From the Guidelines
Immature granulocytes in the bloodstream are primarily caused by bone marrow stimulation in response to infection, inflammation, or other medical conditions, such as leukemia, as seen in chronic myeloid leukemia (CML) where the presence of immature granulocytes is a key criterion for defining the accelerated phase (AP) and blast phase (BP) of the disease 1. When the body detects an infection or inflammatory process, it increases production of white blood cells, sometimes releasing immature forms (like band neutrophils, metamyelocytes, myelocytes, and promyelocytes) into circulation before they fully mature. This process, called a "left shift," commonly occurs during bacterial infections, tissue damage, or inflammatory conditions. Other causes of immature granulocytes include:
- Certain medications (corticosteroids, growth factors)
- Bone marrow disorders (leukemia, myelodysplastic syndromes)
- Severe burns
- Trauma
- Surgery
- Pregnancy
- Cancer Chemotherapy can also trigger immature granulocyte release as the bone marrow recovers. While temporary elevation during infection is normal, persistent elevation may indicate a more serious underlying condition requiring medical evaluation, such as CML, where the presence of immature granulocytes is a key factor in determining the phase of the disease and guiding treatment decisions 1. The presence of immature granulocytes helps clinicians assess the severity of infection and the body's response to it, and in the context of CML, the European LeukemiaNet (ELN) recommendations suggest that the presence of immature granulocytes is a key criterion for defining the accelerated phase (AP) and blast phase (BP) of the disease 1. In addition, the management of chronic myelomonocytic leukemia (CMML) also takes into account the presence of immature granulocytes, with therapy recommended when the disease is symptomatic or progressive, and when immature granulocytes are ≥ 10% in peripheral blood 1.
From the Research
Causes of Immature Granulocytes
The causes of immature granulocytes, also known as immature granulocytic cells, can be attributed to various factors, including:
- Infections, such as bacterial and fungal infections, which trigger an immune response and lead to an increase in immature granulocytes [ 2 , 3 , 4 ]
- Inflammatory conditions, such as severe acute pancreatitis, systemic inflammatory response syndrome, and infectious complications following open-heart surgery under cardiopulmonary bypass [ 2 ]
- Chronic kidney disease, which can lead to chronic inflammation and an increase in immature granulocytes [ 5 ]
- Acute appendicitis, particularly perforated appendicitis, which can cause an increase in immature granulocytes [ 6 ]
Relationship to Infection and Sepsis
Immature granulocytes have been found to be associated with infection and sepsis, with higher levels indicating a more severe infection [ 3 , 4 ]. The percentage of immature granulocytes has been shown to be a better predictor of infection than the total white blood cell count and comparable to the absolute neutrophil count [ 3 ].
Biomarker for Inflammation
Immature granulocytes have been found to be a useful biomarker for inflammation in various conditions, including chronic kidney disease [ 5 ] and acute appendicitis [ 6 ]. The immature granulocyte count and percentage have been shown to be positively correlated with other inflammatory markers, such as C-reactive protein and neutrophil-to-lymphocyte ratio [ 5 ].