Multiple Sclerosis: How the Immune System Attacks the Nervous System

Multiple sclerosis isn’t just a neurological condition-it’s an internal betrayal. Your own immune system, designed to protect you, turns against your brain and spinal cord. It sees the protective coating around your nerves as a threat and starts tearing it apart. This isn’t hypothetical. It’s happening right now in the bodies of nearly 3 million people worldwide. And for those living with it, the effects are real, unpredictable, and deeply personal.

What Happens When Your Immune System Attacks Your Nerves

At the heart of multiple sclerosis is a simple, devastating process: demyelination. Your nerves are wrapped in a fatty insulator called myelin. Think of it like the plastic coating on an electrical wire. It lets signals-your thoughts, your movements, your vision-travel fast and clear. In MS, immune cells breach the blood-brain barrier, a normally tight seal that keeps harmful substances out of your central nervous system. Once inside, they target myelin. T cells, B cells, and macrophages swarm the area, stripping away this insulation. The result? Signals stutter, fade, or disappear entirely.

This isn’t random damage. It follows patterns. In some cases, T cells dominate the attack. In others, antibodies from B cells cling to the myelin, marking it for destruction. Microglia, the brain’s own immune cells, get activated and start chewing up damaged tissue. And here’s the cruel twist: the body tries to repair itself. But the inflammatory environment is so toxic that new myelin rarely forms. Scar tissue-sclerosis-builds up instead. That’s where the name comes from: multiple scars in the nervous system.

Why Does This Happen?

No one person gets MS for the same reason. It’s a perfect storm of genes and environment. You might carry certain genetic markers that make you more vulnerable. But genes alone don’t cause it. Something has to trigger it. And the biggest suspect? Epstein-Barr virus. People who’ve had this common cold-like virus are 32 times more likely to develop MS. That’s not a small risk-it’s a massive one.

Vitamin D deficiency plays a role too. People living farther from the equator, where sunlight is weaker, have higher MS rates. Low vitamin D levels are linked to a 60% increased risk. Smoking? That raises your chance of progression by 80%. And it’s not just lifestyle-it’s timing. Exposure to these triggers during adolescence and early adulthood seems to be the critical window.

Women are two to three times more likely to get MS than men. Why? Hormones, immune system differences, and possibly how genes interact with estrogen are all being studied. But the bottom line: if you’re a woman in your 20s or 30s, your risk is higher than most people realize.

What Does It Actually Feel Like?

MS doesn’t have one face. It wears many. One person might lose vision in one eye for weeks-optic neuritis-then recover. Another might feel numbness in their feet, like walking on cotton. Some describe electric shocks down their spine when they bend their neck. That’s Lhermitte’s sign, a classic symptom caused by damaged nerves in the cervical spine.

Fatigue hits 80% of people with MS. Not just tiredness-bone-deep exhaustion that doesn’t improve with rest. Walking becomes harder. Balance slips. Bladder control falters. Cognitive fog creeps in: forgetting names, struggling to find words, losing focus mid-sentence. These aren’t imagined. They’re direct results of myelin loss in specific brain regions. When the signal from your motor cortex can’t reach your leg muscles, you stumble. When the optic nerve is scarred, your vision blurs. When the brainstem is affected, you feel dizzy or nauseous.

And it’s not always dramatic. Sometimes it’s subtle-a tingling finger, a delayed reaction, a moment of unexplained weakness. That’s why MS is so hard to diagnose. Symptoms come and go. You might think it’s stress, a pinched nerve, or just getting older. But if these episodes repeat, especially in young adults, it’s worth asking: could this be MS?

The Two Main Flavors of MS

Most people-about 85%-start with relapsing-remitting MS. That means flare-ups, followed by recovery. A flare-up, or relapse, lasts days or weeks. New symptoms appear. Old ones return. Then, slowly, things improve. But not always completely. Each attack leaves behind some damage. Over time, those tiny losses add up.

The other 15% have primary progressive MS. No relapses. No remissions. Just a steady, slow decline. Walking gets harder. Strength fades. Balance worsens. There’s no sudden crash-just a relentless slide. This form is harder to treat. The immune attack is quieter, more chronic. It’s not about big inflammatory storms. It’s about slow, smoldering nerve death.

And then there’s secondary progressive MS. Many with relapsing-remitting MS eventually shift into this phase. The flare-ups become less frequent, but the decline continues. The immune system isn’t as active, but the damage is already done. The nervous system can’t keep up. This transition usually happens 10 to 20 years after diagnosis.

What Treatments Exist Today?

Treatment today isn’t about curing MS. It’s about stopping the attack before it destroys more nerves. Disease-modifying therapies (DMTs) are the cornerstone. They don’t fix damaged tissue-but they can stop new damage.

Ocrelizumab targets B cells. It’s one of the few drugs approved for both relapsing and primary progressive MS. In trials, it cut relapses by 46% and slowed disability progression by 24%. Natalizumab blocks immune cells from crossing into the brain. It’s powerful-reducing relapses by 68%-but risky. One in a thousand people develop a rare brain infection called PML. That’s why doctors test for the JC virus before prescribing it.

Newer drugs like siponimod and cladribine work by calming the immune system in different ways. They’re not perfect. Side effects range from headaches to liver stress. But they work. And they’ve changed the game. Twenty years ago, half of untreated MS patients needed a cane within 15 years. Today, with early treatment, that number has dropped to 30%.

And then there’s the hope on the horizon: remyelination. Researchers are testing drugs like clemastine fumarate, which showed a 35% improvement in nerve signal speed in early trials. If we can teach the body to rebuild myelin, we might not just slow MS-we might reverse some of its damage.

What’s on the Horizon?

Science is moving fast. One breakthrough? Identifying biomarkers. Blood tests for neurofilament light chain (sNfL) can now detect active nerve damage before symptoms appear. Levels above 15 pg/mL mean inflammation is happening-even if you feel fine. That’s huge. It lets doctors adjust treatment before more damage occurs.

Another target? Dendritic cells. These immune sentinels in the brain are now known to actively present myelin fragments to T cells, keeping the attack alive. Blocking them could shut down the cycle. Neutrophil extracellular traps (NETs), sticky webs released by immune cells, are also being studied. They help break down the blood-brain barrier. In 78% of MS relapses, NET markers spike. Could stopping NETs prevent attacks?

The International Progressive MS Alliance has poured $65 million into research since 2014. Projects span 14 countries. The goal? Not just to manage MS-but to end it.

Living With It

MS isn’t a death sentence. It’s a lifelong condition-with good days and bad. Many people work, raise families, travel, and live full lives. Physical therapy, exercise, stress management, and a healthy diet help. Avoiding smoking and getting enough vitamin D aren’t just advice-they’re part of treatment.

Support matters. Online communities like Reddit’s r/MS are full of people sharing how they cope: using voice-to-text when fatigue hits, wearing compression socks for leg weakness, adjusting work hours to avoid overheating. These aren’t small things. They’re survival tactics.

And hope? It’s real. Every year, new drugs come to market. Every year, researchers learn more. We’re not there yet. But we’re closer than we’ve ever been.

What Comes Next?

If you’ve been diagnosed, the next step isn’t fear-it’s action. Find a neurologist who specializes in MS. Start treatment early. Track your symptoms. Ask about sNfL blood tests. Join a support group. Learn what helps you feel your best. MS is complex, but you’re not alone. And science is moving faster than ever.

If you’re worried you might have it-pay attention to your body. A sudden change in vision, numbness that doesn’t go away, or unexplained fatigue lasting weeks? Get checked. Early diagnosis means early treatment. And early treatment means more years of living well.