When you think of antibodies, you might picture proteins from your immune system fighting off foreign invaders. But what happens when these proteins go rogue? Autoantibodies — antibodies that attack your own healthy cells and tissues — are found in many diseases, including type 1 diabetes. A doctor may test for autoantibodies when diagnosing type 1 diabetes in children and adults.

In this article, we’ll discuss what autoantibodies are and how they play a role in diseases like type 1 diabetes. We’ll also cover how doctors test for these proteins and what they mean for your diagnosis. If you’d like to learn more about autoantibodies, you can talk to your doctor or endocrinologist (hormone specialist).

What Are Autoantibodies?

Your immune system is constantly working to protect your body from invading viruses and bacteria. When you get sick, you begin making specialized proteins known as antibodies. Every antibody is designed to target a specific piece of a bacteria or virus — known as an antigen.

Your antibodies travel through your bloodstream until they come across an antigen they recognize. They bind (attach) to the antigen, acting as a flag or signal to let your immune system know something is wrong. Specialized immune cells then attack and destroy the tagged invader to keep you from getting sick.

However, your immune system isn’t perfect. Sometimes it makes antibodies that recognize antigens on your own cells and tissues. These are known as autoantibodies — the main drivers behind autoimmune diseases. When autoantibodies tag your cells, your immune system begins attacking them. This eventually damages your tissues.

The Role of Autoantibodies in Type 1 Diabetes

Type 1 diabetes is an autoimmune disease that attacks the pancreas. This organ makes insulin — the hormone that your cells need to use glucose (sugar) from your bloodstream for energy. Without enough insulin, your cells can’t use glucose. This causes your blood sugar levels to rise over time.

In type 1 diabetes, autoantibodies target antigens in the pancreas and attack the tissue. Eventually, your pancreas can’t make enough insulin to keep up with your body’s demands.

Types of Autoantibodies in Type 1 Diabetes

Overall, scientists have found four main types of autoantibodies involved in type 1 diabetes. Collectively, they’re called diabetes-associated antibodies.

Islet cell antibodies (ICAs) target proteins in specialized cells known as islet cells. Your pancreas contains clusters of these cells, which make several hormones, including insulin. ICAs can be found in around 70 percent to 90 percent of people with type 1 diabetes.

Insulinoma associated-2 autoantibodies (IA-2As) target an enzyme found in beta cells. These cells are a specific type of islet cell responsible for making insulin in the pancreas. IA-2As are seen in 54 percent to 75 percent of people with type 1 diabetes, according to the Johns Hopkins Diabetes Guide.

Glutamic acid decarboxylase antibodies (GADAs) target the enzyme GAD65 found in the beta cells of the pancreas. GADAs are common in type 1 diabetes and are found in 80 percent of those with the disease, according to the guide.

Some antibodies attack the insulin hormone itself — known as insulin autoantibodies (IAAs). These proteins are found in around 70 percent of young children when they’re first diagnosed with type 1 diabetes, the guide notes. Research shows that IAAs are usually the first sign that a child is at risk of developing type 1 diabetes.

Researchers have recently discovered the zinc transporter 8 (ZnT8) autoantibodies in type 1 diabetes. ZnT8 is specifically found in the beta cells. Studies estimate that 33 percent to 80 percent of people with newly diagnosed type 1 diabetes have these antibodies.

Does Everyone With Type 1 Diabetes Have Autoantibodies?

Most people with type 1 diabetes test positive for multiple autoantibodies. For example, if you took everyone with type 1 diabetes and tested for GADAs, ICAs, IAAs, and IA-2As, you would find:

• Around 4 percent to 7 percent of people would be negative for all four antibodies.
• Less than 10 percent of people would be positive for one antibody.
• Around 70 percent of people would be positive for three or four antibodies.

When Do Doctors Use Autoantibody Testing for Type 1 Diabetes?

Antibody testing is just one part of diagnosing type 1 diabetes. Your doctor or your child’s pediatrician may choose to look for autoantibodies for a few reasons. Antibody testing is done with a blood sample. The sample is sent to a lab to measure levels of type 1 diabetes autoantibodies. You may hear your doctor or your child’s pediatrician call this test an antibody panel.

Confirming a Type 1 Diabetes Diagnosis

When diagnosing type 1 diabetes, doctors usually start by measuring blood glucose levels with a few different tests. People with type 1 diabetes have higher blood sugar than normal. Antibody tests are less common, but they help doctors confirm you have type 1 diabetes and not another condition.

Screening for Type 1 Diabetes

Those with a family history of type 1 diabetes are more likely to develop the disease themselves. This means if you have a child with type 1 diabetes, their siblings are at a higher risk.

Doctors can test for autoantibodies to determine if someone is at risk of developing type 1 diabetes. This is because autoantibodies show up in blood tests years before symptoms appear.

If you have a family history of type 1 diabetes, ask your doctor or your child’s pediatrician about autoantibody testing for your family members. It’s recommended that everyone with a first-degree relative (parent, sibling, or child) get an antibody screening test. Testing can be done at your doctor’s office or through a research study like TrialNet.

If a family member tests positive for autoantibodies but doesn’t have any symptoms yet, they may be in the early stages of type 1 diabetes. One study involving 585 children from three different countries demonstrated that about 70 percent of children with two or more positive autoantibodies developed diabetes within 10 years and 84 percent developed diabetes within 15 years. The doctor will keep monitoring their blood sugar over time and eventually make an official diagnosis.

Diagnosing Latent Autoimmune Diabetes

Although type 1 diabetes is common in children and adolescents, it can occur at any age. Latent autoimmune diabetes in adults (LADA) is thought to be a form of type 1 diabetes. You may also hear LADA referred to as “type 1.5 diabetes” or “slowly progressing insulin-dependent diabetes.” Like type 1 diabetes, LADA is caused by autoantibodies attacking the pancreas. However, LADA develops slowly over time and is usually diagnosed in adults over 30.

The symptoms of type 2 diabetes and LADA can be confused with one another. However, people with type 2 diabetes don’t have autoantibodies. Instead, their cells become resistant to insulin and can’t use it properly. This also causes blood sugar levels to rise, which may give a person similar symptoms to LADA.

Doctors can mistakenly diagnose someone with type 2 diabetes when they actually have LADA. The best way to confirm the diagnosis is to test for autoantibodies. If your doctor thinks you may have LADA, they’ll run a simple blood test to measure your autoantibody levels. If you have autoantibodies, you’ll be diagnosed with LADA. Your doctor will adjust your treatment plan as needed. Eventually, you’ll need insulin shots because your pancreas won’t be able to make enough hormones anymore.

Talk With Others Who Understand

On myT1Dteam — the social network for people living with type 1 diabetes and their loved ones — members come together to ask questions, give advice, and share their stories with those who understand life with type 1 diabetes.

Have you or your child had autoantibody testing to diagnose type 1 diabetes? What did the results mean for your or your child’s disease? Share your experiences in a comment below, or post to your Activities page.