T cell extravasation

Definition

Target type: biologicalprocess

The migration of a T cell from the blood vessels into the surrounding tissue. [CL:0000084, GOC:BHF, GOC:mah]

T cell extravasation is a critical step in the immune response, allowing T cells to exit the bloodstream and migrate to sites of inflammation or infection. This process is highly regulated and involves a complex interplay of adhesion molecules, chemokines, and signaling pathways.

The first step in T cell extravasation is **tethering and rolling**, mediated by selectins. Selectins are adhesion molecules expressed on both endothelial cells and leukocytes. L-selectin on T cells binds to GlyCAM-1 and CD34 on the endothelial cells, allowing the T cells to slow down and roll along the vessel wall.

Next, the T cells undergo **activation**, triggered by chemokines. Chemokines are small, chemoattractant proteins that are produced by cells at the site of inflammation or infection. They bind to specific receptors on T cells, activating signaling pathways that lead to the upregulation of integrins.

Integrins are another class of adhesion molecules that play a key role in T cell extravasation. They are composed of two subunits, α and β, and their activation leads to strong adhesion to the endothelium.

The activated T cells then undergo **firm adhesion**, mediated by integrins. The most important integrin for T cell extravasation is LFA-1 (αLβ2). LFA-1 binds to ICAM-1 (Intercellular Adhesion Molecule-1) on the endothelium, providing a strong adhesive force that prevents the T cells from being washed away by the blood flow.

Finally, the T cells **transmigrate**, squeezing between the endothelial cells to enter the tissue. This process is facilitated by the chemokine gradient that guides the T cells toward the site of inflammation.

In summary, T cell extravasation is a multi-step process that involves tethering and rolling, activation, firm adhesion, and transmigration. This process is carefully regulated by adhesion molecules, chemokines, and signaling pathways, ensuring that T cells reach the correct location in the body to mount an effective immune response.'
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Proteins (1)

Compounds (13)