Lymphocytes are a type of white blood cell. They help your body’s immune system fight cancer and foreign viruses and bacteria. Your lymphocyte count can be taken during a normal blood test at your healthcare provider’s office. Lymphocyte levels vary depending on your age, race, sex, altitude and lifestyle.
Lymphocytes are a type of white blood cell. They play an important role in your immune system, which helps your body fight disease and infection. Your immune system is made up of an intricate web of immune cells, lymph nodes, lymph tissue and lymphatic organs. Lymphocytes are a type of immune cell. There are two main types of lymphocytes:
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Lymphocytes help your body’s immune system fight cancer and foreign viruses and bacteria (antigens). Lymphocytes help your immune system remember every antigen it comes in contact with. After an encounter, some lymphocytes turn into memory cells. When memory cells run into an antigen again, they recognize it and quickly respond. This is why you don’t get infections like measles or chickenpox more than once. It’s also the reason getting vaccinated can prevent certain diseases.
Your T cells and B cells work together. They each have different roles in your immune system.
Your T cells help kill infected cells and control your body’s immune response to foreign substances. Most of your T cells need the help of another immune cell to become activated. After your T cells are activated, they multiply and specialize into different types of T cells. These types include:
B cells have receptors on their surfaces where antigens attach. B cells learn to recognize the different antigens and produce specific antibodies to attack each one. The B cells respond to antigens in two ways:
Lymphocytes develop in your bone marrow. Then, they mature and exit into your bloodstream. Mature lymphocytes are found in your blood and all parts of your lymphatic system. Some lymphocytes travel to your thymus gland. These lymphocytes become T cells. Other lymphocytes travel to your lymph nodes and organs. These lymphocytes become B cells.
Lymphocytes are bigger than red blood cells, but they’re still microscopic. Each tiny lymphocyte has a large nucleus at its center. The nucleus is dark purple. The surrounding jelly-like fluid (cytoplasm) is purplish.
Lymphocyte levels vary depending on your age, race, sex, altitude and lifestyle.
In adults, the normal range of lymphocytes is between 1,000 and 4,800 lymphocytes in every 1 microliter of blood. In children, the normal range of lymphocytes is between 3,000 and 9,500 lymphocytes in every 1 microliter of blood. About 20% to 40% of your white blood cells are lymphocytes.
High levels of lymphocytes in your blood are called lymphocytosis. Lymphocytosis is usually due to an infection or illness. Your body sometimes produces extra lymphocytes to help fight infections and illnesses. But a more serious condition can also cause a high lymphocyte count, including:
Low levels of lymphocytes in your blood are called lymphocytopenia (or lymphopenia). The flu or other mild infections can cause lymphocytopenia, but it could also be caused by a more serious disease or condition, including:
There are a couple of blood tests that can tell you the number of lymphocytes in your blood. These tests include:
Lymphocytosis and lymphocytopenia alone usually don’t cause any symptoms. But if a blood disorder or cancer causes a high lymphocyte count, you may have symptoms associated with the disease. These symptoms may include:
A note from Cleveland Clinic
Lymphocytes are a type of white blood cell. They’re a part of your immune system, which helps your body fight disease and infection. Your lymphocyte count can be taken during a normal blood test at your healthcare provider’s office. If your lymphocyte count is higher or lower than average, you may be worried about what that means. Many times, a high or low number means your body has been helping you fight an infection. If you’re concerned, reach out to your healthcare provider so they can determine the underlying cause and get you back to normal.
Last reviewed by a Cleveland Clinic medical professional on 06/20/2022.
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