Polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs), also known as polymorphonuclear neutrophils or granulocytes, are a type of white blood cell that plays a crucial role in the immune system. They are the most abundant type of white blood cells in most mammals and are primarily responsible for responding to infections, particularly those caused by bacteria.

Structure and Function

Polymorphonuclear leukocytes are characterized by the presence of a multi-lobed nucleus, which distinguishes them from other types of white blood cells. They are also filled with granules that contain various enzymes and antimicrobial substances.

The primary function of PMNs is to fight infections. They do this by migrating to the site of infection, a process known as chemotaxis, and engulfing the invading bacteria, a process known as phagocytosis. Once the bacteria are engulfed, the PMNs release the enzymes and antimicrobial substances from their granules to kill the bacteria.

Types of Polymorphonuclear Leukocytes

There are three types of polymorphonuclear leukocytes: neutrophils, eosinophils, and basophils. Each type has a different function in the immune response.

• Neutrophils are the most common type of PMNs and are the first to arrive at the site of an infection. They are particularly effective against bacteria and fungi.
• Eosinophils are less common and are primarily involved in the response to parasitic infections and allergic reactions.
• Basophils are the least common type of PMNs and are involved in the response to allergic reactions and other inflammatory responses.

Clinical Significance

Changes in the number of polymorphonuclear leukocytes in the blood can be an indicator of various medical conditions. An increase in the number of PMNs, known as neutrophilia, can indicate an ongoing infection, while a decrease, known as neutropenia, can make an individual more susceptible to infections.

Leukemia, a type of cancer that affects the white blood cells, can also affect the PMNs. In particular, acute myeloid leukemia is a type of leukemia that often involves the PMNs.

See Also

• White blood cell
• Immune system
• Infection
• Leukemia