A count below 2,500 may be a sign of leukemia, infection, vitamin B12 deficiency, chemotherapy, and more. A count above 6,000 may be associated with various conditions and circumstances, including infection, inflammation, leukemia, as well as physical or emotional stress.
This article discusses neutrophils and their role in maintaining your health. It also explains neutrophil blood tests and counts, as well as the causes of neutrophil level changes.
What Are Neutrophils?
Neutrophils are a type of WBC or granulocyte that, among other things, protect you from infection. They make up approximately 40% to 60% of the white blood cells in your body.
Neutrophils are the first cells to arrive on the scene when an individual experiences a bacterial infection and are the primary components of pus, a thick fluid that is made as part of the immune response.
Neutrophils are made in the bone marrow and can be found in the blood, tissues, and lymph nodes throughout the body. Neutrophils have a lifespan of less than 24 hours, but your body makes about 100 billion of these cells each day.
What Neutrophils Do
Neutrophils address foreign invaders by “eating them,” a process referred to as phagocytosis, or by taking them up into the cell in a process called endocytosis. Once the foreign organism is inside the neutrophil, it is “treated” with enzymes which result in the destruction of the organism.
Neutrophils also help regulate the immune response in general.
Importance of Neutrophil Counts
A neutrophil blood test is part of a complete blood count (CBC). This may be done as part of a routine exam or to help your healthcare provider diagnose certain conditions.
If the neutrophil count is higher or lower than the normal range, which is between 2,500 and 6,000 neutrophils per microliter of blood, on a CBC, further evaluation is needed.
Further testing may include:
A bone marrow biopsy to evaluate the cells in the bone marrow Tests to evaluate for infections An additional CBC Blood tests that check thyroid function and vitamin B12 levels A peripheral blood smear for morphology, which looks for specific characteristics, like neutrophil size and shape, to help determine a diagnosis
High Neutrophil Levels
High neutrophil levels above 6,000, or neutrophilia, may be due to a number of mechanisms that increase the number of neutrophils in response to various conditions or circumstances.
Examples of mechanisms may include:
Reactive neutrophilia describes an increase in neutrophils due to stress or infections, as stress hormones can trigger a greater than normal release of these cells from the bone marrow. Proliferative neutrophilia involves high neutrophil levels due to an increase in their production in the bone marrow. This is commonly associated with certain cancers. Demargination involves neutrophils detaching from the lining of blood vessels and circulating the bloodstream due to stress, infections, and exercise.
Conditions That May Cause Neutrophilia
Some specific causes of an increased neutrophil count may include:
When this occurs, an increased number of immature neutrophils can make their way to the blood. Your healthcare provider may mention that you have an increased number of bands—or even less mature neutrophils—on your blood count.
Infections, such as thyroiditis Stress Blood cell-related cancers such as leukemia Autoimmune disorders such as rheumatoid arthritis Trauma and burns Smoking Medications, such as corticosteroids, a drug used to treat inflammation, and lithium, a mood stabilizer Pregnancy Eclampsia, a complication of preclampsia where an individual experiences a seizure during or soon after giving birth
Low Neutrophil Levels
Levels of neutrophils less than 2,500 are referred to as neutropenia. A level of less than 1,000 is the most serious, and can increase the risk of infection.
Several mechanisms can result in a low neutrophil count:
Decreased or absent bone marrow production describes when the bone marrow slows down or ceases to produce white blood cells. This can happen when the bone marrow is injured during chemotherapy, or a vitamin deficiency causes inadequate production. Bone marrow infiltration occurs when the bone marrow is “taken over” by cells, such as cancer cells, or by scar tissue (fibrosis) in conditions such as myelofibrosis. Demand for more neutrophils may occur when more neutrophils are needed in specific situations, such as to fight an infection or in response to trauma. With serious infections, a low neutrophil count may result as the immune system is overwhelmed by the infection. Decreased survival of neutrophils can occur as a result of overwhelming infection, as well as viral and rickettsial infections. Neutrophils may also face destruction due to antibodies produced in autoimmune conditions, such as lupus that attack the body itself. Destruction of neutrophils already produced and circulating in the body can occur in a few ways, including in autoimmune conditions in which antibodies (autoantibodies) are produced that directly destroy the neutrophils. Cyclic neutropenia is a rare condition that can be genetic or acquired, and is marked by intermittent periods of a low white count fluctuating with a normal WBC count.
Conditions That May Cause Neutropenia
Via the mechanisms above, a decreased neutrophil count could be due to:
Chemotherapy, a type of cancer treatment Aplastic anemia, a bone marrow condition Radiation exposure Vitamin B12 deficiency (megaloblastic anemia) and folic acid deficiency Kostmann’s neutropenia, a genetic condition which affects young children Idiosyncratic, meaning nobody knows for certain why a neutrophil count is low Myelodysplasia, a group of bone marrow conditions Blood-related cancers which infiltrate the bone marrow, such as leukemia Viral infections Overwhelming infections (sepsis) Hypersplenism, or an overactive spleen Drug reactions, such as to penicillin, ibuprofen, and phenytoin Rickettsial infections, such as Rocky Mountain spotted fever Typhoid fever High blood sugar
Summary
Neutrophils are a type of white blood cell (WBC) that play a key role in fighting off infection. Your level of neutrophils in the blood can change, depending on a number of factors, including infection, stress, chemotherapy treatment, or nutritional deficiencies.
In some cases, your neutrophil levels will be high. This condition is called neutrophilia. In cases of neutropenia, the level may be low—even dangerously low. Your healthcare provider can begin with blood tests and move forward in diagnosing the cause of any neutrophil level changes.
