Neutrophil

A neutrophil is a granular, nucleated leukocyte, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. They are quick to respond to infection challenge, often within hours. They are ephemeral cells, with a half-life on the order of 6 hours. Neutrophils are more associated with acute inflammatory response than macrophages, which are more involved in chronic inflammation.

While their role has clasically been associated with phagocytosis, a means of cell-mediated immune response in which they are attracted to targets via chemokines, more and more information has been accumulated about their role in releasing cytokines, especially interleukin 12 (IL-12). IL-12 encourages the production of [[interferon#interferon-gamma|interferon gamma (γ-interferon).

Precursors
In the creation of white cells, the original progenitor is the pluripotent stem cell. Under the influence of interleukins IL-1, IL-3, and IL-6, they form committed stem cells (i.e., progenitors). The cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) causes differentiation into the neutrophils, with maturation to polymorphonuclear neutrophils via juvenile and band forms.

Immature forms of neutrophil are juvenile and band. Band neutrophils are immature cells, released by the bone marrow in response to demand. They have a single nucleus resembling a band, a sausage, or the letters C or U.

Polymorphonuclear neutrophil
The mature form of polymorphonuclear neutrophil (PMN) has a nucleus with three to five lobes connected by slender threads of chromatin.