Lymphocytes are types of white blood cells important for fighting off infection and destroying cancer cells inside your body. There are three types of lymphocytes:
- B lymphocytes (B cells). Make five special types of proteins called antibodies to attack and destroy germs.
- T lymphocytes (T cells). Destroy infected cells and also play a role in allergic reactions.
- Natural killer cells. Help your body fight viruses and cancer.
Do you know the best thing about your lymphocytes? Some B lymphocytes have memory to protect you from germs they've run into before.
As a key part of your immune system, abnormal amounts of lymphocytes can impact your health. Learn about lymphocyte function, how to test for them, and tips on how to keep your numbers healthy.
What Is the Function of Lymphocytes?
Lymphocytes regularly check the health of your cells. They control how intense your immune system responds to specific germs, cancer, and substances that cause allergies.
Each type of lymphocyte works differently, as part of your immune response:
- B cells fight germs using antibodies and store your immune memory to fight off future infections.
- T cells kill infected cells, help activate other immune cells, and prevent overactive allergic reactions.
- Natural killer cells search for and destroy infected cells and cancer.
Your lymphocytes are made inside your:
- Bone marrow, the spongy material inside your bones
- Thymus, a small gland over your chestbone
You'll find lymphocytes throughout your body --- in your blood, lymph tissues, and spleen.
First immune response
When you first come into contact with a germ, your lymphocytes work together to attack and destroy it.
Germs can include:
- Virus
- Bacteria
- Fungus
- Parasites
- Toxins
It can take a little longer for your immune system to "learn" how to react if you've never had contact with a germ before. This is called your primary (first) immune response because your lymphocytes don't "remember" the germ.
It may take several days to weeks for your B and T cells to learn how to respond.
Usually, your T cells are the first type of lymphocyte to become active, multiply, and change into:
- Cytotoxic (killer) T cells: These find and destroy any infected cells.
- Helper T cells: Some "help" your B lymphocytes make antibodies, but others "help" your cytotoxic T cells destroy infected cells.
- Regulatory T cells: Also called suppressor T cells, they make substances that stop your allergic response from becoming overactive.
Next, your B cells find germs that have proteins called antigens. Antigens are tags on the germs that tell your lymphocytes which cells are infected and trigger your immune response.
Finally, the infected cells trigger your B cells to multiply and change into:
- Plasma B cells. Make antibodies to fight infection, but this can take several days.
- Memory B cells. "Remember" germs and respond faster, if it comes back (triggers your second immune response).
Second immune response
This is simply the next time your body gets infected with the same germ. Memory B cells "remember" the germ to quickly make antibodies. The antibodies rid your body of infection and prevent illness.
Your B cells can make five different types of antibodies, also called immunoglobulins (Ig):
- IgG attacks viruses, toxins, and bacteria.
- IgA protects your mouth, respiratory tract, and intestines.
- IgM reacts to certain markers on your red blood cells called A and B antigens, which make up the ABO blood types.
- IgE helps fight parasites and responds to allergic reactions.
- IgD can protect your mouth, nose, and respiratory tract.
Natural killer cells
These "smart" lymphocytes can find and destroy any infected, unhealthy, or cancerous cells. They can even get rid of harmful cells in the early stages to keep viruses and cancer cells from spreading.
How Do You Test for Lymphocytes?
There are a few ways to test for lymphocytes. About 30-40 out of 100 white blood cells are lymphocytes. And they usually aren't an issue unless they don't grow or die like they should.
Complete blood count (CBC) with differential
A CBC with differential blood test checks the number of your blood cells. Your doctor can measure:
- Red blood cells, the number of cells carrying oxygen in your blood sample
- White blood cells, the number of neutrophils, eosinophils, basophils, monocytes, and lymphocytes
- Platelets, the number of small cell-like pieces that help your blood clot
- Hemoglobin, the amount of protein that carries oxygen inside your red blood cells
- Hematocrit, the percentage of red blood cells in your blood
Flow cytometry
Your doctor takes a sample of your blood to mix in a fluid before measuring it in an instrument called a flow cytometer. The test looks at many types of blood cells to precisely count your lymphocytes.
The cells scatter light in a certain pattern that the flow cytometer detects. Using lasers, the instrument counts thousands of cells in your blood sample as they pass through an opening.
B and T cell screen, also called lymphocyte subset testing, the flow cytometer counts each type of lymphocyte.
Your doctor might order this test if you:
- Have signs of a weaker immune system
- Show symptoms of blood cancer
- Have certain infections such as HIV or AIDS
This two-step testing takes your lymphocytes out of your blood sample. Then, certain cell tags help the flow cytometer tell the difference between your T cells, B cells, and natural killer cells.
Immunoglobulin testing
This blood test measures the levels of different antibody types: IgG, IgA, IgM, and IgE. The test also shows the total amount of immunoglobulins in your blood.
You can have lower levels of antibodies for many reasons, such as:
- Primary immunodeficiency disorders
- Lower B lymphocytes
- Checking your immune response to a vaccine
Bone marrow testing
Bone marrow testing collects a little bit of the spongy tissue inside your bones. Your doctor uses the test to check on the health and number of blood cells inside your bone marrow — including your lymphocytes.
What Is the Average Lymphocyte Count?
An average lymphocyte count depends on your age and the lab that tests your blood. Labs use many instruments to measure your lymphocytes, which can lead to slightly different counts.
Here are some general numbers to help guide you, but always ask your doctor about your specific test.
Normal lymphocytes
For adults, there are normally about 1,000-4,800 lymphocytes per microliter of blood. But in children, there are usually about 3,000-9,500 lymphocytes per microliter of blood.
High lymphocytes
Lymphocytosis means your lymphocytes are higher than normal. It's often a short-term condition — such as when you're fighting off an infection or you smoke tobacco.
But if you repeatedly have 5,000 lymphocytes or more per microliter of blood without a reason, talk to your doctor.
They can help you figure out the cause and check for medical conditions such as:
Corticosteroids can also briefly cause lymphocytosis, too.
Low lymphocytes
Lymphopenia, also called lymphocytopenia, means you have less than 1,000 lymphocytes in 1 microliter of your blood. Children naturally have higher numbers of lymphocytes because they develop immunity and actively respond to infection.
Although low lymphocytes for children is age-dependent, a general guideline is:
- Fewer than 3,000 lymphocytes in 1 microliter of blood for children under 2 years old
- Fewer than 2,000 lymphocytes in 1 microliter of blood for children under 6 years old
The most common causes for lymphopenia include short-term infections, medications, or a nutritional deficiency.
But many medical conditions can cause chronic lymphopenia, too.
With lymphopenia, you may have:
- Infections such as HIV, AIDS, tuberculosis, and typhoid fever
- Blood cancers such as Hodgkin's lymphoma
- A larger spleen (enlarged)
- Autoimmune disorders, such as lupus and rheumatoid arthritis
- Rare inherited conditions such as ataxia-telangiectasia, DiGeorge syndrome, and severe combined immunodeficiency
- Treatments such as radiation, chemotherapy, or corticosteroids
- Nutrient deficiencies, such as low levels of vitamin B12, folate, or zinc
When to call the doctor
Contact your doctor to check for causes like blood disorders, if your lymphocyte levels stay higher than normal and you have:
- Swollen lymph nodes
- Night sweats
- Fever
- Belly pain
- Lack of appetite
- Shortness of breath
How to Increase Lymphocytes
Mild, short-term lymphopenia often goes away on its own. But if you've had lower lymphocytes for a while, treating your infection and medical condition can help.
Treat your infections
The first step to boosting your lymphocyte number is taking your medication as directed. Be sure to finish the full treatment course, even if you feel better — this helps ensure your infection doesn't return.
Talk to your doctor if your other treatments aren't working. They can offer options such as immunoglobulins to boost your immune system.
Treat your medical conditions
Treating any health condition that causes lymphopenia is a great way to raise your lymphocyte count. There are also some newer treatments, such as blood and bone marrow stem cell transplants. These can help some people recover if other treatments aren't helping.
Boost your lymphocytes naturally
A healthy lifestyle can give your lymphocytes a recovery boost. Here are some lifestyle choices you can try:
- Exercises regularly.
- Get a good night's rest.
- Lower your stress.
- Eat a diet rich in fruits and veggies.
- Avoid smoking.
- Stay hydrated.
Some studies report that eating these foods can help your B and T cells work better:
- Citrus fruits rich in vitamin C, such as papaya, kiwi, and pomegranate
- Foods rich in vitamin E, such as almonds and broccoli
- Lymphocyte-activating foods, such as ginger, garlic, and onion
Takeaways
Lymphocytes are a type of white blood cell that includes T, B, and natural killer cells. They help fight infection, destroy cancer cells, and control your allergic response. Although usually harmless, lymphocytosis or lymphocytopenia can sometimes signal infection, nutritional deficiency, or rarely, cancer. If your lymphocytes have been higher than normal for some time, talk to your doctor about the cause.
Lymphocytes FAQs
What are lymphocytes and what do they do in the body?
Lymphocytes include your T cells, B cells, and natural killer cells. They're a type of white blood cells that help you fight infections, destroy cancer cells, and prevent overactive allergic responses.
What causes changes in lymphocyte levels?
Many health conditions can raise or lower your lymphocyte count. The most common reason for higher lymphocytes is an infection. But if you have lower amounts of lymphocytes, it's usually from medication, nutritional deficiency, or an infection.
How are lymphocyte levels tested in the body?
Depending on the cause, your doctor can measure your lymphocytes using different tests. These include:
- Complete blood count (CBC) with differential: Checks if your lymphocyte amounts are higher or lower than normal, and more.
- Flow cytometry: Can screen your B, T, and natural killer cells and precisely count them using specific cell tags (markers).
- Immunoglobulin testing: Tells your doctor if you're making too many or not enough antibodies.
- Bone marrow testing: Can check the health and number of blood cells (including lymphocytes) inside your bone marrow.
Can infections or diseases impact lymphocyte count?
Yes. That's because your lymphocytes help you fight off infection. And if your medical condition plays a role in your immune response, it can affect your lymphocyte count. If you don't know what's causing your abnormal lymphocyte count, talk to your doctor. They can help you figure out what's going on.
What does it mean if your lymphocyte count is high or low?
A higher-than-normal lymphocyte count is called lymphocytosis, while a lower-than-normal count is known as lymphocytopenia. Most often, abnormal lymphocyte counts can mean you have an infection, a medication reaction, or a nutritional deficiency.
Talk to your doctor to check for blood disorders if your lymphocyte levels stay higher than normal and you have:
- Swollen lymph nodes
- Night sweats
- Fever
- Belly ache
- Lack of appetite
- Shortness of breath