Polymorphonuclear

Polymorphonuclear leukocytes (PMNs, PML, or PMNLs) are a type of white blood cell in the immune system. They are named for the varying shapes of the nucleus, which is usually divided into multiple segments. PMNs are the most abundant type of granulocyte. They are referred to as either neutrophils or polymorphonuclear neutrophils (PMN or PMNs), and are distinguished from other granulocytes due to their multilobed nucleus.

Structure

PMNs are spherical cells, approximately 10-14 micrometers in diameter. They have a multilobed nucleus, which can have two to five lobes - the number of lobes increases with the age of the cell. The cytoplasm is filled with granules that are either specific (secondary) or azurophilic (primary).

Function

PMNs play a key role in the innate immune system. They are short-lived cells that are primarily involved in the first line of defense against invading microorganisms. PMNs are capable of phagocytosis, the process of engulfing and destroying pathogens. They also release a variety of substances that can kill or inhibit microorganisms, including reactive oxygen species and antimicrobial peptides.

Clinical significance

Abnormalities in the number or function of PMNs can lead to disease. For example, a decrease in the number of PMNs, known as neutropenia, can result in an increased susceptibility to infection. On the other hand, an increase in the number of PMNs, known as neutrophilia, can be a sign of an ongoing infection or inflammation.

See also

• Leukocyte
• Granulocyte
• Neutrophil granulocyte
• Phagocyte

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