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WBCS PART 2: BASOPHILS, NEUTROPHILS, AND EOSINOPHILS ("GRANULOCYTES")

Category: Medical

Topic: Hematology

Level: Paramedic

13 minute read

GRANULOCYTES: one of two generalized groupings of different types of leukocytes (WBCs).

They are polymorphonucleated (multi-lobed nuclei) cells:

  1. Neutrophils.
  2. Eosinophils
  3. Basophils

Neutrophils

NEUTROPHILS form half to two-thirds of leukocytes and are the overwhelming majority of the granulocyte cell family (that includes basophils and eosinophils). They are the highest percentage of white blood cells in the body, and they are formed from stem cells in the bone marrow.

The granulocytes, neutrophils, basophils, and eosinophils, get their names from the certain staining characteristics on hematoxylin and eosin histological (H&E stains) or cytological preparations. 

Neutrophils stain a neutral pink, basophils stain dark blue, and eosinophils stain bright red.

Neutrophils are a type of phagocyte that travels in the bloodstream and is one of the first-responders of the inflammation process due to a variety of causes.

Neutrophils travel through the blood vessels and then the interstitial tissue to the site of inflammation where they act to digest pathogens, but often require the help of other types of immune cells.

Neutrophils have a lifespan averaging 1-2 days when active.

Band Cells: the maturation of precursor neutrophils involves many stages, the last stage before the mature neutrophil is the "band cell," so-called because of the elongated nucleus in a horseshoe shape with band-like constrictions between much vaguer lobulations. When band cells are present, this represents stepped-up production of neutrophils provoked from an infectious challenge, called a "shift to the left" on the differential WBC count. Seeing bands is helpful in determining that an infection is present. Other conditions that can cause a shift to the left are

  • Inflammatory diseases.
  • Cancer.
  • Tissue necrosis.
  • Immune reaction (e.g., transplant rejection).\
  • Surgical, orthopedic, and other trauma.
  • Corticosteroids.
  • Third trimester of pregnancy.

 

Eosinophils

EOSINOPHILS are a type of white blood cell involved in the immune response to infection, tumor surveillance, and allergic reactions. They are made in the bone marrow.

They are primarily tissue-dwelling WBCs, a hundred times more abundant in the spleen, lymph nodes, thymus, and digestive tract (except for the esophagus) than in the blood.

Eosinophils are suppressed in fevers, bacterial and viral infections, and with the use of glucocorticoid steroids.

EOSINOPHILIA: Eosinophils are increased in disorders easily remembered by the mnemonic, NAACP.

  • Neoplasms.
  • Addison's disease (adrenal insufficiency, with deficiencies of cortisol and aldosterone).
  • Allergies.
  • Collagen vascular diseases.
  • Parasites.

Targets of the eosinophils in disease are the

  • skin (atopic dermatitis);
  • airway (allergic rhinitis, asthma, other pulmonary diseases); and
  • gastrointestinal tract (esophagitis, gastroenteritis, liver disease).

Less likely but possible are cardiac and renal (cystitis) infiltration of eosinophils.

Eosinophils release toxic granule products that can damage epithelial tissue. They also release factors that activate platelets and other things that mediate smooth muscle contraction and the recruitment of inflammatory cells. Eosinophils are responsible for degranulation and cytokine production that play a role in fighting viral infections, remove fibrin in inflammation, fight parasites, and aid in puberty. Eosinophils have a lifespan average of 1-2 days when active.

 

Basophils

BASOPHILS are the least common of the polymorphonuclear cells family--in fact, the least common of all the WBCs. But they are physically the largest of the granulocytes and are responsible for inflammatory reactions during the immune response as well as in the formation of allergic responses such as anaphylaxis, asthma, and others.

They release

  • histamine which results in vasodilation, as well as making blood vessels more permeable to allow neutrophils and clotting proteins to get into connective tissue more easily;
  • heparin, an anticoagulant that inhibits blood clotting (so blood won't clot too quickly) and promotes WBC movement into the area;
  • serotonin to induce inflammation; and
  • chemical signals that attract eosinophils and neutrophils to the problem area.

IgE: responsible for allergic reactions, binds to the membrane receptors on basophils and degranulation is initiated. Basophils can devour other cells or debris during phagocytosis, produce the vasodilator histamine that promotes blood flow to affected tissues and serotonin to induce inflammation and create heparin that prevents blood clotting too quickly.

Basophils that have migrated into tissues are known as mast cells. Basophils can also release chemical signals that attract eosinophils. Basophils have an average lifespan of hours to days when active.

MAST CELLS: Mast cells and basophils are similar, but originate from different places.

  • Basophils originate in bone marrow.
  • Mast cells originate from precursors in connective tissue.

They both release histamine and heparin via degranulation.

They are situated as the "sentinels" of the body, occupying tissue of portals:

  • mucosal membranes of the respiratory, digestive, and urogenital systems, and
  • throughout the dermis and surrounding blood vessels.
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