In biology and medicine, “blasts” refers to immature, undifferentiated cells that serve as precursors to various mature cell types throughout the body. These cells are fundamental components of many biological processes, particularly in the formation of blood.
What Are Blasts?
Blasts are immature, undifferentiated cells that precede the mature, functional cells found in the body. They play a role in hematopoiesis, the continuous process of blood cell formation that primarily occurs within the bone marrow.
Different types of blasts exist, each committed to developing into specific cell lineages. Myeloblasts are one such type, serving as precursors to myeloid cells, which include various white blood cells like neutrophils, eosinophils, basophils, and monocytes, as well as red blood cells and platelets. Lymphoblasts represent another type, destined to become lymphoid cells, such as T-cells and B-cells, which are types of white blood cells involved in the immune response.
In a healthy individual, blasts are found in controlled numbers, primarily residing within the bone marrow. Less than 5% of the cells in healthy bone marrow are blasts. They undergo a series of divisions and differentiation steps, maturing properly before being released into the bloodstream as functional cells.
The Role of Abnormal Blasts in Disease
When blasts become abnormal, they fail to mature properly and proliferate uncontrollably. This uncontrolled growth leads to an accumulation of immature cells, which can crowd out healthy, mature blood cells within the bone marrow.
The excessive proliferation of these immature cells can also result in their spilling out of the bone marrow and circulating in the bloodstream. This displacement of normal cell production can lead to a range of serious health issues. For instance, the reduced production of healthy red blood cells can cause anemia, characterized by symptoms like fatigue and paleness.
A decrease in functional white blood cells, such as neutrophils, can severely impair the body’s ability to fight infections, leading to frequent or severe infections. Similarly, a lack of platelets, which are essential for blood clotting, can manifest as easy bruising, prolonged bleeding, or even tiny red spots on the skin called petechiae.
Identifying Blasts in the Body
Medical professionals employ specific methods to detect and quantify blasts in the body. One common approach is the peripheral blood smear, where a sample of blood is spread thinly on a glass slide and examined under a microscope. Pathologists analyze the morphology of the cells, looking for the characteristic appearance of blasts, which have a large nucleus, immature chromatin, and scant cytoplasm.
If an unusual number of blasts are observed in the peripheral blood, a bone marrow examination is performed for further assessment. This procedure involves both a bone marrow aspiration, where a liquid sample of marrow is drawn, and a bone marrow biopsy, which collects a small solid piece of bone marrow. These samples are then analyzed to determine the percentage of blasts present and their specific characteristics.
The presence of an unusually high percentage of blasts in either the blood or bone marrow is an indicator of certain medical conditions. For instance, having 20% or more blasts in the bone marrow or blood is a diagnostic criterion for acute leukemia. While morphology provides initial insights, additional laboratory tests like flow cytometry or cytogenetics can further classify the blasts and aid in diagnosis.