neutrophil mediated immunity

Definition

Target type: biologicalprocess

Any process involved in the carrying out of an immune response by a neutrophil. [GO_REF:0000022, GOC:add, ISBN:0781735149]

Neutrophils are a type of white blood cell that play a crucial role in the innate immune system, the body's first line of defense against infection. They are highly specialized cells designed to rapidly respond to invading pathogens, particularly bacteria and fungi. The process of neutrophil-mediated immunity involves a complex interplay of cellular signaling, migration, and effector functions, culminating in the elimination of pathogens.

**1. Recruitment to the Site of Infection:**
- When pathogens breach the body's physical barriers, they encounter resident immune cells, such as macrophages.
- These macrophages release chemokines, signaling molecules that attract neutrophils from the bloodstream.
- Neutrophils follow the chemokine gradient, rolling along the blood vessel walls until they adhere to the endothelium, the inner lining of blood vessels.
- This adhesion is mediated by selectins and integrins, molecules expressed on both neutrophils and endothelial cells.
- Neutrophils then squeeze between endothelial cells through a process called diapedesis, entering the infected tissue.

**2. Phagocytosis and Killing:**
- Once at the site of infection, neutrophils encounter pathogens and engulf them through a process called phagocytosis.
- Phagocytosis is triggered by recognition of pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharide (LPS) on bacteria, by neutrophil receptors.
- Engulfed pathogens are enclosed in phagosomes, which fuse with lysosomes, organelles containing a variety of antimicrobial enzymes and toxic molecules.
- These enzymes degrade the pathogens, killing them and preventing their spread.

**3. Neutrophil Extracellular Traps (NETs):**
- Neutrophils can also release neutrophil extracellular traps (NETs), a web-like structure composed of DNA, histones, and antimicrobial proteins.
- NETs act as a physical barrier to pathogens, trapping them and preventing their spread.
- NETs also contain antimicrobial compounds that directly kill pathogens.

**4. Cytokine Production:**
- Neutrophils produce cytokines, signaling molecules that amplify the inflammatory response.
- These cytokines recruit additional immune cells to the site of infection and enhance the overall immune response.

**5. Apoptosis and Clearance:**
- After clearing pathogens, neutrophils undergo apoptosis, a programmed cell death that prevents the release of harmful substances into the surrounding tissue.
- Apoptotic neutrophils are then engulfed by macrophages, removing them from the site of infection and preventing inflammation.

Neutrophil-mediated immunity is a highly efficient and potent defense mechanism against infection. However, dysregulation of neutrophil function can contribute to inflammatory diseases, autoimmune disorders, and even sepsis. Understanding the complex mechanisms of neutrophil-mediated immunity is essential for developing new therapeutic strategies for treating these conditions.
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Proteins (5)

Compounds (887)