Characteristics of Neutrophil
Neutrophil granulocytes have an average diameter of 12-15micrometers (µm) in peripheral blood smears. When analysing a pure neutrophil suspension on an automated cell center, neutrophil have an average diameter of 8-9µm. The nucleus has a characteristic lobed appearance, the separate lobes connected by chromatin.
The nucleolus disappears as the neutrophil matures, which is something that happens in only a few other types of nucleated cells. A major difference is found between the neutrophils from a male subject and a female subject.
The cell nucleus of a neutrophil from a female subjects shows a small additional x chromosome structure, known as a “neutrophil drumstick”. Neutrophils will show hypersegmentation (many segments of nucleus) in vit B12 and folate deficiency.
They account for approximately 50-70% of all white blood cells. The normal range for human blood count varies from between laboratories, but a neutrophil count of 2.5-7.5 x 109/l is a standard normal range. People of African and middle eastern descent may have lower counts, which are still normal. When circulating in the blood stream and unactivated, neutrophils are spherical. Once activated, they change shape and become more amorphous or amoeba-like and can extend pseudopods as they hunt for antigens (Steven 1994).
Life Span of Neutrophil | Characteristics of Neutrophil
The average life span of (non-activated human) neutrophils in the circulation is about 4-5 days (Pillary et al., 2010). Upon activation, they migrate (position themselves adjacent to the blood vessel endothelium), and undergo selection-dependent capture followed by integrin-dependent adhesion in most cases, after which they migrate into tissue, where they survive for 1-2 days (Paul et al., 2002). Neutrophils will often be phagocytosed themselves by macrophages after digestion of pathogens. PECAM–1 (platelet endothelial cell adhension molecule) and phosphatidylserine (a phospholipids component, usually kept on the innerleaflet of cell membrane by an enzyme called flippase) on the cell surface are involved in this process.
Chemotaxis | Characteristics of Neutrophil
Neutrophil undergo a process called chemotaxis, which allows them to migrate towards the site of infection or inflammation, cell surface receptors allow neutrophil detect chemical gradients of molecules such as interleukin 8 (IL-8). Interferon gamma (IFN-gamma), C5a and leukotriene B4, which these cells use to direct the path of their migration.
Anti-microbial Function | Characteristics of Neutrophil
Being highly motile, neutrophils quickly congregate at a focus of infection, attacked by cytokines expressed by activated endothelium, mast cells, and macrophages. Neutrophils express and release cytokines, which in turn amplify inflammatory reactions by several other cell types (Ear et al., 2008).
In addition to recruiting and activating other cells of immune system, neutrophil play a key role in the front – line defence against invading pathogens. Neutrophils have three strategies for directly attacking micro-organism:
- Phagocytosis (ingestion) through the process called opsonization (Edwards et al., 1994)
- Release of soluble anti-microbials (including granule proteins)
- Generation of neutrophil extracellular traps (NETs) (Hickey et al., 2009).