Throughout human history, our bodies have adapted to the outside environment in various ways, and our immune system is a frank representation of that adaptation. Our blood is a tissue, just like any other, and the cells that make up the blood are not adherent to each other but “swim” in a continuous motion in the fluid connective tissue known as plasma. Those cells are red blood cells, white blood cells and platelets. White blood cells are the only ones that have nuclei and they can be differentiated according to the shape of their nuclei and their color under the microscope. White blood cells are derived from common mother cells called the hemopoietic stem cells that are located mainly in the bone marrow.
Leukopenia is a medical term that means a fall in the number of white blood cells below normal. It may be isolated, which means that only white blood cells are affected, or may be a part of a pancytopenia which is the deficiency of all three blood elements.
Normal count of white blood cells
Neutrophils, basophils and eosinophils are grouped under the term granulocytes because of the appearance of different granules in their cells under the microscope.
The normal number of white blood cells is as follows:
♦ Total number = 4000-11000 per cubic milliliter
♦ Neutrophils = 2500-7500 per cubic milliliter
♦ Lymphocytes = 1500-3500 per cubic milliliter
♦ Monocytes = 200-800 per cubic milliliter
♦ Eosinophils = 40-400 per cubic milliliter
♦ Basophils = 10-100 per cubic milliliter
Leukopenia is when the total number if white blood cells falls below 4000 per cubic milliliter.
How is leukopenia diagnosed?
The number of white blood cells is counted by collecting a blood sample, then using a machine called an analyzer that counts different blood cells then classifies them according to their type.
The main drawback of the automated method is that it usually mistakes abnormal white blood cells and considers them normal, therefore overestimating the number of true cells, and that’s why most CBCs will be followed by a manual blood film examination under the microscope by a clinical pathologist.
What do white blood cells do?
White blood cells or leukocytes have a variety of functions and such functions depend on the type of white blood cell as follows:
Neutrophils
They function mainly as antibacterial cells; they are lethal to bacteria and produce many enzymes for such a purpose. They also have some antifungal action and an important role in tissue healing and mediating inflammation. Neutrophils form the majority of white blood cells, with more than 60% of the total leukocyte count being of this type.
Lymphocytes
Lymphocytes are divided into T and B lymphocytes according to their function and cell of origin. They have a broad variety of functions. B lymphocytes are the main site of formation of antibodies, while T lymphocytes are responsible for what we call a “cell-mediated immunity” which is the main defense mechanism against viral infections and cancer. They also have a central role in regulating the immune system by keeping it strong enough to fight intruders and weak enough not to attack the body itself in a process known as “autoimmunity”. Almost all autoimmune diseases result from abnormalities in T-cells. They also contribute to tissue healing.
A third type of lymphocytes is called natural killer cells, and they function as a rapid response to any intruder. Whenever any abnormal antigen or protein is detected, they sacrifice themselves to keep it at bay until the body can mount a sufficient immune response.
Eosinophils
Eosinophils are concerned with two main functions: mediating allergic conditions as asthma and fighting parasites.
Basophils
Basophils are responsible for the release of histamine which is one of the main chemical mediators of inflammation and has a central role in most allergic conditions, such as urticaria and asthma.
Monocytes
Monocytes are cells that are underdeveloped, which means that they undergo further development when they reach the cells in which they reside. They differentiate into macrophages which are cells that eat other cells and foreign particles.
Leukopenia and neutropenia
Both neutropenia and leukopenia terms may be used instead of each other, and this is largely not false. Neutrophils form the majority of white blood cells and a fall of neutrophils will almost certainly cause a fall in the total number of white blood cells, however if the number of neutrophils falls alone, it might be a different diagnosis, and is therefore important for doctors to check what is called a differential count of white blood cells to see what type of white blood cells fell in number.
Does AIDS cause leukopenia?
AIDS is the end stage of a clinical condition caused by the human immunodeficiency virus, and the unique thing about this virus is that it infects white blood cells, especially T-lymphocytes, causing their destruction. This causes a variety of symptoms and increased susceptibility to certain infections and cancers.
The progression of the disease and the response to therapy is largely measured by the T-lymphocyte count or what we call a CD4 count. CD being the cluster of differentiation or an “ID” for a certain type of T-lymphocytes.
Can leukopenia be treated?
Leukopenia is a result, and the only way it can be directly treated is by transfusing white blood cells, which is almost never done. To treat leukopenia effectively, we have to treat the underlying cause, be it a viral infection, a cancer, an autoimmune disease or even a rare genetic condition.
In most cases, the immediate threat to your life is not leukopenia but what caused it in the first place, and a thorough examination as well as necessary investigations by your treating physician ensure the correct diagnosis. When the main condition is treated, your white blood cells or leukocytes will return to their normal levels.