Overview
White blood cells (WBCs), also called leukocytes, are an important part of the immune system. These cells help fight infections by attacking bacteria, viruses, and germs that invade the body. White blood cells originate in the bone marrow, but circulate throughout the bloodstream. There are five major types of white blood cells:
neutrophils
lymphocytes
eosinophils
monocytes
basophils
A WBC count is a test that measures the number of white blood cells in your body. This test is often included with a complete blood count (CBC). Your blood contains a percentage of each type of white blood cell. Sometimes, however, your white blood cell count can fall or rise out of the healthy range.