leukocyte migration

Definition

Target type: biologicalprocess

The movement of a leukocyte within or between different tissues and organs of the body. [GOC:add, ISBN:0781735149, PMID:14680625, PMID:14708592, PMID:7507411, PMID:8600538]

Leukocyte migration is a complex and essential process that allows white blood cells (leukocytes) to move from the bloodstream into tissues where they are needed to fight infection, inflammation, or tissue repair. This process involves a coordinated interplay of cellular adhesion molecules, chemokines, and signaling pathways.

**1. Margination and Rolling:**
- Leukocytes circulating in the bloodstream normally flow freely in the center of the vessel, away from the vessel wall.
- During inflammation, the endothelial cells lining the blood vessel become activated and express adhesion molecules like selectins.
- These selectins bind weakly to carbohydrate ligands on leukocytes, causing them to slow down and roll along the vessel wall.

**2. Activation and Firm Adhesion:**
- Rolling leukocytes are exposed to chemokines, signaling molecules that attract them to the site of inflammation.
- Chemokines bind to their receptors on leukocytes, triggering intracellular signaling cascades that lead to the activation of integrins, another type of adhesion molecule.
- Activated integrins bind tightly to their ligands, including ICAM-1 and VCAM-1, on the endothelial cells.
- This firm adhesion stops the rolling and anchors the leukocyte to the vessel wall.

**3. Transmigration (Diapedesis):**
- Once firmly attached, leukocytes migrate between endothelial cells, a process called diapedesis.
- This involves the rearrangement of the cytoskeleton and the expression of specific molecules that allow the cell to squeeze through the tight junctions between endothelial cells.

**4. Chemotaxis:**
- After transmigration, leukocytes are guided by chemokines to the site of inflammation or injury.
- They follow a concentration gradient of chemokines, moving towards the area with the highest concentration.

**5. Phagocytosis and Immune Response:**
- At the site of inflammation, leukocytes perform their specific functions:
- Neutrophils, the first responders, phagocytose and kill invading pathogens.
- Macrophages engulf debris and pathogens, and also release signaling molecules to activate other immune cells.
- T lymphocytes recognize and destroy infected cells.

**Overall, leukocyte migration is a precisely regulated process that ensures the delivery of immune cells to sites of infection, inflammation, or tissue damage, allowing the body to mount an effective immune response.**'
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Proteins (21)

Compounds (667)