Blood work:
A complete guide for monitoring HIV

May 2007     View PDF     En español

White Blood Cells: Infection Fighters

White Blood Cell (WBC) Count:
WBCs, or leukocytes, help prevent and fight infections. A normal count ranges from 4,000–11,000/mm3 in a healthy adult. A high count may mean that your body is fighting an infection. Low counts may result from taking certain drugs (AZT or ganciclovir), minor viral infections, stress or more serious opportunistic infections such as tuberculosis, histoplasmosis or other infection. Low counts also indicate a greater risk to infection. White Cell Differential: This is a breakdown of the different types of white blood cells as percentages of the total WBC count. The three main groups of WBCs are: 1. lymphocytes, 2. granulocytes and 3. monocytes.

Lymphocytes:
Lymphocytes are WBCs that produce antibodies and keep the immune system working. They make up 10–45% of your WBCs. There are two main types: B cells and T cells, and they fight infection in different ways. CD4+ cells—a type of T cell—are cells that HIV uses to infect and/or destroy. You may have heard the term “CD4+ count” or “T cell count.” This refers to a kind of T cell that controls the activity of other immune cells. (See Lymphocyte Subsets for more information.)

Granulocytes (polymorphonuclear cells or PMNs):
These are the most common types of WBCs, making up 55–80% of your total WBC count. PMNs help fight bacterial infections. Specific PMNs include:

Neutrophils
The most common PMN. They fight infection and play a key role in destroying bacteria and other foreign matters in the body. Some drugs used to treat HIV or HIV-related conditions can decrease neutrophil counts.

Eosinophils
These PMNs are involved in fighting parasitic infections and allergic reactions. Their numbers will rise during an allergic reaction or asthma attack.

Basophils
These are very important for releasing histamine. This is the substance that makes you feel congested and miserable during a cold or allergies. However, they help your body heal by making the blood vessels “leakier” so that cells can travel faster to the areas of infection.

Monocytes:
These circulate in the blood for about 24 hours. From there they move into tissues and mature into macrophages, which then eat up infection and foreign bodies. (Macrophage means “big eater”.)