Chronic lymphocytic leukemia (CLL) is a type of cancer that affects white blood cells (WBCs). Since these blood cells are part of the immune system, CLL affects the body’s ability to fight germs.

CLL originates in the bone marrow, which is where stem cells are. These cells can become any other type of cell. CLL causes an increasing number of stem cells to grow into immature WBCs. Eventually, these unhealthy WBCs start crowding out the healthy ones, impairing a person’s immune system.

People with CLL have an increased risk of infection, autoimmune conditions, and severe complications from COVID-19.

This article explores CLL and the immune system, including how both the condition and its treatment impact immunity. It also discusses how people with CLL can reduce their risk of infection.

A doctor and patient talking in an office, wearing masks due to the impact of CLL on the immune system.Share on Pinterest
Maskot/Getty Images

CLL affects the development of a type of WBC known as lymphocytes. These are part of the immune system and protect the body from viral, bacterial, and fungal infections.

However, when someone has CLL, their bone marrow produces unhealthy lymphocytes that do not function as they should. These immature cells cannot effectively protect against pathogens.

Over time, the unhealthy cells begin to crowd out healthy lymphocytes, reducing their ability to respond to infections. The unhealthy cells multiply more quickly and live longer. As this happens, a person’s immunity decreases.

Besides an increased risk of infections, people with CLL can develop other complications, including Richter’s syndrome, also known as Richter’s transformation. This is a rare condition in which CLL suddenly transforms into an aggressive form of large-cell lymphoma.

People can also develop other types of cancer, such as:

Up to 25% of individuals with CLL develop autoimmune complications, meaning their immune system mistakenly attacks healthy tissue. Usually, this involves the immune system attacking blood cells. Doctors call this autoimmune cytopenia, and there are several forms:

Autoimmune hemolytic anemia

If the immune system destroys red blood cells (RBCs) faster than the body makes them, health experts call this autoimmune hemolytic anemia.

Symptoms include:

Immune thrombocytopenia

When the immune system attacks the blood’s platelets, or clotting cells, doctors call this immune thrombocytopenia.

Symptoms include:

Pure red blood cell aplasia

In this rare complication of CLL, the bone marrow does not make enough RBCs, but the numbers of WBCs and platelets are within optimal ranges.

People with aplasia may experience symptoms such as fatigue and skin paleness.

Yes, a person with CLL is immunocompromised, meaning the condition weakens their immune system. As a result, their body is less able to fend off infections and other health conditions.

Moreover, some of the medications doctors use to treat CLL can affect how the immune system functions. Health experts call this immunosuppression.

Doctors typically use chemotherapy to treat CLL. Chemotherapy agents target rapidly dividing cells, but they cannot distinguish between cancerous cells and healthy cells. This means they can affect healthy cells too.

Chemotherapy can destroy any cells that divide rapidly, including healthy bone marrow cells, hair follicle cells, and the cells that line the digestive system. As a result, they also impair the immune system.

Chemotherapy treatment has some risks. It may cause:

Before chemotherapy begins, a doctor will order a complete blood count to check the person’s baseline levels of different blood cells. They will repeat these tests periodically throughout treatment to monitor the effects of chemotherapy.

Usually, neutrophil levels decrease around 1 week after the chemotherapy cycle begins, reach the lowest point in another week, and then slowly climb again before the next cycle.

Blood tests allow the doctor to tailor the dose and timing of treatments.

It is important for people with CLL to take extra precautions to avoid acquiring infections. This involves:

  • washing the hands frequently with warm water and soap, especially after using the bathroom, after touching animals, and before eating
  • using a hand sanitizer when washing the hands is not possible
  • disinfecting surfaces, door handles, and cellphones regularly
  • avoiding large crowds of people
  • bathing every day
  • brushing teeth and flossing
  • cleaning cuts and scrapes and covering them with a bandage
  • avoiding animal waste and dirty diapers
  • avoiding hot tubs, ponds, and rivers
  • not sharing towels, toothbrushes, or utensils

It is not possible to fully restore the optimal level of health of the immune system when a person has CLL. However, self-care can help support the immune system to work as well as it can during this time.

Individuals with CLL or other type of cancer can help boost the immune system by:

  • Getting enough sleep: Sleep deprivation suppresses the immune system, so a person should aim for 7 hours or more of uninterrupted sleep.
  • Eating a balanced diet: Consuming plenty of fruits, vegetables, and whole grains is helpful for immunity and overall health.
  • Exercising regularly: Physical activity boosts the immune system. A person should aim for at least 30 minutes of exercise per day.
  • Reducing stress: High levels of stress hormones, such as epinephrine and cortisol, suppress the immune system. Therefore, stress reduction activities, such as meditation, yoga, and massage, can help.

People with CLL may be more susceptible to COVID-19 because of the effects of CLL and the treatment-related immunosuppression.

Some studies show that almost 8 in 10 people with CLL who have COVID-19 develop serious disease requiring hospitalization. Of these individuals, around 3 in 10 die.

In a 2021 study following 941 people with CLL and confirmed COVID-19, the risk of mortality was higher for those who:

Individuals with CLL need to take special care to avoid coming into contact with those who may have SARS-CoV-2, the virus that causes COVID-19. People around them also need to ensure they follow safety precautions.

Learn about CLL and the COVID-19 vaccine here.

CLL is cancer of the blood and bone marrow. It results in the growth of unhealthy lymphocytes that cannot fight infection. Lymphocytes are a type of WBC, and they are part of the immune system.

Treatment of CLL involves chemotherapy agents that target rapidly dividing cells. Although this includes cancer cells, chemotherapy also affects the bone marrow and suppresses the immune system. Therefore, people with CLL undergoing this type of treatment are more susceptible to infections, including SARS-CoV-2.

A person with CLL can help lower their risk of infection by maintaining personal hygiene, eating a balanced diet, and engaging in physical activity regularly.