How Do Biologics Work to Treat Autoimmune Diseases?

How Do Biologics Work to Treat Autoimmune Diseases?

by Sue Jones
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If your doctor has recommended biologics to treat your autoimmune disease, you might find yourself wondering: How do biologics work? There are many different treatments1 for autoimmune diseases, and you may be curious about how biologics differ from other medications you’ve tried in the past.

Biologics are one of the newer treatments for autoimmune conditions like rheumatoid arthritis (RA), Crohn’s disease, and ankylosing spondylitis. These drugs are genetically engineered to block the overactive parts of your immune system that can damage your joints, skin, and other parts of your body2.

To hopefully help you feel more knowledgeable if you’re prescribed this kind of medication, below, we answer the all-important question,“How do biologics work?” But keep in mind that your treatment options may change over time based on new research and newly available therapies. Make sure you have ongoing conversations with your doctor about which treatment options may be best for you.

How do autoimmune diseases work?

To understand autoimmune diseases, it’s important to know how your immune system normally works. We all have B cells3 that patrol our bodies looking for foreign invaders like harmful bacteria and viruses. To assist with this, our B cells produce proteins called antibodies that help identify those invaders. Our body’s T cells also step in to help fight off any foreign substances with the goal of keeping us healthy.

“T cells recognize the antibodies and go and attack those foreign molecules,” David Frame4, PharmD, assistant professor in the University of Michigan College of Pharmacy, tells SELF. T cells also activate a chain of reactions that lead to the production of cytokines—chemicals such as interleukins and tumor necrosis factor (TNF) that produce inflammation to fight off germs.

When you have an autoimmune disease, your immune system misfires and instead aims inflammation against your own organs and tissues. In this situation, either your B cells make antibodies against your own cells, or your T cells mistakenly see your cells as foreign5. This process causes bodily inflammation, which manifests in symptoms like joint pain, rashes, and fatigue.

What is a biologic, anyway?

Biologics are different from older drugs for autoimmune disorders that tone down the entire immune system response, like methotrexate6. “Methotrexate is something we’ve been using for over 30 years,” M. Elaine Husni, M.D., M.P.H., vice chair in the Cleveland Clinic Department of Rheumatic and Immunologic Diseases, tells SELF.

You can think of conventional drugs as throwing a blanket over your whole immune system, whereas using biologics is like putting on socks when your feet are cold. Basically, biologic drugs work in a much more targeted and precise way. They block the specific parts of your immune system that are behind your autoimmune disease and its symptoms.

Biologics tend to be very effective drugs, so they’re usually recommended for people who haven’t responded to other medications or who have very severe symptoms. Dr. Husni likens using biologics against mild forms of autoimmune disease to using a grenade against a mosquito. “If you have one mosquito, you probably just use a flyswatter,” she says.

What happens inside my body when I take a biologic?

There are numerous cytokines that can trigger inflammation and cause symptoms in each autoimmune disease. “In rheumatoid arthritis, TNF plays a really big role [in triggering inflammation],” Dr. Husni says. “In psoriatic arthritis, IL-17 and IL-23 play a bigger role.”

Before cytokines can produce inflammation, they need to attach to receptors on the surface of your cells. Think of it as opening the lock on your front door with a key. You can’t turn on the lights until you unlock and open the door. Cytokines can’t affect your cells until they open the lock. Biologics prevent cytokines from unlocking your cells and causing inflammation and possible damage in a few ways. Some of these medications block11 the receptors on cells so that cytokines can’t attach to them. Other drugs fill the receptor themselves, leaving no room for the cytokine.

Each biologic works against a specific cytokine. But some autoimmune diseases are fueled by more than one cytokine. So how does your doctor know which one to choose?

“We don’t really have an easy mechanism to say, ‘If I have four or five cytokines that commonly cause an autoimmune disorder…it’s absolutely this cytokine,’” Dr. Frame says. The decision comes down to which biologic most people with your condition responded well to in studies, and your doctor’s preference, he adds. Your insurance coverage, if you have it, can also factor into the decision, Dr. Husni says.

What types of biologics are there?

Biologics are divided up into groups, or classes, based on the inflammatory pathway they target7. Each works by preventing a particular cytokine from causing inflammation. Below are the common biologic classes used to treat autoimmune diseases:

TNF inhibitors

What they target: These prevent the tumor necrosis factor protein from binding to its corresponding receptors and causing inflammation8.

Autoimmune diseases they commonly treat: ankylosing spondylitis, Crohn’s disease, ulcerative colitis, psoriatic arthritis, rheumatoid arthritis

IL-1 inhibitors

What they target: interleukin-1, interleukin-6, interleukin-12, interleukin-23

Autoimmune diseases they commonly treat: juvenile idiopathic arthritis

IL-6 inhibitors

What they target: interleukin-6

Autoimmune diseases they commonly treat: giant cell arteritis, juvenile idiopathic arthritis, rheumatoid arthritis

IL-17 inhibitors

What they target: interleukin-17

Autoimmune diseases they commonly treat: psoriasis, psoriatic arthritis, ankylosing spondylitis 

IL-12 and IL-23 inhibitors

What they target: interleukin-12, interleukin-23

Autoimmune diseases they commonly treat: psoriasis, psoriatic arthritis, Crohn’s disease

B-cell inhibitors

What they target: B cells

Autoimmune diseases they commonly treat: rheumatoid arthritis, lupus

T-cell inhibitors

What they target: T cells

Autoimmune diseases they commonly treat: rheumatoid arthritis

How do I take biologics?

Biologics are very sensitive to the acid in your stomach and can’t be taken orally like many conventional medications. “If you try to give most of these biologics orally, they will mostly be chewed up by the stomach acid,” Dr. Frame says. “We have to give them either through an IV directly into the blood or injected under the skin,” he says.

How often you need treatment and the way you receive it depends on your type of autoimmune disease, and which biologic you take. For example, some medications can be self-administered through an injection under your skin weekly. Other drugs are given through an intravenous infusion monthly or every few months.

What about side effects?

Any drug you take can cause side effects, and biologics are no exception. It’s common to feel tired for a couple of days after your infusion or injection, or to have headaches. Other side effects of taking a biologic include reactions near your injection site, a mild sore throat, and stomach pains.

Since these drugs work by dampening your immune system (which normally protects you against germs), you may be more susceptible to getting illnesses like the common cold. “We’re not wiping out [the immune system], but we’re lowering it. When you suppress it, you can get more infections,” Dr. Husni says. There’s also a chance that your body might mistake the biologic itself as a foreign invader and produce antibodies against it, which could make it less effective, according to the Mayo Clinic12. If that happens, you may need to try a new medication.

Biologics are complex drugs, and they can take some time to figure out. Getting familiar with how they work to reduce your symptoms can make you more comfortable with your treatment plan.


1. U.S. Department of Health & Human Services, Autoimmune Diseases
2. Indian Journal of Dermatology, Biologics: Target-Specific Treatment of Systemic and Cutaneous Autoimmune Diseases
3. National Human Genome Research Institute, Lymphocyte
4. University of Michigan College of Pharmacy, David Frame, PharmD
5. The American Journal of Pathology, T-Cell-Mediated Autoimmunity
6. U.S. National Library of Medicine, Methotrexate
7. Current Pharmaceutical Biotechnology, Biologics in Inflammatory and Immune Mediated Arthritis
8. StatPearls, Tumor Necrosis Factor Inhibitors
9. Polish Archives of Internal Medicine: Biologic Agents and Small-Molecule Inhibitors In Systemic Autoimmune Conditions: An Update
10. Current Opinion in Immunology, Cell Targeted Therapies In Autoimmune Disease
11. International Journal of Cell Biology, Biologics for Targeting Inflammatory Cytokines, Clinical Uses, and Limitations
12. Mayo Clinic Laboratories, Biologics Management


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