Anatomy & Organs

Myeloblast – Structure, Function & Diseases


Myeloblasts are the most immature form of granulocytes within the granulopoiesis and arise from multipotent stem cells of the bone marrow . Granulocytes are involved in the defense against infections. If there is a lack of granulocytes, this deficiency can be traced back to a previous lack of myeloblasts and results in immune deficiency in the sense of a weakened immune system.

What is a myeloblast?

Granulocytes belong to the leukocytes . They are the group of white blood cells that perform important tasks in the immune system and are therefore significantly involved in fighting off infections. For example, leukocytes are involved in the recognition of foreign antibodies , in the formation of antigens and in phagocytosis .

To be more precise, granulocytes attack pathogens and render them harmless to the organism. The formation of the cells takes place in the bone marrow and is based on multipotent progenitor cells. The formation processes are summarized under the term granulopoiesis, which is considered part of hematopoiesis . The so-called myeloblasts, which are known as the smallest precursor of granulocytes within granulopoiesis, develop from multipotent stem cells in the bone marrow. They arise from hematopoietic stem cells and represent their first differentiation on the way to granulocytes. As a result, the cells are also referred to as the most immature form of granulocytes.

Anatomy & Structure

Myeloblasts are the only cells in granulopoiesis that do not exhibit granulation. The cells have a round or oval nucleus with vaguely defined nucleoli. The cytoplasm of myeloblasts appears slightly bluish because of its basophilia.All myeloblasts are between 12 and 20 micrometers in size. The chromatin structure of myeloblasts is considered to be reticular. A Golgi apparatus is located around the nucleus of the cells , which appears as a perinuclear clearing zone. Unlike the so-called proerythroblasts, myeloblasts do not have any plasma protuberances. The myeloblasts belong to the so-called “white series”. They make up less than five percent of the nucleated cells. Their progenitor cells are called hemocytoblasts.

In the stage after the myeloblast, the resulting granulocyte precursors are called promyelocytes. There are other cell stages on the way from the myeloblast to the full-fledged granulocyte. The metamyelocytes are followed by the rod-nucleated granulocyte and finally the segmented-nucleated granulocyte.

Function & Tasks

The task of the myeloblasts is to differentiate into granulocytes. Myeloblasts therefore have no active role in the human immune system and are not yet involved in recognizing and defending against exogenous pathogens. They are merely a developmental stage of the granulocytes, which are responsible for recognizing and defending against pathogens. With their involvement in granulopoiesis, they are also involved in hematopoiesis on a larger scale.

This is what blood formation in the bone marrow is called. Without the formation of granulocytes from myeloblasts, the patient’s defense against infection is impaired. If, for example, there are too few myeloblasts from which granulocytes are formed, there are too few defense cells of the immune system available in the patient’s blood. This means that the patient has a weak immune system and is more susceptible to infections of all kinds. The excessive development of granulocytes from myeloblasts is an indication of an excessively strong immune system and can be a sign of the disease.

The term neutropenia refers to a lack of granulocytes. In granulocytosis, there is an increased number of granulocytes. The myeloblasts, as the precursor stage of the granulocytes, are involved in both the one and the other. Although the myeloblasts themselves do not have an active immunological function, they still have a significant impact on the functionality of the immune system.


In a so-called neutrophilic granulocytosis, neutrophilic granulocytes exceed the limit of 6.3 G/l. This form of excessive formation of granulocytes from myeloblasts can indicate leukemia or other malignant tumor diseases , but can also accompany infectious diseases, inflammation or stress .Eosinophilic granulocytosis refers to a pathological increase in the number of eosinophilic granulocytes in the peripheral blood . In most cases, the abnormal granulopoiesis is due to an allergic reaction. In some cases, the phenomenon is also observed in the presence of parasites . In basophilic granulocytosis, the basophilic granulocytes multiply beyond the limit. This form of granulocytosis usually occurs together with eosinophilic granulocytosis and is favored by allergies or hypersensitivity reactions. Parasitosis and hyperlipidemia are also conceivable causes.

In the case of a pathological reduction in neutrophilic granulocytes, neutrophilic and other granulocytes are proportionately absent within the blood. This neutropenia is the most common leukopenia . The phenomenon is critical for the patient, since his ability to fight off infections is significantly reduced due to the reduction in granulocytes. Those affected are much more susceptible to bacterial infections in particular. Neutropenia can occur when too few granulocytes are formed from myeloblasts. This is the case with inadequate bone marrow proliferation.

In this phenomenon, a reduced differentiation of granulocytes from myeloblasts is triggered due to a lack of certain substances, for example due to a lack of folic acid . In addition, suppression of hematopoiesis can lead to reduced granulocyte formation from myeloblasts. Such displacement occurs, for example, in the case of neoplasia, but can also be a side effect of cytotoxic drugs that disrupt hematopoiesis. Theoretically, the processes and cell stages of granulopoiesis can also be impaired on a genetic basis, for example in the context of certain mutations .

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.