DefinitionBy Mayo Clinic staff
Lymphocytosis (lim-foe-sie-TOE-sus), 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.
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.
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