White blood cells are a part of the immune system that helps fight infection and defend the body against other foreign materials.
There are several different types of white blood cells, including lymphocytes, granulocytes (neutrophils, eosinophils, basophils), and monocytes.
With lung cancer, chemotherapy can decrease the number of white blood cells produced by the bone marrow and increase the risk of an infection. Oncologists order a complete blood count (CBC) before and after chemotherapy to check on the number of white blood cells.


