The body produces two main categories of white blood cells, granulocytes, cells containing granules suspended within their plasma and agranulocytes which have no granules. Neutrophils, eosinophils and basophils are types of granulocytes. Lymphocytes and monocytes are agranulocytes. Each white blood cell type supports the immune system by performing specific functions in response to pathogens such as bacteria, viruses, allergens or parasites. When white blood count declines, immunity is compromised. Fever can ensue from a number of white blood cell related disorders.
Acquired immunodeficiency syndrome can severely deplete white blood cell counts. This disease attacks the immune system and destroys its ability to fight off illnesses. KidsHealth explains that the AIDS virus specifically attacks lymphocyte cells called T-cells, taking control of them and causing them to multiply. This process causes damage to other T-cells, destroying them and lowering the white blood cell count. MedlinePlus notes that fever is a symptom of AIDS that may not manifest for years after the initial infection by the virus.
Bone Marrow Disorders
MayoClinic.com notes that numerous diseases that affect the bone marrow can lower the level of white blood cells and cause fever. This occurs because most white blood cells are formed in the bone marrow, though some are formed within the lymphatic glands as well. Myelodysplastic syndromes are bone marrow disorders that occur when the marrow produces immature and defective blood cells with an abnormally short life span. While myelokathexis is a congenital bone marrow disorder wherein the granulocytes contain genetic codes that predispose them to apoptosis, or cellular suicide. These cells die younger, causing lowered white blood cell counts.
A person undergoing some medical treatments may find themselves with lower than normal white blood cell counts due to the effects of chemotherapy drugs or bone marrow transplants, according to MayoClinic.com, and with fever due to the effects of the underlying condition.
Radiation therapy can also destroy marrow tissue and lower white blood cell counts. Antibiotic drugs and diuretics have been implicated in lowering white blood cells levels as well.
When an infection is severe enough to overwhelm the immune system, a depletion of white blood cells may result. MayoClinic.com notes that some infections consume neutrophils at rates that are faster than the body can produce them, resulting in a white blood cell deficiency.