WBCs are called leukocytes. They appear white when blood is separated (hence their name). They originate from the stem cell within the bone marrow.
An increased WBC count (greater than 10,000) is often indicative of infection, while a decreased WBC count (less than 5,000) indicates the patient is becoming immunosuppressed. Remember that steroids will elevate the WBC count even though the patient is not having an infection.
Neutrophils are the primary acting leukocyte in the body. It is a phagocytic cell that responds to an inflammatory response.
Bands are immature neutrophils. If there is an increase of bands in the system, it is called a “shift to the left,” which is seen in patients with an acute infection.
Segs are mature neutrophils. They are the most effective at phagocytosis. An increase in Segs indicates that the body has and is responding to an infection or tissue injury.
Lymphocytes are primarily activated during an immune response (cellular and humoral). There are three different types of lymphocytes: Natural Killer (NK) cells, B cells, and T cells. They are increased in chronic bacterial and viral infections, but decreased in sepsis.
Monocytes are found in the bloodstream and are effective phagocytic cells. However, when a monocyte migrates into the tissue, they are known as macrophages.
Eosinophils have a phagocytic function, but are not as effective. These cells assist in engulfing antigen-antibody complexes during an allergic response. The exact mechanism is unknown, but they also help in defending against parasitic infections.
Basophils have a similar function as mast cells. When activated they release histamine and serotonin, which helps stimulate an immune response.
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