Normal White Blood Cell Count
Normal White Blood Cell Counts and Deviations from Normal Values
In a laboratory hematological study, comparing white blood cell values with the normal white blood cell count will determine plenty of possible underlying conditions a patient could have. By finding out other signs and symptoms, the physician, coupled with the laboratory findings, can come up with an accurate diagnosis.
What are white blood cells? White blood cells are a special category of blood cells that help in immune responses. There are many types of white blood cells, with each type performing a highly specialized function.
(1) Granulocytes are phagocytic white blood cells which are distinguished by their granules. Their main function is to swallow foreign particles entering the bloodstream. Normal white blood cell count for granulocytes in general is 47-72%.The types of granulocytes are:
(a) Neutrophils, which are the all-purpose granulocytes that aid in the normal body defense against invading pathogens. Normal white blood cell count for neutrophils is 47-63% for segs and 0-4% for bands.
(b) Eosinophils, distinguished by their red stain when dyed with the acidic dye eosin, release detoxifiers of allergic agents and enzymes that digest parasites. Normal white blood cell count for eosinophils is 0-3%.
(c) Basophils, distinguished by their blue stain when dyed with basic dyes, release histamine, a chemical that aids in immune responses and vasodilation, and heparin, an anticoagulant. Normal white blood cell count for basophils is 0-2%.
(2) Lymphocytes originate from lymphoid stem cells in the bone marrow; hence, the name. Unlike granulocytes, most lymphocytes contain no granules Lymphocytes help greatly in defending against microbes or mediating the immune response as they wander in the bloodstream or stay for a long time inside lymphoid tissues. Normal white blood cell count for lymphocytes is 24-40%. The types of lymphocytes are:
(a) B lymphocytes aid in humoral immunity, one of two types of immunity. Humoral immunity is immune response that causes the production of antibodies that initiate the antigen-antibody response.
(b) T lymphocytes aid in cell-mediated immunity. Cell-mediated immunity is an immune response that involves the activation of T lymphocytes, destruction of pathogens, and production of cytokines, or chemicals that sharply stimulate other cells and get them involved in the immune response.
(c) Natural killer cells, or NK cells, are potent granular lymphocytes that aid in apoptosis, elimination of viral pathogens, and destruction of tumors. Because they are very powerful compared to the other lymphocytes, they require a activation in order to begin functioning.
(3) Monocytes, the largest white blood cells, are distinguished by their bean shape and by their sizable cytoplasm, compared to other white blood cells. Monocytes typically leave the bloodstream and enter various tissues, where they turn into macrophages. Macrophages have greater phagocytic capacity than neutrophils, and they also involve themselves in the inflammatory response by signaling lymphocytes. What’s normal for monocytes is 4-9%. What’s normal for mononuclear leukocytes, or lymphocytes and monocytes combined, is 20-35%.
All in all, the normal count ranges from 4800-10800/mL (microliter) of blood. Readings above or below this range signify abnormalities.
An above-normal figure (greater than 10800/mL) usually indicates an infection, because the bacteria or the virus involved in the infection cause the white blood cells to defend against them, thus, more white blood cells are produced in order to counteract more efficiently the pathogens. An inflammation can also cause an above-normal figure because white blood cells, especially basophils, are involved in the entire inflammatory process. Other conditions leading to such are: leukemia; malnutrition; removal of the spleen (which releases white blood cells from the spleen to the blood); high levels of stress; tissue damage or trauma; Pregnancy also causes an above-normal figures, although it has no pathological etiology. Some drugs, like aspirin, heparin, quinine, or steroids, also cause an above normal white blood cell count.
A below-normal figure (less than 4800/mL) may indicate one of the following: bone marrow, liver, or spleen disorders; autoimmune disorders (like systemic lupus erythrematosus) or immune deficiency disorders (like AIDS); accelerated removal following an infection; and Felty syndrome (destruction of white blood cells in the spleen). A below-normal figure indicates, in general, inhibition or destruction. Some drugs, like antibiotics, antihistamines, chemotherapy drugs, barbiturates, and thyroid-suppressing agents, also cause a below normal white blood cell count.
Usually, the normal white blood cell count of each type of white blood cells also has diagnostic value – they can be used to find out the precise cause of an abnormality. Above-normal for neutrophils indicate bacterial infection. Above-normal for eosinophils count indicates parasitic infection. An above normal basophil count indicate pronounced allergic reactions. Increased lymphocyte count indicates leukemia or bone marrow cancer; decreased lymphocyte count indicates immune disorders. Increased monocyte count indicates infection, inflammation, or leukemia; decreased monocyte count indicates bone marrow disorders or other types of leukemia.