What Are Lymphocytes in a Blood Test?

Lymphocytes are white blood cells central to your adaptive immune system. They include T-cells, B-cells, and natural killer cells.

Normal Range

• Absolute: 1,000–4,800/µL
• Percentage: 20–40%

High Lymphocytes (Lymphocytosis)

• Viral infection — mononucleosis (EBV), CMV, hepatitis
• Chronic lymphocytic leukemia (CLL) — marked elevation in older adults
• Acute lymphoblastic leukemia (ALL) — common in children
• Smoking — mild chronic elevation

Low Lymphocytes (Lymphopenia)

• HIV/AIDS — destroys CD4+ T-cells
• Corticosteroids — prednisone
• Chemotherapy and radiation
• Severe acute infection
• Autoimmune disease
• Malnutrition
• Kidney failure

CD4 Count

• A specific lymphocyte subset used to monitor HIV and define stage of immunosuppression