Page 133 - Veterinary Immunology, 10th Edition

VetBooks.ir Neutrophils

Polymorphonuclear neutrophil granulocytes, otherwise called
neutrophils, predominate in the blood of many mammals (Fig. 5.3).

As a result, about two thirds of the hematopoietic activity of the
bone marrow is devoted to neutrophil production. Neutrophils are
formed by stem cells at a rate of about 8 million per minute in
humans; they migrate to the bloodstream and about 12 hours later
move into the tissues. They live for only a few days unless activated

by inflammation and must therefore be constantly replaced.
Neutrophils constitute about 60% to 75% of the blood leukocytes in
most carnivores, about 50% in the horse, and 20% to 30% in cattle,

sheep, and laboratory rodents. However, blood neutrophils account
for only 1% to 2% of their total population. The vast majority of
neutrophils are sequestered in capillaries within the liver, spleen,
lungs, and bone marrow. During bacterial infections, the numbers
of circulating neutrophils may increase 10-fold as these stored cells

are released from these organs. These neutrophils migrate to the
bloodstream and eventually the tissues, where they die by
apoptosis.

FIG. 5.3 The major structural features of a neutrophil. Note the
characteristic nucleus and the plentiful cytoplasmic granules.

The production of neutrophils by stem cells is regulated by a
cytokine called granulocyte colony-stimulating factor (G-CSF). The

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