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Definition
By Mayo Clinic staffLymphocytosis, or high lymphocyte count, is an increase in white blood cells called lymphocytes (LIM-foe-sites). There are five primary subtypes of white blood cells, each with a different disease-fighting activity.
There are two major types of lymphocytes. T lymphocytes, or T cells, identify foreign substances in your body and begin an immune response. B lymphocytes, or B cells, produce antibodies to foreign substances. In autoimmune disorders, lymphocyte cells misidentify some of your own tissues as foreign substances.
A count of more than 2,900 lymphocytes in a microliter of blood is generally considered to be lymphocytosis in adults. However, the threshold for lymphocytosis varies from one medical practice to another. In children the threshold for lymphocytosis varies with age.
- Laboratory reference values. Lymphocyte. Rochester, Minn.: Mayo Foundation for Medical Education and Research; Oct. 2008.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2007.
- Pagana K, et al. Mosby's Manual of Diagnostic and Laboratory Tests. St. Louis, Mo.: Mosby, Inc.; 2002.
