University of Babylon



White blood cells count:

A WBC count is a blood test to measure the number of white blood cells (WBCs).

White blood cells help fight infections. They are also called leukocytes. There are five major types of white blood cells:

• Neutrophils

• Lymphocytes (T cells and B cells)

• Monocytes

• Eosinophils

• Basophils

• Total white blood cells - All the white cell types are given as a percentage and as an absolute number per litre.

Neutrophil granulocytes - May indicate bacterial infection. May also be raised in acute viral infections.

Neutrophils are phagocytes, capable of ingesting microorganisms or particles. They can internalize and kill many microbes, each phagocytic event resulting in the formation of a phagosome into which reactive oxygen species and hydrolytic enzymes are secreted. The consumption of oxygen during the generation of reactive oxygen species has been termed the "respiratory burst," although unrelated to respiration or energy production.

The respiratory burst involves the activation of the enzyme NADPH oxidase, which produces large quantities of superoxide, a reactive oxygen species. Superoxide dismutates, spontaneously or through catalysis via enzymes known as superoxide dismutases (Cu/ZnSOD and MnSOD), to hydrogen peroxide, which is then converted to hypochlorous acid HOCl, by the green heme enzyme myeloperoxidase. It is thought that the bactericidal properties of HOCl are enough to kill bacteria phagocytosed by the neutrophil, but this may instead be step necessary for the activation of proteases.

• Lymphocytes - Higher with some viral infections such as glandular fever and. Also raised in lymphocytic leukemia. Can be decreased by HIV infection. In adults, lymphocytes are the second most common WBC type after neutrophils. In young children under age 8, lymphocytes are more common than neutrophils.

|LYMPHOCYTE CLASS |FUNCTION OF LYMPHOCYTE |PROPORTION |

|NK cells |Lysis of virally infected cells and tumour cells |7% (2-13%) |

|Helper T cells |Release cytokines and growth factors that regulate other |46% (28-59%) |

| |immune cells | |

|Cytotoxic T cells |Lysis of virally infected cells, tumour cells and |19% (13-32%) |

| |allografts | |

|γδ T cells |Immunoregulation and cytotoxicity | |

|B cells |Secretion of antibodies |23% (18-47%) |

• Monocytes - May be raised in bacterial infection, tuberculosis, malaria, monocytic leukemia, chronic ulcerative colitis and regional enteritis. Monocyte is a type of white blood cell, part of the human body's immune system. Monocytes have two main functions in the immune system: (1) replenish resident macrophages and dendritic cells under normal states, and (2) in response to inflammation signals, monocytes can move quickly (approx. 8-12 hours) to sites of infection in the tissues and divide/differentiate into macrophages and dendritic cells to elicit an immune response. Half of them are stored in the spleen. Monocytes are usually identified in stained smears by their large bilobate nucleus.

• Eosinophil granulocytes - Increased in parasitic infections, asthma, or allergic reaction.

• Basophil granulocytes- May be increased in bone marrow related conditions such as leukemia or lymphoma.

Overview table

Type |Microscopic Appearance |Approx. %

in adults

Blood values |Diameter (μm) |Main targets |Nucleus |Granules |Lifetime | |Neutrophil |[pic] |54–62% |10–12 |bacteria

• fungi |multilobed |fine, faintly pink (H&E Stain) |6 hours–few days

(days in spleen and other tissue) | |Eosinophil |[pic] |1–6% |10–12 |parasites

• in allergic reactions |bi-lobed |full of pink-orange (H&E Stain) |8–12 days (circulate for 4–5 hours) | |Basophil |[pic] | ................
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