoglobulin D and E. These are secondary antibodies. E has the important job of detecting allergens that enter the body. It is responsible for the allergic reaction you have to bites, stings, and even snake venom. The immunoglobulin E is also important in detecting malignancies and other inflammatory diseases in the body.


In the battle of antibody vs antigen, the antigen is the villain in the story. Antigens are large protein molecules, and we typically find them on the outside of bacteria or other harmful microorganisms. When they enter the body, they stimulate a response from our immune system. Specifically, they trigger a response from the lymphocytes, or white blood cells. These white blood cells are tasked with fighting off infections. There are two main divisions of antigens, and we discuss these below:


The most prominent division of antigens are those that are foreign to the human body. These antigens are also referred to as heteroantigen, and they are typically attached to viruses or other harmful microorganisms. If these antigens enter the body, they are recognized by our immune systems as being intruders that are not welcome. Some heteroantigen include food allergens, snake venom, and foreign bacteria.

There are antigens that naturally occur in some people's red blood cells. They call these the Rh factor. If your blood type ends with a positive, then you have this factor. This is important during pregnancy because if the baby's blood is Rh positive, and the mother's is negative, the mother's immune system could produce antibodies to attack the baby's red blood cells during child birth. If this is the case, medical professionals take precautions during childbirth to ensure a safe delivery for mom and baby.


This division of antigens is referred to as self antigens or auto-antigens. Unlike division I antigens that can immediately be recognized as the villains in the body, these antigens originate in our own cells. If a person has an autoimmune disorder, it is caused by these antigens. When our own antibodies attack naturally occurring antigens in our cells, it is usually B lymphocytes or T lymphocytes antibodies that attack. Most often these division II antigens are made of proteins and nucleic acids.

Is There A Need For Antibodies And Antigens?

Based on what we know so far, it would seem that while antibodies are the heros of the story, antigens are just trouble makers that must be eliminated. While it is true that antibodies are extremely important for our immune systems, antigens have a role to play in keeping us healthy as well. As noted, antigens trigger our immune system to make the antibodies that fight off the harmful intruders like bacteria and viruses.

Importance Of Antigens

Scientists have used antigens to help our bodies be better prepared when the worst of these harmful microorganisms show up. Through the 19th and 20th centuries, scientists like Louis Pasteur started creating what we know as vaccines. Using new discoveries in bacteriology these scientists could determine that, if presented with dead or near dead bacteria, our immune system would still recognize the antigens on these dead bacteria and viruses and still produce antibodies to fight them.

Then, after creating antibodies to fight the dead cells of diseases like measles, mumps, and rubella, not to mention cholera and even the plague, our bodies would carry a memory of those harmful elements, and then if they ever attacked the body again, our body would immediately make the correct antibody to fight them off before they caused us harm. Thus, vaccines were created and are still used today. They allow our body to prepare for some of the most harmful and deadly diseases, so that if we are ever confronted with them, our antibodies can fight and kill them off before they cause us harm.

Importance Of Antibodies

We have discussed why antibodies are so important. They are the worker bees of our immune systems. These micro-heros are constantly identifying and capturing harmful substances that enter our bodies. Antibodies are so important to our life and health that these proteins are passed from a mother to her baby during pregnancy.

These are known as pre-birth antibodies, and they are passed from a mom to the baby in what's called passive immunization. Once the baby has this first batch of antibodies from the mother, she will start making her own antibodies in response to antigens she comes in contact with. On average the human body can produce over one billion different antibodies to defend against a plethora of antigens it might encounter.

Antibody And Antigen Comparisons And Difference

The Make-Up Of Antibody Vs Antigen

While antibodies are always proteins, antigens can either be proteins, polysaccharides, lipids, or nucleic acids. Even though antigens are typically foreign to the body, our bodies make the division II antigens. Antibodies are always made by our immune systems, and this is in response to antigens it comes in contact with. Each antigen is unique to whatever pathogen or harmful substance it is attached to. This is an important part of the antigen make up because this is how the immune system knows which antibodies need to be made to fight the harmful bacteria and pathogens.

Paratopes And Epitopes

The region of an antigen that interacts with the antibody is the epitopes. These are unique identifiers on each harmful bacteria, and they are normally comprised of five to eight amino acids linked together. They hang out on the surface of the bacteria or other harmful element. This is key because this is how our antibodies recognize and capture the pathogens that could hurt us. The paratopes are located at the two tips of the "Y" of the antibody. They bind and lock on to the epitopes and then dispose of them by either destroying them or tagging them to be destroyed by other elements in the immune system.

Forget Me Not

A very important factor when considering antibody vs antigen is the fact that antigens are unique and distinct to the pathogen they are connected to, and the antibodies produced by our immune systems will never forget it. The antibodies that are made in response to a particular antigen are actually stored in cells called Memory B cells.

When not needed, these antibodies remain dormant, but as soon as that same virus or bacteria, or even one that is similar, attacks the body, these antibodies jump into action. This means that if one string of bacteria makes you sick, the next time it attacks your body will be ready, and you might not even get sick, but if you do your downtime will be minimal, thanks to the great memory of your antibodies.


It's almost as if the antigen was created as the perfect villain for our heros the antibodies. When you think about antibody vs antigen, they compliment each other as worthy opponents. The human body is amazing in so many ways. The fact that we have a tiny army just waiting in our plasma ready and willing to fight off the harmful particles that dare to invade our organs is amazing to think about. 

Author: Emma Campbell

I am a director at the Phlebotomy Training Institute