A white blood cell (leukocyte) is a cell of the immune system that helps protect the body against infections, foreign substances, and abnormal cells.
White blood cells circulate in the blood and lymphatic system and move into tissues when needed. Different types of white blood cells perform specialized roles, such as engulfing bacteria, producing antibodies, coordinating immune responses, or destroying virus-infected and cancerous cells.
Although they make up only a small fraction of blood cells, white blood cells are essential for defending the body against disease.
TYPES
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
QUICK FACT
A single drop of blood contains thousands of white blood cells, ready to respond to infection.
COMMONLY CONFUSED WITH
- Red blood cell: primarily transports oxygen and carbon dioxide rather than coordinating immune defense.
- Platelet: a blood component involved primarily in clot formation.
SEE ALSO