White blood cells serve a vital role as the body's first line of defense against foreign invaders. As a key component of the immune system, white blood cells circulate through the blood stream and scavenge for bacteria and viruses. While a high white cell count is not itself a disease state, high white cell levels may indicate a serious underlying medical condition.
Infection
The Mayo Clinic explains that bacterial, viral or fungal infections are common causes of elevated white blood cell counts. Infections associated with increased white cell production include influenza and tuberculosis. As foreign invaders multiply in the body, the bone marrow will increase production of white blood cells to fight off infection. As infections persist, they may lead to inflammation, which can further trigger white blood cell production.
Stress
White blood cell production serves as an important link between physical and emotional well-being and immune system function. Physical or emotional stress can increase white blood cells levels. The American Academy of Family Physicians explains that stress only temporarily increases white cell counts and does not involve an increase in white cell production by the bone marrow. Once an underlying stress is resolved, white cell numbers typically return to normal levels. Stresses related to high white cell counts include anxiety, overexertion and anesthesia or epinephrine administration.
Smoking and Airway Restriction
The Mayo Clinic lists smoking as a well-known cause of elevated white cell levels. Persistent smoking can lead to airway restriction and lung inflammation that can lead to an increased white cell response. The National Heart Lung and Blood Institute explains that emphysema and bronchitis, common symptoms of chronic smokers, can also increase white cell levels and inflammation in the lungs.
Leukemia
The Mayo Clinic describes leukemia as a cancer of the white cell producing cells of the bone marrow. Leukemia causes a large increase in white cell production from the bone marrow. While such cells are produced in large numbers, they are typically abnormal and non-functional and interfere with normal physiological and immune processes.
Autoimmune Disorders
A high white cell count can also be a hallmark of an autoimmune disorder such as arthritis, multiple sclerosis, Crohn's disease or Graves' disease. The Merck Manual explains that as the body wages war against itself, it produces more white blood cells to mediate such autoimmune reactions and inflammation.
