Leukocytes are classified broadly as granulocytes and agranulocytes. These terms tell you something about these cells. If a leukocyte possesses cytoplasmic granules it is a granulocyte and if these granules are lacking, it is an agranulocyte. Once this distinction is made, more specific identification can follow.
|Granulocytes include:||Agranulocytes include:|
|1. neutrophils||4. monocytes|
|2. eosinophils(acidophils)||5. lymphocytes|
The chemical constituents of the five leukocyte types vary and they subsequently respond to stains in different ways. Two common stains for WBC's are the Giemsa and Wright's stains. Both are considered differential blood stains as they enable the differentiation/identification of the five leukocyte types in a typical blood stain.
Differential blood stains incorporate acid and basic stains together that react with cellular components. Staining reactions that result determine how leukocytes appear under the microscope. In fact, the names of granulocytes are based on how the granules respond to the stain components. Granulocytes are subsequently named neutrophils(being neutral), acidophils(acid loving), or basophils(basic loving) due to how the granules attract these stains. Eosin is the acid component of the Wright's and Giemsa stains and as a result, acidophils are more commonly called eosinophils. Remember, cellular components that attract acid stains appear red while those attracting basic stains appear dark blue. Now take another look at our image and see if you can find granules in the cytoplasm of some cells. Are they present (a granulocyte) or absent(an agranulocyte)? If present, are they red(an eosinophil) or blue(a basophil) or small and difficult to determine(a neutrophil)? Also, notice the nuclei of all leukocytes. Nuclei contain large amounts of RNA and DNA. These substances attract the basic components of stains and subsequently stain blue.
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