Neutralizing Antibodies

Neutralizing antibodies are antibodies (small proteins that help you fight disease) that prevent germs (pathogens) or toxins from getting inside your cells. This is particularly important for fighting viruses, which need to get inside your cells to make more copies of themselves and cause an infection.

Neutralizing antibodies are part of your immune system, your body’s security system against intruders like viruses. Like many security systems, the parts of your immune system have many jobs. Some antibodies sound an alarm when they find an intruder, while others identify it for your immune system to destroy. These antibodies block a pathogen’s way into your cells so the intruder can’t do damage.

What’s the difference between neutralizing and non-neutralizing antibodies?

Neutralizing and non-neutralizing antibodies work in different ways to fight infections. Neutralizing antibodies prevent germs from entering your cells or making more copies of themselves. Non-neutralizing antibodies have different functions, like labeling germs so that cells of your immune system can find and destroy them. Non-neutralizing antibodies don’t block germs from entering your cells.

How do these antibodies work?

Neutralizing antibodies are named by the role they perform: They work by attaching to viruses and toxins and blocking the way that they enter cells (neutralizing). Pathogens use proteins on the outside of cells (receptors) like a lock. When the antibodies attach to a virus or toxin, they block the “key” that it uses in these receptors. Since viruses can’t make more copies of themselves on their own — they need to use your cell’s machinery to do it — this prevents them from making more viruses.

Neutralizing antibodies and vaccines

Neutralizing antibodies play an important role in developing vaccines. The purpose of vaccines is to get your body to make antibodies so that it can quickly recognize, prevent and destroy infections. If your body only makes non-neutralizing antibodies, you’ll likely still get sick, though you’ll fight off an infection faster. If your body makes large amounts of neutralizing antibodies, you’re less likely to get sick at all.

Do neutralizing antibodies only work against viruses?

Not necessarily — they’re most effective on viruses, but there are some antibodies that can neutralize certain bacteria and bacterial toxins.

“Neutralizing” describes how an antibody works. In viruses and toxins, some antibodies can attach to them in a way that prevents them from getting into your cells. In viruses, this neutralizes them because they can’t make more copies of themselves.

But most bacteria are extracellular, which means they live and reproduce outside of your cells. Antibodies can attach to extracellular bacteria, but it doesn’t neutralize them because they don’t need to get inside your cells to reproduce, release toxins and make you sick. Instead, antibodies use other methods, like opsonization, to fight bacterial infections. So, similar to how a baby gate might keep your toddler in a safe space while your puppy has no problem going elsewhere to cause trouble, antibodies can neutralize in some situations and not others.

A few types of bacteria can also live and reproduce inside your cells (intracellular). Neutralizing antibodies are effective on these bacteria. They can also be effective against toxins that damage your cells if they get inside.

Which antibodies can neutralize viruses?

IgA, IgG and IgM antibodies most commonly have the ability to neutralize.

Where are neutralizing antibodies found in your body?

These antibodies can be found in your blood, lymph and body tissues.

What do neutralizing antibodies look like?

Neutralizing antibodies are so small that you need a microscope to see them. If you were to look at them under a microscope, you’d see proteins in the shape of a “Y.” The forked end (“receptor”) has a specific shape that only matches one type of pathogen or toxin.

What is a neutralizing antibody titer?

A neutralizing antibody titer is the level of neutralizing antibodies against a specific pathogen in your blood. Testing for antibody titers can give you an idea of whether you’ve had a specific infection in the past or if you’ve had a response to a vaccine. Higher levels of neutralizing antibodies generally mean more protection against getting an infection.

Your provider might order a blood test to check your neutralizing antibodies to a certain disease — like measles or mumps — to see if you still have protection or if you need a booster dose of a vaccine.

What is neutralizing antibody immunogenicity?

Neutralizing antibody immunogenicity is when your body develops antibodies to a medication, making it less effective. This can happen with biologic drugs — medications made with proteins similar to those found in your body.