A high absolute lymphcyte count, or lymphocytosis, indicates an increase in white blood cells and is normal after a bacterial or viral infection, according to Mayo Clinic. Lymphocytes, or white blood cells, play a role in the immune system by warding off disease.
Lymphocytosis can be caused by cancer of the blood or lymphatic system or by chronic inflammation, states Mayo Clinic. Other conditions that elevate lymphocyte counts include mononucleosis, tuberculosis, whooping cough, vasculitis and HIV/AIDS.
Lymphocytosis in adults is generally considered a count of lymphocytes significantly over 3,000 in a microliter of blood, according to Mayo Clinic. The threshold range for children is generally between 7,000 and 9,000 lymphocytes per microliter.