Leukocyte Extravasation

Leukocyte extravasation is the movement of leukocytes out of the circulatory system and towards the site of tissue damage or infection. This process is regulated by a concerted action between endothelial cells and leukocytes, whereby endothelial cells activate leukocytes and direct them to extravasation sites, and leukocytes in turn instruct endothelial cells to open a path for transmigration.

To learn more about leukocyte extravasation and some of the mechanisms involved in this process check out these resources:

Below is a figure from the Nature Immunolog review, that I mentioned above, with an illustration of the steps involved in leukocyte extravasation.

The multistep cascade of leukocyte extravasation. A range of cell adhesion receptors on endothelial cells (as shown at the bottom of the panel) mediates the capture, rolling, arrest and crawling of leukocytes on the luminal endothelial cell surface.

 

References:

Wikipedia

Immunobiology, 5th edition The Immune System in Health and Disease

How leukocytes cross the vascular endothelium Nature Reviews Immunology