What Are Immature Neutrophils?

Immature neutrophils are a type of white blood cell (neutrophil) that have not fully matured. Neutrophils are the most common type of white blood cell. Like all white blood cells, they are involved in fighting infection and healing from injury and disease.

Neutrophils are especially associated with bacterial and fungal infections. They are produced in the bone marrow, where they usually mature from myeloblasts to promyelocytes, myelocytes, metamyelocytes, band neutrophils, and finally, mature segmented neutrophils.

An increase in immature neutrophils in the blood is often a sign of infection. It can also be caused by other issues, including injury, physical stress, and cancer.

This article describes the symptoms of conditions causing immature neutrophils and what to expect if your blood tests show that you have an abnormal amount or abnormal morphology (shape, size, and other characteristics) of these cells. 

Why Are Some Neutrophils Immature? 

Neutrophils are formed in the bone marrow. The neutrophils in the bone marrow in the healthy person contain a different population of the neutrophil lineage than that which is found in the peripheral blood.

The majority of the neutrophils in the bone marrow are immature. These include myeloblasts, promyelocytes, myelocytes, metamyelocytes, and bands. As immature neutrophils develop into band neutrophils, the nucleus (the structure that contains the cell's genetic material) begins to show a band-like structure.

Immature neutrophils generally mature before being released into the blood to help fight infection, and normally, most neutrophils in the blood are mature.

Mature neutrophils are described as segmented neutrophils because their nuclei have a segmented appearance when examined with a microscope.

Sometimes, neutrophils are released into the blood before they mature, and this can cause neutrophilia (a high number of neutrophils) with a predominance of immature neutrophils. This is typically due to an infection and is called a left shift.

What Are the Symptoms and Causes of Immature Neutrophils? 

Immature neutrophils are usually associated with an infection. The symptoms you may experience when you have a high number of immature neutrophils are typically the effects of the infection.

Symptoms include:

• Fever, chills, sweats 
• Fatigue, muscle soreness 
• Sore throat, coughing, chest tightness, or wheezing with a respiratory infection 
• Deceased appetite, abdominal discomfort, vomiting, or diarrhea with a gastrointestinal infection
• An area of pain, swelling, and redness with a skin abscess 

Immature neutrophils are associated with sepsis, a severe systemic (whole-body) reaction to an infection. Symptoms can include a high fever, trouble breathing, fluctuating blood pressure, alterations in blood sugar, tachycardia (rapid heart rate), and confusion. Sepsis can be life-threatening, and prompt medical attention and treatment are needed. 

Other conditions can also lead to an excess of immature neutrophils in the blood, and if this is the case, the symptoms of these other conditions can occur. 

Immature neutrophils are associated with:

• Cancer, especially leukemia and lymphoma, which cause fatigue, weight loss, and infection
• Graft-versus-host disease, a reaction that can occur after a stem cell transplant (a procedure that replaces unhealthy bone marrow with healthy cells)
• Trauma or injury
• Heart attack 
• Autoimmune disease (in which the immune system mistakenly attacks the body's own cells)
  

How Are Immature Neutrophils Diagnosed? 

Immature neutrophils can be identified with a complete blood count (CBC), which is a blood test. This test measures the total number of red blood cells, platelets, and leukocytes (white blood cells) in a blood sample, as well as the number and percent of each type.

Depending on the automated instrument the laboratory has, immature neutrophils may be reported as part of the automated CBC with differential.

If the instrument detects a higher than normal number of immature neutrophils, this will usually trigger a WBC differential to be manually performed with a peripheral blood smear. In this test, lab professionals stain a blood smear and examine it under the microscope to identify types of white blood cells and any abnormalities of the red blood cells or platelets.

If you have immature neutrophils, your healthcare provider will consider your symptoms, medical history, and the number and percent of your other blood cells when formulating a plan for further diagnosis and treatment. 

You might have a repeat CBC or need additional tests to identify the cause. 

Examples of additional tests can include:

• Throat swab 
• Urinalysis 
• Blood culture (blood is drawn in small bottles and incubated in the lab to check for bacterial growth and identify any organisms that grow)
• Imaging tests, such as chest X-ray or abdominal computed tomography (CT), if there is concern about an infection in these areas 
• Bone marrow biopsy (a needle is used to take a sample of bone marrow to be analyzed by a hematopathologist—a physician specializing in diagnosis of blood disorders by laboratory methods)

How Do You Treat Immature Neutrophils? 

In general, immature neutrophils will reach a normal level after treatment of the underlying cause. Even though they are immature, it has been shown that these cells are effective in fighting infections.

It isn’t necessarily considered beneficial to try to lower the number of immature neutrophils in the blood if they are there to fight a mild or moderate infection. You might need treatment for the infection and managing symptoms of the infection. Treatments can include antibiotics for a bacterial infection, medication to lower a fever, pain medication, intravenous fluid, or decongestants. 

If the excess immature neutrophils are caused by a severe infection, cancer, or another disease, it’s important to get treatment for the underlying condition. 

Treatments for serious causes of immature neutrophils include:

• Chemotherapy, radiation, or surgery for cancer treatment 
• Supportive care, including blood pressure control, respiratory support, and oxygen for
  management of sepsis 
• Anti-inflammatory treatment for the treatment of autoimmune disease or graft versus host disease

Immature neutrophils should normalize with effective treatment of the causative condition.

Summary

Immature neutrophils, which are also called band neutrophils, are normally present in low amounts in the blood. An increase in band neutrophils is usually temporary and indicative of an infection. Sometimes band neutrophils can increase due to inflammatory diseases or cancer.

Your medical history, symptoms, and blood tests would guide your treatment plan. Treatment is directed at the underlying problem.

A Word From Verywell

Immature neutrophils can be a sign of illness, but this result is expected in case of infection. They are a sign that your body is actively making more neutrophils than usual to battle the infection. You may even be already recovering from a mild or moderate infection.

You might need a repeat test, especially if you have not been feeling well for a while, and this can help determine whether you could have a medical illness that requires further testing and treatment.