What is diapedesis?

Diapedesis is the process by which white blood cells (leukocytes) pass through the walls of blood vessels and enter the surrounding tissues. It is an essential part of the immune response and plays a crucial role in fighting infections and inflammation within the body.

During diapedesis, white blood cells, specifically neutrophils and monocytes, adhere to the inner endothelial lining of blood vessels. They then undergo a series of steps to migrate through the endothelial cells and the basement membrane that surrounds the blood vessels.

The process of diapedesis involves:

1. Margination: White blood cells move closer to the walls of blood vessels due to the influence of adhesion molecules on the endothelial cells.
2. Rolling: White blood cells interact weakly with the endothelial cells through selectin molecules, causing them to "roll" along the inner surface.
3. Activation: In response to chemotactic signals like cytokines, white blood cells become activated and firmly adhere to the endothelium through integrin molecules.
4. Transmigration: Specialized proteins, such as PECAM-1, facilitate the passage of white blood cells in between endothelial cells and through the basement membrane.
5. Migration: Once in the surrounding tissues, white blood cells move along a chemical gradient towards the site of infection or inflammation, guided by chemotactic signals.

Diapedesis is a tightly regulated process that is crucial for the immune system to effectively respond to infections. It allows white blood cells to exit the bloodstream and reach the site of infection, where they can engulf and destroy pathogens, produce immune responses, and promote tissue repair.

Disruptions in diapedesis can lead to various health conditions, such as impaired immune response or excessive inflammation. Research is ongoing to better understand the mechanisms and regulation of diapedesis, which may lead to new strategies for treating immune-related disorders.