A low WBC is also called leukopenia , a finding common in persons with HIV disease. It takes from several days to weeks for lymphocytes to recognize and attack a new foreign substance. Neutrophils are a major part of your body's defense against bacterial infections. When the WBC is low, there may not be enough neutrophils to defend you against bacterial infections. Neutrophils are made in the bone marrow and circulate in the bloodstream.
Neutrophils move out of the blood vessels into the infected tissue to attack the bacteria.
If your ANC is below 500 for an extended period of time, your risk of serious bacterial infection may increase significantly. A low neutrophil count is also called neutropenia . Neutrophils die continuously from age or from fighting infections, and your bone marrow must make new neutrophils to replace them. When something reduces the production of neutrophils in your bone marrow, the neutrophil count will drop and may eventually be low enough to become dangerous. Common causes of reduced neutrophil production are medications, infections, and tumors.