According to the Mayo Clinic, "A complete blood count (CBC) is a blood test used to evaluate your overall health and detect a wide range of disorders, including anemia, infection and leukemia." Part of the CBC test includes a visual evaluation of the white blood cells circulating in the blood. The WBC's per cubic milliliter are separated and counted by a machine. A blood smear is made and the white blood cells are visually evaluated and differentiated. Blood smears are prepared with Wright's stain to bring out details on the microscopic slide. Each type of white blood cell has specific stain characteristics as well as an overall size and appearance.
Segmented Neutrophils or Granulocytic White Blood Cells
According to the Wadsworth Center, which is part of the New York State Department of Health, Neutrophils vary nine to sixteen micrometers in size. The cytoplasm looks granular in appearance. The inner nucleus contains segmented material with 3 to 5 lobes. Immature granulocytes will not contain segments and the nuclear material will appear as a band. The cytoplasm may contain inclusions such as bacteria or cellular debris. The cytoplasm stains light blue on the blood smear with darker inclusions. The nucleus will stain dark blue and appear coarse on the blood smear seen under the microscope.
Neutrophils prove the most common white blood cells seen and a normal range equals 40 to 75 percent of the total white cells seen.
Eosinophils
Eosinophils are the same size and shape of neutrophilic white blood cells. The granulocytic inclusions found in the cytoplasm of an eosinophil will stain bright orange and prove easily recognizable on the slide under a microscope.
Eosinophils have a normal range of one to four percent of the total white cells seen.
Basophils
Basophilic white blood cells will have granulocytic inclusions that will stain a dark blue on the blood smear. It proves quite difficult to see the nuclear material in a basophil, but it has similar size and shape to neutrophils.
The Wadsworth Center says that basophils normally equal less than one percent of the total differential count.
Lymphocytic White Blood Cells
Lymphocytes range from six to ten micrometers in size. The nucleus generally stains dark blue on the blood smear and is surrounded by a lighter blue cytoplasm. The cytoplasm is usually seen as a ring around the large nuclear material. The nucleus can contain darker stained material called a centrosome or chromatin.
Lymphocytes prove the second most common white cell seen with a reference range of 25 percent of the white cells seen.
Monocytes
Monocytes vary from ten to thirty micrometers in diameter. The outer cytoplasm sometimes appears indented and has a ground glass or frothy look. The cytoplasm is abundant and can have holes in it, reports the Wadsworth Center. The nucleus stains moderately blue on a blood smear and has a horseshoe appearance.
Monocytes have a normal reference range of two to twelve percent of the circulating white blood cells.
Immature White Blood Cells
White blood cells are produced in the bone marrow or the lymphatic system. All of the cell lines start out as immature cells that rapidly develop into the typical circulating white cells seen on a blood smear. In certain diseases and conditions, the white cells produce so quickly that the immature forms become visible. Young white blood cells tend to be larger than mature cells. The cytoplasm contains few inclusions. Blood disorders can be determined based on the number and appearance of the different type of white blood cells.
References
- Wadsworth Center: New York State Department of Health: Neutrophils
- Wadsworth Center: New York State Department of Health: Eosinophils
- Wadsworth Center: New York State Department of Health: Basophils
- Wadsworth Center: New York State Department of Health: Lymphocytes
- Wadsworth Center: New York State Department of Health: Monocytes
