what is white blood cells
How Blood Works. White blood cells (WBCs), or leukocytes, are a part of the immune system and help our bodies fight infection. They circulate in the blood so that they can be transported to an area where an infection has developed. In a normal adult body there are 4,000 to 10,000 (average 7,000) WBCs per microliter of blood. When the number of WBCs in your blood increases, this is a sign of an infection somewhere in your body. Here are the six main types of WBCs and the average percentage of each type in the blood: 1  Neutrophils - 58 percent.  Eosinophils - 2 percent.