From the Guidelines
Segmented neutrophils are mature white blood cells characterized by their multi-lobed nucleus and pale cytoplasm, playing a crucial role in the body's immune defense system, particularly against bacterial infections. They are the primary first responders to infection and make up about 50-70% of all circulating white blood cells in healthy adults. These cells migrate from the bloodstream to infected tissues where they engulf and destroy pathogens through a process called phagocytosis, and also release antimicrobial substances and neutrophil extracellular traps (NETs) to kill microorganisms. In laboratory blood tests, they are reported as part of the differential white blood cell count, with elevated levels (neutrophilia) often indicating acute infection, inflammation, or stress, while decreased levels (neutropenia) may suggest bone marrow disorders, certain medications, or viral infections, as seen in conditions like severe congenital neutropenia (SCN) 1. Some key points to note about segmented neutrophils include:
- They are the mature form of neutrophils, distinguished from their immature precursors called band neutrophils or "bands," which have a horseshoe-shaped nucleus rather than a segmented one.
- Abnormalities in neutrophil count or function can be associated with various hematopoietic malignancies, as discussed in the context of hematopoietic malignancy predisposition syndromes 1.
- Conditions like Shwachman–Diamond syndrome (SDS) and severe congenital neutropenia (SCN) can affect neutrophil counts and increase the risk of myeloid malignancies, highlighting the importance of understanding neutrophil biology in the context of these disorders 1.
From the Research
Definition of Segmented Neutrophils
- Segmented neutrophils refer to a type of neutrophil, a white blood cell, characterized by a unique segmented nucleus 2.
- This segmentation is thought to facilitate the neutrophil's migration through narrow channels and confined spaces, allowing them to reach sites of infection or damage more efficiently 2.
Role of Segmented Neutrophils
- Segmented neutrophils play a crucial role in the innate immune system, helping to control infectious diseases and repair damaged tissues 3, 4.
- They are able to counteract infection through phagocytosis and/or the release of neutrophil extracellular traps (NETs) 3.
- However, when inflammation is recurrent or the inciting agent persists, segmented neutrophils can release NETs to exacerbate tissue damage during inappropriate inflammation 3.
Characteristics of Segmented Neutrophils
- Segmented neutrophils have a multilobed nucleus, which is a distinctive feature of these cells 2.
- The number of nuclear lobes can vary, and neutrophils with more than two nuclear lobes have been shown to migrate more quickly through narrow channels compared to those with fewer lobes 2.
- Segmented neutrophils are also characterized by their ability to phagocytose debris and release granules to capture and destroy invading microorganisms 5.