White blood cells (WBCs), also known as leukocytes, are microscopic immune cells that constantly patrol the body, acting as a defense against infection and foreign invaders. Produced in the bone marrow, these cells circulate throughout the bloodstream and tissues. Leukemia is a group of cancers originating in the blood-forming cells within the bone marrow, primarily affecting white blood cell production and function. This condition disrupts the body’s ability to maintain healthy blood cell counts, leading to various health complications.
Understanding White Blood Cells
White blood cells are a diverse group of immune cells responsible for protecting the body from illness and disease. They make up a small percentage, typically around 1%, of the total blood volume. There are five main types of white blood cells, each with distinct roles in the immune response.
Neutrophils are the most abundant type, typically making up 55% to 70% of the total white blood cell count, and are the first responders to bacterial and fungal infections. Lymphocytes, which include T cells, B cells, and natural killer cells, are responsible for recognizing and eliminating infected or cancerous cells, as well as producing antibodies to fight specific pathogens. Monocytes, larger than other WBCs, help clean up cellular debris and communicate with other immune cells.
Eosinophils primarily target parasitic infections and play a role in allergic reactions and inflammatory responses. Basophils, representing less than 1% of WBCs, are involved in allergic reactions by releasing chemicals like histamine. Each of these cell types originates from hematopoietic stem cells in the bone marrow, continuously produced to maintain immune vigilance.
Leukemia’s Impact on White Blood Cells
Leukemia develops when genetic mutations occur within the DNA of blood-forming stem cells in the bone marrow. These mutations cause affected cells to grow and divide uncontrollably, disrupting normal blood cell development. The abnormal cells, often immature or dysfunctional white blood cells (blasts), do not mature properly and cannot perform their protective functions.
These rapidly multiplying abnormal cells accumulate in the bone marrow, crowding out the healthy production of other blood cells, including red blood cells, platelets, and functional white blood cells. This uncontrolled proliferation can lead to an excess of non-functional white blood cells, while simultaneously reducing the numbers of healthy blood components. Leukemia is classified based on the type of white blood cell affected—either lymphoid cells (leading to lymphocytic leukemia) or myeloid cells (leading to myelogenous leukemia)—and how quickly the disease progresses, either acutely or chronically.
For instance, acute myeloid leukemia (AML) involves an overproduction of myeloblasts, which are immature white blood cells that would normally develop into granulocytes, red blood cells, or platelets. In contrast, acute lymphoblastic leukemia (ALL) results from too many abnormal lymphocytes. These dysfunctional cells not only fail to fight infections but also interfere with the bone marrow’s ability to produce the necessary healthy cells for the body to function properly.
How Abnormal White Blood Cells Affect the Body
The overproduction of dysfunctional white blood cells and the resulting deficiency of healthy blood cells lead to various symptoms throughout the body. When the bone marrow is overwhelmed by leukemic cells, it cannot produce enough healthy white blood cells, making individuals highly susceptible to frequent and severe infections. These infections may be difficult to treat and can present with symptoms like fever, chills, sore throat, or persistent illness.
The crowding out of healthy red blood cells leads to anemia, a shortage of oxygen-carrying red blood cells. Symptoms of anemia include persistent fatigue, weakness, pale skin, shortness of breath, and feeling cold. The lack of healthy platelets, which are essential for blood clotting, results in easy bruising, prolonged bleeding, frequent nosebleeds, bleeding gums, or tiny red or purple spots on the skin (petechiae).
In some cases, a very high number of leukemia cells can cause leukostasis, where the abnormal cells clog tiny blood vessels, potentially impairing blood flow to organs. This can lead to serious complications such as headaches, slurred speech, confusion, or even stroke-like symptoms if the brain is affected. The combination of these deficiencies and cellular overloads contributes to the overall feeling of being unwell and can impact various organ systems.
Diagnosing Leukemia Through White Blood Cell Analysis
White blood cell analysis plays a central role in diagnosing leukemia. Diagnosis often begins with a complete blood count (CBC) with differential, a common blood test measuring red blood cells, white blood cells, and platelets. In individuals with leukemia, this test reveals abnormal white blood cell counts, which can be unusually high or, less commonly, very low.
The CBC with differential also assesses the proportion of different types of white blood cells and can identify the presence of immature or abnormal white blood cells (blasts) in the bloodstream. While a small percentage (up to 5%) of blasts are normal in the bone marrow, their presence in peripheral blood or an abnormally high percentage in the bone marrow (over 20%) indicates leukemia.
If initial blood tests suggest leukemia, further diagnostic procedures confirm the diagnosis and classify the specific type. A bone marrow aspiration and biopsy, usually taken from the hip bone, is conducted to examine the bone marrow directly for cancerous cells. Additional tests like immunophenotyping, genetic testing, and molecular profiling identify specific markers on white blood cells or genetic mutations within the cells. These help determine the exact type and subtype of leukemia and guide treatment decisions.