myeloid leukocyte migration

Definition

Target type: biologicalprocess

The movement of a myeloid leukocyte within or between different tissues and organs of the body. [GOC:cvs, PMID:22342843, PMID:24157461]

Myeloid leukocyte migration is a complex and essential process that involves the coordinated movement of these cells from the bloodstream to sites of inflammation or injury. This process is critical for immune surveillance and host defense, as myeloid leukocytes are responsible for recognizing and eliminating pathogens, clearing cellular debris, and promoting tissue repair.

The migration of myeloid leukocytes is initiated by chemotactic signals, which are chemical attractants that guide the cells towards their target. These signals can be derived from various sources, including damaged tissues, invading pathogens, and activated immune cells.

**1. Chemotaxis:**

* Myeloid leukocytes express a variety of receptors on their cell surface that can bind to chemotactic signals. These receptors include chemokine receptors, such as CCR2, CCR5, and CXCR4, as well as receptors for other chemoattractants, such as complement proteins and bacterial products.
* Upon binding to their respective ligands, these receptors activate intracellular signaling pathways that lead to changes in cell morphology and motility.
* These changes include the polymerization of actin filaments, which provides the structural support for cell movement, and the formation of pseudopodia, which are temporary extensions of the cell membrane that allow the cell to move forward.

**2. Adhesion and Rolling:**

* As myeloid leukocytes approach the site of inflammation, they encounter the endothelial cells lining the blood vessels.
* These cells express adhesion molecules, such as selectins and integrins, which mediate the initial interactions between leukocytes and the endothelium.
* Selectins are responsible for the initial rolling of leukocytes along the endothelium, while integrins provide the stronger adhesion necessary for leukocytes to stop rolling and adhere firmly to the vessel wall.
* The rolling process allows leukocytes to sample the local environment for chemotactic signals and to assess the strength of the inflammatory response.

**3. Diapedesis:**

* Once leukocytes are firmly attached to the endothelium, they begin to squeeze between the endothelial cells and enter the surrounding tissue. This process, known as diapedesis, requires the coordinated activity of several cell signaling pathways and cytoskeletal rearrangements.
* Leukocytes use specialized adhesion molecules, such as PECAM-1 (platelet endothelial cell adhesion molecule-1) and CD31, to interact with the endothelial cell junctions and facilitate their passage through the vessel wall.

**4. Migration through Tissues:**

* Once in the tissues, myeloid leukocytes continue to migrate towards the source of the chemotactic signal, guided by a gradient of chemoattractants.
* This migration is driven by the same mechanisms that were involved in chemotaxis and diapedesis, including actin polymerization, pseudopodia formation, and the activation of specific signaling pathways.
* Leukocytes can navigate complex tissue environments and avoid obstacles, such as collagen fibers and other cells, by using a combination of chemotaxis, haptotaxis (movement along a surface), and chemokinesis (random movement).

**5. Phagocytosis and Effector Functions:**

* Upon reaching the site of inflammation, myeloid leukocytes perform their effector functions, which include phagocytosis of pathogens and cellular debris, the release of antimicrobial peptides and cytokines, and the activation of other immune cells.
* Phagocytosis is the process by which leukocytes engulf and destroy pathogens or cellular debris. This process requires the recognition of the target by specific receptors on the leukocyte surface, the engulfment of the target into a phagosome, and the fusion of the phagosome with lysosomes, which contain enzymes that degrade the target.

**Conclusion:**

* The migration of myeloid leukocytes is a highly regulated and complex process that is essential for immune surveillance and host defense.
* This process involves a coordinated interplay of chemotactic signals, adhesion molecules, and cytoskeletal rearrangements, which allows leukocytes to navigate through the bloodstream and tissues to reach their target sites and perform their effector functions.'"

Proteins (1)

Compounds (34)