• Lymphocytosis is an increase in numbers of lymphocytes in the blood.
  • Occurs:
    • In tumours in which there is a substantial increase in their number.
      • Some of the lymphocytes are immature - lymphoblasts.
      • For example, Bovine Leukosis.
    • Following adrenaline release in fear, excitement and so on.
    • In some cases of chronic infection.
      • However, reactive hyperplasia in associated lymph nodes may not correlate with the numbers of circulating lymphocytes.
    • Commonly in growing swine.
      • Possibly associated with aMycoplasma infection.