Neutrofili

Neutrofili, or neutrophils, are the most abundant type of white blood cells and a central component of the innate immune system. In humans they normally make up about 40 to 70 percent of circulating leukocytes. They develop in the bone marrow from myeloid precursors and are released as mature segmented neutrophils, with a smaller fraction released as band forms during periods of increased demand.

Morphologically, neutrophils have a multi-lobed nucleus and granule-rich cytoplasm. They are rapid responders to infection and tissue injury, migrating from blood into affected sites in response to chemotactic signals and adhesion cues.

Their primary roles include phagocytosis of microbes and debris, production of reactive oxygen species during the respiratory burst, and degranulation with antimicrobial enzymes. Neutrophils can also form neutrophil extracellular traps (NETs) in certain situations, which help trap and kill pathogens.

Clinically, neutrophil counts are used to assess immune status. Elevated counts, or neutrophilia, occur with acute bacterial infections, systemic inflammation, stress, corticosteroid use, or smoking. A left shift—an increased proportion of immature band neutrophils—often accompanies acute infection. Decreased counts, or neutropenia, raise infection risk and can result from chemotherapy, bone marrow failure, autoimmune destruction, or certain medications.

Diagnosis typically relies on a complete blood count with differential to determine the absolute neutrophil count. In cases of abnormal results or suspected functional disorders, further testing such as repeat counts, bone marrow analysis, or specialized assays may be warranted. Neutrophil function and regulation are important in a wide range of infectious, inflammatory, and hematologic conditions.