Multiple Myeloma and the Immune System: Understanding the Connection

Multiple myeloma is a complex blood cancer that develops in plasma cells, a type of white blood cell found primarily in the bone marrow. Plasma cells normally play an important role in the immune system by producing antibodies that help the body recognize and fight infections.

In multiple myeloma, abnormal plasma cells multiply uncontrollably. As these myeloma cells accumulate in the bone marrow, they can interfere with the production and function of healthy blood cells and produce abnormal proteins that can affect other parts of the body.

This creates an unusual relationship between multiple myeloma and immunity:

Myeloma is a cancer of cells that are themselves part of the immune system.

Understanding that relationship can help explain why infections are such an important concern for people living with the disease.

What Happens to the Immune System in Multiple Myeloma?

Healthy plasma cells produce a wide variety of antibodies, also called immunoglobulins, that recognize different threats.

Myeloma changes that process.

A clone of abnormal plasma cells begins producing large amounts of one abnormal immunoglobulin—or part of one—often referred to as a monoclonal protein, M-protein, or light chain, depending on the type of myeloma.

At the same time, production of normal antibodies may decrease. This is known as immunoparesis.

In other words, a person with myeloma may have plenty of immunoglobulin protein circulating in the blood, but much of it isn't providing the diverse protection against infections that healthy antibodies normally provide.

Myeloma can also interfere with other components of immune function.

The result is an immune system that may have greater difficulty responding effectively to viruses, bacteria, and other pathogens.

Why Infections Matter So Much

Infections are a significant concern throughout the myeloma journey.

The disease itself can weaken immune defenses, but treatment can add another layer of immune suppression. Chemotherapy, corticosteroids, targeted therapies, stem cell transplantation, CAR-T therapy, bispecific antibodies, and other treatments can affect different parts of the immune system.

Some treatments can also cause neutropenia, a reduction in infection-fighting neutrophils.

This means infection risk isn't identical for every myeloma patient. It can change depending on disease activity, treatment, blood counts, age, other medical conditions, and the specific therapy being used.

That's why fever or signs of infection should never automatically be dismissed as "just a cold" when you're undergoing myeloma treatment.

Your healthcare team can tell you which symptoms require an immediate call.

Myeloma Can Affect More Than the Immune System

Multiple myeloma begins in plasma cells, but its effects can extend far beyond the bone marrow.

Some of the classic problems associated with active myeloma are remembered using the acronym CRAB:

C – Calcium elevation (hypercalcemia)
R – Renal or kidney problems
A – Anemia
B – Bone damage

Not every person with myeloma develops all four, and today's diagnostic criteria include additional biomarkers beyond CRAB features.

Still, these complications help demonstrate why myeloma is much more than a problem with abnormal blood cells.

The Kidneys

Kidney health deserves particular attention in multiple myeloma.

Abnormal light chains produced by myeloma cells can travel through the bloodstream and reach the kidneys. In some patients, these proteins can damage the kidney's filtering structures and tubules.

Dehydration, high calcium levels, infections, certain medications, and other factors can further stress kidney function.

Kidney impairment can range from relatively mild changes in laboratory results to severe kidney injury requiring dialysis.

The encouraging news is that kidney function can sometimes improve when myeloma is brought under control and contributing factors are treated promptly.

Protecting kidney health is therefore an important part of myeloma care.

Bones

Our bones are constantly remodeling themselves.

Cells called osteoclasts break down old bone while osteoblasts build new bone. Normally, these processes remain relatively balanced.

Multiple myeloma can disrupt that balance.

Myeloma cells interact with the bone marrow environment in ways that encourage bone breakdown while interfering with normal bone formation. This can contribute to the characteristic lytic lesions associated with myeloma.

Patients may experience bone pain, osteoporosis, compression fractures, or other fractures.

Bone damage can also release calcium into the bloodstream, potentially causing hypercalcemia.

This is one reason new or worsening bone pain should be discussed with your healthcare team rather than automatically attributed to aging, arthritis, or normal aches and pains.

Anemia and Other Blood-Count Problems

As myeloma cells occupy more space within the bone marrow, normal blood-cell production can be affected.

A reduction in red blood cells can cause anemia, resulting in symptoms such as:

• Fatigue

• Weakness

• Dizziness

• Shortness of breath

• Reduced stamina

Platelet counts can also fall in some patients, increasing the risk of bruising or bleeding.

Low white blood cell counts—whether from myeloma, treatment, or both—can further increase vulnerability to infection.

Regular blood tests allow your healthcare team to monitor these changes.

Blood Clots

People with multiple myeloma can also have an increased risk of venous thromboembolism (VTE).

Several factors can contribute, including the cancer itself, reduced mobility, hospitalization, other medical conditions, and certain myeloma treatments.

A clot that forms in a deep vein is called a deep vein thrombosis (DVT). If part of that clot travels to the lungs, it can cause a pulmonary embolism (PE).

Symptoms such as sudden shortness of breath, chest pain, coughing up blood, fainting, or new swelling and pain in a limb require prompt medical attention.

Some patients receiving treatments associated with increased clotting risk may be prescribed preventive medication.

What About the Heart, Lungs, and Liver?

People with multiple myeloma can also have other medical conditions involving the heart, lungs, liver, or other organs.

Here it's important to distinguish between a comorbidity and a complication.

A comorbidity is another health condition that exists alongside myeloma—for example, hypertension, diabetes, asthma, or coronary artery disease.

A complication develops as a consequence of the disease or its treatment.

The distinction matters because not every medical problem experienced by someone with myeloma is caused by myeloma.

Some treatments may affect cardiovascular or other organ function, while certain myeloma-related conditions can also involve organs outside the bone marrow. Your healthcare team considers all of these factors when selecting and monitoring treatment.

This becomes particularly important because multiple myeloma occurs most frequently in older adults, who are more likely to already be managing other chronic health conditions.

Treating the whole person, rather than focusing exclusively on the cancer, is essential.

Mental Health Is Part of Myeloma Care Too

Not every consequence of myeloma appears on a blood test.

Living with an incurable cancer can bring fear, uncertainty, anxiety, depression, and ongoing concern about progression or relapse.

Appointments and laboratory results can become sources of anxiety themselves.

Then there are the practical concerns:

Will treatment work?

Will I be able to continue working?

How will treatment affect my family?

Can we afford this?

What happens if my numbers increase?

Those concerns are real.

Anxiety and depression aren't signs that someone isn't handling cancer "well enough." Mental and emotional health deserve the same attention as physical health.

Talking with your healthcare team, counselor, psychologist, social worker, support group, family, or trusted friends can help.

Can You "Boost" Your Immune System?

You'll frequently hear advertisements, supplements, foods, and wellness programs claiming to boost the immune system.

That phrase is misleading.

The immune system is extraordinarily complicated. You don't necessarily want every part of it operating at maximum intensity. An overactive or poorly regulated immune response can cause problems of its own.

For someone with multiple myeloma, this is especially important because the disease itself involves abnormal immune cells, and many modern myeloma treatments intentionally manipulate parts of the immune system.

A better goal is to support healthy immune function.

There isn't one food, vitamin, supplement, exercise, or lifestyle habit that can prevent myeloma progression or replace appropriate treatment.

But there are things you can do to support your overall health.

Supporting Your Body While Living With Myeloma

Healthy habits may include eating a balanced diet, staying physically active when medically appropriate, getting adequate sleep, managing stress, practicing good hygiene, avoiding tobacco, and staying hydrated according to your healthcare team's recommendations.

Vaccinations are another important part of infection prevention, although recommendations may differ depending on your treatment and immune status.

Always discuss vaccines and supplements with your healthcare team.

Supplements deserve particular caution. "Natural" doesn't automatically mean harmless, and some products can interact with cancer medications or create additional problems for the kidneys, liver, or other organs.

The Chicken-or-the-Egg Question

Perhaps one of the most fascinating areas of myeloma research involves the relationship between cancer cells and the immune system.

Most multiple myeloma develops through precursor conditions known as monoclonal gammopathy of undetermined significance (MGUS) and, in some people, smoldering multiple myeloma (SMM) before progressing to active disease.

Researchers are studying why some people remain stable for years—or never progress—while others eventually develop active myeloma.

Part of that investigation involves the bone marrow microenvironment.

Myeloma cells don't exist in isolation. They interact with immune cells, bone cells, blood vessels, signaling molecules, and other components of their surroundings.

Scientists are investigating whether changes in immune surveillance help abnormal plasma cells escape the body's defenses and progress—or whether changes created by the abnormal plasma cells themselves reshape the immune environment in ways that allow the disease to advance.

The answer may not be one or the other.

It may be both.

Why This Research Matters

Understanding the relationship between myeloma and the immune system isn't merely an academic exercise.

It has already helped transform treatment.

Modern myeloma therapies increasingly use the immune system itself to recognize and attack cancer cells. Treatments such as monoclonal antibodies, CAR-T cell therapies, and bispecific antibodies demonstrate just how powerful that approach can be.

At the same time, these therapies remind us how complicated immunity really is. Manipulating the immune system to fight myeloma can produce remarkable responses, but it can also create new infection risks and other side effects that require careful monitoring.

We still don't have every answer about why myeloma develops, why one person's disease behaves differently from another's, or why some people progress from MGUS while others never do.

But every discovery teaches researchers a little more about the complicated relationship between abnormal plasma cells, the bone marrow environment, and our immune defenses.

And understanding that relationship may help lead to even better treatments in the future.

Over the coming weeks, we'll take a closer look at ways to support overall health and immune function while living with multiple myeloma—including nutrition, exercise, sleep, stress management, infection prevention, and other everyday considerations.

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Medical Disclaimer: This information is provided for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always discuss questions about multiple myeloma, medications, supplements, vaccines, diet, exercise, or other health concerns with your healthcare team.