Granulocytes — the most common type of white blood cell — have small granules that release enzymes when your immune system is under attack. This occurs during an infection, allergic reaction or asthma episode. Granulocytes are produced from stem cells in your bone marrow and only live for a few days.
Granulocytes are the most common type of white blood cell. They contain enzyme granules, which form in the cytoplasm (a thick, semi-fluid solution that fills each cell). When infection or inflammation enters the body, granulocytes rush to the area, releasing their granules to fight infection. Granulocytes are sometimes called granular leukocytes, polymorphonuclear leukocytes or PMN.
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There are three specific types of granulocytes. These are neutrophils, eosinophils and basophils.
Granulocytes work together to rid your body of infection or allergens. Each type of granulocyte has its own combination of chemicals and enzymes in its granules. As a result, each type has a different function:
Neutrophils are the most abundant type of granulocyte. They make up about 40% to 60% of all granulocytes in your body. That’s about two-thirds of all of your white blood cells.
Granulocytes form in the bone marrow and release into the bloodstream when necessary.
About 50% to 70% of all the white blood cells in your body should be neutrophils. Eosinophils should account for 1% to 3%, and basophils should make up approximately 0.4% to 1%.
A high granulocyte count (granulocytosis) could indicate a number of issues, including infection, blood cell cancer or some type of autoimmune disease. Bone marrow conditions are also a primary cause of granulocytosis. (Bone marrow is the spongy tissue inside of your bones. It contains platelets, red blood cells, and stem cells to produce white blood cells.) Granulocytosis may be a symptom of several conditions, including chronic myelogenous leukemia (CML), primary thrombocythemia, polycythemia vera and primary myelofibrosis.
Treatment depends on the cause of your condition. For example, if infection resulted in granulocytosis, then your provider will prescribe antibiotics. If the root cause is an autoimmune disorder, then immunosuppressants — such as prednisone — may be given. If granulocytosis is due to cancer, your healthcare provider may recommend chemotherapy, radiation therapy or a bone marrow transplant.
A low granulocyte count (granulocytopenia, or neutropenia) is usually caused by a blood/bone marrow condition, such as aplastic anemia or leukemia. It may also develop as a side effect of cancer treatment. When you don’t have enough granulocytes, your body is more vulnerable to infections. As a result, you may develop fever or sore throat more often. Other illnesses — such as the flu or pneumonia — may develop faster than normal because your body can’t effectively fight off the infection. Severe neutropenia is called agranulocytosis.)
The recommended treatment depends on the cause of your neutropenia. If you have an accompanying fever (febrile neutropenia), prompt treatment is imperative. You may be admitted to the hospital so you can be given antibiotics intravenously (through a vein). Left untreated, febrile neutropenia could be life-limiting.
Some types of neutropenia may not require treatment. In most cases, however, the underlying condition must be addressed. For example, if neutropenia is due to an autoimmune disorder, then your healthcare provider may prescribe corticosteroids. If neutropenia is caused by a medication, then your provider will likely change your prescription. You may also be given granulocyte colony-stimulating factor (G-CSF) injections, which help promote the production of white blood cells.
Cyclic neutropenia is a condition in which neutrophil counts dip periodically and then return to normal. This type of neutropenia is not present all of the time. In most cases, periods of neutropenia last about three to five days. This condition may be inherited. The majority of cases are evident immediately following birth.
Cyclic neutropenia is treated the same way as granulocytopenia (neutropenia). This includes antibiotics for infections, G-CSF injections or rarely, a bone marrow transplant.
Typically granulocytes fully develop in your bone marrow before traveling into your bloodstream. If immature granulocytes are found in your bloodstream, it could mean that there’s a problem with your bone marrow. Or, it may simply indicate an early-stage response to infection. (Note: Pregnant people and newborn babies may naturally have immature granulocytes in their bloodstream. In these cases, immature granulocytes indicate a healthy bone marrow response and it's not a cause for concern.)
If immature granulocytes show up in your bloodwork, your healthcare provider may run further tests to determine why. If the root cause is an infection, then the appropriate medications will be prescribed. If cancer is the cause, then your provider will talk with you about treatment options, including surgery, chemotherapy and radiation therapy.
Eosinophilia is characterized by a higher than normal level of eosinophils. When your eosinophil levels are high, it could indicate an allergic reaction, a parasitic infection or cancer.
Like other granulocyte conditions, eosinophilia treatment depends on the cause. If certain medications are causing your eosinophils to increase, then your healthcare provider will likely change your prescription. Currently, the FDA has approved treatments that target eosinophils in asthma.
Basophilia occurs when there are too many basophils in your blood. Normally, basophils only make up a small number of your body’s white blood cell count.
Treatment depends on the underlying cause. Bacterial infections require antibiotics. Inflammatory diseases — such as irritable bowel syndrome (IBS) and rheumatoid arthritis — require immunosuppressants. If there’s a problem with your bone marrow, your healthcare provider will talk to you about treatment options, including surgery, chemotherapy or radiation therapy.
In most cases, you can’t prevent these conditions from occurring. However, they can be adequately managed with proper care. If you notice that something isn’t quite right, call your healthcare provider right away. They can determine the root cause of your condition and recommend appropriate treatment.
A note from Cleveland Clinic
Granulocytes play a major role in attacking infection, allergens and other irritants that invade your body. When these white blood cells work as they should, your body can effectively protect itself. However, if your body doesn’t make enough granulocytes — or if your granulocyte count is too low or too high — it could mean there’s something more significant going on. If you get sick often, or are prone to infections, schedule an appointment with your healthcare provider. They can run tests to find the underlying cause and plan appropriate treatment.
Last reviewed by a Cleveland Clinic medical professional on 11/05/2021.
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