Blood Smear_ Details on RBCs, WBCs 2
Details: White Blood Cells
NEUTROPHILS (also called segmented neutrophils, segs, polymorphonuclear cells, polys, or PMNs) are about 12 microns in diameter and their function is to engulf and destroy invading organisms. They normally make up about 50-70% of the total WBC count in the blood of older children and adults and may have two to five nuclear lobes connected by a thin strand of nuclear material. This type of WBC may be seen in greater numbers during infections, malignancies, or extreme stress situations. The cytoplasm of neutrophils is pale and often contains small pink to purple granules. These granules (specific granules and azurophilic granules) contain certain enzymes and proteins that neutralize or destroy microorganisms. Bands are immature neutrophils with a U-shaped nucleus.
Anomalies of neutrophils may include:
- Toxic granulation: large dark blue granules in the cytoplasm, associated with severe infection, burns, trauma, and G-CSF colony stimulating factor therapy; often reflects accelerated neutrophil maturation.
- Vacuolization: vacuoles appear as holes in the cytoplasm and are frequently found in association with toxic granulation but can also be a degenerative feature seen when the blood is stored for a prolonged period of time before preparing the blood smear.
- Dohle bodies: irregular grayish or bluish inclusions in the peripheral cytoplasm of neutrophils; they are denatured aggregates of free ribosomes or rough endoplasmic reticulum that are often seen in association with toxic granules and vacuoles. They may be present in association with infections, burns, trauma, or with exposure to cytotoxic agents (i.e., chemotherapy). They may also be seen after cytokine stimulation (e.g., G-CSF) or during a normal pregnancy.
- Auer rods: unique, pink or red rod-shaped inclusions that are seen in very immature myeloid cells ("blasts") or rarely more mature neutrophils in people with acute myeloid leukemia or high-grade myelodysplastic syndrome.
- Bands - increased numbers: slightly immature neutrophils are normal in the circulation in small numbers, but if there is a percentage increase of them, there is said to be a "left shift." This may happen when an acute infection stimulates increased neutrophil production, causing the bone marrow to prematurely release some WBCs before they have matured to the neutrophil stage. Other immature forms that may sometimes be seen on a blood smear include myelocyte and metamyelocyte or even promyelocyte and myeloblast.
- Hypersegmentation: neutrophils with six or more nuclear segments; this is mainly associated with vitamin B12 and folate deficiency and myelodysplasia but can also be seen with alcoholism and rarely as a hereditary condition.
- Pelger-Huet anomaly: hereditary anomaly where neutrophils appear with fewer than two lobes; the nucleus is often in the shape of a peanut or dumbbell, or may consist of two lobes connected with an obvious filament. They may also appear with certain immunosuppressant drugs or in certain disease states such as myelodysplasia and is referred to a "pseudo- Pelger-Huet anomaly".
- Alder-Reilly granules: large, dark leukocyte granules that stain purple; they suggest mucopolysaccharidosis (an inherited enzyme deficiency disorder, examples being Hurler's and Hunter's syndromes).
- Chediak-Higashi granules: an inherited anomaly characterized by the presence of big red, blue, or greenish granules that may be found in granulocytes, lymphocytes, and monocytes. People with this syndrome may have oculocutaneous albinism as well as a compromised immune system and photophobia.
LYMPHOCYTES are relatively small (7-10 µm) and round in shape. The nucleus is generally large in relation to the amount of cytoplasm. The cytoplasm is pale blue and normally only a small proportion of lymphocytes has any granules. The nucleus of most lymphocytes is smooth in appearance and is dark blue. There are two major types of lymphocytes, B cell and T cell, but they cannot be distinguished when viewed under the microscope using standard staining techniques. B cells can be differentiated from T cells using specific fluorescent-labeled antibody stains in conjunction with a special instrument called a flow cytometer. B cells create specific antibodies while T cells can activate B cells as well as recognize and destroy invading organisms. Lymphocytes normally make up about 20% to 40% of the total WBC count in adults and a higher proportion in infants and young children.
- Reactive lymphocyte (atypical lymphocyte, activated lymphocyte): these cells are large lymphocytes that contain a greater amount of cytoplasm and can vary in size and shape. Often a characteristic bluish tinge of cytoplasm is seen where the cell abuts with surrounding RBCs. Increased numbers of atypical lymphocytes are found in viral illnesses such as infectious mononucleosis.
- Hairy cells: these lymphocytes have tiny projections that make them appear hairy under the microscope; they are found in hairy cell leukemia.
EOSINOPHILS have two or three lobes to their nucleus and contain characteristic reddish/orange granules in their cytoplasm. They are most often involved in allergic responses and parasitic infections. Normally only about 1-4% of WBCs in the blood are eosinophils.
MONOCYTES are the largest in size of the WBCs and comprise less than 6% in normal blood. They are characterized by their abundant blue-grey cytoplasm that is irregular in shape and have a folded nucleus. The main function of monocytes is to ingest microorganisms and respond to infection and inflammation by releasing certain proteins (monokines) that can inactivate bacteria. When stimulated by cytokines, monocytes can move out of the bloodstream and become tissue macrophages.
BASOPHILS have a multi-lobed nucleus and have many dark blue granules (which contain histamines) in their cytoplasm. Only about 1% of WBCs are basophils. A sight elevation in number may be seen during an allergic response, ulcerative colitis, chronic sinusitis, chickenpox, or immunizations. A significant increase is not uncommon in chronic myeloid leukemia.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
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