You’ve probably heard of antibodies before — whether in the news about COVID-19 vaccines, as autoantibodies that trigger multiple sclerosis (MS) attacks, or as disease-modifying therapies (DMTs). Antibodies are an important part of your immune system. In this article, we’ll discuss what antibodies are and how they work to fight infections and keep you healthy.

What Are Antibodies?

Antibodies, also known as immunoglobulins, are proteins made by your immune system. These proteins act like big red flags, attaching themselves to invading pathogens, such as bacteria or viruses. They tell your immune system something’s in your body that shouldn’t be. Other immune cells recognize these “flags” and destroy the pathogens.

While antibody proteins are generally Y-shaped, they do differ slightly in their overall structure. There are five groups of antibodies, known as isotypes, that each have specialized roles in the immune system. These are:

• Immunoglobulin G (IgG) — The most common type of antibody in your body, IgG protects against infections and can be transferred in breast milk from parent to baby.
• Immunoglobulin M (IgM) — IgM antibodies are the first antibodies your immune system makes when it detects a new infection.
• Immunoglobulin E (IgE) — IgE helps your body fight parasitic infections or allergic reactions by triggering immune cells to release histamine.
• Immunoglobulin A (IgA) — Found in your gastrointestinal and respiratory tracts, IgA protects your body from any pathogens in your food or the air you breathe.
• Immunoglobulin D (IgD) — Researchers aren’t quite sure what IgD does, but they’re continuing to look into its role in the immune system.

Antibodies are specialized proteins with specific functions. Let’s look at how antibodies are made and how they know what to flag as a foreign invader in the body.

B Cells Produce Antibodies

Antibodies are made by specialized immune cells known as B cells or B lymphocytes. These cells are made in the bone marrow, the spongy tissue inside of your bones. As B cells grow and mature, their genes rearrange to provide instructions for unique combinations of antibody proteins. In total, researchers believe the human body can make 1 quintillion (1 million trillion) different antibodies.

Once B cells finish growing in your bone marrow, they travel to different tissues in your lymphatic system. The lymphatic system carries white blood cells and other immune cells around your body. B cells can be found in your lymph nodes, spleen, and tonsils and in the lining of your digestive tract. There, they wait for other immune cells to signal that there’s an infection.

Your immune system is made up of dozens of cells, each with special roles. Some cells travel around your body, looking for signs of infection. If they find a pathogen, they break it down into small proteins known as antigens.

The immune cell then travels into your lymph tissues to “present” the antigen to your B cells. If a certain B cell recognizes the antigen, it begins rapidly dividing, making thousands of identical copies of itself. These newly activated B cells (known as plasma cells) also begin to make identical antibodies that recognize that specific antigen, which are then released into your bloodstream.

With so many terms, it can be confusing to remember all of these cells and proteins. To help you remember the difference between antigens and antibodies, think of this — antigens are like name tags that tell your immune system exactly who is invading. Antibodies are the security guards that recognize these name tags and help kick out unwanted guests from the body.

The Functions of Antibodies

Antibodies perform three main functions to help deactivate pathogens and clear infections from your body. First, after they’re released into your bloodstream, antibodies begin attaching themselves to any viruses or bacteria floating around. This inactivates them in a process known as neutralization, preventing them from infecting your body’s healthy cells.

Second, antibodies help create an immune response to recruit other cells and proteins to clear away infections. When an antibody is attached to an antigen on the outside of an infected cell, it activates a specialized part of your immune system known as the complement system. Complement proteins help create holes in the outer layer of infected cells or viruses, causing them to burst. This prevents the bacteria or virus from creating new copies of itself, stopping the infection from spreading.

Finally, antibodies attached to infected cells can also act as a flag for destruction in a process known as opsonization. The antibodies recruit proteins that are recognized by specialized cells known as phagocytes. These cells “eat” the infected cells to destroy them and the pathogen inside.

As your antibodies begin activating more of your immune system, you may notice symptoms like fever, chills, and swollen lymph nodes.

Memory B Cells and Immunity

Remember how B cells turn into plasma cells that make antibodies after they come in contact with an antigen? Some of these activated cells can also turn into memory B cells, which “remember” antigens from invading bacteria and viruses. After an infection is cleared, these memory B cells live in your lymph tissues, waiting on guard in case the same pathogen infects you again.

Once a memory B cell comes in contact with an antigen again, it begins producing antibodies much more quickly than before and with a stronger response. Vaccines work because the inactive antigen you’re given in a vaccine injection creates memory B cells in your immune system. For example, if you’re exposed to the measles virus after you’ve had a measles vaccine, your memory B cells will immediately recognize it and create antibodies that stop the infection before it can spread.

Abnormal Antibodies and Diseases

While your immune system usually works to keep you safe, sometimes it can create abnormal antibodies that do more harm than good. Autoimmune diseases and certain types of blood cancer are caused by the immune system making autoantibodies that flag the body’s own healthy tissues as foreign invaders. This activates the immune system against these tissues, causing inflammation and damage.

In MS, your immune system makes autoantibodies against the fatty covering on the outside of your nerve cells, damaging your brain, optic nerves, and spinal cord. Your body may also make antibodies targeted against DMTs used to treat MS, neutralizing them so they’re ineffective. This is one reason why doctors may recommend switching DMTs over time.

Medical Uses of Antibodies

Doctors and researchers have found they can artificially engineer specific antibodies to target certain parts of the immune system. Known as monoclonal antibodies, these proteins are used as drugs to dampen inflammation and stop your immune system from attacking your body in autoimmune diseases. For example, many DMTs are monoclonal antibodies. These antibody drugs are also used to activate other parts of the immune system to fight cancer.

Talk With Others Who Understand

MyMSTeam is the social network for people with multiple sclerosis and their loved ones. On MyMSTeam, more than 195,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Do you have more questions about how antibodies work to keep your body safe? Do you take an antibody drug to manage your MS? Share your questions in the comments below, or start a conversation by posting on your Activities page.