Lymphocytes are a type of white blood cell that play a crucial role in the immune system by helping the body fight infections, viruses, bacteria, and even cancer cells. They are produced in the bone marrow and circulate throughout the blood and lymphatic system
. There are three main types of lymphocytes:
- B cells : Produce antibodies to neutralize foreign substances (antigens)
- T cells : Destroy infected or cancerous cells and regulate immune responses
- Natural Killer (NK) cells : Quickly respond to infected or cancerous cells by killing them
In a blood test, lymphocytes are measured as part of a complete blood count (CBC) and are expressed as the number of cells per microliter (µL) of blood. Normal lymphocyte counts vary by age but generally range from about 1,000 to 4,800 lymphocytes per microliter in adults and 3,000 to 9,500 per microliter in children. They typically make up about 20% to 40% of the total white blood cells
. Abnormal lymphocyte levels can indicate health issues:
- High lymphocyte count (lymphocytosis) often occurs during infections or inflammatory conditions, but can also signal blood cancers like leukemia or lymphoma
- Low lymphocyte count (lymphocytopenia or lymphopenia) may be caused by infections like the flu, autoimmune diseases, or more serious conditions affecting the immune system
Doctors use lymphocyte counts to assess immune system health and diagnose various conditions. Additional tests like flow cytometry or specific B and T cell screens can further analyze lymphocyte types and functions when needed
. In summary, lymphocytes in a blood test reflect the status of your immune system and help detect infections, immune disorders, and certain cancers. Normal ranges vary, and deviations may require further medical evaluation
